Tesis: "Mechanical ventilation"

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Walsh, Brian Kendall. "Computer-aided mechanical ventilation". Thesis, Rush University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10111109.

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Statement of the problem: The systematic implementation of evidence-based practice through the use of guidelines, checklists and protocols has been shown to mitigate the risks associated with MV, yet variation in practice remains prevalent. Recent advances in MV, physiologic monitoring, device-to-device communication, computer processing and software engineering have allowed for the development of an automated point-of-care access to real-time goal setting and practice variance identification. Our aim was to assess the utility of a computer-aided MV (CAMV) system that displays variances and scores the overall MV course. Methods: A retrospective categorization of the ventilation and oxygenation statuses of patients within our pediatric intensive care unit (PICU) over a 2 '/z years period utilizing 15 rule-based algorithms was initiated as a proof of concept. Goals were predetermined based on generally accepted values. All patient categories were calculated and presented as a percent of recording time. Following the feasibility study, a retrospective observational study (baseline), followed by two sequential interventions made over a 2-month period was conducted. Phase I comprised a survey of goals of MV by clinicians caring for patients being monitored by the CAMV system. Phase II intervention was the setting and monitoring of goals of MV with a web browser based data visualization system (T3). An outcome measurement tool was developed to score each MV course. The MV score (MVS) evaluated four outcomes: (1) acceptable ventilation, (2) acceptable oxygenation, (3) barotrauma free and (4) volutrauma-free states as a percent of recording time. Results: Pilot consisted of 222 patients. The Baseline phase evaluated 130 patients, Phase I enrolled 31 patients and Phase II enrolled 36 patients. There were no differences in demographic characteristics between cohorts. One hundred and seventy-one surveys were completed in Phase I. An increase in the use of T3 by 87% was observed in Phase II from Phase I. MVS improved by 8.4% in Phase I and 11.3% in Phase II from Baseline. The largest improvement was in the volutraumafree category. MVS was 9% higher on average in those who survived. Conclusion: The use of CAMV was associated with an improvement in MVS. Further research is needed to determine if improvements in MVS through a targeted, process-oriented intervention such as CAMV will lead to improved patient outcomes.

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2

Howe, Kimberly Palazzo. "Mechanical Ventilation Antioxidant Trial". Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1112877564.

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3

Sperber, Jesper. "Protective Mechanical Ventilation in Inflammatory and Ventilator-Associated Pneumonia Models". Doctoral thesis, Uppsala universitet, Infektionssjukdomar, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-282602.

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Severe infections, trauma or major surgery can each cause a state of systemic inflammation. These causes for systemic inflammation often coexist and complicate each other. Mechanical ventilation is commonly used during major surgical procedures and when respiratory functions are failing in the intensive care setting. Although necessary, the use of mechanical ventilation can cause injury to the lungs and other organs especially under states of systemic inflammation. Moreover, a course of mechanical ventilator therapy can be complicated by ventilator-associated pneumonia, a factor greatly influencing mortality. The efforts to avoid additional ventilator-induced injury to patients are embodied in the expression ‘protective ventilation’. With the use of pig models we have examined the impact of protective ventilation on systemic inflammation, on organ-specific inflammation and on bacterial growth during pneumonia. Additionally, with a 30-hour ventilator-associated pneumonia model we examined the influence of mechanical ventilation and systemic inflammation on bacterial growth. Systemic inflammation was initiated with surgery and enhanced with endotoxin. The bacterium used was Pseudomonas aeruginosa. We found that protective ventilation during systemic inflammation attenuated the systemic inflammatory cytokine responses and reduced secondary organ damage. Moreover, the attenuated inflammatory responses were seen on the organ specific level, most clearly as reduced counts of inflammatory cytokines from the liver. Protective ventilation entailed lower bacterial counts in lung tissue after 6 hours of pneumonia. Mechanical ventilation for 24 h, before a bacterial challenge into the lungs, increased bacterial counts in lung tissue after 6 h. The addition of systemic inflammation by endotoxin during 24 h increased the bacterial counts even more. For comparison, these experiments used control groups with clinically common ventilator settings. Summarily, these results support the use of protective ventilation as a means to reduce systemic inflammation and organ injury, and to optimize bacterial clearance in states of systemic inflammation and pneumonia.

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4

Hammash, Muna Hassan. "CARDIAC RHYTHM DURING MECHANICAL VENTILATION AND WEANING FROM VENTILATION". UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/56.

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The transition from mechanical ventilation (MV) to spontaneous ventilation during weaning is associated with hemodynamic alterations and autonomic nervous system (ANS) alterations (reflected by heart rate variability [HRV]). Although cardiac dysrhythmias are an important manifestation of hemodynamic alterations, development of dysrhythmias during MV and weaning and subsequent impact on length of MV has received little attention. The purposes of this dissertation were to 1) evaluate the relationship of heart rate variability (HRV) during weaning to the development of cardiac dysrhythmias and 2) determine the relationship of cardiac dysrhythmias to length of MV. A convenience sample of 35 patients (66.7% men; mean age 53.3 years) who required MV was enrolled in this study. Continuous 3-lead electrocardiographic data were collected for 24 hours at baseline during MV and for the first 2 hours during the initial weaning trial. HRV was evaluated using spectral power analysis. Twenty- seven patients out of 30 were exposed to a combination of pressure support (8-15 cm H2O) and continuous positive airway pressure 5 cm H2O during weaning trial. Three patients self- extubated and received supplemental oxygen through either a partial rebreathing or non-rebreathing mask. Low frequency (LF) power HRV decreased, while high frequency (HF) and very low frequency (VLF) power HRV did not change during weaning. Multiple regression analyses showed that LF and HF HRV were significant predictors of occurrence of ventricular and supraventricular ectopic beats during weaning, while VLF power predicted occurrence of ventricular ectopic beats only. The mean of occurrence of supraventricular ectopic beats per hour during weaning was double the mean at baseline, while the mean of ventricular ectopic beats per hour did not change. Mean number of supraventricular ectopic beats per hour during weaning was a significant predictor of length of MV. This dissertation has fulfilled an important gap in the evidence base for cardiac dysrhythmias during weaning from MV. Cardiac dysrhythmias and HRV alterations should be systemically evaluated during MV and weaning trials in order to decrease length of MV.

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5

van, Drunen Erwin Johan. "Mechanical Ventilation Modelling and Optimisation". Thesis, University of Canterbury. Mechanical Engineering, 2013. http://hdl.handle.net/10092/8400.

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Acute Respiratory Distress Syndrome (ARDS) is associated with lung inflammation and fluid filling, resulting in a stiffer lung with reduced intrapulmonary gas volume. ARDS patients are admitted to the Intensive Care Unit (ICU) and require Mechanical Ventilation (MV) for breathing support. Positive End Expiratory Pressure (PEEP) is applied to aid recovery by improving gas exchange and maintaining recruited lung volume. However, high PEEP risks further lung injury due to overstretching of healthy lung units, and low PEEP risks further lung injury due to the repetitive opening and closing of lung units. Thus, selecting PEEP is a balance between avoiding over-stretching and repetitive opening of alveoli. Furthermore, specific protocols to determine optimal PEEP do not currently exist, resulting in variable PEEP selection. Thus, ensuring an optimal PEEP would have significant impact on patient mortality, and the cost and duration of MV therapy. Two important metrics that can be used to aid MV therapy are the elastance of the lungs as a function of PEEP, and the quantity of recruited lung volume as a function of PEEP. This thesis describes several models and model-based methods that can be used to select optimal PEEP in the ICU. Firstly, a single compartment lung model is investigated for its ability to capture the respiratory mechanics of a mechanically ventilated ARDS patient. This model is then expanded upon, leading to a novel method of mapping and visualising dynamic respiratory system elastance. Considering how elastance changes, both within a breath and throughout the course of care, provides a new clinical perspective. Next, a model using only the expiratory portion of the breathing cycle is developed and presented, providing an alternative means to track changes in disease state throughout MV therapy. Finally, four model-based methods are compared based on their capability of estimating the quantity of recruited lung volume due to PEEP. The models and model-based methods described in this thesis enable rapid parameter identification from readily available clinical data, providing a means of tracking lung condition and selecting optimal patient-specific PEEP. Each model is validated using data from clinical ICU patients and/or experimental ARDS animal models.

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6

Young, Peter Jeffrey. "Pulmonary aspiration in mechanical ventilation". Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323263.

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Pulmonary aspiration in mechanical ventilation occurs despite appropriate inflation of the tracheal tube cuff. After anaesthesiath is can causep ostoperative and, in critically ill patients, ventilator-associated pneumonia. Cuff over-inflation exerts excessive pressure on the tracheal mucosa causing injury. High volume low pressure (HVLP) cuffs permit wall pressure control as the intracuff pressure (CP) is the tracheal wall pressure (TWP). Unfortunately, at the cuff wall, folds and channels and, therefore, fluid leakage occur. Low volume high pressure (LVHP) cuffs develop neither folds nor associated leakage, but TWP is not easily inferred from CP and excessive pressures can result in tracheal injury. This thesis examines the problem of aspiration in a model, in anaesthetised patients and in the critically ill. In the model, protection against leakage resulted from positive end-expiratory pressure and cuff lubrication. Two tracheal cuff prototypes are introduced. Firstly, the compliant HVLP cuff is one with a tapered shape made of highly compliant material. Within the model this produced a circumferential band at the cuff wall without folds thus effectively eliminating channels and leakage. Secondly, the prototype pressure limited cuff (PLC) is a latex LVHP cuff with inflation characteristics such that TWP can be inferred from CP and maintained at an acceptable level. Within the model the PLC prevented leakage at acceptable TWPs. For clinical use a constant pressure inflation device is required to provide uninterrupted protection, although notably HVLP cuffs allow leakage despite this. The PLC prevented dye aspiration in 100% of tracheally intubated critically ill patients compared with 13% of the control HVLP group (p<0.01). A silicone cuff with similar inflation characteristics, yet improved biocompatability and shelf life, prevented dye aspiration in 100% of patients with tracheostomies compared to 0% of the HVLP control group (p=0.001). HVLP cuff lubrication delayed dye aspiration for 1 to 5 days (p<0.05).

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7

Balaji, Ravishankar. "Breathing Entrainment and Mechanical Ventilation in Rats". Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1307743446.

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8

Bengtsson, Patrik y Joel Blomfelt. "Variabel Ventilation". Thesis, KTH, Energiteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190163.

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A lot of people today spend most of their lives indoors. Both at home and at work time is spent in areas where the climate is not governed by the weather but by ventilation systems meant to create a suitable indoor climate. Despite having such a central part in society the subject of ventilation seldom gets very much attention, and in the current situation it is not a foregone conclusion that indoor air quality and climate is satisfactory. Those who build the homes and premises normally explain this as a result of cost considerations, but essentially the situation originates from other issues. A more accurate explanation is that there are some problems concerning the planning stage of ventilation systems, which implies both a highly simplified designing approach and the price, not the function and quality, being decisive. The problems have been confirmed by several sources and research is in progress within the area in order to address the underlying issues. Among other things, various types of test-bed housing is constructed in several parts of the world, designed for measurement and data collection in a real living environment. Such projects can both verify different system´s function and promote the development of new innovations, but also help in creating well-justified research material regarding, among other things, different ventilation solutions such as for example variable ventilation. One of these projects, called KTH Live-in Lab, is located at KTH in Stockholm. This report presents a work regarding comparisons of different ventilation solutions for such a student apartment as constructed in the ongoing research project KTH Live-in Lab. The work focuses on both finding a suitable system and then link the results to an adequate combination for use with variable ventilation. In order to deal with today´s problems within the area, the work is focused on deviating from the current conventional approach and ventilation design. The result is illustrated digitally in the form of computer simulations of air flow in a virtual model of the apartment, and comparisons led both to a number of conclusions, and proposals of suitable and unconventional solutions. For non-variable ventilation systems, a suitable system consisted of one ventilation inlet placed at ceiling level and two outlets whereof one at ceiling level and one at floor level. For variable ventilation, the results showed that the system solution should suitably be combined with the ability to switch to an inlet at floor level at nights and other scenarios without activity and movement in the apartment. Other conclusions are mainly about findings regarding how certain design variations affect the characteristics of the ventilation system.
Många människor spenderar idag större delen av sitt liv inomhus. Det är vanligt att man både hemma och på jobbet vistas i utrymmen där klimatet inte styrs av väder och vind utan av ventilationssystem som är tänkta att skapa ett lämpligt inomhusklimat. Trots ventilationens centrala del av samhället hamnar ämnet dock ofta i skymundan, och i dagens läge är det ingen självklarhet att inomhusklimaten och dess luftkvalité är tillfredställande. Av dem som bygger bostäderna och lokalerna förklaras detta ofta bero på kostnadsaspekter, men i grund och botten är det annat som ligger till grund för dagens situation. En bättre förklaring är att det finns viss problematik kring ventilationens planeringsskede, vilket innebär ett väldigt förenklat arbetssätt och att kostnad prioriteras framför funktion och kvalité. Problemen har bekräftats från flera håll och forskning pågår inom området i syfte att möta de bakomliggande orsakerna. Bland annat uppförs på flera håll i världen olika typer av testbädd-bostäder utformade för mätning och datainsamling i en verklig boendemiljö. Med hjälp av dessa kan man både verifiera olika systems funktion och gynna framtagning av nya innovationer och välgrundat forskningsmaterial gällande bland annat olika ventilationslösningar som exempelvis variabel ventilation. Ett av dessa projekt, med namnet KTH Live-in Lab, utförs på KTH i Stockholm. I denna rapport presenteras ett arbete gällande jämförelser av olika ventilationslösningar för en sådan studentlägenhet som uppförs i det pågående bygg- och forskningsprojektet KTH Live-in Lab. Arbetet fokuseras på att dels hitta en lämplig ventilationslösning och sedan även koppla resultatet till en möjlig kombination att använda för variabel ventilation. I syfte att möta dagens problematik fokuserades på att frångå dagens konventionella arbetssätt och ventilationsdesign. Resultatet illustreras digitalt i form av datorsimuleringar av luftflöden i en virtuell modell av bostaden, och jämförelserna ledde till ett antal slutsatser och förslag på lämpliga okonventionella lösningar. För icke-variabel ventilation var det lämpligt att placera ett inlopp i taknivå, samt två utlopp varav ett i taknivå och ett i golvnivå. För variabel ventilation visade det sig att denna systemlösning bör kombineras med möjlighet att växla inloppet till lågt inlopp på nätter och andra scenarion utan aktivitet och rörelse i bostaden. Övriga slutsatser gäller vilka egenskaper som bör varieras beroende på vad man vill uppnå med ventilationen.

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Svantesson, Cecilia. "Respiratory mechanics during mechanical ventilation in health and in disease". Lund : Dept. of Clinical Psychology, Lund University, 1997. http://catalog.hathitrust.org/api/volumes/oclc/38987113.html.

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10

Kostic, Peter. "New methods for optimization of mechanical ventilation". Doctoral thesis, Uppsala universitet, Anestesiologi och intensivvård, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-249172.

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Mechanical ventilation saves lives, but it is an intervention fraught with the potential for serious complications. Prevention of these complications has become the focus of research and critical care in the last twenty years. This thesis presents the first use, or the application under new conditions, of three technologies that could contribute to optimization of mechanical ventilation. Optoelectronic plethysmography was used in Papers I and II for continuous assessment of changes in chest wall volume, configuration, and motion in the perioperative period. A forced oscillation technique (FOT) was used in Paper III to evaluate a novel positive end-expiratory pressure (PEEP) optimization strategy. Finally, in Paper IV, FOT in conjunction with an optical sensor based on a self-mixing laser interferometer (LIR) was used to study the oscillatory mechanics of the respiratory system and to measure the chest wall displacement. In Paper I, propofol anesthesia decreased end-expiratory chest wall volume (VeeCW) during induction, with a more pronounced effect on the abdominal compartment than on the rib cage. The main novel findings were an increased relative contribution of the rib cage to ventilation after induction of anesthesia, and the fact that the rib cage initiates post-apneic ventilation. In Paper II, a combination of recruitment maneuvers, PEEP, and reduced fraction of inspired oxygen, was found to preserve lung volume during and after anesthesia. Furthermore, the decrease in VeeCW during emergence from anesthesia, associated with activation of the expiratory muscles, suggested that active expiration may contribute to decreased functional residual capacity, during emergence from anesthesia. In the lavage model of lung injury studied in Paper III, a PEEP optimization strategy based on maximizing oscillatory reactance measured by FOT resulted in improved lung mechanics, increased oxygenation, and reduced histopathologic evidence of ventilator-induced lung injury. Paper IV showed that it is possible to apply both FOT and LIR simultaneously in various conditions ranging from awake quiet breathing to general anesthesia with controlled mechanical ventilation. In the case of LIR, an impedance map representing different regions of the chest wall showed reproducible changes during the different stages that suggested a high sensitivity of the LIR-based measurements.

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SPADARO, SAVINO. "Diaphragmatic dysfunctionin criticallyill patients undergone mechanical ventilation". Doctoral thesis, Università di Foggia, 2017. http://hdl.handle.net/11369/363289.

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INTRODUCTION. Prolonged mechanical ventilation (MV) can cause mus- cle atrophy and adversely affect diaphragmatic force-generating capacity, a con- dition referred to as ventilator-induced diaphragmatic dysfunction (VIDD). Dia- phragmatic ultrasound has been proposed as a bedside daily monitoring of dia- phragm function; however, to date there are no specific serum biomarkers for muscular damage and dysfunction. Foster et al. suggested that skeletal troponin I (sTnI) could be a sensitive marker to detect early signs of muscle injury. OB- JECTIVES. Firstly, to study the trend of a novel biomarker (sTnI) in mechani- cally ventilated ICU patients; secondly, to determine whether this trend was as- sociated with the development of VIDD as assessed with diaphragmatic ultra- sound. METHODS. Serial serum samples were obtained from 24 mechanically ven- tilated ICU patients at 24 (T0), 48 (T1) and 72 (T3) hours after admission. Pa- tients were not considered for inclusion if they had a history of neuromuscular disease or a previously documented diaphragm paralysis. Specimens were ana- lysed and specific isoforms for sTnI (slow (ssTnI) and fast (fsTnI)) were assayed by commercially available ELISA kits (Human TNNI ELISA kit, Mybiosource). Simultaneously, in 16 patients diaphragmatic displacement (DD), thickness at end expiration (T EE ) and thickening fraction (TF) were measured with ultrasound. Data are reported as median [IQR]. Values were compared using Friedman's analysis for repeated measures and Wilcoxon test for paired samples; p < 0.05 was considered statistically significant. RESULTS. Ventilatory variables did not change over time. The two sTnI isoforms had a different behaviour over time: ssTnI levels remained unchanged during the course of MV (p=0.957), while sfTnI significantly decreased over time (p<0.003), with the lowest level after 72 hours from admission (T0 vs T2, p = 0.004). Both DD (p = 0.004) and TF (< 0.0001) decreased over time, while T EE remained stable. We found a statistically significant correlation between the per- cent change from baseline of sfTnI and TF at 72 hours from admission (r = 0.661, p = 0.007). CONCLUSIONS. Our results seem to demonstrate that both sTnI and ultra- sound describe adequately the decrease in diaphragmatic function over time in mechanically ventilated ICU patients. Moreover, fsTnI seems to be better corre- lated with echographical signs of diaphragmatic dysfunction.

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12

Koombua, Kittisak. "Multiscale Modeling of Airway Inflammation Induced by Mechanical Ventilation". VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1841.

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Mechanical ventilation (MV) is a system that partially or fully assists patients whose respiratory system fails to achieve a gas exchange function. However, MV can cause a ventilator-associated lung injury (VALI) or even contribute to a multiple organ dysfunction syndrome (MODS) in acute respiratory distress syndrome (ARDS) patients. Despite advances in today technologies, mortality rates for ARDS patient are still high. A better understanding of the interactions between airflow from mechanical ventilator and the airway could provide useful information used to develop a better strategy to ventilate patients. The mechanisms, which mechanical ventilation induces airway inflammation, are complex processes and cover a wide range of spatial scales. The multiscale model of the airway have been developed combining the computational models at organ, tissue, and cellular levels. A model at the organ level was used to study behaviors of the airway during mechanical ventilation. Strain distributions in each layer of the airway were investigated using a model at the tissue level. The cellular inflammatory responses during mechanical ventilation were investigated through the cellular automata (CA) model incorporating all biophysical processes during inflammatory responses. The multiscale modeling framework started by obtaining airway displacements from the organ-level model. They were then transferred to the tissue-level model for determining the strain distributions in each airway layer. The strain levels in each layer were then transferred to the cellular-level model for inflammatory responses due to strain levels. The ratio of the number of damage cells to healthy cells was obtained through the cellular-level model. This ratio, in turn, modulated changes in the Young’s modulus of elasticity at the tissue and organ levels. The simulation results showed that high tidal volume (1400 cc) during mechanical ventilation can cause tissue injury due to high concentration of activated immune cells and low tidal volume during mechanical ventilation (700 cc) can prevent tissue injury during mechanical ventilation and can mitigate tissue injury from the high tidal volume ventilation. The multiscale model developed in this research could provide useful information about how mechanical ventilation contributes to airway inflammation so that a better strategy to ventilate patients can be developed.

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Tomasi, Roberta. "Energy performance, comfort and ventilation effectiveness of radiant systems coupled with mechanical ventilation". Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422467.

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This work presents the results of different numerical and experimental studies about energy performance, thermal comfort and ventilation effectiveness of radiant systems combined with different types of mechanical ventilation. Experimental studies have been carried out in Italy, in a test room in the laboratories of the company RHOSS S.p.A in Codroipo (Udine) and in Denmark, in a test room in the laboratories of the International Centre for Indoor Environment and Energy (ICIEE), at DTU (Danish Technical University), in Lyngby. Radiant systems in residential and in office buildings are increasingly used because of the low heating or cooling demand and, at the same time, for the good thermal comfort they assure. The thermal output estimation of radiant system in steady state condition needs the determination of the convective heat transfer coefficient from the surface to the room; a critical review among the correlations available in literature have been carried out and correlations for heated ceiling and cooled floor have been presented. Furthermore the variation of convective heat transfer coefficients, depending on the considered ventilation systems, has been estimated by means of the Computational Fluid Dynamics (CFD) technique. The energy performance and thermal behavior of radiant systems during transient conditions have been predicted by using experimental tests and numerical calculations with the software Digithon that was developed by the University of Padua. In this work the validation of this software by comparison with experimental data has been presented. In new and renovated buildings the high tightness and high insulation determine a potential risk of poor indoor air quality and condensation at the surfaces; for this reason an efficient ventilation system is necessary to provide for fresh air in the rooms. In a low polluted building air quality depends on human bioeffluents, among which carbon dioxide is considered the most significant one. By using numerical simulations (CFD) the effects of the supply and extract air terminals on contaminants distribution in offices equipped with a cooled ceiling has been investigated. Besides, in order to fully characterize the indoor climate of residential rooms or offices, an extensive experimental study has been carried out in a test room to determine both thermal comfort and ventilation effectiveness for different solutions of mixing ventilation and displacement ventilation combined with floor radiant systems. In particular, the effects of supply and extract air terminals positions by using low air change rates in mixing ventilation and the effects of different ventilation rates with displacement ventilations terminals have been analyzed. Results from experiments have been used for the validation of a CFD model for the prediction of air distribution in rooms equipped with mixed or displacement ventilation, combined with heating/cooling floor systems.
In questo lavoro di dottorato vengono presentati i risultati di uno studio sui sistemi radianti per il raffrescamento ed il riscaldamento in ambito civile e sulla loro integrazione con opportuni sistemi di ventilazione meccanica. Le prestazioni energetiche in regime stazionario e transitorio, così come le prestazioni di comfort termico e di qualità dell’aria garantita, sono state studiate mediante l’ausilio di prove sperimentali, di simulazioni fluidodinamiche e di altri codici di calcolo. Gli studi sperimentali sono stati realizzati in parte in Italia, presso i laboratori dell’azienda RHOSS S.p.A di Codroipo (Udine), e in parte presso i laboratori dell’ICIEE (International Centre for Indoor Environment and Energy), dell’Università Tecnica di Danimarca, (DTU) a Lyngby (DK). L’aspetto più rilevante di questo lavoro è legato alla sempre maggiore diffusione dei sistemi radianti come soluzione per il riscaldamento ed il raffrescamento di ambienti interni, in quanto combinano vantaggi energetici ad elevati livelli di comfort termico. Per ragioni dovute alla piccola differenza di temperatura tra l’ambiente e il fluido termovettore, i sistemi radianti si interfacciano molto bene con caldaie a condensazione, pompe di calore, sistemi free cooling, collettori solari e altre sorgenti rinnovabili e soluzioni ad alta efficienza energetica. Il calcolo della resa termica di tali sistemi viene eseguito mediante le equazioni valide per la convezione in regime stazionario, come quelle fornite dalle norme Europee EN 1264 ed EN 15377. In letteratura esistono numerose correlazioni valide per il calcolo della potenza convettiva di superfici orizzontali e verticali e di superfici interne di stanze reali; le norme EN 1264 ed EN 15377 consigliano correlazioni diverse e lo stesso accade per codici si simulazione energetica degli edifici. Ad oggi non è disponibile una chiara definizione di coefficiente di scambio termico convettivo per i sistemi radianti, specialmente per quanto riguarda pavimenti freddi e soffitti caldi. Il primo obiettivo di questa tesi è stato di realizzare un’analisi critica delle correlazioni disponibili in letteratura adatte ai sistemi radianti e di proporre delle equazioni per ogni configurazione di riscaldamento o raffrescamento da soffitto, pavimento o parete. In ambito residenziale il pavimento radiante rappresenta una delle soluzioni più richieste grazie all’elevato livello di comfort termico garantito; tuttavia, al fine di migliorare la qualità dell’aria e specialmente a causa della necessità di deumidificare l’aria in estate per evitare formazione di condensa, accanto al sistema radiante andrebbe installato un sistema di ventilazione meccanica. L’aria primaria in estate è solitamente a temperatura più bassa della temperatura della stanza e dotata di una certa velocità; nel caso di immissione da bocchette installate vicino ad una superficie radiante, lo scambio convettivo potrebbe venire variato rispetto ad una soluzione senza ventilazione. Mediante uno studio con simulazioni fluidodinamiche CFD è stato possibile valutare l’incremento dello scambio convettivo da un soffitto freddo mediante lo sfruttamento di aria primaria. I sistemi radianti, in particolare i sistemi a soffitto, rappresentano un’ottima soluzione per rimuovere i carichi termici degli uffici durante il periodo estivo, ma allo stesso tempo possono essere usati per il riscaldamento invernale degli stessi con buone prestazioni energetiche e di comfort termico. La differenza sostanziale è che durante la stagione invernale il sistema radiante si trova a lavorare prevalentemente in regime stazionario, mentre durante la stagione estiva i carichi esterni dovuti alla radiazione solare e all’escursione diurna, accompagnati da carichi interni dovuti all’occupazione umana, determinano condizioni piuttosto variabili durante la giornata. Il comportamento di sistemi radianti a regimi stazionari e transitori sono state studiate mediante prove in camera climatica; inoltre un modello di calcolo chiamato Digithon, sviluppato all’interno del Dipartimento di Fisica Tecnica dell’Università di Padova, è stato validato mediante un confronto con dati sperimentali. Seguendo un’opportuna procedura, riportata nella tesi, è stato possibile impostare dei profili di carico che simulano una tipica giornata estiva o invernale su una parete della stanza ed è stato studiato come il soffitto radiante reagisca per cercare di mantenere una certa temperatura di comfort nella stanza. Al fine di mantenere una buona qualità dell’aria, evitare la formazione di condensa, ma anche per incrementare la capacità di raffrescamento quando richiesto, i sistemi radianti per gli uffici andrebbero sempre associati a sistemi di ventilazione meccanica. Accanto ai tradizionali sistemi a soffitto con ventilazione a miscelazione, le soluzioni con ventilazione a dislocamento accoppiate a sistemi a pavimento o a soffitto sono alternative di crescente interesse per gli uffici. In edifici dove sia bassa la quantità di inquinanti emessi dai materiali edili, dai mobili e dalle attrezzature, la quantità di bioeffluenti dagli occupanti, dei quali l’anidride carbonica CO2 è normalmente usata come principale indicatore, è determinante per la qualità dell’aria interna. La capacità di rimozione dei contaminanti e, parallelamente, la capacità di immettere aria pulita negli ambienti sono espresse dall’efficienza di ventilazione (ventilation effectiveness). Mediante simulazione fluidodinamiche CFD è stato possibile confrontare l’efficienza di rimozione dei contaminanti utilizzando diverse soluzioni di ventilazione a dislocamento piuttosto che soluzioni tradizionali a miscelazione. La qualità di un ambiente interno andrebbe misurata in termini sia di comfort termico garantito all’occupante che di qualità dell’aria. Attraverso prove sperimentali in laboratorio, i principali indici di comfort termico e di efficienza di ventilazione sono stati determinati per diverse configurazioni di ventilazione a miscelazione e di ventilazione a dislocamento in ambienti rappresentativi di applicazioni residenziali o del terziario. I risultati sono stati in seguito utilizzati per effettuare una validazione di un modello fluidodinamico (CFD) creato per la previsione del movimento dell’aria in ambienti residenziali o uffici.

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Vimláti, László. "Benefits of Spontaneous Breathing : Compared with Mechanical Ventilation". Doctoral thesis, Uppsala universitet, Anestesiologi och intensivvård, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-182564.

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When spontaneous breathing (SB) is allowed during mechanical ventilation (MV), atelectatic lung areas are recruited and oxygenation improves thereby. Whether unsupported SB at its natural pattern (without PEEP and at low pressure/small tidal volume) equally recruits and improves oxygenation, and if so by which mechanism, has not been studied. A porcine lung collapse model was designed to study this question. The cardiac output dependency of the pulmonary shunt was investigated with healthy lungs and with major shunt (during one-lung ventilation) and with SB, MV and continuous positive airway pressure (CPAP). The hypoxic pulmonary vasoconstriction (HPV) was blocked with sodium nitroprusside (SNP) to see whether HPV is the only mechanism available for ventilation/perfusion (VA/Q) matching during MV and SB. In all experiments, respiratory rate and tidal volume during MV were matched to SB. Oxygenation was assessed by serial blood gas measurements, recruitment by thoracic CTs; pulmonary shunt was assessed by multiple inert gas elimination or venous admixture. SB attained better oxygenation and lower pulmonary shunt compared with MV, although it did not recruit collapsed lung. Pulmonary shunt did not correlate with cardiac output during SB, whereas a correlation was found during MV and CPAP. With blocked HPV, pulmonary shunt was considerably lower during SB than MV. In conclusion, SB improves VA/Q matching as compared with MV, even when no recruitment occurs. In contrast to MV and CPAP, cardiac output has no major effect on pulmonary shunt during SB. The improved VA/Q matching during SB despite a blocked HPV might indicate the presence of a SB-specific mechanism that improves pulmonary blood flow redistribution towards ventilated lung regions independent of or supplementary to HPV.

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Mishra, Ankit Nidhishchandra. "Mechanical Ventilation and Optimisation through Analytical Lung Model". Thesis, University of Canterbury. Mechanical Engineering, 2012. http://hdl.handle.net/10092/7005.

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Mechanical Ventilation (MV) therapy is one of the most common treatments offered to patients with respiratory failure in ICU. MV assists patient recovery by completely or partially taking over the breathing process and helping with oxygen delivery and removal of carbon dioxide. However, inappropriate MV settings mismatched to a given patient’s condition can cause further damage. On the other hand, suboptimal MV settings can increase the length of stay of the patient in ICU and increase the cost of treatment. Acute Respiratory Distress Syndrome (ARDS) is a major form of Acute Lung Injury (ALI) where clinicians offer a supportive environment for patient recovery by application of MV. ARDS is characterised by inflamed and fluid filled lungs that result in alveolar collapse and thus severe hypoxemia. Application of positive end expiratory pressure (PEEP) is employed to recruit and retain lung units to maximise gas exchange. However, a delicate trade-off is required between maximising gas exchange and preventing further unintended damage to the lungs, when determining optimum PEEP level. Currently, no specific protocols to determine optimum PEEP level exist and selection of PEEP is dependent on medical intuition and experience, primarily due to lack of easy methods to determine patient – specific condition at the patient’s bedside. A mathematical recruitment model is developed in Labview to help determine patient – specific condition based on fundamental lung physiology and engineering principals in this thesis. The model utilises readily available clinical data to determine parameters that identify underlying patient – specific lung characteristics and conditions. Changes in these parameters can be monitored over time and compared between patients to determine the severity of the disease and evolution of disease with time. A second model is developed to determine dynamic functional residual capacity (dFRC), that represents the extra volume retained in a lung through application of PEEP. The model extends previous efforts in the field that applied the stress – strain theory to lung mechanics to estimate dFRC. This model estimates the patient’s dFRC using readily available clinical data (PV data) and can be monitored over time to determine changes in a xiii given patient’s condition. The dFRC model introduces a new parameter, , which is considered a population constant for the particular PEEP. The model offers an easy and reliable method to determine dFRC since other methods are normally invasive or require interruption of MV. The models developed were validated against real – time clinical data obtained through clinical trials. The recruitment model was found to fit the clinical data well with error values within acceptable limits. It also enabled identification of parameters that reflect the underlying patient – specific lung condition. The dFRC model was able to estimate the dFRC for a patient with high level of accuracy for clinically applicable PEEP levels. The two models work well in conjunction with each other and provide a novel and easy method to clinicians to determine patient – specific lung characteristics and ultimately determine optimal MV treatment parameters, especially PEEP.

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Chiew, Yeong Shiong. "Model-Based Mechanical Ventilation for the Critically Ill". Thesis, University of Canterbury. Mechanical Engineering, 2013. http://hdl.handle.net/10092/8311.

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Mechanical ventilation (MV) is the primary form of therapeutic support for patients with acute respiratory failure (ARF) or acute respiratory distress syndrome (ARDS) until the underlying disease is resolved. However, as patient disease state and response to MV are highly variable, clinicians often rely on experience to set MV. The result is more variable care, as there are currently no standard approaches to MV settings. As a result of the common occurrence of MV and variability in care, MV is one of the most expensive treatments in critical care. Thus, an approach capable of guiding patient-specific MV is required and this approach could potentially save significant cost. This research focuses on developing models and model-based approaches to analyse and guide patient-specific MV care. Four models and metrics are developed, and each model is tested in experimental or clinical trials developed for the purpose. Each builds the understanding and methods necessary for an overall approach to guide MV in a wide range of patients. The first model, a minimal recruitment model, captures the recruitment of an injured lung and its response to positive end expiratory pressure (PEEP). However, the model was only previously validated in diagnosed ARDS patients, and was not proven to capture behaviours seen in healthy patients. This deficiency could potentially negate its ability to track disease state, which is crucial in providing rapid diagnosis and patient-specific MV in response to changes in patient condition. Hence, the lack of validation in disease state progression monitoring from ARDS to healthy, or vice-versa, severely limits its application in real-time monitoring and decision support. To address this issue, an experimental ARDS animal model is developed to validate the model across the transition between healthy and diseased states. The second model, a single compartment linear lung model, models the lung as a conducting airway connected to an elastic compartment. This model is used to estimate the respiratory mechanics (Elastance and Resistance) of an ARDS animal model during disease progression and recruitment manoeuvres. This model is later extended to capture high resolution, patient-specific time-varying respiratory mechanics during each breathing cycle. This extended model is tested in ARDS patients, and was used to titrate patient-specific PEEP using a minimum elastance metric that balances recruitment and the risk of lung overdistension and ventilation-induced injury. Studies have revealed that promoting patients to breathe spontaneously during MV can improve patient outcomes. Thus, there is significant clinical trend towards using partially assisted ventilation modes, rather than fully supported ventilation modes. In this study, the patient-ventilator interaction of a state of the art partially assisted ventilation mode, known as neurally adjusted ventilatory assist (NAVA), is investigated and compared with pressure support ventilation (PS). The matching of patient-specific inspiratory demand and ventilator supplied tidal volume for these two ventilation modes is assessed using a novel Range90 metric. NAVA consistently showed better matching than PS, indicating that NAVA has better ability to provide patient-specific ventilator tidal volume to match variable patient-specific demand. Hence, this new analysis highlights a critical benefit of partially assisted ventilation and thus the need to extend model-based methods to this patient group. NAVA ventilation has been shown to improve patient-ventilator interaction compared to conventional PS. However, the patient-specific, optimal NAVA level remains unknown, and the best described method to set NAVA is complicated and clinically impractical. The Range90 metric is thus extended to analyse the matching ability of different NAVA levels, where it is found that response to different NAVA levels is highly patient-specific. Similar to the fully sedated MV case, and thus requiring models and metrics to help titrate care. More importantly, Range90 is shown to provide an alternative metric to help titrate patient-specific optimal NAVA level and this analysis further highlights the need for extended model-based methods to better guide these emerging partially assisted MV modes. Traditionally, the respiratory mechanics of the spontaneously breathing (SB) patient cannot be estimated without significant additional invasive equipment and tests that interrupt normal care and are clinically intensive to carry out. Thus, respiratory mechanics and model-based methods are rarely used to guide partially assisted MV. Thus, there is significant clinical interest to use respiratory mechanics to guide MV in SB patients. The single compartment model is extended to effectively capture the trajectory of time-varying elastance for SB patients. Results show that without additional invasive equipment, the model was able estimate unique and clinically useful respiratory mechanics in SB patients. Hence, the extended single compartment model can be used as ‘a one model fits all’ means to guide patient-specific MV continuously and consistently, for all types of patient and ventilation modes, without interrupting care. Overall, the model-based approaches presented in this thesis are capable of capturing physiologically relevant patient-specific parameters, and thus, characterise patient disease state and response to MV. With additional, larger scale clinical trials to test the performance and the impact of model-based methods on clinical outcome, the models can aid clinicians to guide MV decision making in the heterogeneous ICU population. Hence, this thesis develops, extends and validates several fundamental model-based metrics, models and methods to enable standardized patient-specific MV to improve outcome and reduce the variability and cost of care.

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Sands, Kirsty M. "Dynamics of oral biofilms associated with mechanical ventilation". Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/97010/.

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Critically ill patients often require mechanical ventilation (MV) to facilitate treatment for respiratory failure or airway protection when consciousness is impaired. Whilst the endotracheal tube (ETT) is an essential interface between the patient and ventilator, it may promote VAP by impeding host defence mechanisms and by translocating microorganisms from dental plaque to the lower airways. Ventilator-associated pneumonia (VAP), which may be challenging to diagnose, is the most frequent hospital-acquired infection in critical care. It has been reported that when patients receive MV the composition of dental plaque changes to include respiratory pathogens such as Meticillin-Resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. The primary aim of this research was to confirm that dental plaque communities altered during MV and to identify the potential causes of these changes. A combination of culture-based microbiology, community profiling molecular techniques and proteomic analysis of saliva was performed to analyse the microbiological content of the oral cavity, and to also quantify changes in dental plaque composition and saliva. For the first time, this study comprehensively analysed the dental plaque of mechanically ventilated patients and documented considerable species richness and diversity. Numerous potential respiratory pathogens were detected including Staphylococcus aureus, P. aeruginosa and Streptococcus pneumoniae in approximately one-third of mechanically ventilated patients. In addition, salivary flow rate was decreased and both the salivary pH and concentration of pro-inflammatory cytokines were significantly elevated during intubation. Dental plaque is a reservoir for VAP, and preventing or reducing respiratory colonisation may play a role in the management of ventilated patients. Interventions to prevent colonisation could include the modulation of salivary parameters such as pH and volume and further work may lead to the identification of specific proteins that are significant. Reducing the incidence of VAP will not only reduce mortality in the ICU, but will also have a great impact on hospital economics by reducing inpatient stay.

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Frazier, Susan K. "Right Heart Hemodynamics During Weaning From Mechanical Ventilation /". The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487933648650383.

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Rolle, Trenicka. "Lung Alveolar and Tissue Analysis Under Mechanical Ventilation". VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3398.

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Mechanical ventilation has been a major therapy used by physicians in support of surgery as well as for treating patients with reduced lung function. Despite its many positive outcomes and ability to maintain life, in many cases, it has also led to increased injury of the lungs, further exacerbating the diseased state. Numerous studies have investigated the effects of long term ventilation with respect to lungs, however, the connection between the global deformation of the whole organ and the strains reaching the alveolar walls remains unclear. The walls of lung alveoli also called the alveolar septum are characterized as a multilayer heterogeneous biological tissue. In cases where damage to this parenchymal structure insist, alveolar overdistension occurs. Therefore, damage is most profound at the alveolar level and the deformation as a result of such mechanical forces must be investigated thoroughly. This study investigates a three-dimensional lung alveolar model from generations 22 (alveolar ducts) through 24 (alveoli sacs) in order to estimate the strain/stress levels under mechanical ventilation conditions. Additionally, a multilayer alveolar tissue model was generated to investigate localized damage at the alveolar wall. Using ANSYS, a commercial finite element software package, a fluid-structure interaction analysis (FSI) was performed on both models. Various cases were simulated that included a normal healthy lung, normal lung with structural changes to model disease and normal lung with mechanical property changes to model aging. In the alveolar tissue analysis, strains obtained from the aged lung alveolar analysis were applied as a boundary condition and used to obtain the mechanical forces exerted as a result. This work seeks to give both a qualitative and quantitative description of the stress/strain fields exerted at the alveolar region of the lungs. Regions of stress/strain concentration will be identified in order to gain perspective on where excess damage may occur. Such damage can lead to overdistension and possible collapse of a single alveolus. Furthermore, such regions of intensified stress/strain are translated to the cellular level and offset a signaling cascade. Hence, this work will provide distributions of mechanical forces across alveolar and tissue models as well as significant quantifications of damaging stresses and strains.

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Ray, Stephen D. (Stephen Douglas). "Modeling buoyancy-driven airflow in ventilation shafts". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74930.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 185-191).
Naturally ventilated buildings can significantly reduce the required energy for cooling and ventilating buildings by drawing in outdoor air using non-mechanical forces. Buoyancy-driven systems are common in naturally ventilated commercial buildings because of their reliable performance in multi-story buildings. Such systems rely on atria or ventilation shafts to provide a pathway for air to rise through the building. Although numerous modeling techniques are used to simulate naturally ventilated buildings, airflow network tools (AFNs) are most commonly used for annual simulations. These AFNs, however, assume minimal momentum within each zone, which is a reasonable approximation in large atria, but is inappropriate in smaller ventilation shafts. This thesis improves AFNs by accounting for momentum effects within ventilation shafts. These improvements are validated by Computation Fluid Dynamics (CFD) models that haven been validated by small scale and full scale experiments. The full scale experiment provides a detailed data set of an actual atrium that can be used in further validations and demonstrates the first use of a neutrally buoyant bubble generator for flow visualization and particle image velocimetry within a buoyancy driven naturally ventilated space. Small scale experiments and CFD simulations indicate an "ejector effect" within the shaft that uses momentum from lower floors to induce flow through upper floors. In some configurations, upper floors achieve higher flow rates than lower floors. Existing AFNs do not predict this "ejector effect" and are shown to significantly under predict flow rates through ventilation shafts by 30-40%. Momentum effects are accounted for in AFNs using empirical relationships for discharge coefficients. This approach maintains the current structure of AFNs while enhancing their ability to simulate airflow through ventilation shafts. These improvements are shown to account for the "ejector effect" and predict airflow rates that agree with CFD simulations to within 1-25%.
by Stephen Douglas Ray.
Ph.D.

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21

Mallya, Prashant Moodabidri. "Pressure support ventilation or synchronised intermittent mandatory ventilation for weaning premature babies on mechanical ventilation : a multi centre randomised controlled trial". Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3820.

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Mechanical ventilation is life saving as a respiratory support for preterm infants with respiratory distress syndrome. There is good evidence now that any form of volume-targeted modality of mechanical ventilation is superior over pressure-targeted modality to reduce chronic lung disease and death. It is perceived by minimising the duration of mechanical ventilation would reduce the exposure to positive pressure breaths and thereby could reduce long term morbidities such as chronic lung disease. An area of lacunae is defining what is weaning on mechanical ventilation. Whilst most clinicians will agree when to commence mechanical ventilation there is paucity of consensus on when to commence weaning on mechanical ventilation and the best way for weaning to prevent extubation failure. Pressure support ventilation (PSV) is pressure-targeted modality of ventilation designed to support spontaneous breathing. It was designed as a weaning mode to facilitate extubation. Pure PSV has no back up rate. Currently, PSV is used in combination with other modes such as SIMV to provide some back up respiratory rate for the unreliable respiratory drive due to apnoea in preterm infants. However, there is inadequate understanding of the appropriate PSV level for weaning preterm infants on mechanical ventilation. Clinicians routinely use 50%-70% of peak inflation pressures used prior to commencing the weaning mode. Use of Pressure support ventilation (PSV) could be variable- with one extreme utilising minimal pressure to just overcome the tube resistance (PSmin) with the aim to prevent fatigue and avoid extubation failure. The other extreme is augmenting spontaneous breathing effort to provide a full tidal volume breath (PSmax). Features of flow triggering and flow cycling aid synchrony at inspiration and expiration and this allows greater autonomy to the infant to control all aspects of its breathing cycle. Addition of some PSV to aid spontaneous breaths has shown to reduce the duration of weaning. A randomised controlled study was designed to compare duration of weaning using PSmax and SIMV. Infants less than 32 weeks gestation at birth with respiratory distress syndrome from surfactant deficiency were eligible to participate. 93 infants stratified in three groups based on their gestation at birth were randomised over 30-month period. Weaning was commenced in the randomised mode when infants reached a set priori of MAP < 10 cm H2O, FiO2 < 40% and had a reliable respiratory drive for at least 2 consecutive hours. In the control arm (SIMV with PSmin)– clinicians reduced the back up rate to wean. In the intervention arm (PSmax with ten SIMV breaths)- clinicians reduced the PSVmax to PSVmin for weaning. A minute ventilation test was performed to assess readiness to extubation when both arms reached PSmin with ten back up SIMV breaths. Primary outcome for the study was duration of weaning on mechanical ventilation. Our study suggests there is no difference between the two groups but there is a trend towards faster extubation in the PSV arm (the median time to extubate in the SIMV arm was 42 (95%CI, 28.23 to 55.76) hours and the median time to achieve the primary outcome in the PSV arm was 31 (95% CI, 12.59 to 49.40) hours). The survival distribution between the interventions was statistically not significant, Chi-square 0.768, p 0.381. This effect was more evident in bigger infants weighing at least 1500 grams. There was no difference in the secondary outcomes between the two groups and common preterm morbidities were equally balanced. There were no adverse events during the study period to report. Contrary to the general belief, infants are not disadvantaged by weaning on PSVmax. Clinical outcomes were comparable with the traditional SIMV method of weaning on mechanical ventilation.

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Capps, Laura. "Whole-house mechanical ventilation in a mixed-humid climate". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43734.

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As building codes and green building programs require tighter home construction, the need for outdoor air ventilation to improve indoor air quality increases. Major improvements in building envelopes and duct systems have led to decreases in heating and cooling loads causing fewer HVAC system run-time hours, and increasing the probability for air stagnation within homes with poor outdoor air ventilation. ASHRAE Standard 62.2 quantifies the amount of whole-house ventilation required based on the number of occupants and the square footage of conditioned space, but leaves the design of the ventilation system up to the mechanical engineer or HVAC contractor. In 2010, ASHRAE began requiring flow testing for confirmation of outdoor air ventilation rates, yet few municipalities and green building programs have adopted the new standard. Builders in mixed-humid climates are forced to balance the need for outdoor air ventilation with the upfront costs for mechanical ventilation systems, and the potential for increased humidity loads and energy costs associated with mechanical ventilation strategies. One common solution employed in the southeastern United States involves a central fan integrated supply (CFIS) ventilation system controlled with an air-cycler for minimum run-time to meet ASHRAE Standard 62.2. While this system has been tested and proven to meet design ventilation rates, those tests were often conducted on homes constructed by well trained builders receiving strong oversight from building scientists and the design ventilation rates were not always ASHRAE compliant. The following report analyzes whether the CFIS ventilation system with air-cycler controller provides ventilation meeting ASHRAE Standard 62.2 when employed by builders with minimal training and support.

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Gillott, Mark C. "A novel mechanical ventilation heat recovery/heat pump system". Thesis, University of Nottingham, 2000. http://eprints.nottingham.ac.uk/12148/.

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The trend towards improving building airtightness to save energy has increased the incidence of poor indoor air quality and associated problems, such as condensation on windows, mould, rot and fungus on window frames. Mechanical ventilation/heat recovery systems, combined with heat pumps, offer a means of significantly improving indoor air quality, as well as providing energy efficient heating and cooling required in buildings. This thesis is concerned with the development of a novel mechanical ventilation heat recovery/heat pump system for the domestic market. Several prototypes have been developed to provide mechanical ventilation with heat recovery. These systems utilise an annular array of revolving heat pipes which simultaneously transfer heat and impel air. The devices, therefore, act as fans as well as heat exchangers. The heat pipes have wire finned extended surfaces to enhance the heat transfer and fan effect. The systems use environmentally friendly refrigerants with no ozone depletion potential and very low global warming potential. A hybrid system was developed which incorporated a heat pump to provide winter heating and summer cooling. Tests were carried out on different prototype designs. The type of tinning, the working fluid charge and the number and geometry of heat pipes was varied. The prototypes provide up to 1000m3/hr airflow, have a maximum static pressure of 220Pa and have heat exchanger efficiencies of up to 65%. At an operating supply rate of 200m3/hr and static pressure 100Pa, the best performing prototype has a heat exchanger efficiency of 53%. The heat pump system used the hydrocarbon isobutane as the refrigerant. Heating COPs of up to 5 were measured. Typically the system can heat air from 0°C to 26°C at 200m3/hr with a whole system COP of 2. The contribution to knowledge from this research work is the development of a novel MVHR system and a novel MVHR heat pump system and the establishment of the performances of these systems.

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24

Chatburn, Robert. "Determining the Basis for a Taxonomy of Mechanical Ventilation". Youngstown State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1277403555.

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Ip, Kiun Chong Karine. "Natural ventilation in buildings : modeling, control and optimization". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93829.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 192-195).
Natural ventilation in buildings has the potential to reduce the energy consumption usually associated with mechanical cooling while maintaining thermal comfort and air quality. It is important to know how building parameters, in particular its thermal mass properties and heat loads incurred, affect a building's transient thermal response to incoming outdoor air. A proper ventilation schedule is also needed to make optimal use of the free direct or night cooling. To investigate these factors, a first principles heat transfer energy model is developed to numerically simulate in MATLAB the air temperature profile of a single-zone cross-ventilated room. The physics behind natural ventilation at building level is also investigated using multi-zone modeling, as done in CoolVent, an existing MIT airflow modeling tool. In the process, the simulation capabilities of MIT Design Advisor, an existing building energy simulation tool, are expanded upon from shoe-box to interconnected multi-zone modeling. Optimal natural ventilation scheduling, with a view to maximizing thermal comfort, is then studied using two optimization techniques: dynamic programming and global search optimization, using the simple room energy model as the simulation engine. In the process, an algorithm framework is developed to optimize the ventilation scheduling on a rolling day-horizon basis based on input weather data and occupancy schedule. The use of rule-based control, as opposed to the aforementioned model-optimized control, is also explored due to its ease of implementation in building automation software. The former form of control is found to maintain comparable thermal comfort when separate rules for specific scenarios, such as night-overcooling or day-overheating, are gathered together to constrain the room air temperature. It is however critical to identify and calculate proper set-points for these rules.
by Karine Ip Kiun Chong.
S.M.

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Hamilton, Sephir D. (Sephir David) 1977. "Designing aero-acoustic wall openings for natural ventilation". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/88900.

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AlRefaie, Abdulaziz M. "Flow Control Around Circular Cylinder: Ventilation holes Method". University of Toledo / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1260201547.

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Ali, Sadaqat y Possavee Thummakul. "Mapping and analyzing Ventilation system in University building". Thesis, Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-12397.

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This Master Studies Thesis of Quality in Process Technology deals with Process Improvement. The ventilation system of University building is dealt as a Process and is looked for improvements. The ventialtion system for two computer rooms is studied and analyzed for the variaitons in the operating conditions.

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29

Ward, Paul. "A computational and experimental study on respiratory oscillation mechanics for the control of mechanical ventilation". Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435804.

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Van, Gammeren Darin L. "Mechanisms of mechanical ventilation-induced oxidative stress in the diaphragm". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010240.

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Törnberg, Daniel C. F. "Exhaled nitric oxide : influence of mechanical ventilation and vasoactive agents /". Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-070-2/.

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Petersson, Johan. "Quantification of lipid accumulation in the diaphragm after mechanical ventilation". Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-206940.

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During mechanical ventilation the diaphragm experiences an extreme case of muscleunloading. In many cases this results in respiratory muscle dysfunctions making it difficult towean the patient off the ventilator. One component in this dysfunction is the accumulation ofintramyocellular lipids (IMCL) in the diaphragm muscle fibres. Using Oil Red O stainingsand confocal microscopy on rat diaphragm sections we have quantified this process. Theresults show a sudden increase in IMCL contents between 18 and 24 hours. No significantdifference between fibre types could be seen.

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Das, Anup. "Modelling and optimisation of mechanical ventilation for critically ill patients". Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3701.

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This thesis is made up of three parts: i) the development of a comprehensive computational model of the pulmonary (patho)physiology of healthy and diseased lungs, ii) the application of a novel optimisation-based approach to validate this computational model, and iii) the use of this model to optimise mechanical ventilator settings for patients with diseased lungs. The model described in this thesis is an extended implementation of the Nottingham Physiological Simulator (NPS) in MATLAB. An iterative multi-compartmental modelling approach is adopted, and modifications (based on physiological mechanisms) are proposed to characterise healthy as well as diseased states. In the second part of the thesis, an optimisation-based approach is employed to validate the robustness of this model. The model is subjected to simultaneous variations in the values of multiple physiologically relevant uncertain parameters with respect to a set of specified performance criteria, based on expected levels of variation in arterial blood gas values found in the patient population. Performance criteria are evaluated using computer simulations. Local and global optimisation algorithms are employed to search for the worst-case parameter combination that could cause the model outputs to deviate from their expected range of operation, i.e. violate the specified model performance criteria. The optimisation-based analysis is proposed as a useful complement to current statistical model validation techniques, which are reliant on matching data from in vitro and in vivo studies. The last section of the thesis considers the problem of optimising settings of mechanical ventilation in an Intensive Therapy Unit (ITU) for patients with diseased lungs. This is a challenging task for physicians who have to select appropriate mechanical ventilator settings to satisfy multiple, sometimes conflicting, objectives including i) maintaining adequate oxygenation, ii) maintaining adequate carbon dioxide clearance and iii) minimising the risks of ventilator associated lung injury (VALI). Currently, physicians are reliant on guidelines based on previous experience and recommendations from a very limited number of in vivo studies which, by their very nature, cannot form the basis of personalised, disease-specific treatment protocols. This thesis formulates the choice of ventilator settings as a constrained multi-objective optimisation problem, which is solved using a hybrid optimisation algorithm and a validated physiological simulation model, to optimise the settings of mechanical ventilation for a healthy lung and for several pulmonary disease cases. The optimal settings are shown to satisfy the conflicting clinical objectives, to improve the ventilation perfusion matching within the lung, and, crucially, to be disease-specific.

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34

黎自強 y Chi-keung Peter Lai. "Protocol-led weaning of mechanical ventilation in adult intensive careUnit". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40720895.

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Stamiris, Angela. "Effect of prolonged mechanical ventilation on sepsis-induced diaphragm dysfunction". Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121461.

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Severe sepsis is a systemic inflammatory response to an infection that often leads to respiratory failure which requires patients to be mechanically ventilated. Mechanical ventilation (MV) also leads to atrophy and weakness what is termed ventilatory induced diaphragm dysfunction (VIDD). Both these conditions are associated with upregulation of proteolytic pathways such as the ubiquitin proteasome pathway and the autophagy-lysosomal pathway. However, the influence of combining MV on sepsis-induced diaphragm dysfunction remains unknown. In this study, we evaluate the influence of prolonged MV on sepsis-induced diaphragm dysfunction. We studied four groups of rats. Group 1 animals were spontaneously breathing and served as controls. Group 2 (LPS) animals received intraperitoneal injection of E. coli lipopolysaccharide (LPS) and served as the sepsis group. Group 3 animals were mechanically ventilated for 12h. Group 4 animals received LPS injection first and were then mechanically ventilated for 12h. Diaphragm contractility was measured in-vitro and diaphragm fiber type atrophy was evaluated by measuring fiber cross sectional areas. Activation of the proteasome, calpains, caspase-3 and autophagy proteolytic pathways were evaluated using specific assays. Injection of LPS and MV for 12 resulted in significant attenuation of diaphragm contractility and the development of fiber atrophy. Combining MV with LPS administration resulted in additional decline in muscle contractile performance but not additional atrophy. Proteasome, calpain, caspase-3 and the autophagy proteolytic pathways were activated in the LPS and MV groups and the combination of prolonged MV with sepsis resulted in the potentiation of autophagy pathway but not proteasome, calpain and capase-3 activation. The AKT and mTORC1 pathways (inhibitors of proteolytic pathways and activators of protein synthesis) were activated in response to LPS administration but not by prolonged MV. Combining sepsis with prolonged MV resulted in attenuation of AKT and mTORC1 activation compared to sepsis alone. Interestingly, the AMPK pathway (activator of autophagy) is inhibited in response to LPS administration and prolonged MV. Combining sepsis with prolonged MV resulted in a milder degree of AMPK inhibition compared to LPS administration alone. Finally, oxidative stress develops in response to LPS administration and prolonged MV. Combining MV and sepsis resulted in worsening of oxidative stress. These results indicate that prolonged MV worsens sepsis-induced diaphragm contractile dysfunction and this worsening of function may be mediated by substantial induction of autophagy and the development of severe oxidative stress.
Le sepsis sévère est une réponse inflammatoire systémique consécutive à une infection, pouvant conduire à la détresse respiratoire nécessitant le recours à la ventilation mécanique. La ventilation mécanique (MV) est responsable de l'atrophie et de la faiblesse du diaphragme connue sous le nom de dysfonction diaphragmatique induite par la ventilation (DDIV). Ces deux mécanismes étiopathogéniques sont associés à l'activation de plusieurs voies protéolytiques comme la voie du protéasome et la voie de l'autophagie médiée par les lysosomes. Cependant, l'effet combiné de la ventilation mécanique associée au sepsis n'est pas encore connu. Dans cette étude nous avons évalué l'influence d'une ventilation mécanique prolongée sur la dysfonction diaphragmatique induite par le sepsis. Nous avons étudié quatre groupes de rats : le groupe 1 représentait le groupe contrôle (animaux en ventilation spontanée) ; le groupe 2 (LPS) représentait le groupe « sepsis » dans lequel les animaux recevaient une injection intrapéritonéale de lipopolyssaccharide (LPS) d'E. Coli ; dans le groupe 3, les animaux étaient ventilés pendant 12h et dans le groupe 4 les animaux recevaient d'abord l'injection de LPS avant d'être ventilés pendant 12h.La contractilité diaphragmatique était mesurée in vitro et l'atrophie musculaire était évaluée en mesurant la surface de section des fibres. L'activation du protéasome et des autres voies protéolytiques (calpaines, caspase 3 et autophagie) ont été étudiées par tests spécifiques. L'injection de LPS et la ventilation mécanique entraînait une diminution significative de la contractilité diaphragmatique et le développement d'une atrophie des fibres musculaires. La combinaison de la VM à l'injection de LPS montrait une altération plus importante de la contractilité diaphragmatique mais pas d'atrophie supplémentaire. Les différentes voies protéolytiques (protéasome, calpain, caspase-3 et autophagie) étaient activées dans les groupes VM et LPS alors que la combinaison des deux résultait en une potentialisation de l'autophagie mais pas de l'activation du protéasome, des calpaines et de caspase 3. Les voies AKT et MTORC1 (inhibitrice de la protéolyse et activatrice de la synthèse protéique) étaient activées en réponse à l'injection de LPS mais pas par la VM prolongée. La combinaison du sepsis et de la VM entraînait une atténuation de l'activation des deux voies AKT et MTORC1 en comparaison au sepsis seul. Par ailleurs, la voie AMPK (activatrice de l'autophagie) était inhibée en réponse à l'injection de LPS et à la VM alors que la combinaison des deux entraînait seulement une inhibition modérée de l'AMPK en comparaison à l'injection de LPS seule.Enfin l'injection de LPS et la VM entraînait un stress oxydatif d'autant plus important quand on combinait les deux facteurs. Ces résultats montrent que la VM prolongée aggrave la dysfonction diaphragmatique induite par le sepsis et que cette aggravation est due en partie à l'activation de l'autophagie et au développement d'un stress oxydatif sévère.

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36

Allocca, Camille 1977. "Single-sided natural ventilation : design analysis and general guidelines". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/37561.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
Includes bibliographical references (p. 102-104).
Natural ventilation is an effective measure to save energy consumed in buildings and to improve indoor air quality. This study focuses specifically on the principles of single-sided natural ventilation design. Single-sided ventilation is very common in building designs and has been shown to produce very complicated, fluctuating airflow patterns at the openings of buildings. An ongoing challenge in natural ventilation design is therefore the ability to control the mechanisms of wind and temperature for desirable indoor environment conditions. Understanding these effects is important in determining the feasibility of natural ventilation designs. The current research approach used mainly (CFD) tools, together with analytical solutions, empirical models, and experimental results. CFD models were created and analyzed to determine the validity of using this tool for single-sided ventilation analysis and design. The impact of using computational modeling tools for the development of natural ventilation design is great to the building industry field. The focus of this CFD study was on a single room within a residential building in Cambridge, MA. Simulations were performed under varying conditions of temperature, wind speed, wind direction, opening layout and size, and internal heat load, in order to evaluate parameter trends. Airflow rates, velocity fields, and temperature distributions were derived from analytical equations and empirical models as well as from experimental measurements, in order to validate and perform further research in this area. Consequently, this investigation found CFD tools to be valid for studying single-sided natural ventilation strategies with respect to indoor, outdoor, and combined indoor and outdoor flow. From this validation, CFD was applied further to determine the effects of buoyancy, wind, and combined flow on natural ventilation rates and overall indoor conditions. For buoyancy driven flow, CFD performed well when modeling both the indoor and outdoor environment in the calculation, resulting in a 10% difference between semi-analytical and CFD results. However, for wind-driven flow, CFD was found to under predict empirical model results by approximately 25%. This under prediction was attributed to mean or time-averaged, rather than instantaneous calculations of the CFD technique applied to this study. In addition to evaluating the effects of buoyancy and wind on ventilationrates, this study also focused on the effects of wind direction, opposing buoyancy and wind forces, and mixed-mode ventilation. The results from these studies provided further insight into the field of single-sided ventilation and revealed the need for further research in this valuable area. To fully understand and utilize this natural ventilation strategy, the results from the complete single-sided ventilation study were compiled and developed into a computer design tool and a set of general design guidelines. These tools were created in such a way so that designers can use them to evaluate ventilation performance and see immediate results for an indoor environment that they propose to design. The level of analysis that is desired by designers in this area calls for a tool such as this one. This total investigation has been essential in evaluating and analyzing the important areas of the single-sided ventilation field and in providing a strong foundation for further research in improving natural ventilation design as well as in improving CFD and turbulence modeling.
by Camille Allocca.
S.M.

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37

Sylvestre, Michel J. G. "Heating and ventilation study of Inco's Creighton Mine". Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30273.

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As near surface deposits are depleted, it becomes increasingly apparent that we will have to mine deeper in order to meet future world demand for metals.
Along with deeper mining comes its associated challenges: increased stresses and seismicity, increased heat load and increased inefficiencies due to hoisting constraints and travel time. All of these challenges, and more, contribute to safety concerns, higher initial capital costs and higher operating costs, which combined, can make deep reserves uneconomic.
In order to meet these challenges, we must closely examine present deep mining infrastructures and operating practices with a view to learn and enhance upon "Best Practices".
This thesis will examine the challenges of providing ventilation within deep, hot mines. Specifically, we will examine Inco Limited's Creighton Mine. A current expansion at Creighton will see mining progress to the 7660 level within the next few years. A key issue, which arises, is the question as to whether Creighton will need a refrigeration system or can it continue to rely on its natural heat exchange capacity.

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38

Arens, Anthony D. (Anthony Daniel) 1971. "Evaluation of displacement ventilation for use in high-ceiling facilities". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9305.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.
Includes bibliographical references (p. 113, 1st group).
A experimental study was conducted to assess the performance of displacement ventilation in high ceiling facilities found in North America. Such areas include commercial and industrial manufacturing facilities often featuring high internal heat loads and contaminants associated with heat sources. These areas can range from 5 to 20 meters in height. Very little performance data exists for displacement ventilation installations in high-ceiling areas, particularly any which account for the influence of wall temperature. More performance data is needed to support design guidelines for displacement ventilation in such buildings. In this study, several experiments were conducted in a room equipped with both a high ceiling (6.5 meters) and a displacement ventilation system. The performance of the system in the presence of a variety of modeled loads was evaluated by use of strategically placed temperature, tracer gas, and velocity measurements. The modeled loads consisted of traditional person, computer, and lighting loads found in offices as well as simulators constructed to represent generic welding, engine exhaust and control panel enclosures in a manufacturing environment. Wall, floor, and ceiling temperatures were recorded in these experiments. The resulting data has been used to judge the suitability of displacement ventilation for a building equipped with each process. These experimental results are also used to test existing guidelines for displacement ventilation. Walls in this high ceiling room were found to have significant impact by generating large plume flows and contributing substantially to the total radiative incident loading to the floor. Experimental results could not justify the use of a constant temperature gradient assumption to estimate the temperature difference between head and foot levels. Plume modeling was found to work well in estimating the room stratification heights. Distance from the supply diffusers was found to have an impact upon air temperature near the floor as well as the temperature difference between the head and foot levels. A five node temperature model was found to work quite well in predicting five key temperature values in this high ceiling space. A design guideline was proposed for displacement ventilation in high spaces which incorporates the five node temperature model, plume modeling, and the fractional coefficient method. Results of the experimental data are being used to validate a CFD program previously validated for small office and classroom simulations with a ceiling height of 2.4 meters.
by Anthony D. Arens.
S.M.

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39

Domínguez, Espinosa Francisco Alonso. "Determining thermal stratification in rooms under mixing and displacement ventilation". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104255.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 322-331).
Computational Fluid Dynamics (CFD) simulations of a typical office under both mixing and displacement ventilation were performed to study the effects of room geometry (height and area of the supply), ventilation parameters (supply momentum and heat gain intensity) and radiation heat transfer on the thermal stratification of the air and the temperatures of the surfaces in the space. The air stratification and the temperatures of the surfaces are two important parameters when determining thermal comfort conditions in the room. Different room configurations were characterized in terms of their Archimedes number, which compares the effects of buoyancy and supply momentum, and dimensionless geometric variables. A high Archimedes space was found to be divided into a warm region of uniform temperature above the occupants and a zone where the temperature increases approximately linearly with height. In a low Archimedes space the air is mixed by the supply jet in the lower part of the room, especially near the outlet, resulting in this area having uniform temperature. However, the supply jet was found to be less efficient at mixing the air near the ceiling, resulting in higher temperatures in this zone than with higher Archimedes numbers. For a given Archimedes number, as the supply area increased, the air temperature was found to decrease in the lower part of the room but increase near the ceiling. The supply height was found to increase the vertical mixing in the room. Correlations were proposed to establish the temperature profile within 5% of the temperature rise of the room, which include the effects of the Archimedes number and room geometry. Correlations were developed to estimate the temperatures of the surfaces in a room, based on a dimensionless parameter that characterizes the amount of free area to convect heat to the air. The temperatures of the surfaces were found to be a function of this convective area, regardless of the view factors and convective heat transfer coefficients of the surfaces. A larger amount of convective area was found to result in lower surfaces temperatures but higher air temperatures. A simple methodology to estimate all of the radiative view factors in an occupied office for use in multizone models was proposed. It was shown that the commonly ignored view factor among occupants can be of importance, not only because occupants exchange radiation among themselves, but also because they block radiation that would otherwise reach other surfaces in the room. In addition, techniques to estimate the view factors between other surfaces, such as partitions and furniture, were also developed. Estimated view factors between surfaces encountered in practical situations were found to be within 10% of the results from ray tracing software. The estimated view factors were then incorporated into a thermal resistor network akin to the thermal circuits used to model heat transfer in multizone software. Results from the resistor network showed good agreement with CFD results, although the accuracy depends on the convective heat transfer coefficients used. Finally, it was demonstrated that scale models that use water as the working fluid are not capable of replicating the air thermal stratification, the temperatures of the surfaces or the mass flow rate of a full-sized space, because they neglect the effects of thermal radiation transfer.
by Francisco Alonso Francisco Alonso.
Ph. D.

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40

Siddiqui, Muniza. "The Use of Pulmonary Dead Space Fraction to Identify Risk of Prolonged Mechanical Ventilation in Children after Cardiac Surgery". Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/623533.

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A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.
Children with prolonged mechanical ventilation after cardiac surgery have a higher risk for poor outcome due to a variety of ventilator‐associated morbidities. It therefore becomes essential to identify these children at higher risk of prolonged mechanical ventilation as well as find methods to identify children ready to be extubated as early as possible to avoid these complications. One physiological variable, the pulmonary dead space fraction (VD/VT), has been suggested as a possible indicator of prolonged mechanical ventilation. VD/VT essentially measures the amount of ventilated air that is unable to participate in gas exchange. Can VD/VT be used successfully in children undergoing cardiac surgery to identify those at risk for prolonged mechanical ventilation and identify those ready for extubation? Retrospective chart review of 461 patients at Phoenix Children’s Hospital in the Pediatric Cardiac Intensive Care Unit since the initiation of standard application of the Philips NM3 monitors in October 2013 through December 2014. From the 461 patients screened, only 99 patients met all the inclusion criteria. These 99 patients consisted of 29 patients with balanced single ventricle physiology and 61 patients with two ventricle physiology. Initial postoperative and pre‐extubation VD/VT values correlated with length of mechanical ventilation for patients with two ventricle physiology but not for patients with single ventricle physiology. Additionally, pre‐extubation VD/VT values of greater than 0.5 indicated higher rates of extubation failure in two ventricle patients. Conclusion: For children with two ventricle physiology undergoing cardiac surgery, VD/VT should be used clinically to estimate the length of mechanical ventilation for these children. VD/VT should also be checked in these patients before attempting to extubate. If VD/VT is found to be higher than 0.5, extubation should not be attempted since the patient is at a much higher risk for extubation failure.

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41

Carteaux, Guillaume. "Optimisation des interactions patient-ventilateur en ventilation assistée : intérêt des nouveaux algorithmes de ventilation". Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC0027/document.

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En ventilation assistée, les interactions patient-ventilateur, qui sont associés au pronostic, dépendent pour partie des algorithmes de ventilation. Objectifs : Caractériser l'intérêt potentiel des nouveaux algorithmes de ventilation dans l'optimisation des interactions patient-ventilateur : 1) en ventilation invasive, deux modes et leurs algorithmes nous ont semblé novateurs et nous avons cherché à personnaliser l'assistance du ventilateur en fonction de l'effort respiratoire du patient au cours de ces modes proportionnels : ventilation assistée proportionnelle (PAV+) et ventilation assistée neurale (NAVA) ; 2) en ventilation non-invasive (VNI) nous avons évalué si les algorithmes VNI des ventilateurs de réanimation et des ventilateurs dédiés à la VNI diminuaient l'incidence des asynchronies patient-ventilateur. Méthodes : 1) En PAV+ nous avons décrit un moyen de recalculer le pic de pression musculaire réalisée par le patient à chaque inspiration à partir du gain réglé et de la pression des voies aériennes monitorée par le respirateur. Nous avons alors évalué la faisabilité clinique d'ajuster l'assistance en ciblant un intervalle jugé normal de pression musculaire. 2) Nous avons comparé une titration de l'assistance en NAVA et en aide inspiratoire (AI) en se basant sur les indices d'effort respiratoire. 3 et 4) En VNI, nous avons évalué l'incidence des asynchronies patient-ventilateur avec et sans l'utilisation d'algorithmes VNI : sur banc d'essai au cours de conditions expérimentales reproduisant la présence de fuites autour de l'interface ; en clinique chez des patients de réanimation. Résultats : En PAV+, ajuster le gain dans le but de cibler un effort respiratoire normal était faisable, simple et souvent suffisant pour ventiler les patients depuis le sevrage de la ventilation mécanique jusqu'à l'extubation. En NAVA, l'analyse des indices d'effort respiratoire a permis de préciser les bornes d'utilisation et de comparer les interactions patient-ventilateur avec l'AI dans des intervalles d'assistance semblables. En VNI, nos données pointaient l'hétérogénéité des algorithmes VNI sur les ventilateurs de réanimation et retrouvaient une meilleure synchronisation patient-ventilateur avec l'utilisation de ventilateurs dédiés à la VNI pour des qualités de pressurisation par ailleurs identiques. Conclusions : En ventilation invasive, personnaliser l'assistance des modes proportionnels optimise les interactions patient-ventilateur et il est possible de cibler une zone d'effort respiratoire normale en PAV+. En VNI, les ventilateurs dédiés améliorent la synchronisation patient-ventilateur plus encore que les algorithmes VNI sur les ventilateurs de réanimation, dont l'efficacité varie grandement selon le ventilateur considéré
During assisted mechanical ventilation, patient-ventilator interactions, which are associated with outcome, partly depend on ventilation algorithms.Objectives: : 1) during invasive mechanical ventilation, two modes offered real innovations and we wanted to assess whether the assistance could be customized depending on the patient's respiratory effort during proportional ventilatory modes: proportional assist ventilation with load-adjustable gain factors (PAV+) and neurally adjusted ventilator assist (NAVA); 2) during noninvasive ventilation (NIV): to assess whether NIV algorithms implemented on ICU and dedicated NIV ventilators decrease the incidence of patient-ventilator asynchrony.Methods: 1) In PAV+ we described a way to calculate the muscle pressure value from the values of both the gain adjusted by the clinician and the airway pressure. We then assessed the clinical feasibility of adjusting the gain with the goal of maintaining the muscle pressure within a normal range. 2) We compared titration of assistance between neurally adjusted ventilator assist (NAVA) and pressure support ventilation (PSV) based on respiratory effort indices. During NIV, we assessed the incidence of patient-ventilator asynchrony with and without the use of NIV algorithms: 1) using a bench model; 2) and in the clinical settings.Results: During PAV+, adjusting the gain with the goal of targeting a normal range of respiratory effort was feasible, simple, and most often sufficient to ventilate patients from the onset of partial ventilatory support until extubation. During NAVA, the analysis of respiratory effort indices allowed us to precise the boundaries within which the NAVA level should be adjusted and to compare patient-ventilator interactions with PSV within similar ranges of assistance. During NIV, our data stressed the heterogeneity of NIV algorithms implemented on ICU ventilators. We therefore reported that dedicated NIV ventilators allowed better patient-ventilator synchronization than ICU ventilators, even with their NIV algorithms engaged.Conclusions: During invasive mechanical ventilation, customizing the assistance during proportional ventilatory modes with the goal of targeting a normal range of respiratory effort optimizes patient-ventilator interactions and is feasible with PAV+. During NIV, dedicated NIV ventilators allow better patient-ventilator synchrony than ICU ventilators, even with their NIV algorithm engaged. ICU ventilators' NIV algorithms efficiency is however highly variable among ventilators

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42

Åhlander, Gunnar. "The air distribution in buildings with combined natural and mechanical ventilation". Licentiate thesis, KTH, Civil and Architectural Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1762.

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This work describes result from both measurements on anumber of one family houses, an analytical study of a one-zonemodel and multi zone studies of a two storey building. Thesimulations are performed as both parametric studies, withcombined values of outside temperature, wind velocity and winddirection, and whole year simulations. For the latter, aclimate file for the northern Swedish city Östersund isused.

The results, for the whole year simulations, are presentedas ventilation availabilities. The ventilation availability isdefined as the relative time of the heating season during whicha specified airflow is exceeded. This specified airflow maye.g. be a Building Code requirement if such exists.

The influence of different measures, and combinations ofmeasures, on the ventilation availability has been determinedfor the different rooms. It is found that acceptableventilation availability is possibly to achieve with naturalventilation. However, it requires large supply and overflowopenings and extended ventilation chimneys. These chimneys maybe difficult to accept from an esthetical point of view. Thenatural system is also very sensitive for changes in winddirection.

To ensure required airflows at all times, an exhaust orhybrid ventilation system may be necessary.

Some recommendations may be based on this study.

-Consider the predominating wind direction. Itsan advantage to have more supply openings on the leeward side,i.e. to placehumidrooms towards the knownwindward side.-Use different chimney heights from the differenthumidrooms, to balance the internal airflows. Ifmechanical exhaust is used, it may be used only from some ofthehumidrooms, preferable the ones with closeddoors.-Use as large supply and overflow openings aspossible. Different opening areas may be used to balance theairflows, especially if the predominating wind direction isknown. Acoustic problems may be a limiting factor for theopening area. There may also exist a maximum opening area abovewhich stability problems occur.-Construct ventilation chimneys and chimney outlets ina way, that the windgenerated pressure at the outlet is alwaysnegative and independent of wind direction. Insulate thechimneys to avoid cooling of the air and decreased buoyancyforces.

-Use different chimney heights from the differenthumidrooms, to balance the internal airflows. Ifmechanical exhaust is used, it may be used only from some ofthehumidrooms, preferable the ones with closeddoors.

-Use as large supply and overflow openings aspossible. Different opening areas may be used to balance theairflows, especially if the predominating wind direction isknown. Acoustic problems may be a limiting factor for theopening area. There may also exist a maximum opening area abovewhich stability problems occur.

-Construct ventilation chimneys and chimney outlets ina way, that the windgenerated pressure at the outlet is alwaysnegative and independent of wind direction. Insulate thechimneys to avoid cooling of the air and decreased buoyancyforces.

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43

Nilsson, Linus. "Real-time simulation of diaphragm displacement during physiological and mechanical ventilation". Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-202329.

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This thesis presents a tunable 3D real-time interactive simulator of the geometrical displacement of the thoracic diaphragm during physiological and mechanical ventilation. Particular attention is placed on capturing the heterogeneous tissue composition while maintaining computational efficiency and accuracy. The long term goal is to establish an accurate theoretical model to complement the experimental and clinical studies of the side effects associated with mechanical ventilation and to overcome the ethical difficulties of performing time resolved studies on human patients. The deformations are modelled using a commercial 3D model and a mass-spring model together with distance constraints and Verlet integration. The simulator is easily adjusted in real-time to many different cases of ventilation and validated through inspection and comparison with existing models. More research is needed to validate the model using patient specific data, as well as extending the model to include additional physiological and pathophysiological components. Long term goals includes considering the microscopic aspects of cellular mechanics to capture the underlying causes of ventilator-induced diaphragmatic dysfunction.

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44

Spieth, Peter M., Andreas Güldner, Christopher Uhlig, Thomas Bluth, Thomas Kiss, Marcus J. Schultz, Paolo Pelosi, Thea Koch y de Abreu Marcelo Gamba. "Variable versus conventional lung protective mechanical ventilation during open abdominal surgery". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-164891.

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Background: General anesthesia usually requires mechanical ventilation, which is traditionally accomplished with constant tidal volumes in volume- or pressure-controlled modes. Experimental studies suggest that the use of variable tidal volumes (variable ventilation) recruits lung tissue, improves pulmonary function and reduces systemic inflammatory response. However, it is currently not known whether patients undergoing open abdominal surgery might benefit from intraoperative variable ventilation. Methods/Design: The PROtective VARiable ventilation trial ('PROVAR') is a single center, randomized controlled trial enrolling 50 patients who are planning for open abdominal surgery expected to last longer than 3 hours. PROVAR compares conventional (non-variable) lung protective ventilation (CV) with variable lung protective ventilation (VV) regarding pulmonary function and inflammatory response. The primary endpoint of the study is the forced vital capacity on the first postoperative day. Secondary endpoints include further lung function tests, plasma cytokine levels, spatial distribution of ventilation assessed by means of electrical impedance tomography and postoperative pulmonary complications. Discussion: We hypothesize that VV improves lung function and reduces systemic inflammatory response compared to CV in patients receiving mechanical ventilation during general anesthesia for open abdominal surgery longer than 3 hours. PROVAR is the first randomized controlled trial aiming at intra- and postoperative effects of VV on lung function. This study may help to define the role of VV during general anesthesia requiring mechanical ventilation.

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45

Lai, Chi-keung Peter. "Protocol-led weaning of mechanical ventilation in adult intensive care Unit". Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40720895.

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46

Betters, Jenna Leigh Jones. "Trolox supplementation during mechanical ventilation attenuates contractile dysfunction and protein degradation". [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004290.

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47

Turowski, Paweł [Verfasser]. "Molecular mechanisms of ventilator-induced acute kidney injury : Mechanical ventilation can modulate neutrophil recruitment to the kidney / Paweł Turowski". Gießen : Universitätsbibliothek, 2012. http://d-nb.info/1064838820/34.

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48

Hult, Erin L. (Erin Luelle) 1982. "Experimental simulation of wind driven cross-ventilation in a naturally ventilated building". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32808.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (p. 29).
A device was designed and constructed to simulate cross-ventilation through a building due to natural wind. The wind driver device was designed for use with a one tenth scale model of an open floor plan office building in Luton, England. The air flow patterns produced by the wind driver were observed, and the uniformity of the velocity of the flows into the model windows was measured for the three settings of the wind driver fans. The temperatures and velocities of flows on the interior of the building and at the exhaust windows were also examined. The wind driver device was capable of producing uniform velocities across the face of the model to within 20 to 27%, depending on the fan setting. The consistency of certain features of the velocity distributions produced by the wind driver operating at different speeds suggest that improvements made to the design of the wind driver could lower this variation to about 15%. The velocities measured on the interior of the model seem consistent with interior velocities in the Luton building, although further experimentation is needed to confirm this trend. Cross-ventilation was effective in reducing interior model temperatures by up to 10⁰C from the natural convection case.
by Erin L. Hult.
S.B.

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49

Greenblatt, Elliot (Elliot Eliyahu). "The impact of pathological ventilation on aerosol deposition : imaging, insight and intervention". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/97769.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, February 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis. "February 2015."
Includes bibliographical references (pages 141-147).
Aerosol therapies are often used to treat lung diseases in which ventilation is distributed heterogeneously throughout the lung. As therapeutic aerosols are transported by the inhaled air, it is likely that deposition is diminished within poorly ventilated regions of the lung. These regions are often the most in need of therapy. We measured the effects of heterogeneous ventilation on aerosol deposition in a group of bronchoconstricted asthmatic subjects. We then developed a new image processing technique which allowed us to identify the anatomical location of aerosol deposition. This technique accounted for blurring due to limited resolution of the PET image, motion artifacts due to breathing, and registration uncertainty. We introduced a theoretical framework to characterize four mechanisms of variability in deposition between peripheral regions of the lung. This framework added insight into the interaction between ventilation and deposition, and will permit the future comparison of the experimental data with computational models. Together, the imaging data and theoretical framework suggested that more than a third of the observed variability in the deposition per unit volume among lung lobes was due to heterogeneous ventilation. Using helium-oxygen as a carrier gas for aerosol has been considered as a potential intervention to homogenize deposition in the lung periphery. To investigate this, we repeated the PET-CT measurements in a second group of bronchoconstricted asthmatic subjects breathing helium-oxygen, and compared the results to those of the group breathing room air. We did not find systematic differences in the deposition patterns of the two groups, although the relationship between ventilation and aerosol deposition tended to be stronger in the group that used helium-oxygen as the carrier gas. Finally, we used analytical tools and an in-silico model of bronchoconstriction to illustrate the emergence of pendelluft gas transport between parallel regions of the lung. We found that though pendelluft may emerge in asthma, the overall volume passed between parallel regions of the lung is likely less than 2% of the tidal volume, and thus is not likely to substantially influence aerosol deposition.
by Elliot Greenblatt.
Ph. D.

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50

Herrmann, Jacob. "Frequency-dependent ventilation heterogeneity in the acutely injured lung". Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6590.

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The goal of lung-protective mechanical ventilation is to provide life-sustaining support of gas exchange while minimizing the risk of ventilator-induced lung injury. Multi-frequency oscillatory ventilation (MFOV) was proposed as an alternative lung-protective modality, in which multiple frequencies of pressure and flow oscillations are delivered simultaneously at the airway opening and allowed to distribute throughout the lung in accordance with regional mechanical properties. The distribution of oscillatory flow is frequency-dependent, such that regions overventilated at one frequency may be underventilated at another. Thus the central thesis of this work was that ventilation heterogeneity is frequency-dependent, and therefore ventilation with multiple simultaneous frequencies can be optimized to reduce the risk of ventilator-induced lung injury. Simulations in computational models of distributed oscillatory flow and gas transport demonstrated the sensitivity of regional ventilation heterogeneity to subject size, ventilation frequency, and injury severity. Although the risk of injury in the model associated with strain or strain rate individually was minimized by single-frequency ventilation, the risk of injury associated with mechanical power in lung parenchymal tissue was minimized by MFOV. In an experimental model of acute lung injury, MFOV was associated with reductions in the magnitude and spatial gradient of regional lung strain estimated by four-dimensional CT image registration, as well as increased rates of regional gas transport estimated by wash-in of xenon tracer gas. In conclusion, computational models demonstrated the potential for optimization of MFOV waveforms, and experimental trials demonstrated evidence of improved regional ventilation during MFOV.

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