Journal articles on the topic 'Ventilation Waveform Data'
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Rehm, Gregory, Jinyoung Han, Brooks Kuhn, Jean-Pierre Delplanque, Nicholas Anderson, Jason Adams, and Chen-Nee Chuah. "Creation of a Robust and Generalizable Machine Learning Classifier for Patient Ventilator Asynchrony." Methods of Information in Medicine 57, no. 04 (September 2018): 208–19. http://dx.doi.org/10.3414/me17-02-0012.
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Summary Background: As healthcare increasingly digitizes, streaming waveform data is being made available from an variety of sources, but there still remains a paucity of performant clinical decision support systems. For example, in the intensive care unit (ICU) existing automated alarm systems typically rely on simple thresholding that result in frequent false positives. Recurrent false positive alerts create distrust of alarm mechanisms that can be directly detrimental to patient health. To improve patient care in the ICU, we need alert systems that are both pervasive, and accurate so as to be informative and trusted by providers. Objective: We aimed to develop a machine learning-based classifier to detect abnormal waveform events using the use case of mechanical ventilation waveform analysis, and the detection of harmful forms of ventilation delivery to patients. We specifically focused on detecting injurious subtypes of patient-ventilator asynchrony (PVA). Methods: Using a dataset of breaths recorded from 35 different patients, we used machine learning to create computational models to automatically detect, and classify two types of injurious PVA, double trigger asynchrony (DTA), breath stacking asynchrony (BSA). We examined the use of synthetic minority over-sampling technique (SMOTE) to overcome class imbalance problems, varied methods for feature selection, and use of ensemble methods to optimize the performance of our model. Results: We created an ensemble classifier that is able to accurately detect DTA at a sensitivity/specificity of 0.960/0.975, BSA at sensitivity/specificity of 0.944/0.987, and non-PVA events at sensitivity/specificity of .967/.980. Conclusions: Our results suggest that it is possible to create a high-performing machine learning-based model for detecting PVA in mechanical ventilator waveform data in spite of both intra-patient, and inter-patient variability in waveform patterns, and the presence of clinical artifacts like cough and suction procedures. Our work highlights the importance of addressing class imbalance in clinical data sets, and the combined use of statistical methods and expert knowledge in feature selection.
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Lutchen, K. R., K. Yang, D. W. Kaczka, and B. Suki. "Optimal ventilation waveforms for estimating low-frequency respiratory impedance." Journal of Applied Physiology 75, no. 1 (July 1, 1993): 478–88. http://dx.doi.org/10.1152/jappl.1993.75.1.478.
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We present a broad-band optimal ventilator waveform (OVW), the concept of which was to create a computer-driven ventilator waveform containing increased energy at specific frequencies (f). Values of f were chosen such that nonlinear harmonic distortion and intermodulation were minimized. The phases at each f were then optimized such that the resulting flow waveform delivered sufficient volume to maintain gas exchange while minimizing peak-to-peak airway opening pressure. Simulations with a linear anatomically consistent branching airway model and a nonlinear viscoelastic model showed that respiratory resistance (Rrs) and elastance (Ers) estimates at 0.1–2 Hz from the OVW are far superior to those from a standard step ventilator waveform (SVW) during healthy and obstructed conditions and that the OVW reduces the influences of harmonic interactions. Using a servo-controlled oscillator, we applied individual sine waves, an OVW containing energy at 0.15625–2.4 Hz, and an SVW to healthy humans and one symptomatic asthmatic subject before and after bronchodilation. The OVW was markedly superior to the SVW and always provided smooth estimates of Rrs and Ers. Before bronchodilation in the asthmatic subject Rrs was highly elevated and Ers was markedly increased with f; after bronchodilation the level of Rrs and the f dependence of Ers decreased. Although based on results from only one asthmatic subject, these data suggest a dominant influence of airway constriction and lung inhomogeneities during asthmatic bronchoconstriction that is alleviated by bronchodilators. These and other results indicate that the OVW approach has high potential for simultaneously probing f and amplitude dependence in the mechanical properties of clinical subjects during physiological breathing conditions and perhaps during dynamic bronchoconstriction.
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Luijendijk, S. C., and J. Milic-Emili. "Breathing patterns in anesthetized cats and the concept of minimum respiratory effort." Journal of Applied Physiology 64, no. 1 (January 1, 1988): 31–41. http://dx.doi.org/10.1152/jappl.1988.64.1.31.
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Theoretical studies dealing with the principle of minimal respiratory effort usually make use of sinusoidal or saw-tooth-like breathing patterns. Recent observations in anesthetized cats have shown that the driving pressure waveform for inspiration can be described by a power function of time and that most of expiration is passive. This driving pressure waveform, however, results in breathing patterns that differ from those described above. For this reason, we have reevaluated in anesthetized cats the principle of minimal respiratory effort by computing optimal duration of inspiration (TI) and optimal tidal volume (VT) for different ventilatory conditions using actual driving pressure waveforms. The results are in qualitative agreement with the experimental observations; i.e., optimal TI decreases and optimal VT increases with increasing minute ventilation. On the average, a good agreement is found between measured and computed values of TI. In some cats, however, there are substantial differences between observed and predicted values of TI, which can probably be ascribed to inaccuracies in the data used in our computations. Despite its limitations, the present model analysis is more realistic than previous ones because actual driving pressure waveforms are used together with actual values of effective inspiratory impedance.
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Herrmann, Jacob, Merryn H. Tawhai, and David W. Kaczka. "Regional gas transport in the heterogeneous lung during oscillatory ventilation." Journal of Applied Physiology 121, no. 6 (December 1, 2016): 1306–18. http://dx.doi.org/10.1152/japplphysiol.00097.2016.
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Regional ventilation in the injured lung is heterogeneous and frequency dependent, making it difficult to predict how an oscillatory flow waveform at a specified frequency will be distributed throughout the periphery. To predict the impact of mechanical heterogeneity on regional ventilation distribution and gas transport, we developed a computational model of distributed gas flow and CO2 elimination during oscillatory ventilation from 0.1 to 30 Hz. The model consists of a three-dimensional airway network of a canine lung, with heterogeneous parenchymal tissues to mimic effects of gravity and injury. Model CO2 elimination during single frequency oscillation was validated against previously published experimental data (Venegas JG, Hales CA, Strieder DJ, J Appl Physiol 60: 1025–1030, 1986). Simulations of gas transport demonstrated a critical transition in flow distribution at the resonant frequency, where the reactive components of mechanical impedance due to airway inertia and parenchymal elastance were equal. For frequencies above resonance, the distribution of ventilation became spatially clustered and frequency dependent. These results highlight the importance of oscillatory frequency in managing the regional distribution of ventilation and gas exchange in the heterogeneous lung.
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Menon, A. S., S. J. England, E. Vallieres, A. S. Rebuck, and A. S. Slutsky. "Influence of phasic afferent information on phrenic neural output during hypercapnia." Journal of Applied Physiology 65, no. 2 (August 1, 1988): 563–69. http://dx.doi.org/10.1152/jappl.1988.65.2.563.
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We measured the moving time average (MTA) of the phrenic neurogram before and after removal of phasic afferent information from the lungs, chest wall, and oscillations in blood gases by using constant-flow ventilation (CFV). Anesthetized dogs were studied at various levels of steady-state and progressive hypercapnia during spontaneous breathing and during CFV. When steady-state and progressive hypercapnia were compared, the frequency and height of the MTA phrenic neurogram were independent of the rate of induction of hypercapnia during each mode of ventilation. During spontaneous ventilation, the response to hypercapnia comprised mainly an increase in frequency with only a slight increase in the amplitude of the MTA phrenic waveform. During muscular paralysis and CFV, the responses were similar to those observed after vagotomy with mainly an increase in the amplitude and only a small increase in frequency. For both spontaneous breathing and CFV, increases in frequency were achieved mainly by a shortening in expiratory time with the inspiratory time remaining relatively constant. Our data support the concept of a centrally patterned respiratory generator, whose inherent pattern is modified by phasic feedback from peripheral receptors mainly of vagal origin.
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Burke, W. C., P. S. Crooke, T. W. Marcy, A. B. Adams, and J. J. Marini. "Comparison of mathematical and mechanical models of pressure-controlled ventilation." Journal of Applied Physiology 74, no. 2 (February 1, 1993): 922–33. http://dx.doi.org/10.1152/jappl.1993.74.2.922.
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Recent evidence that volume-cycled mechanical ventilation may itself produce lung injury has focused clinical attention on the pressure waveform applied to the respiratory system. There has been an increasing use of pressure-controlled ventilation (PCV), because it limits peak cycling pressure and provides a decelerating flow profile that may improve gas exchange. In this mode, however, the relationships are of machine adjustments to ventilation and alveolar pressure are not straightforward. Consequently, setting selection remains largely an empirical process. In previous work, we developed a biexponential model of PCV that provides a conceptual framework for understanding these interactions (J. Appl. Physiol. 67: 1081–1092, 1989). We tested the validity of this mathematical model in a single-compartment analogue of the respiratory system across wide ranges of clinician-set variables (frequency, duty cycle, applied pressure) and impedance conditions (inspiratory and expiratory resistance and system compliance). Our data confirm the quantitative validity of the proposed model when approximately rectilinear waves of pressure are applied and appropriate values for impedance are utilized. Despite a fixed-circuit configuration, however, resistance proved to be a function of each clinician-set variable, requiring remeasurement of system impedance as adjustments in these variables were made. With further modification, this model may provide a practical as well as a conceptual basis for understanding minute ventilation and alveolar pressure fluctuations during PCV in the clinical setting.
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Ito, Satoru, Kenneth R. Lutchen, and Béla Suki. "Effects of heterogeneities on the partitioning of airway and tissue properties in normal mice." Journal of Applied Physiology 102, no. 3 (March 2007): 859–69. http://dx.doi.org/10.1152/japplphysiol.00884.2006.
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We measured the mechanical properties of the respiratory system of C57BL/6 mice using the optimal ventilation waveform method in closed- and open-chest conditions at different positive end-expiratory pressures. The tissue damping (G), tissue elastance (H), airway resistance (Raw), and hysteresivity were obtained by fitting the impedance data to three different models: a constant-phase model by Hantos et al. (Hantos Z, Daroczy B, Suki B, Nagy S, Fredberg JJ. J Appl Physiol 72: 168–178, 1992), a heterogeneous Raw model by Suki et al. (Suki B, Yuan H, Zhang Q, Lutchen KR. J Appl Physiol 82: 1349–1359, 1997), and a heterogeneous H model by Ito et al. (Ito S, Ingenito EP, Arold SP, Parameswaran H, Tgavalekos NT, Lutchen KR, Suki B. J Appl Physiol 97: 204–212, 2004). Both in the closed- and open-chest conditions, G and hysteresivity were the lowest and Raw the highest in the heterogeneous Raw model, and G and H were the largest in the heterogeneous H model. Values of G, Raw, and hysteresivity were significantly higher in the closed-chest than in the open-chest condition. However, H was not affected by the conditions. When the tidal volume of the optimal ventilation waveform was decreased from 8 to 4 ml/kg in the closed-chest condition, G and hysteresivity significantly increased, but there were smaller changes in H or Raw. In summary, values of the obtained mechanical properties varied among these models, primarily due to heterogeneity. Moreover, the mechanical parameters were significantly affected by the chest wall and tidal volume in mice. Contribution of the chest wall and heterogeneity to the mechanical properties should be carefully considered in physiological studies in which partitioning of airway and tissue properties are attempted.
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Dellacà, Raffaele L., Lauren D. Black, Haytham Atileh, Antonio Pedotti, and Kenneth R. Lutchen. "Effects of posture and bronchoconstriction on low-frequency input and transfer impedances in humans." Journal of Applied Physiology 97, no. 1 (July 2004): 109–18. http://dx.doi.org/10.1152/japplphysiol.00721.2003.
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We simultaneously evaluated the mechanical response of the total respiratory system, lung, and chest wall to changes in posture and to bronchoconstriction. We synthesized the optimal ventilation waveform (OVW) approach, which simultaneously provides ventilation and multifrequency forcing, with optoelectronic plethysmography (OEP) to measure chest wall flow globally and locally. We applied an OVW containing six frequencies from 0.156 to 4.6 Hz to the mouth of six healthy men in the seated and supine positions, before and after methacholine challenge. We measured mouth, esophageal, and transpulmonary pressures, airway flow by pneumotachometry, and total chest wall, pulmonary rib cage, and abdominal volumes by OEP. We computed total respiratory, lung, and chest wall input impedances and the total and regional transfer impedances (Ztr). These data were appropriately sensitive to changes in posture, showing added resistance in supine vs. seated position. The Ztr were also highly sensitive to lung constriction, more so than input impedance, as the former is minimally distorted by shunting of flow into alveolar gas compression and airway walls. Local impedances show that, during bronchoconstriction and at typical breathing frequencies, the contribution of the abdomen becomes amplified relative to the rib cage. A similar redistribution occurs when passing from seated to supine. These data suggest that the OEP-OVW approach for measuring Ztr could noninvasively track important lung and respiratory conditions, even in subjects who cannot cooperate. Applications might range from routine evaluation of airway hyperreactivity in asthmatic subjects to critical conditions in the supine position during mechanical ventilation.
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Kaczka, David W., Edward P. Ingenito, Bela Suki, and Kenneth R. Lutchen. "Partitioning airway and lung tissue resistances in humans: effects of bronchoconstriction." Journal of Applied Physiology 82, no. 5 (May 1, 1997): 1531–41. http://dx.doi.org/10.1152/jappl.1997.82.5.1531.
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Kaczka, David W., Edward P. Ingenito, Bela Suki, and Kenneth R. Lutchen. Partitioning airway and lung tissue resistances in humans: effects of bronchoconstriction. J. Appl. Physiol. 82(5): 1531–1541, 1997.—The contribution of airway resistance (Raw) and tissue resistance (Rti) to total lung resistance (R l ) during breathing in humans is poorly understood. We have recently developed a method for separating Raw and Rti from measurements of Rland lung elastance (El) alone. In nine healthy, awake subjects, we applied a broad-band optimal ventilator waveform (OVW) with energy between 0.156 and 8.1 Hz that simultaneously provides tidal ventilation. In four of the subjects, data were acquired before and during a methacholine (MCh)-bronchoconstricted challenge. The Rland Eldata were first analyzed by using a model with a homogeneous airway compartment leading to a viscoelastic tissue compartment consisting of tissue damping and elastance parameters. Our OVW-based estimates of Raw correlated well with estimates obtained by using standard plethysmography and were responsive to MCh-induced bronchoconstriction. Our data suggest that Rti comprises ∼40% of total Rlat typical breathing frequencies, which corresponds to ∼60% of intrathoracic Rl. During mild MCh-induced bronchoconstriction, Raw accounts for most of the increase in Rl. At high doses of MCh, there was a substantial increase in Rlat all frequencies and in El at higher frequencies. Our analysis showed that both Raw and Rti increase, but most of the increase is due to Raw. The data also suggest that widespread peripheral constriction causes airway wall shunting to produce additional frequency dependence in El.
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Fuhrman, B. P., D. L. Smith-Wright, T. J. Kulik, and J. E. Lock. "Effects of static and fluctuating airway pressure on intact pulmonary circulation." Journal of Applied Physiology 60, no. 1 (January 1, 1986): 114–22. http://dx.doi.org/10.1152/jappl.1986.60.1.114.
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The direct effects on the pulmonary circulation of static and fluctuation airway pressure were compared in intact close-chest infant lambs with reactive pulmonary vasculature under alpha-chloralose anesthesia. A preparation developed to permit independent ventilation of right and left lungs and independent measurement of right and left lung blood flow was employed to separate direct from indirect effects of unilateral airway pressure changes on pulmonary vascular resistance (PVR). Both static and fluctuating unilateral airway pressure interventions directly elevated ipsilateral PVR. For purposes of comparison mean alveolar pressure (PA) was estimated for both static and fluctuating trials. Fluctuating interventions increased PVR more than did static trials at comparable levels of PA. Substantially less PA was needed to double ipsilateral PVR by fluctuating than by static interventions (16 vs. 26 mmHg, respectively). These data indicate that, in the intact animal with reactive pulmonary vasculature, both PA and the waveform of airway pressure applied can influence PVR.
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Katz, Trixie A., Danielle D. Weinberg, Claire E. Fishman, Vinay Nadkarni, Patrice Tremoulet, Arjan B. te Pas, Aleksandra Sarcevic, and Elizabeth E. Foglia. "Visual attention on a respiratory function monitor during simulated neonatal resuscitation: an eye-tracking study." Archives of Disease in Childhood - Fetal and Neonatal Edition 104, no. 3 (June 14, 2018): F259—F264. http://dx.doi.org/10.1136/archdischild-2017-314449.
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ObjectiveA respiratory function monitor (RFM) may improve positive pressure ventilation (PPV) technique, but many providers do not use RFM data appropriately during delivery room resuscitation. We sought to use eye-tracking technology to identify RFM parameters that neonatal providers view most commonly during simulated PPV.DesignMixed methods study. Neonatal providers performed RFM-guided PPV on a neonatal manikin while wearing eye-tracking glasses to quantify visual attention on displayed RFM parameters (ie, exhaled tidal volume, flow, leak). Participants subsequently provided qualitative feedback on the eye-tracking glasses.SettingLevel 3 academic neonatal intensive care unit.ParticipantsTwenty neonatal resuscitation providers.Main outcome measuresVisual attention: overall gaze sample percentage; total gaze duration, visit count and average visit duration for each displayed RFM parameter. Qualitative feedback: willingness to wear eye-tracking glasses during clinical resuscitation.ResultsTwenty providers participated in this study. The mean gaze sample captured wa s 93% (SD 4%). Exhaled tidal volume waveform was the RFM parameter with the highest total gaze duration (median 23%, IQR 13–51%), highest visit count (median 5.17 per 10 s, IQR 2.82–6.16) and longest visit duration (median 0.48 s, IQR 0.38–0.81 s). All participants were willing to wear the glasses during clinical resuscitation.ConclusionWearable eye-tracking technology is feasible to identify gaze fixation on the RFM display and is well accepted by providers. Neonatal providers look at exhaled tidal volume more than any other RFM parameter. Future applications of eye-tracking technology include use during clinical resuscitation.
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Rehm, Gregory B., Brooks T. Kuhn, Jean-Pierre Delplanque, Edward C. Guo, Monica K. Lieng, Jimmy Nguyen, Nicholas R. Anderson, and Jason Y. Adams. "Development of a research-oriented system for collecting mechanical ventilator waveform data." Journal of the American Medical Informatics Association 25, no. 3 (October 28, 2017): 295–99. http://dx.doi.org/10.1093/jamia/ocx116.
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Abstract Lack of access to high-frequency, high-volume patient-derived data, such as mechanical ventilator waveform data, has limited the secondary use of these data for research, quality improvement, and decision support. Existing methods for collecting these data are obtrusive, require high levels of technical expertise, and are often cost-prohibitive, limiting their use and scalability for research applications. We describe here the development of an unobtrusive, open-source, scalable, and user-friendly architecture for collecting, transmitting, and storing mechanical ventilator waveform data that is generalizable to other patient care devices. The system implements a software framework that automates and enforces end-to-end data collection and transmission. A web-based data management application facilitates nontechnical end users’ abilities to manage data acquisition devices, mitigates data loss and misattribution, and automates data storage. Using this integrated system, we have been able to collect ventilator waveform data from >450 patients as part of an ongoing clinical study.
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He, Huaiwu, Qinhe Hu, Yun Long, Xu Wang, Rui Zhang, Longxiang Su, Dawei Liu, and Can Ince. "Effects of high PEEP and fluid administration on systemic circulation, pulmonary microcirculation, and alveoli in a canine model." Journal of Applied Physiology 127, no. 1 (July 1, 2019): 40–46. http://dx.doi.org/10.1152/japplphysiol.00571.2018.
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This study aimed to determine the response of systemic circulation, pulmonary microcirculation, and alveoli to high positive end-expiratory pressure (PEEP) in a canine model. This study was conducted in nine mixed-breed dogs on mechanical ventilation under anesthesia. The PEEP was initially set at 5 cmH2O (PEEP5), the PEEP was then increased to 25 cmH2O (PEEP25), and then saline was used for fluid loading. Data were obtained at the following time points: PEEP5; PEEP25 prefluid loading; and PEEP25 postfluid loading. The images of subpleural lung microcirculation were assessed by sidestream dark-field microscopy, and the hemodynamic data were collected from pulse contour waveform-derived measurements. Compared with PEEP5, the lung microvascular flow index (MFI, 2.3 ± 0.8 versus 0.9 ± 0.8, P = 0.001), lung perfused vessel density (PVD, 4.2 ± 2 versus 1.5 ± 1.8, P = 0.004), lung proportion of perfused vessel (PPV, 93 ± 14 versus 40 ± 4, P = 0.003), cardiac output (2.5 ± 0.6 versus 1.4 ± 0.5, P = 0.001), and mean blood pressure (116 ± 24 versus 91 ± 31, P = 0.012) were significantly lower at PEEP25 prefluid loading. After fluid loading, there were no significant differences in cardiac output or mean arterial pressure between the PEEP5 and PEEP25 postfluid loading levels. However, the lung microcirculatory MFI, PVD, and PPV at PEEP25 postfluid loading remain lower than at PEEP5. A significant increase in septal thickness was found at PEEP25 postfluid loading relative to septal thickness at PEEP25 prefluid loading (25.98 ± 5.31 versus 40.76 ± 7.9, P = 0.001). Under high PEEP, systemic circulation was restored after fluid loading, but lung microcirculation was not. Moreover, the septal thickness of alveoli significantly increased after fluid loading. NEW & NOTEWORTHY An excessively high positive end-expiratory pressure (PEEP) can impair the systemic circulation and alveolar microcirculation. In the high-PEEP condition, fluid loading restored the systemic circulation but did not affect the impaired lung microcirculation. The septal thickness of the alveoli significantly increased after fluid loading in the high-PEEP condition.
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Fredberg, J. J., G. M. Glass, B. R. Boynton, and I. D. Frantz. "Factors influencing mechanical performance of neonatal high-frequency ventilators." Journal of Applied Physiology 62, no. 6 (June 1, 1987): 2485–90. http://dx.doi.org/10.1152/jappl.1987.62.6.2485.
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Factors influencing the mechanical performance of neonatal high-frequency ventilators of diverse design were assessed under controlled conditions. Each of eight ventilators was coupled to in vitro models of the neonatal respiratory system simulating disease of varying severity. The principal performance characteristics examined were frequency dependence and load dependence of tidal volume delivered, peak inspiratory flow rate, and waveforms of pressure at either end of the endotracheal tube. Despite wide diversity of ventilator designs, including jets, flow interrupters, and oscillators, common features emerged. In almost all devices tidal volume increased with endotracheal tube size, was invariant with respiratory system compliance, and decreased with frequency of oscillation. Peak inspiratory flow rates for a given tidal volume and frequency were smallest in the group of oscillators compared with jets and flow interrupters. Proximal pressure was a poor indicator of distal pressure. These findings suggest that delivered tidal volume may be sensitive to endotracheal tube size and airway patency but relatively insensitive to changes in lung tissue or chest wall mechanical properties. In these regards high-frequency ventilation differs from pressure-limited conventional mechanical ventilation. Comparison of data obtained at different clinical centers using high-frequency ventilators of varying design may be possible by taking these factors into account.
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Rehm, Gregory B., Irene Cortés-Puch, Brooks T. Kuhn, Jimmy Nguyen, Sarina A. Fazio, Michael A. Johnson, Nicholas R. Anderson, Chen-Nee Chuah, and Jason Y. Adams. "Use of Machine Learning to Screen for Acute Respiratory Distress Syndrome Using Raw Ventilator Waveform Data." Critical Care Explorations 3, no. 1 (January 2021): e0313. http://dx.doi.org/10.1097/cce.0000000000000313.
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Lutchen, K. R., D. W. Kaczka, B. Suki, G. Barnas, G. Cevenini, and P. Barbini. "Low-frequency respiratory mechanics using ventilator-driven forced oscillations." Journal of Applied Physiology 75, no. 6 (December 1, 1993): 2549–60. http://dx.doi.org/10.1152/jappl.1993.75.6.2549.
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We evaluated the potential for using a fast Fourier transform (FFT) analysis applied to a standard ventilator waveform to estimate (< 2 Hz) frequency dependence of respiratory or lung resistance (R) and elastance (E). In four healthy humans we measured pressure and flow at the airway opening while applying sine wave forcing from 0.2 to 0.6 Hz at two tidal volumes (VT; 250 and 500 ml). We then applied a step inspiratory ventilator flow wave with relaxed expiration at the same VT and only 0.2 Hz. Step waveform data were also acquired from nine mechanically ventilated patients under intensive care unit conditions. Finally, we simultaneously measured total respiratory (rs), lung (L), and chest wall (cw) impedance data from two dogs (0.156–2 Hz) before and after severe pulmonary edema. Rrs and Ers were estimated by the FFT approach. Humans displayed a small frequency dependence in Rrs and Ers from 0.2 to 0.6 Hz, and both Rrs and Ers decreased at the higher VT. The spectral estimates of Rrs and Ers with the step ventilator wave were often qualitatively comparable to sine wave results below 0.6 Hz but became extremely erratic above the third harmonic. Conversely, in dogs the step wave produced reliable and stable estimates up to 2 Hz in all conditions. Nevertheless, Ecw and Ers still displayed clear and correlated oscillations with increasing frequency, whereas EL showed none. This suggests that nonlinear processes, most likely at the chest wall, contribute to periodic-like fluctuations in respiratory mechanical properties when estimated by applying FFT to a step ventilator wave. Moreover, in humans, but not dogs, a ventilator flow cycle contains insufficient signal energy beyond the third harmonic. We show that the amount of energy available at higher frequencies is largely governed by the mechanical time constant contributing to passive expiratory flow. In dogs the shorter time constant contributes to increased energy. In essence, the frequency content of the flow is subject dependent, and this is not a desirable situation for controlling the quality of the impedance spectra available from a standard ventilator wave.
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Curtis, S. E., B. P. Fuhrman, and D. F. Howland. "Airway and alveolar pressures during perfluorocarbon breathing in infant lambs." Journal of Applied Physiology 68, no. 6 (June 1, 1990): 2322–28. http://dx.doi.org/10.1152/jappl.1990.68.6.2322.
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Previous studies exploring the utility of liquid breathing using perfluorocarbon have reported proximal airway pressures (Paw) as high as 70 Torr during inspiration, generating concern about the safety of this form of mechanical ventilation. Effects on the pulmonary capillary bed are, however, more likely related to alveolar pressure (PA) than to Paw, and data on PA during liquid breathing are limited. In this study in infant lambs, we reconstructed the pressure waveforms of PA during liquid breathing by using an occlusion technique and compared these with Paw waveforms. Peak PA (18.6 +/- 10.4 Torr) was significantly less than peak Paw (31.5 +/- 10.5 Torr, P less than 0.001), indicating a large resistive pressure drop (14.4 +/- 4.5 Torr) across the bronchial tree. Mean PA (mPA) was very similar to mean Paw (mPaw) [bias = -2.0 Torr, standard error of the average difference = 0.27 Torr, predictive value of mPaw for mPA (r2) = 0.978], suggesting that mPaw, which is easily measured, may be used to estimate mPA during perfluorocarbon liquid breathing. These data show that alveoli do not experience the same large swings in pressure as the proximal airway does during liquid breathing and that simple measurements of mPaw can be used to approximate mPA during liquid breathing.
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Shabbir, Noman, Lauri Kütt, Bilal Asad, Muhammad Jawad, Muhammad Naveed Iqbal, and Kamran Daniel. "Spectrum Analysis for Condition Monitoring and Fault Diagnosis of Ventilation Motor: A Case Study." Energies 14, no. 7 (April 5, 2021): 2001. http://dx.doi.org/10.3390/en14072001.
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In modern power systems, since most loads are inductive by nature, there is an ongoing power quality issue and researchers’ interest in improving the power factor is widespread, as inductive loads have a low power factor that depletes the system’s capacity and has an adverse effect on the voltage level. The measurement and acute analysis of voltage- and current-level waveforms is essential to tackle power quality issues. This article presents a detailed case study and analysis of real-time data measured from a frequency converter, which is used to operate the motor of a ventilation system. The output of the frequency converter is a highly distorted current wave. A hybrid Fourier transform (FT)- and wavelet transform-based solution has been proposed here to diagnose and identify the causes of motor failure in the ventilation system. The traditional FT did not give a detailed analysis of this type of signal, which is highly contaminated by noise. Therefore, first, the signal is preprocessed for data denoising using the wavelet transform. Second, the Fourier analysis is performed on the filtered signal for frequency analysis and segregation of fundamental frequency components, higher-order harmonics, and suppressed noise. The spectrum analysis reveals that the noise is generated due to the rapidly switching circuits in the frequency converter and this unfiltered signal at the output of the frequency converter causes motor failure.
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Sakai, Hiroaki, Edward P. Ingenito, Rene Mora, Senay Abbay, Francisco S. A. Cavalcante, Kenneth R. Lutchen, and Béla Suki. "Hysteresivity of the lung and tissue strip in the normal rat: effects of heterogeneities." Journal of Applied Physiology 91, no. 2 (August 1, 2001): 737–47. http://dx.doi.org/10.1152/jappl.2001.91.2.737.
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We measured lung impedance in rats in closed chest (CC), open chest (OC), and isolated lungs (IL) at four transpulmonary pressures with a optimal ventilator waveform. Data were analyzed with an homogeneous linear or an inhomogeneous linear model. Both models include tissue damping and elastance and airway inertance. The homogeneous linear model includes airway resistance (Raw), whereas the inhomogeneous linear model has a continuous distribution of Raw characterized by the mean Raw and the standard deviation of Raw (SDR). Lung mechanics were compared with tissue strip mechanics at frequencies and operating stresses comparable to those during lung impedance measurements. The hysteresivity (η) was calculated as tissue damping/elastance. We found that 1) airway and tissue parameters were different in the IL than in the CC and OC conditions; 2) SDR was lowest in the IL; and 3) η in IL at low transpulmonary pressure was similar to η in the tissue strip. We conclude that η is primarily determined by lung connective tissue, and its elevated estimates from impedance data in the CC and OC conditions are a consequence of compartment-like heterogeneity being greater in CC and OC conditions than in the IL.
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Costello, John M., Mjaye L. Mazwi, Mary E. McBride, Katherine E. Gambetta, Osama Eltayeb, and Conrad L. Epting. "Critical care for paediatric patients with heart failure." Cardiology in the Young 25, S2 (August 2015): 74–86. http://dx.doi.org/10.1017/s1047951115000864.
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AbstractThis review offers a critical-care perspective on the pathophysiology, monitoring, and management of acute heart failure syndromes in children. An in-depth understanding of the cardiovascular physiological disturbances in this population of patients is essential to correctly interpret clinical signs, symptoms and monitoring data, and to implement appropriate therapies. In this regard, the myocardial force–velocity relationship, the Frank–Starling mechanism, and pressure–volume loops are discussed. A variety of monitoring modalities are used to provide insight into the haemodynamic state, clinical trajectory, and response to treatment. Critical-care treatment of acute heart failure is based on the fundamental principles of optimising the delivery of oxygen and minimising metabolic demands. The former may be achieved by optimising systemic arterial oxygen content and the variables that determine cardiac output: heart rate and rhythm, preload, afterload, and contractility. Metabolic demands may be decreased by a number of ways including positive pressure ventilation, temperature control, and sedation. Mechanical circulatory support should be considered for refractory cases. In the near future, monitoring modalities may be improved by the capture and analysis of complex clinical data such as pressure waveforms and heart rate variability. Using predictive modelling and streaming analytics, these data may then be used to develop automated, real-time clinical decision support tools. Given the barriers to conducting multi-centre trials in this population of patients, the thoughtful analysis of data from multi-centre clinical registries and administrative databases will also likely have an impact on clinical practice.
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Ni, Y., K. Dunhsm, L. Cunningham, and R. Thomas. "0661 Comparison Between Ventilator Detected Apnea Hypopnea Index and Manual Scored Results." Sleep 43, Supplement_1 (April 2020): A252. http://dx.doi.org/10.1093/sleep/zsaa056.657.
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Abstract Introduction The apnea hypopnea index and percentage of periodic breathing detected by the ventilator machine are often used by sleep doctors to evaluate whether sleep apnea has been adequately treated or need further interventions. There are concerns about the accuracy of this autodetection. Methods Patients with sleep apnea who were treated with positive airway pressure at the Beth Israel Deaconess Medical Center (Boston) and tracked by the EncoreAnywhere system were included. The machine detected AHI(AHIm) and PB(PBm) were extracted from the first week data in every month from the start of use. The manual scored AHI(AHIs) and PB(PBs) were calculated from the last waveform graph during every month. The apnea hypopnea index as well as periodic breathing in 1st, 2nd, 3rd,6th month AHIm, AHIs, PBm and PBs were compared respectively. Results A total of 128 patients were included. The mean age was 56.5 and 66% of them were male. In the first month, the mean AHIs was significantly higher than AHIm, 16.27 vs. 5.36, p<0.001. There was also a large difference between percentage of PBs and PBm, 15.55% vs. 1.96, p<0.001. 78% patients whose AHIm <5 were actually has AHIs >5. The Kappa value for the AHIm and AHIs were 0.074, p=0.069; the value of PBm and PBs was 0.216, p=0.015. In the 2nd, 3rd and 6th months, the mean difference between AHIs and AHIm was 10.58, 10.68, 10.12, respectively. The mean difference between PBs and PBm was 12.32%,11.53%,and 9.18%. Conclusion Autodetection of respiratory events consistently under-estimates the severity of residual events. Mean differences remained stable over 6 months. Caution is recommended when attributing non-apnea reasons for residual symptoms in patients with apparently low machine estimated AHI and PB. Support This study is supported by American Academy of Sleep Medicine Foundation, category-I award to RJT
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Bennett, S. H. "Modeling methodology for vascular input impedance determination and interpretation." Journal of Applied Physiology 76, no. 1 (January 1, 1994): 455–84. http://dx.doi.org/10.1152/jappl.1994.76.1.455.
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The significance of pulse wave reflections in the pulmonary vascular system is elaborated using a new method to determine the broadband frequency response of input impedance up to frequencies of 100 Hz. A simple data model, based on the signal construct of a wavelet, is used to generalize and reconcile the common approaches to vascular frequency response estimation so that an accurate response can be calculated from physiological waveforms. Input impedance interpretation is accomplished using a structural and functional modeling methodology. To identify internal structural system properties, the methodology of inverse scattering is used to relate observed pulse wave echoes in the frequency response to a longitudinal distribution of reflection sites of anatomic significance. To identify functional interactions with pulmonary vascular wave mechanics, a time series analysis methodology is proposed to describe vascular interactions using a generalized principle of superposition. The methods of determination and interpretation are applied to a sample pressure-flow data set from the pulmonary circulation of a lamb experiencing vascular-ventilatory interaction. The example suggests that the frequency response is consistent with a discrete longitudinal distribution of reflection sites that may be affected by the ventilator.
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Peslin, R., C. Saunier, C. Duvivier, and M. Marchand. "Analysis of low-frequency lung impedance in rabbits with nonlinear models." Journal of Applied Physiology 79, no. 3 (September 1, 1995): 771–80. http://dx.doi.org/10.1152/jappl.1995.79.3.771.
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Lung mechanics was studied in six paralyzed tracheotomized rabbits ventilated with a specially devised computer-controlled ventilator. The target flow waveform contained noninteger multiple frequencies ranging from 0.83 to 6–10 Hz and met a neither-sum-nor-difference criterion to minimize the effects of nonlinearity (B. Suki and K. Lutchen. IEEE Trans. Biomed. Eng. 39: 1142–1151, 1992). The actual flow, however, contained harmonics of the two lowest frequencies. Measurements were performed at mean airway pressure (Paw) levels of 8 and 12 hPa and during histamine-induced bronchoconstriction. Smooth impedance curves were observed in unchallenged rabbits at low mean Paw levels. In contrast, unrealistic impedance fluctuations, suggestive of cross talk from the unwanted frequency components in the flow input, were seen at high mean Paw levels and during acute bronchoconstriction. Model analysis was performed by using the actual flow signal as an input to various nonlinear models. The impedance fluctuations observed at high mean Paw levels were well simulated by a model featuring a volume-dependent elastance, and those observed after histamine were almost perfectly reproduced by a model where resistance increased with the reciprocal of lung volume. We conclude that impedance data biased by cross talk may provide useful information on the presence and nature of respiratory system nonlinearities.
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Mathis, Michael R., Samuel A. Schechtman, Milo C. Engoren, Amy M. Shanks, Aleda Thompson, Sachin Kheterpal, and Kevin K. Tremper. "Arterial Pressure Variation in Elective Noncardiac Surgery: Identifying Reference Distributions and Modifying Factors." Anesthesiology 126, no. 2 (February 1, 2017): 249–59. http://dx.doi.org/10.1097/aln.0000000000001460.
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Abstract Background Assessment of need for intravascular volume resuscitation remains challenging for anesthesiologists. Dynamic waveform indices, including systolic and pulse pressure variation, are demonstrated as reliable measures of fluid responsiveness for mechanically ventilated patients. Despite widespread use, real-world reference distributions for systolic and pulse pressure variation values have not been established for euvolemic intraoperative patients. The authors sought to establish systolic and pulse pressure variation reference distributions and assess the impact of modifying factors. Methods The authors evaluated adult patients undergoing general anesthetics for elective noncardiac surgery. Median systolic and pulse pressure variations during a 50-min postinduction period were noted for each case. Modifying factors including body mass index, age, ventilator settings, positioning, and hemodynamic management were studied via univariate and multivariable analyses. For systolic pressure variation values, effects of data entry method (manually entered vs. automated recorded) were similarly studied. Results Among 1,791 cases, per-case median systolic and pulse pressure variation values formed nonparametric distributions. For each distribution, median values, interquartile ranges, and reference intervals (2.5th to 97.5th percentile) were, respectively, noted: these included manually entered systolic pressure variation (6.0, 5.0 to 7.0, and 3.0 to 11.0 mmHg), automated systolic pressure variation (4.7, 3.9 to 6.0, and 2.2 to 10.4 mmHg), and automated pulse pressure variation (7.0, 5.0 to 9.0, and 2.0 to 16.0%). Nonsupine positioning and preoperative β blocker were independently associated with altered systolic and pulse pressure variations, whereas ventilator tidal volume more than 8 ml/kg ideal body weight and peak inspiratory pressure more than 16 cm H2O demonstrated independent associations for systolic pressure variation only. Conclusions This study establishes real-world systolic and pulse pressure variation reference distributions absent in the current literature. Through a consideration of reference distributions and modifying factors, the authors’ study provides further evidence for assessing intraoperative volume status and fluid management therapies.
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Staśko, Tomasz, Martyna Tomala, Mirosław Majkut, Krzysztof Nawrat, and Krystian Smołka. "Influence of Geometrical Parameters on the Shape of the Cycloidal Function Curve of a Fan with a Cycloidal Rotor." Energies 15, no. 7 (March 29, 2022): 2504. http://dx.doi.org/10.3390/en15072504.
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Even though the cycloidal rotor concept has been around for almost a century, it is still not as popular as it should be. Most often it is used to propel unmanned aerial vehicles or sea-going ships, or it is applied as a river- or sea-energy converter. Despite the possibility of directing the flow by changing the inclination angle of blades and the possibility of working in both directions, there are no scientific studies on the use of the concept in HVAC (heat, ventilation and air conditioning). One of the most important elements characterizing the operation of the cycloidal rotor is the cycloidal function describing the change in the angles of the blades during rotation. To properly design a cycloidal rotor for a preferred application, an analysis of the rotor geometrical parameters must be performed and analyzed. This was performed on a four-blade rotor equipped with CLARK Y blades. Using Ansys CFX software, a CFD model of a fan operating with various cycloidal functions was created. The results were compared with the experimental data with the use of the LDA technique. Different velocity profiles were obtained despite the use of cycloidal functions with similar waveforms and small angular differences. This is due to the considerable sensitivity of the cycloidal regulation system to differences in the geometrical sizes that describe it.
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Eke, Csaba, András Szabó, Ádám Nagy, Balázs Szécsi, Rita Szentgróti, András Dénes, Miklós D. Kertai, et al. "Association between Hepatic Venous Congestion and Adverse Outcomes after Cardiac Surgery." Diagnostics 12, no. 12 (December 15, 2022): 3175. http://dx.doi.org/10.3390/diagnostics12123175.
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Introduction: Hepatic venous flow patterns reflect pressure changes in the right ventricle and are also markers of systemic venous congestion. Fluid management is crucial in patients undergoing cardiac surgery. Methods: Our goal was to determine which factors are associated with the increased congestion of the liver as measured by Doppler ultrasound in patients undergoing cardiac surgery. This prospective, observational study included 41 patients without preexisting liver disease who underwent cardiac surgery between 1 January 2021 and 30 September 2021 at a tertiary heart center. In addition to routine echocardiographic examination, we recorded the maximal velocity and velocity time integral (VTI) of the standard four waves seen in the common hepatic vein (flow profile) using Doppler ultrasound preoperatively and at the 20–24th hour of the postoperative period. The ratios of the retrograde and anterograde hepatic venous waves were calculated, and the waveforms were compared to the baseline value and expressed as a delta ratio. Demographic data, pre- and postoperative echocardiographic parameters, intraoperative variables (procedure, cardiopulmonary bypass time), postoperative factors (fluid balance, vasoactive medication requirement, ventilation time and parameters) and perioperative laboratory parameters (liver and kidney function tests, albumin) were used in the analysis. Results: Of the 41 patients, 20 (48.7%) were males, and the median age of the patients was 65.9 years (IQR: 59.8–69.9 years). Retrograde VTI growth showed a correlation with positive fluid balance (0.89 (95% CI 0.785–0.995) c-index. After comparing the postoperative echocardiographic parameters of the two subgroups, right ventricular and atrial diameters were significantly greater in the “retrograde VTI growth” group. The ejection fraction and decrement in ejection fraction to preoperative parameters were significantly different between the two groups. (p = 0.001 and 0.003). Ventilation times were longer in the retrograde VTI group. The postoperative vs. baseline delta VTI ratio of the hepatic vein correlated with positive fluid balance, maximum central venous pressure, and ejection fraction. (B = −0.099, 95% CI = −0.022–0.002, p = 0.022, B = 0.011, 95% CI = 0.001–0.021, p = 0.022, B = 0.091, 95% CI = 0.052–0.213, p = 0.002, respectively.) Conclusion: The increase of the retrograde hepatic flow during the first 24 h following cardiac surgery was associated with positive fluid balance and the decrease of the right ventricular function. Measurement of venous congestion or venous abdominal insufficiency seems to be a useful tool in guiding fluid therapy and hemodynamic management.
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Smith, Bradford J., Sarah Lukens, Eiichiro Yamaguchi, and Donald P. Gaver III. "Lagrangian transport properties of pulmonary interfacial flows." Journal of Fluid Mechanics 705 (November 9, 2011): 234–57. http://dx.doi.org/10.1017/jfm.2011.391.
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AbstractDisease states characterized by airway fluid occlusion and pulmonary surfactant insufficiency, such as respiratory distress syndrome, have a high mortality rate. Understanding the mechanics of airway reopening, particularly involving surfactant transport, may provide an avenue to increase patient survival via optimized mechanical ventilation waveforms. We model the occluded airway as a liquid-filled rigid tube with the fluid phase displaced by a finger of air that propagates with both mean and sinusoidal velocity components. Finite-time Lyapunov exponent (FTLE) fields are employed to analyse the convective transport characteristics, taking note of Lagrangian coherent structures (LCSs) and their effects on transport. The Lagrangian perspective of these techniques reveals flow characteristics that are not readily apparent by observing Eulerian measures. These analysis techniques are applied to surfactant-free velocity fields determined computationally, with the boundary element method, and measured experimentally with micro particle image velocimetry ($\ensuremath{\mu} $-PIV). We find that the LCS divides the fluid into two regimes, one advected upstream (into the thin residual film) and the other downstream ahead of the advancing bubble. At higher oscillatory frequencies particles originating immediately inside the LCS experience long residence times at the air–liquid interface, which may be conducive to surfactant transport. At high frequencies a well-mixed attractor region is identified; this volume of fluid cyclically travels along the interface and into the bulk fluid. The Lagrangian analysis is applied to velocity data measured with 0.01 mg ml−1 of the clinical pulmonary surfactant Infasurf in the bulk fluid, demonstrating flow field modifications with respect to the surfactant-free system that were not visible in the Eulerian frame.
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Roubík, Karel, and Martin Muller. "COMPARISON OF END-EXPIRATORY LUNG VOLUME MEASUREMENT BY ELECTRICAL IMPEDANCE TOMOGRAPHY AND NITROGEN WASHOUT METHOD IN PIGS." Lékař a technika - Clinician and Technology 50, no. 4 (December 31, 2020): 146–51. http://dx.doi.org/10.14311/ctj.2020.4.05.
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End-expiratory lung volume (EELV) can be determined using several methods that allow clinically accurate measurements, but it is difficult to apply these methods to the patient's bedside. Electrical impedance tomography (EIT) is offered as another method for measuring EELV. The aim of the study is to compare changes in EELV measured by nitrogen washout method with changes of EELV calculated from the change in end-expiratory lung impedance (EELI) measured by EIT and to determine whether changes in EELV calculated from changes in chest impedance can be used as one of the parameters for EIT data analysis and description. The prospective interventional animal study was performed on ten pigs. The animals received total intravenous anesthesia with muscle relaxation. Mechanical lung ventilation was conducted in the volume-controlled mode. 16-electrode EIT system was used for data acquisition. End-expiratory lung volume was measured by a modified nitrogen wash-in/wash-out technique developed by Olegard et al. The study protocol consisted of the baseline phase, two incremental PEEP steps, two decremental PEEP steps and from normal saline i. v. administration. For each animal, a reference frame (baseline frame) was selected from the initial baseline phase and was used for the reconstruction of EIT images and impedance waveforms. For each breath cycle, tidal variation image was calculated as a difference between the end-inspiratory and the previous end-expiratory EIT image. An equivalent end-expiratory volume change (ΔEELVequiv) was calculated from EELI. The values of ΔEELVequiv were compared with reference EELV data measured by a modified nitrogen wash-in/wash-out technique (ΔEELVmeas). The measured and the estimated changes in EELV were statistically compared and correlation between ΔEELVequiv and ΔEELVmeas was calculated. Statistically significant difference between ΔEELVequiv and ΔEELVmeas was observed only in administration of normal saline bolus. Pearson’s correlation coefficients were 0.29 for increase in PEEP, 0.45 for decrease in PEEP and -0.1 during administration of normal saline bolus. The study showed that during changes in PEEP in the porcine model, there was no linear relationship between ΔEELVequiv and ΔEELVmeas. Although there was no linear relationship between ΔEELVequiv and ΔEELVmeas with changes in PEEP, no statistically significant difference was demonstrated between these two methods, which justifies the use of ΔEELVequiv as a parameter suitable for description and evaluation of EIT data.
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Arn Ng, Qing, Christopher Yew Shuen Ang, Yeong Shiong Chiew, Xin Wang, Chee Pin Tan, Mohd Basri Mat Nor, Nor Salwa Damanhuri, and J. Geoffrey Chase. "CAREDAQ: Data acquisition device for mechanical ventilation waveform monitoring." HardwareX, September 2022, e00358. http://dx.doi.org/10.1016/j.ohx.2022.e00358.
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Agrawal, Deepak K., Bradford J. Smith, Peter D. Sottile, and David J. Albers. "A Damaged-Informed Lung Ventilator Model for Ventilator Waveforms." Frontiers in Physiology 12 (October 1, 2021). http://dx.doi.org/10.3389/fphys.2021.724046.
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Motivated by a desire to understand pulmonary physiology, scientists have developed physiological lung models of varying complexity. However, pathophysiology and interactions between human lungs and ventilators, e.g., ventilator-induced lung injury (VILI), present challenges for modeling efforts. This is because the real-world pressure and volume signals may be too complex for simple models to capture, and while complex models tend not to be estimable with clinical data, limiting clinical utility. To address this gap, in this manuscript we developed a new damaged-informed lung ventilator (DILV) model. This approach relies on mathematizing ventilator pressure and volume waveforms, including lung physiology, mechanical ventilation, and their interaction. The model begins with nominal waveforms and adds limited, clinically relevant, hypothesis-driven features to the waveform corresponding to pulmonary pathophysiology, patient-ventilator interaction, and ventilator settings. The DILV model parameters uniquely and reliably recapitulate these features while having enough flexibility to reproduce commonly observed variability in clinical (human) and laboratory (mouse) waveform data. We evaluate the proof-in-principle capabilities of our modeling approach by estimating 399 breaths collected for differently damaged lungs for tightly controlled measurements in mice and uncontrolled human intensive care unit data in the absence and presence of ventilator dyssynchrony. The cumulative value of mean squares error for the DILV model is, on average, ≈12 times less than the single compartment lung model for all the waveforms considered. Moreover, changes in the estimated parameters correctly correlate with known measures of lung physiology, including lung compliance as a baseline evaluation. Our long-term goal is to use the DILV model for clinical monitoring and research studies by providing high fidelity estimates of lung state and sources of VILI with an end goal of improving management of VILI and acute respiratory distress syndrome.
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Jaureguibeitia, Xabier, Elisabete Aramendi, Unai Irusta, Ahamed H. Idris, and Henry E. Wang. "Abstract 203: Thoracic Impedance Reflects Differences Between Endotracheal and Laryngeal Advanced Airway During Mechanical Chest Compressions." Circulation 142, Suppl_4 (November 17, 2020). http://dx.doi.org/10.1161/circ.142.suppl_4.203.
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Background: Ventilations during out-of-hospital cardiac arrest (OHCA) produce thoracic impedance(TI) waveforms due to air volume changes in the lungs. Different airway management techniques, i.e. laryngeal tube (LT) and endotracheal intubation (ETI), may produce distinct TI waveforms as a result of different air flows and dead space volumes. Methods: Adult OHCA cases from the Pragmatic Airway Resuscitation Trial were analyzed. Cases recorded with Philips MRx monitor-defibrillators and treated with LUCAS mechanical CPR devices were considered, ensuring homogeneous TI acquisition and compression therapy. Impedance and capnogram signal intervals were extracted after successful airway insertion and during ongoing chest compressions. Ventilations were confirmed in the capnogram, and the associated TI waveforms were analyzed. Adaptive filtering was applied to remove compression artifacts, and the amplitudes (A i , A e ) and durations (D i , D e ) of the insufflation and exhalation phases were computed (see Figure). Each case was characterized by its observed median values. Differences between airway groups were assessed with a Wilcoxon rank sum test. Results: Data from 100 OHCA cases (57 LT and 43 ETI) were analyzed, totaling 10348 ventilations, with median (IQR) of 87 (51 - 146) ventilations per case. Median TI amplitudes for ETI and LT groups showed significant differences (p<0.05), with 1.1 (0.7 - 1.8) Ω and 0.7 (0.3 - 1.3) Ω for A i , and 1.0 (0.7 - 1.6) Ω and 0.6 (0.3 - 1.2) Ω for A e . No significant differences were observed for phase durations, 1.6 (1.3 - 2.0) s and 1.6 (1.2 - 1.8) s for D i , and 2.3 (1.8 - 3.3) s and 2.6 (2.0 - 3.3) s for D e . Conclusions: Significant differences on ventilation impedance waveform amplitudes were observed between patients treated with ETI and LT. This might be related to higher insufflated air volumes for ETI or larger dead space volumes for LT.
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Joseph, Jeffrey I., Josiah Verkiak, Marc Torjman, Channy Loeum, Ji-Bin Liu, Denise Devine, and Nance K. Dicciani. "Abstract P187: Testing Of A Long-term Implantable Blood Pressure Waveform Monitoring System." Hypertension 76, Suppl_1 (September 2020). http://dx.doi.org/10.1161/hyp.76.suppl_1.p187.
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The long-term Implantable Blood Pressure Waveform Monitoring System consists of a miniature applanation tonometer sensor head connected to a battery powered electronics module via a flexible lead. The BP Sensor continuously monitors the arterial BP waveform with data transmitted to a smart phone for real-time data analysis and display. Key data can be transmitted via the cellular network to a central monitoring station for advanced analysis by a computer and clinician. The BP Sensor has been evaluated for safety, accuracy, stability, and reliability for up to 10 months surrounding the external carotid arteries of large canine. Serial ultrasound studies of the artery-sensor interface shows normal artery shape, diameter, and blood flow velocity. BP Sensor performance remained stable for ~ 60 days between calibrations and correlated with reference BP waveform measurement (± 2.5 mm Hg). The BP Sensor head has a novel design that securely couples the diaphragm to the outside wall of a peripheral artery in optimal alignment with minimal flattening (~ 15 %). The Figure below shows the BP Sensor output signal’s detailed BP waveform four months after implantation. The waveform shows subtle and consistent fluctuations in the peaks and valleys of the BP waveform due to positive pressure mechanical ventilation with a respiratory rate of 14 breaths per minute. This is a significant observation which indicates that the BP Sensor has very good sensitivity (± 1 mm Hg) in the normal hemodynamic range (reference BP ~100/60). The real-time and recorded BP Sensor waveform data will be used to make a diagnosis and adjust medication in a more timely and effective manor, leading to improved clinical outcomes.
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McDannold, Robyn, Tyler Bronnenkant, Christopher Crowe, Annemarie Silver, Frederick Geheb, Uli Herken, Daniel Spaite, and Bentley Bobrow. "Abstract 346: Passive Ventilation During Cardiopulmonary Resuscitation Inside the Emergency Department." Circulation 130, suppl_2 (November 25, 2014). http://dx.doi.org/10.1161/circ.130.suppl_2.346.
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Background: Continuing high quality chest compressions (CC) without interruption for active positive pressure ventilation (PPV) early in CPR has been demonstrated to improve patient outcomes in out-of-hospital cardiac arrest (OHCA). During the first minutes of CPR, passive oxygenation may be sufficient for oxygenating vital tissues. However, less is known about the later minutes of CPR. To evaluate this issue, in OHCA patients after hospital arrival, we quantified ventilation volumes during CCs in the ED. Methods: CPR quality metrics were obtained on patients who had CPR inside the ED with the E-Series defibrillator/monitor (Zoll Medical). Detailed ventilation data were obtained using a Non-Invasive Cardiac Output (NICO) Monitor (Philips/Respironics) with a CO2/flow sensor placed at the endotracheal tube. NICO waveform and breath-by-breath data were captured to measure ventilation volume associated with CCs. Results: Data files on 21 cardiac arrest patients who presented to the ED were included. [Male: 17, median age: 59 (IQR 47, 72)]. A total of 29,935 compressions (CCs) were analyzed [median depth 2.1 in (IQR=1.9, 2.5), median rate 126 CC/min (IQR=122-129). The median passive tidal volume during CCs was 5.8 mL, (IQR 3.4, 11.0). The highest volume was 124 mL, however 81% of the measured tidal volumes were <20 mL. Conclusion: This quantified analysis of ventilation volumes during chest compressions in the ED suggests that significant passive ventilation volumes may not occur later in CPR. Even in patients who were receiving effective compressions, passive tidal volumes were extremely low overall, suggesting that the value of compression only CPR may, in part, be due to the avoidance of the harmful effects of hyperventilation rather than any potential effect of passive ventilation.
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Chapman, Jennifer D., Andrew S. Geneslaw, John Babineau, and Anita I. Sen. "Improving Ventilation Rates During Pediatric Cardiopulmonary Resuscitation." Pediatrics, August 24, 2022. http://dx.doi.org/10.1542/peds.2021-053030.
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BACKGROUND: Excessive ventilation at rates of 30 breaths per minute (bpm) or more during cardiopulmonary resuscitation (CPR) decreases venous return and coronary perfusion pressure, leading to lower survival rates in animal models. A review of our institution’s pediatric CPR data revealed that patients frequently received excessive ventilation. METHODS: We designed a multifaceted quality improvement program to decrease the incidence of clinically significant hyperventilation (≥30 bpm) during pediatric CPR. The program consisted of provider education, CPR ventilation tools (ventilation reminder cards, ventilation metronome), and individual CPR team member feedback. CPR events were reviewed pre- and postintervention. The first 10 minutes of each CPR event were divided into 20 second epochs, and the ventilation rate in each epoch was measured via end-tidal carbon dioxide waveform. Individual epochs were classified as within the target ventilation range (<30 bpm) or clinically significant hyperventilation (≥30 bpm). The proportion of epochs with clinically significant hyperventilation, as well as median ventilation rates, were analyzed in the pre- and postintervention periods. RESULTS: In the preintervention period (37 events, 699 epochs), 51% of CPR epochs had ventilation rates ≥30 bpm. In the postintervention period (24 events, 426 epochs), the proportion of CPR epochs with clinically significant hyperventilation decreased to 29% (P < .001). Median respiratory rates decreased from 30 bpm (interquartile range 21–36) preintervention to 21 bpm (interquartile range 12–30) postintervention (P < .001). CONCLUSIONS: A quality improvement initiative grounded in improved provider education, CPR team member feedback, and tools focused on CPR ventilation rates was effective at reducing rates of clinically significant hyperventilation during pediatric CPR.
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Miao, Ming-Yue, Wei Chen, Yi-Min Zhou, Ran Gao, De-Jing Song, Shu-Peng Wang, Yan-Lin Yang, Linlin Zhang, and Jian-Xin Zhou. "Validation of the flow index to detect low inspiratory effort during pressure support ventilation." Annals of Intensive Care 12, no. 1 (September 26, 2022). http://dx.doi.org/10.1186/s13613-022-01063-z.
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Abstract Background Bedside assessment of low levels of inspiratory effort, which are probably insufficient to prevent muscle atrophy, is challenging. The flow index, which is derived from the analysis of the inspiratory portion of the flow–time waveform, has been recently introduced as a non-invasive parameter to evaluate the inspiratory effort. The primary objective of the present study was to provide an external validation of the flow index to detect low inspiratory effort. Methods Datasets containing flow, airway pressure, and esophageal pressure (Pes)–time waveforms were obtained from a previously published study in 100 acute brain-injured patients undergoing pressure support ventilation. Waveforms data were analyzed offline. A low inspiratory effort was defined by one of the following criteria, work of breathing (WOB) less than 0.3 J/L, Pes–time product (PTPes) per minute less than 50 cmH2O•s/min, or inspiratory muscle pressure (Pmus) less than 5 cmH2O, adding “or occurrence of ineffective effort more than 10%” for all criteria. The flow index was calculated according to previously reported method. The association of flow index with Pes-derived parameters of effort was investigated. The diagnostic accuracy of the flow index to detect low effort was analyzed. Results Moderate correlations were found between flow index and WOB, Pmus, and PTPes per breath and per minute (Pearson’s correlation coefficients ranged from 0.546 to 0.634, P < 0.001). The incidence of low inspiratory effort was 62%, 51%, and 55% using the definition of WOB, PTPes per minute, and Pmus, respectively. The area under the receiver operating characteristic curve for flow index to diagnose low effort was 0.88, 0.81, and 0.88, for the three respective definition. By using the cutoff value of flow index less than 2.1, the diagnostic performance for the three definitions showed sensitivity of 0.95–0.96, specificity of 0.57–0.71, positive predictive value of 0.70–0.84, and negative predictive value of 0.90–0.93. Conclusions The flow index is associated with Pes-based inspiratory effort measurements. Flow index can be used as a valid instrument to screen low inspiratory effort with a high probability to exclude cases without the condition.
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Balzer, Claudius, Franz J. Baudenbacher, Antonio Hernandez, Michele M. Salzman, Matthias L. Riess, and Susan S. Eagle. "Abstract 20: Peripheral Intravenous Analysis Detects Return of Spontaneous Circulation Without Interruption of Chest Compressions in a Rat Model of Cardiopulmonary Resuscitation." Circulation 140, Suppl_2 (November 19, 2019). http://dx.doi.org/10.1161/circ.140.suppl_2.20.
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Introduction: A higher chest compression fraction (CCF) or percentage of time providing chest compressions is associated with improved survival after cardiac arrest (CA). Pauses in chest compression duration during cardiopulmonary resuscitation (CPR) to palpate a pulse can reduce the CCF. Peripheral Intravenous Analysis (PIVA) is a novel method for determining cardiac and volume status using waveforms from a standard peripheral intravenous (IV) line. We hypothesize that PIVA will demonstrate the onset of return of spontaneous circulation (ROSC) without interruption of CPR. Methods: Eight Zucker Diabetic Fatty (ZDF) rats (4 lean, 4 diabetic) were intubated, ventilated, and cannulated with a 24g IV in the tail vein and a 22g IV in the femoral artery, each connected to a TruWave pressure transducer. Mechanical ventilation was discontinued to achieve CA. After 8 minutes, CPR began with mechanical ventilation, IV epinephrine, and chest compressions using 1.5 cm at 200 times per minute until mean arterial pressure (MAP) increased to 120 mmHg per arterial line. All waveforms were recorded and analyzed in LabChart. PIVA was measured using a Fourier transform of the peripheral venous waveform. Data are mean ± SD. Statistics: Unpaired student’s t-test (two-tailed), α = 05. Results: CA and ROSC were achieved in all 8 rats. Within 1 minute of CPR, there was a 70 ± 35 fold increase/decrease in PIVA during CPR that was temporally associated with ROSC. Within 8 ± 13 seconds of a reduction in PIVA, there was a rapid increase in end-tidal CO 2 . In all rats, ROSC occurred within 38 ± 9 seconds of the maximum PIVA value. Peripheral venous pressure decreased by 1.2 ± 0.9 mmHg during resuscitation and ROSC, which was not significant different at p=0.05. Conclusion: In this pilot study, PIVA detected ROSC without interrupting CPR. Use of PIVA may obviate the need pause CPR for pulse checks, and may result in a higher CCF and survival. Future studies will focus on PIVA and CPR efficacy.
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Gaertner, Vincent D., Andreas D. Waldmann, Peter G. Davis, Dirk Bassler, Laila Springer, Jessica Thomson, David Gerald Tingay, and Christoph Martin Rüegger. "Lung volume distribution in preterm infants on non-invasive high-frequency ventilation." Archives of Disease in Childhood - Fetal and Neonatal Edition, January 31, 2022, fetalneonatal—2021–322990. http://dx.doi.org/10.1136/archdischild-2021-322990.
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IntroductionNon-invasive high-frequency oscillatory ventilation (nHFOV) is an extension of nasal continuous positive airway pressure (nCPAP) support in neonates. We aimed to compare global and regional distribution of lung volumes during nHFOV versus nCPAP.MethodsIn 30 preterm infants enrolled in a randomised crossover trial comparing nHFOV with nCPAP, electrical impedance tomography data were recorded in prone position. For each mode of respiratory support, four episodes of artefact-free tidal ventilation, each comprising 30 consecutive breaths, were extracted. Tidal volumes (VT) in 36 horizontal slices, indicators of ventilation homogeneity and end-expiratory lung impedance (EELI) for the whole lung and for four horizontal regions of interest (non-gravity-dependent to gravity-dependent; EELINGD, EELImidNGD, EELImidGD, EELIGD) were compared between nHFOV and nCPAP. Aeration homogeneity ratio (AHR) was determined by dividing aeration in non-gravity-dependent parts of the lung through gravity-dependent regions.Main resultsOverall, 228 recordings were analysed. Relative VT was greater in all but the six most gravity-dependent lung slices during nCPAP (all p<0.05). Indicators of ventilation homogeneity were similar between nHFOV and nCPAP (all p>0.05). Aeration was increased during nHFOV (mean difference (95% CI)=0.4 (0.2 to 0.6) arbitrary units per kilogram (AU/kg), p=0.013), mainly due to an increase in non-gravity-dependent regions of the lung (∆EELINGD=6.9 (0.0 to 13.8) AU/kg, p=0.028; ∆EELImidNGD=6.8 (1.2 to 12.4) AU/kg, p=0.009). Aeration was more homogeneous during nHFOV compared with nCPAP (mean difference (95% CI) in AHR=0.01 (0.00 to 0.02), p=0.0014).ConclusionAlthough regional ventilation was similar between nHFOV and nCPAP, end-expiratory lung volume was higher and aeration homogeneity was slightly improved during nHFOV. The aeration difference was greatest in non-gravity dependent regions, possibly due to the oscillatory pressure waveform. The clinical importance of these findings is still unclear.
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Albani, Filippo, Federica Fusina, Gianni Ciabatti, Luigi Pisani, Valeria Lippolis, Maria Elena Franceschetti, Alessia Giovannini, et al. "Flow Index accurately identifies breaths with low or high inspiratory effort during pressure support ventilation." Critical Care 25, no. 1 (December 2021). http://dx.doi.org/10.1186/s13054-021-03855-4.
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Abstract Background Flow Index, a numerical expression of the shape of the inspiratory flow-time waveform recorded during pressure support ventilation, is associated with patient inspiratory effort. The aim of this study was to assess the accuracy of Flow Index in detecting high or low inspiratory effort during pressure support ventilation and to establish cutoff values for the Flow index to identify these conditions. The secondary aim was to compare the performance of Flow index,of breathing pattern parameters and of airway occlusion pressure (P0.1) in detecting high or low inspiratory effort during pressure support ventilation. Methods Data from 24 subjects was included in the analysis, accounting for a total of 702 breaths. Breaths with high inspiratory effort were defined by a pressure developed by inspiratory muscles (Pmusc) greater than 10 cmH2O while breaths with low inspiratory effort were defined by a Pmusc lower than 5 cmH2O. The areas under the receiver operating characteristic curves of Flow Index and respiratory rate, tidal volume,respiratory rate over tidal volume and P0.1 were analyzed and compared to identify breaths with low or high inspiratory effort. Results Pmusc, P0.1, Pressure Time Product and Flow Index differed between breaths with high, low and intermediate inspiratory effort, while RR, RR/VT and VT/kg of IBW did not differ in a statistically significant way. A Flow index higher than 4.5 identified breaths with high inspiratory effort [AUC 0.89 (CI 95% 0.85–0.93)], a Flow Index lower than 2.6 identified breaths with low inspiratory effort [AUC 0.80 (CI 95% 0.76–0.83)]. Conclusions Flow Index is accurate in detecting high and low spontaneous inspiratory effort during pressure support ventilation.
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Nakayama, Ryuichi, Naofumi Bunya, Shinshu Katayama, Yuya Goto, Yusuke Iwamoto, Kenshiro Wada, Keishi Ogura, et al. "Correlation between the hysteresis of the pressure–volume curve and the recruitment-to-inflation ratio in patients with coronavirus disease 2019." Annals of Intensive Care 12, no. 1 (November 12, 2022). http://dx.doi.org/10.1186/s13613-022-01081-x.
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Abstract Background Since the response to lung recruitment varies greatly among patients receiving mechanical ventilation, lung recruitability should be assessed before recruitment maneuvers. The pressure–volume curve (PV curve) and recruitment-to-inflation ratio (R/I ratio) can be used bedside for evaluating lung recruitability and individualing positive end-expiratory pressure (PEEP). Lung tissue recruitment on computed tomography has been correlated with normalized maximal distance (NMD) of the quasi-static PV curve. NMD is the maximal distance between the inspiratory and expiratory limb of the PV curve normalized to the maximal volume. However, the relationship between the different parameters of hysteresis of the quasi-static PV curve and R/I ratio for recruitability is unknown. Methods We analyzed the data of 33 patients with severe coronavirus disease 2019 (COVID-19) who received invasive mechanical ventilation. Respiratory waveform data were collected from the ventilator using proprietary acquisition software. We examined the relationship of the R/I ratio, quasi-static PV curve items such as NMD, and respiratory system compliance (Crs). Results The median R/I ratio was 0.90 [interquartile range (IQR), 0.70–1.15] and median NMD was 41.0 [IQR, 37.1–44.1]. The NMD correlated significantly with the R/I ratio (rho = 0.74, P < 0.001). Sub-analysis showed that the NMD and R/I ratio did not correlate with Crs at lower PEEP (− 0.057, P = 0.75; and rho = 0.15, P = 0.41, respectively). On the contrary, the ratio of Crs at higher PEEP to Crs at lower PEEP (Crs ratio (higher/lower)) moderately correlated with NMD and R/I ratio (rho = 0.64, P < 0.001; and rho = 0.67, P < 0.001, respectively). Conclusions NMD of the quasi-static PV curve and R/I ratio for recruitability assessment are highly correlated. In addition, NMD and R/I ratio correlated with the Crs ratio (higher/lower). Therefore, NMD and R/I ratio could be potential indicators of recruitability that can be performed at the bedside.
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Wijshoff, Ralph, Jakob Van de Laar, Jens Muehlsteff, and Gerrit Jan Noordergraaf. "Abstract 267: Photoplethysmography-Based Algorithm Uninterruptedly Supports Pulse Detection in Porcine Automatic 30:2 Cardiopulmonary Resuscitation Data by Handling Transitions Between Compressions and Pauses." Circulation 138, Suppl_2 (November 6, 2018). http://dx.doi.org/10.1161/circ.138.suppl_2.267.
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Introduction: Pulse checks by manual palpation during CPR are challenging, time-consuming and interrupt chest compressions. To support pulse checks during 30:2 CPR, we developed an algorithm to uninterruptedly detect pulse in a photoplethysmography (PPG) signal by handling transitions between compressions and ventilation pauses. We retrospectively evaluated the algorithm on porcine automated-CPR (ACPR) data. Methods: In 10 anesthetised pigs, VF was induced, followed by 20 min of 30:2 ACPR with 2.5 s ventilation pauses (Phase 1). Next, up to four defibrillation attempts were made, each shock followed by 2 min of 30:2 ACPR (Phase 2). Infrared nasal PPG and thoracic impedance (TI) signals were measured, with aortic blood pressure (ABP) as reference. The developed algorithm detected pulse rate (PR) in the PPG signal, by estimating the main frequencies present in the signal and ignoring compression frequencies, where the compression rate (CR) was determined from the TI waveform. The PPG signal was analysed by sliding a 5 s window by 1 s shifts. When analysing a signal with an abrupt change due to the start/end of a compression series, frequency estimates will be compromised. Therefore, the algorithm identified the start/end of compressions in the TI signal and analysed in the 5 s window (1) a compression-free interval of at least 2 s or (2) a compression interval of at least 2.8 s. The window was ignored if no such interval was found. Pulse detection performance was quantified by comparison to pulse presence annotations determined from the protocol and visual inspection of ABP and PPG signals. Results: Table I gives sensitivity for pulse presence (SNV), specificity for arrest (SPC) and positive and negative predictive values (PPV/NPV). Conclusions: Overall, SPC, PPV and NPV are high. In Phase 2, SNV is reasonable in pauses, but compromised during compressions when PR and CR are close. In 30:2 CPR the algorithm can provide frequent detections from 2 s pauses. Table I: detection results.
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van der Ven, Ward H., Lotte E. Terwindt, Nurseda Risvanoglu, Evy L. K. Ie, Marije Wijnberge, Denise P. Veelo, Bart F. Geerts, Alexander P. J. Vlaar, and Björn J. P. van der Ster. "Performance of a machine-learning algorithm to predict hypotension in mechanically ventilated patients with COVID-19 admitted to the intensive care unit: a cohort study." Journal of Clinical Monitoring and Computing, November 13, 2021. http://dx.doi.org/10.1007/s10877-021-00778-x.
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AbstractThe Hypotension Prediction Index (HPI) is a commercially available machine-learning algorithm that provides warnings for impending hypotension, based on real-time arterial waveform analysis. The HPI was developed with arterial waveform data of surgical and intensive care unit (ICU) patients, but has never been externally validated in the latter group. In this study, we evaluated diagnostic ability of the HPI with invasively collected arterial blood pressure data in 41 patients with COVID-19 admitted to the ICU for mechanical ventilation. Predictive ability was evaluated at HPI thresholds from 0 to 100, at incremental intervals of 5. After exceeding the studied threshold, the next 20 min were screened for positive (mean arterial pressure (MAP) < 65 mmHg for at least 1 min) or negative (absence of MAP < 65 mmHg for at least 1 min) events. Subsequently, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and time to event were determined for every threshold. Almost all patients (93%) experienced at least one hypotensive event. Median number of events was 21 [7–54] and time spent in hypotension was 114 min [20–303]. The optimal threshold was 90, with a sensitivity of 0.91 (95% confidence interval 0.81–0.98), specificity of 0.87 (0.81–0.92), PPV of 0.69 (0.61–0.77), NPV of 0.99 (0.97–1.00), and median time to event of 3.93 min (3.72–4.15). Discrimination ability of the HPI was excellent, with an area under the curve of 0.95 (0.93–0.97). This validation study shows that the HPI correctly predicts hypotension in mechanically ventilated COVID-19 patients in the ICU, and provides a basis for future studies to assess whether hypotension can be reduced in ICU patients using this algorithm.
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Salcido, David D., Matthew L. Sundermann, Allison C. Koller, Rena Sufrin, John Kucewicz, Graham Nichol, Adeyinka Adedipe, and James J. Menegazzi. "Abstract 21301: Effect of Chest Compression Parameter Variation on Waveform Characteristics of the Ventricular Fibrillation Electrocardiogram." Circulation 136, suppl_1 (November 14, 2017). http://dx.doi.org/10.1161/circ.136.suppl_1.21301.
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Introduction: The ventricular fibrillation (VF) electrocardiogram (ECG) waveform is known to deteriorate over time if untreated, recover with CPR, and to predict defibrillation success. VF ECG measures could inform CPR quality feedback algorithms based on patient physiologic response. Objectives: Investigate the effects of chest compression parameters (rate, depth and duty cycle (DC)) on VF ECG waveform characteristics in a swine cardiac arrest model. Methods: Twelve mixed-breed domestic swine were sedated, anesthetized and paralyzed, followed by endotracheal intubation and mechanical ventilation. Animals were instrumented with a battery of physiological sensors, including multi-lead ECG, recorded continuously with a high-fidelity data acquisition unit at 1000Hz. VF was induced with a 3-second 100mA transthoracic shock. After 7 minutes, animals were randomized to receive continuous CPR with a custom robotic device using 1 of 6 pre-programmed, cross-over 2-phase CPR schemes that varied 1 parameter in 5 x 1-minute intervals per phase while holding the other 2 parameters fixed. Frequency (AMSA) and slope-based (MS) quantitative ECG characteristics of the ECG were calculated at the end of each 1-minute interval and compared between rate, depth and DC schemes, as well as experimental phases. Correlations between CPR parameter settings and ECG characteristics were calculated. Results: Compression rate showed a low-to-moderate correlation (0.454) with change in MS in Phase I, however neither DC nor depth showed a correlation with either AMSA or MS. In ANOVA models, MS differed between CPR groups at the end of Phase I (p = 0.046) but not AMSA, suggesting similar response of quantitative ECG measures after extended time intervals. Conclusions: In this study only chest compression rate in early phase CPR appeared to be related to quantitative characteristics of the VF ECG. Rate may be important clinically in the early phase of CPR.
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Zhang, Yanshan, Xiaojun Li, Yihe Zhang, Yancheng Ye, Yee-Min Jen, Xin Pan, Xiaowei Li, et al. "Non-invasive high frequency oscillatory ventilation inhibiting respiratory motion in healthy volunteers." Scientific Reports 12, no. 1 (December 30, 2022). http://dx.doi.org/10.1038/s41598-022-27288-3.
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AbstractPrecision radiotherapy needs to manage organ movements to prevent critical organ injury. The purpose of this study is to examine the feasibility of motion control of the lung by suppressing respiratory motion. The non-invasive high frequency oscillatory ventilation (NIHFOV) is a technique commonly used in the protection of lung for patients with acute lung disease. By using a very high respiratory frequency and a low tidal volume, NIHFOV allows gas exchange, maintains a constant mean airway pressure and minimizes the respiratory movements. We tested healthy volunteers NIHFOV to explore the optimal operational parameter setting and the best possible motion suppression achievable. This study was conducted with the approval of Institutional Review Boards of the Wuwei Cancer hospital (approval number: 2021-39) and carried out in accordance with Declaration of Helsinki. The study comprises two parts. Twenty three healthy volunteers participated in the first part of the study. They had 7 sessions of training with the NIHFOV. The duration of uninterrupted, continuous breathing under the NIHFOV and the optimal operational machine settings were defined. Eight healthy volunteers took part in the second part of the study and underwent 4-dimensional CT (4DCT) scanning with and without NIHFOV. Their respiratory waveform under free breathing (FB) and NIHFOV were recorded. The maximum range of motion of the diaphragm from the two scannings was compared, and the variation of bilateral lung volume was obtained to evaluate the impact of NIHFOV technique on lung volume. The following data were collected: comfort score, transcutaneous partial pressure of oxygen (PtcO2), transcutaneous partial pressure of carbon dioxide (PtcCO2), and pulse rate. Data with and without NIHFOV were compared to evaluate its safety, physiological impacts and effect of lung movement suppression. All the volunteers completed the training sessions eventlessly, demonstrating a good tolerability of the procedure. The median NIHFOV-on time was 32 min (22–45 min), and the maximum range of motion in the cephalic-caudal direction was significantly reduced on NIHFOV compared with FB (1.8 ± 0.8 cm vs 0.3 ± 0.1 cm, t = − 3.650, P = 0.003); the median range of motion was only 0.3 ± 0.1 cm on NIHFOV with a good reproducibility. The variation coefficient under NIHFOV of the right lung volume was 2.4% and the left lung volume was 9.2%. The PtcO2 and PtcCO2 were constantly monitored during NIHFOV. The medium PtcCO2 under NIHFOV increased lightly by 4.1 mmHg (interquartile range [IQR], 4–6 mmHg) compared with FB (t = 17.676, P < 0.001). No hypercapnia was found, PtcO2 increased significantly in all volunteers during NIHFOV (t = 25.453, P < 0.001). There was no significant difference in pulse rate between the two data sets (t = 1.257, P = 0.233). NIHFOV is easy to master in healthy volunteers to minimize respiratory movement with good tolerability and reproducibility. It is a feasible approach for lung motion control and could potentially be applied in accurate radiotherapy including carbon-ion radiotherapy through suppression of respiratory movement.
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Nagraj, V. Peter, Douglas E. Lake, Louise Kuhn, J. Randall Moorman, and Karen D. Fairchild. "Central Apnea of Prematurity: Does Sex Matter?" American Journal of Perinatology, June 18, 2020. http://dx.doi.org/10.1055/s-0040-1713405.
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Objective Apnea is common among infants in the neonatal intensive care unit (NICU). Our group previously developed an automated algorithm to quantitate central apneas with associated bradycardia and desaturation (ABDs). Sex differences in lung disease are well described in preterm infants, but the influence of sex on apnea has not been established. Study Design This study includes infants < 34 weeks' gestation admitted to the University of Virginia NICU from 2009 to 2014 with at least 1 day of bedside monitor data available when not on mechanical ventilation. Waveform and vital sign data were analyzed using a validated algorithm to detect ABD events of low variance in chest impedance signal lasting at least 10 seconds with associated drop in heart rate to < 100 beats/minute and drop in oxygen saturation to < 80%. Male and female infants were compared for prevalence of at least one ABD event during the NICU stay, treatment with caffeine, occurrence of ABDs at each week of postmenstrual age, and number of events per day. Results Of 926 infants studied (median gestational age 30 weeks, 53% male), median days of data analyzed were 19 and 22 for males and females, respectively. There was no sex difference in prevalence of at least one ABD event during the NICU stay (males 62%, females 64%, p = 0.47) or in the percentage of infants treated with caffeine (males 64%, females 67%, p = 0.40). Cumulative prevalence of ABDs from postmenstrual ages 24 to 36 weeks was comparable between sexes. Males had 18% more ABDs per day of data, but this difference was not statistically significant (p = 0.16). Conclusion In this large cohort of infants < 34 weeks' gestation, we did not detect a sex difference in prevalence of central ABD events. There was a nonsignificant trend toward a greater number of ABDs per day in male infants. Key Points
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van Diepen, A., T. H. G. F. Bakkes, A. J. R. De Bie, S. Turco, R. A. Bouwman, P. H. Woerlee, and M. Mischi. "A model-based approach to generating annotated pressure support waveforms." Journal of Clinical Monitoring and Computing, February 10, 2022. http://dx.doi.org/10.1007/s10877-022-00822-4.
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AbstractLarge numbers of asynchronies during pressure support ventilation cause discomfort and higher work of breathing in the patient, and are associated with an increased mortality. There is a need for real-time decision support to detect asynchronies and assist the clinician towards lung-protective ventilation. Machine learning techniques have been proposed to detect asynchronies, but they require large datasets with sufficient data diversity, sample size, and quality for training purposes. In this work, we propose a method for generating a large, realistic and labeled, synthetic dataset for training and validating machine learning algorithms to detect a wide variety of asynchrony types. We take a model-based approach in which we adapt a non-linear lung-airway model for use in a diverse patient group and add a first-order ventilator model to generate labeled pressure, flow, and volume waveforms of pressure support ventilation. The model was able to reproduce basic measured lung mechanics parameters. Experienced clinicians were not able to differentiate between the simulated waveforms and clinical data (P = 0.44 by Fisher’s exact test). The detection performance of the machine learning trained on clinical data gave an overall comparable true positive rate on clinical data and on simulated data (an overall true positive rate of 94.3% and positive predictive value of 93.5% on simulated data and a true positive rate of 98% and positive predictive value of 98% on clinical data). Our findings demonstrate that it is possible to generate labeled pressure and flow waveforms with different types of asynchronies.
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Letellier, Christophe, Manel Lujan, Jean-Michel Arnal, Annalisa Carlucci, Michelle Chatwin, Begum Ergan, Mike Kampelmacher, et al. "Patient-Ventilator Synchronization During Non-invasive Ventilation: A Pilot Study of an Automated Analysis System." Frontiers in Medical Technology 3 (July 7, 2021). http://dx.doi.org/10.3389/fmedt.2021.690442.
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Background: Patient-ventilator synchronization during non-invasive ventilation (NIV) can be assessed by visual inspection of flow and pressure waveforms but it remains time consuming and there is a large inter-rater variability, even among expert physicians. SyncSmart™ software developed by Breas Medical (Mölnycke, Sweden) provides an automatic detection and scoring of patient-ventilator asynchrony to help physicians in their daily clinical practice. This study was designed to assess performance of the automatic scoring by the SyncSmart software using expert clinicians as a reference in patient with chronic respiratory failure receiving NIV.Methods: From nine patients, 20 min data sets were analyzed automatically by SyncSmart software and reviewed by nine expert physicians who were asked to score auto-triggering (AT), double-triggering (DT), and ineffective efforts (IE). The study procedure was similar to the one commonly used for validating the automatic sleep scoring technique. For each patient, the asynchrony index was computed by automatic scoring and each expert, respectively. Considering successively each expert scoring as a reference, sensitivity, specificity, positive predictive value (PPV), κ-coefficients, and agreement were calculated.Results: The asynchrony index assessed by SynSmart was not significantly different from the one assessed by the experts (18.9 ± 17.7 vs. 12.8 ± 9.4, p = 0.19). When compared to an expert, the sensitivity and specificity provided by SyncSmart for DT, AT, and IE were significantly greater than those provided by an expert when compared to another expert.Conclusions:SyncSmart software is able to score asynchrony events within the inter-rater variability. When the breathing frequency is not too high (<24), it therefore provides a reliable assessment of patient-ventilator asynchrony; AT is over detected otherwise.
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Zhou, Cong, J. Geoffrey Chase, Qianhui Sun, Jennifer Knopp, Merryn H. Tawhai, Thomas Desaive, Knut Möller, Geoffrey M. Shaw, Yeong Shiong Chiew, and Balazs Benyo. "Reconstructing asynchrony for mechanical ventilation using a hysteresis loop virtual patient model." BioMedical Engineering OnLine 21, no. 1 (March 7, 2022). http://dx.doi.org/10.1186/s12938-022-00986-9.
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Abstract Background Patient-specific lung mechanics during mechanical ventilation (MV) can be identified from measured waveforms of fully ventilated, sedated patients. However, asynchrony due to spontaneous breathing (SB) effort can be common, altering these waveforms and reducing the accuracy of identified, model-based, and patient-specific lung mechanics. Methods Changes in patient-specific lung elastance over a pressure–volume (PV) loop, identified using hysteresis loop analysis (HLA), are used to detect the occurrence of asynchrony and identify its type and pattern. The identified HLA parameters are then combined with a nonlinear mechanics hysteresis loop model (HLM) to extract and reconstruct ventilated waveforms unaffected by asynchronous breaths. Asynchrony magnitude can then be quantified using an energy-dissipation metric, Easyn, comparing PV loop area between model-reconstructed and original, altered asynchronous breathing cycles. Performance is evaluated using both test-lung experimental data with a known ground truth and clinical data from four patients with varying levels of asynchrony. Results Root mean square errors for reconstructed PV loops are within 5% for test-lung experimental data, and 10% for over 90% of clinical data. Easyn clearly matches known asynchrony magnitude for experimental data with RMS errors < 4.1%. Clinical data performance shows 57% breaths having Easyn > 50% for Patient 1 and 13% for Patient 2. Patient 3 only presents 20% breaths with Easyn > 10%. Patient 4 has Easyn = 0 for 96% breaths showing accuracy in a case without asynchrony. Conclusions Experimental test-lung validation demonstrates the method’s reconstruction accuracy and generality in controlled scenarios. Clinical validation matches direct observations of asynchrony in incidence and quantifies magnitude, including cases without asynchrony, validating its robustness and potential efficacy as a clinical real-time asynchrony monitoring tool.
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Ge, Huiqing, Qing Pan, Yong Zhou, Peifeng Xu, Lingwei Zhang, Junli Zhang, Jun Yi, et al. "Lung Mechanics of Mechanically Ventilated Patients With COVID-19: Analytics With High-Granularity Ventilator Waveform Data." Frontiers in Medicine 7 (August 21, 2020). http://dx.doi.org/10.3389/fmed.2020.00541.
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Gao, Mengqi, Chenguang Liu, Stacy Gehman, Thomas Rea, Jennifer E. Blackwood, Jonathan R. Studnek, Steven Vandeventer, Allison E. Infinger, Patricia L. Dowbiggin, and Dawn Jorgenson. "Abstract 296: Quality Analysis of Cardiopulmonary Resuscitation From Two Emergency Medical Service Systems Using a Feedback Device." Circulation 140, Suppl_2 (November 19, 2019). http://dx.doi.org/10.1161/circ.140.suppl_2.296.
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Background: High quality cardiopulmonary resuscitation (CPR) plays a critical role in the success of out-of-hospital resuscitation from sudden cardiac arrest (SCA). AHA guidelines provide protocol to achieve recommended targets for CPR quality metrics including chest compression fraction (CCF), percentage of chest compressions (CCs) with full chest recoil, CC rate and CC depth. Our objective was to report the CPR quality of two emergency medical services (EMS) agencies with different basic life support (BLS) CPR protocols. Methods: Data from 673 patients, 2015 to 2017, suffering out-of-hospital SCA were obtained from Philips FR3 AEDs. The Philips Q-CPR tool was used for real-time CPR feedback, and CC waveforms were recorded for retrospective CPR analysis using Philips Event Review Pro 5.0 and custom software. The two EMS systems had BLS protocol differences: Site 1(King County, WA, n = 93) applied a compression - ventilation ratio of 30:2, while Site 2 (Mecklenburg County, NC, n = 580) applied 200 compressions in each CPR interval and ventilations were performed during CCs. Analyses were performed comparing CPR metrics between sites and to AHA targets. Results: There were 3,460 minutes of resuscitation data analyzed, representing the initial phase of resuscitation prior to ALS. The proportion of cases with shocks was 21.5% (20 of 93) for site 1 and 16.9% (98 of 580) for site 2 (p = 0.3). Both sites achieved guideline metrics though there were statistical differences (Table 1). Compared to site 1, site 2 was associated with a higher CCF, faster CC rate, but less CC depth on average (p < 0.001). Conclusions: High quality CPR defined by AHA guidelines was achieved with both sites during the early phase of AED resuscitation though some differences were observed. Additional investigation should identify equipment, or rescuer characteristics that are important to consistently achieve high quality CPR and how the combination might be tailored to optimize individual patient outcome.
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Gaertner, Vincent D., Christoph Martin Rüegger, Dirk Bassler, Eoin O'Currain, C. Omar Farouk Kamlin, Stuart B. Hooper, Peter G. Davis, and Laila Springer. "Effects of tactile stimulation on spontaneous breathing during face mask ventilation." Archives of Disease in Childhood - Fetal and Neonatal Edition, December 3, 2021, fetalneonatal—2021–322989. http://dx.doi.org/10.1136/archdischild-2021-322989.
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ObjectiveWe sought to determine the effect of stimulation during positive pressure ventilation (PPV) on the number of spontaneous breaths, exhaled tidal volume (VTe), mask leak and obstruction.DesignSecondary analysis of a prospective, randomised trial comparing two face masks.SettingSingle-centre delivery room study.PatientsNewborn infants ≥34 weeks’ gestation at birth.MethodsResuscitations were video recorded. Tactile stimulations during PPV were noted and the timing, duration and surface area of applied stimulus were recorded. Respiratory flow waveforms were evaluated to determine the number of spontaneous breaths, VTe, leak and obstruction. Variables were recorded throughout each tactile stimulation episode and compared with those recorded in the same time period immediately before stimulation.ResultsTwenty of 40 infants received tactile stimulation during PPV and we recorded 57 stimulations during PPV. During stimulation, the number of spontaneous breaths increased (median difference (IQR): 1 breath (0–3); padj<0.001) and VTe increased (0.5 mL/kg (−0.5 to 1.7), padj=0.028), whereas mask leak (0% (−20 to 1), padj=0.12) and percentage of obstructed inflations (0% (0–0), padj=0.14) did not change, compared with the period immediately prior to stimulation. Increased duration of stimulation (padj<0.001) and surface area of applied stimulus (padj=0.026) were associated with a larger increase in spontaneous breaths in response to tactile stimulation.ConclusionsTactile stimulation during PPV was associated with an increase in the number of spontaneous breaths compared with immediately before stimulation without a change in mask leak and obstruction. These data inform the discussion on continuing stimulation during PPV in term infants.Trial registration numberAustralian and New Zealand Clinical Trial Registry (ACTRN12616000768493).