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1
Wijesinghe, Meme. "Oxygen therapy in respiratory disorders". Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/2511.
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Oxygen therapy remains a cornerstone of medical practice and is generally regarded as being safe. However, there is a lack of clinical evidence to support the routine use of oxygen therapy, and in certain conditions, injudicious oxygen may cause harm. In this thesis, I will present two audits and three randomised controlled trials of oxygen therapy. Methods A prospective audit of the prescription and use of oxygen therapy before and after the introduction of an oxygen prescription section on a drug chart A retrospective audit of ambulance oxygen administration, in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) Two randomised controlled trials of high flow versus titrated oxygen in 150 patients with community acquired pneumonia and 106 patients with acute severe asthma A randomised controlled trial of 24 subjects with obesity hypoventilation syndrome (OHS) comparing 100% oxygen with air Results Oxygen prescription is suboptimal in hospital inpatients. Whilst an oxygen prescription section improved prescription, this intervention did not improve clinical practice Over 70% of patients presenting with AECOPD received high flow oxygen prior to presentation to the emergency department. The risk of adverse outcomes increased progressively with increased PaO2 High concentration oxygen leads to a rise in PaCO2 compared to titrated oxygen, when administered to patients presenting with asthma or pneumonia Breathing 100% oxygen leads to a rise in PaCO2 in patients with OHS Conclusion This series of studies has shown that further measures are warranted to ensure the safe practice of oxygen therapy in the pre-hospital and hospital setting. In addition, the findings suggest that the potential for high concentration oxygen therapy to increase PaCO2 is not limited to COPD but may occur in other respiratory conditions in which abnormal gas exchange or respiratory drive are present.
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Maia, Mariana Cervaens Costa. "Hyperbaric oxygen therapy in sports medicine". Doctoral thesis, [s.n.], 2013. http://hdl.handle.net/10284/4224.
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Doutoramento em Biotecnologia e Saúde, especialidade em Epidemiologia e Saúde PúblicaAs lesões desportivas são um grande problema no que diz respeito à sua rápida reabilitação. Inúmeros estudos tentam encontrar a técnica mais rápida capaz de acelerar o processo da recuperação. A oxigenoterapia hiperbárica (OTH) é a aplicação de 100% de oxigénio numa câmara hiperbárica a pressões mais elevadas do que o nível do mar. A inalação de OTH comporta-se como um fármaco multifacetado dotado de efeitos anti-isquémicos, anti-hipóxicos, anti-edematosos, pós-lesão e anti-infecciosos. Portanto, o objetivo desta tese foi analisar a influência da OTH na recuperação de lesões desportivas, como contusão muscular e do ligamento cruzado anterior (LCA) pós ruptura. Em primeiro lugar, verificou-se se a aplicação de OTH melhorou as propriedades biomecânicas, tais como rigidez, alongamento máximo e peso máximo, dos gastrocnémios de ratos após induzir contusão muscular. Em segundo lugar, era de nosso interesse analisar, após de se ter induzido uma contusão muscular nos gastrocnémios dos ratos, a influência da OTH na bioenergética mitocondrial avaliada através do consumo de oxigénio e potencial transmembranar e susceptibilidade à indução do poro de transição de permeabilidade mitocondrial, em mitocôndrias isoladas. Finalmente, no último trabalho experimental, tentou-se verificar se a aplicação de OTH tem a capacidade de melhorar a neovascularização, por meio da análise do factor de crescimento do endotélio vascular (VEGF), bem como analisar a proliferação e a produção de proteína, em coelhos com ruptura do LCA. A OTH parece desempenhar um papel importante na recuperação de lesões musculares, mais especificamente, na contusão muscular em ratos, melhorando as propriedades biomecânicas musculares, tais como a rigidez e peso máximo e na bioenergética mitocondrial, onde o tempo até que o inchaço na mitocôndria iniciasse em grande escala foi menor no grupo submetido a OTH, assim como a amplitude de inchaço foi maior, o que atrasou a apoptose mitocondrial. Contudo, em relação à ruptura do LCA, a OTH promoveu a neovascularização, activando VEGF, mas no entanto, contribuindo para o aumento da espessura da cápsula. VII Palavras-chave: Oxigenoterapia hiperbárica, gastrocnémios, contusão muscular, propriedades biomecânicas, bioenergética mitocondrial, ligamento cruzado anterior, neovascularização, colagénio tipo I. Sports injuries is a major problem what concerns to its rapid rehabilitation. There is innumerous attempting to find the faster technique to apply to the injured ones to accelerate its recovery. Hyperbaric oxygen therapy (HBO) is the application of 100% oxygen in a hyperbaric chamber at pressures higher than sea level. The inhalation of HBO has already shown that behaves like a multifaceted drug endowed with anti-ischemic, anti-hypoxic, anti-edematous, pro-healing and anti-infective effects. Therefore, the objective of this thesis was to analyze the influence of HBO in the recovery from sports injuries such as muscle contusion and anterior cruciate ligament (ACL) rupture. Firstly, it was verified if HBO improved the biomechanical properties, such as hardness, maximum elongation and maximum weight, of rats’ gastrocnemius after inducing muscle contusion. Secondly, it was of our interest to analyze skeletal muscle mitochondrial energetic of rats’ gastrocnemius after induced muscle contusion, by determining end points related to oxygen consumption, transmembrane electric potential and permeability transition pore susceptibility in isolated mitochondria. At last, our last experimental work aimed to verify if HBO has the ability to improve neovascularization, through the analysis of vascular endothelial growth factor (VEGF) as well the proliferation and protein production, of rabbit ruptured ACL. HBO seems to play an important role in the recovery of muscle injuries, more specifically, muscle contusion in rats, by improving muscle biomechanical properties, such as hardness and maximum weight and in mitochondria energetic, where the time until large scale swelling initiates in mitochondria was lower in HBO and the swelling amplitude was higher, which delayed mitochondria apoptosis. However, concerning to ACL rupture, HBO increased neovascularization by activating VEGF, contributing for the increasing of capsule thickness. Les lésions sportives sont un grand problème en ce qui concerne la rapidité de sa réhabilitation. De nombreux études essayent de trouver la plus rapide et moins douloureuse technique capable d’accélérer le processus de récupération. L’oxygénothérapie hyperbare (OHB) consiste à l’inhalation de 100% d’oxygène dans un caisson étanche avec une pression plus élevée que celui de la mer. Il a été démontré que l’inhalation de l’OHB se comporte comme une drogue à multiple facette, qui permet d'agir sur l'ischémie tissulaire qu'elle qu'en soit la cause : vasculaire, traumatique, toxique, ou infectieuse. Pourtant, l’objectif de cette étude a été d’analyser l’influence de l’OHB dans la récupération des lésions sportifs, l’ecchymose du ligament croisé antérieur post rupture. Dans un premier temps, on a vérifié si l’utilisation de l’OHB améliore les propriétés biomécaniques, comme la rigidité, l’étirement maximum et le poids maximum, des Gastrocnémiens chez les rats après induire une ecchymose. Deuxièmement, cela été dans notre intérêts d’analyser, après induire une ecchymose des Gastrocnémiens chez les rats, l’influence du OBH dans la bioénergétique mitochondriale, évalué à travers la consommation d’oxygène, le potentiel transmembranaire et la susceptibilité d’induction du pore de transition de perméabilité mitochondrial, des mitochondries isolés. Pour finir, lors du dernier travail expérimental, nous avons essayé de vérifier si l’application de l’OHB a la capacité d’amélioré la néo vascularisation, en analysant le facteur de croissance de l’endothélium vasculaire (en anglais Vascular endothelial growth factor, VEGF), en analysant aussi la prolifération et la production de protéine, sur des lapins avec rupture du LCA. L’OHB semble avoir un rôle important dans la récupération des lésions musculaires, plus précisément sur l’ecchymose chez les rats, améliorant ainsi les propriétés biomécaniques musculaires, comme la rigidité, le poids maximum et la bioénergétique mitochondriale. Le temps pour que l’oedème dans la mitochondrie arrive à grande échelle a été plus faible dans le groupe soumis à l’OHB, comme l’amplitude de l’oedème fut plus grand, ce qui a retardé XI l’apoptose mitochondrial. Toutefois, en ce qui concerne la rupture du LCA, l’OHB a promu la néo vascularisation, activant le VEGF, contribuant à une capsule épaisse.
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Kunin, Wendy. "Hyperbaric oxygen therapy following arthroscopic meniscectomy surgery". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80308.
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This study investigated the effects of hyperbaric oxygen (HBO2) therapy following partial arthroscopic meniscectomy surgery on swelling, perceived pain, range of motion at the knee joint, isokinetic strength, and leg function. Subjects were 8 males and 1 female with an acute tear to the meniscus. Subjects were randomly assigned to either a control group (n = 5) or an HBO2 treatment group (n = 5). The HBO 2 group received 5 HBO2 treatments at 2.5 ATA for 90 minutes at 95% O2 beginning 24 hours post-operation. Both groups were tested pre-operation (day 0) and on days 1, 2, 3, 4, 5, 20, 35, and 50 post-surgery. No significant difference was found between groups for any of the dependant variables. The results indicated that the control and HBO2 groups responded in a similar pattern when assessed for swelling, perceived pain, range of motion at the knee joint, leg function and isokinetic strength.
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Iobbi, Mario Gabriel. "Saturation driven flow controller for oxygen therapy". Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/43396.
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Despite receiving oxygen therapy, many COPD patients experience extended periods of hypoxemia during routine daily activities. In others, inappropriately high oxygen flow rates can depress hypoxic drive leading to worsening CO2 retention. As flow-rates during LTOT are fixed, oxygen delivery will not respond to patients' fluctuations in oxygen demand. The research project has aimed to develop and evaluate a closed-loop control method capable of actively varying flow-rates in response to the measured oxygen demand. We demonstrate how SpO2 from ambulatory or overnight pulse oximetry can be used as feedback into an automated O2 flow-rate controller. A model to mimic the patient oxygen saturation response has been developed in a computer simulation to help characterize the closed-loop system. With the collaboration of the Academic Unit for Sleep and Breathing at the Royal Brompton Hospital, the controller response has also been validated against patient saturation measurements recorded during overnight pulse oximetry monitoring. Preclinical computer simulations indicated an improved matching between oxygen supply and demand, maintaining SpO2 above threshold to maximize therapeutic efficacy. An investigational system capable of regulating the Saturation Driven Oxygen Therapy (SDOT) was constructed. In a randomised cross-over clinical pilot study, we further evaluated the SDOT system against constant-flow LTOT during exercise. The clinical results indicate that compared to standard oxygen therapy, SDOT produced a significant reduction in time spent with hypoxemia, decreased the extent of hypoxemia and lowered mean heart rates during exercise. Moreover, for patients with acceptable resting oxygen levels, SDOT provided conservation benefits by reducing the rate of oxygen consumption. The study established the potential to significantly improve the efficacy and economic delivery of this gold standard therapy.
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Hodge, Rachel Elizabeth. "Coping During Hyperbaric Oxygen Therapy: Predictors and Intervention". Thesis, University of Canterbury. Psychology, 2008. http://hdl.handle.net/10092/2167.
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The present research sought to understand patient experiences during Hyperbaric Oxygen Therapy (HBOT) by using 24 HBOT patients (17 men, 7 women) to examine the relationship between individual variables and anxiety, and providing One Session Exposure Therapy (OSET; Öst, 1989) if necessary. Pre-HBOT participants completed the following measures: State-Trait Anxiety Inventory (STAI; Spielberger, 1983), Claustrophobia Questionnaire (CLQ; Radomsky, Rachman, Thordarson, McIsaac, & Teachman, 2001), Anxiety Sensitivity Index (ASI; Reiss, Peterson, Gursky, & McNally, 1986), and Treatment Credibility/Expectancy Questionnaire (CEQ; Devilly & Borkovec, 2000). State Anxiety was assessed pre-HBOT and at the tenth and last sessions. Findings suggest Dispositional Anxiety (STAI-Trait + ASI), Expectancy of symptom improvement (CEQ), and gender were significantly predictive of State Anxiety before and during HBOT. Limitations and directions for future research are discussed.
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Perrin, Kyle Gareth. "High concentration oxygen therapy in acute respiratory disease". Thesis, University of Canterbury. Health Sciences Centre, 2010. http://hdl.handle.net/10092/5079.
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Uncontrolled oxygen is often administered to breathless patients regardless of whether hypoxaemia is present. In acute exacerbations of Chronic Obstructive Pulmonary Disease (AECOPD) this may result in carbon dioxide (CO2) retention and worsening respiratory failure in some patients. In AECOPD the main mechanism is the release of hypoxic pulmonary vasoconstriction and an increase in the physiological dead space to tidal volume ratio (VD/VT). Acute asthma and pneumonia have features in common with AECOPD, namely significant ventilation – perfusion mismatch; and there is the potential for CO2 retention to occur if uncontrolled high concentration oxygen is given. There have been no randomised controlled trials of oxygen therapy in pneumonia and only one in asthma. The potential mechanisms of any change in arterial CO2 that may occur with oxygen therapy in respiratory disorders other than COPD remain uncertain.
This thesis presents work from three clinical studies. In two randomised controlled trials, high concentration oxygen was compared to titrated oxygen therapy in patients with either acute severe asthma and suspected community acquired pneumonia. Oxygen was administered for one hour in conjunction with standard medical treatment. Transcutaneous CO2 (PtCO2) was continuously monitored and the number of patients with pre-specified increases in PtCO2 were calculated. The proportion of patients with a rise in PtCO2 4 mmHg was significantly higher in the high concentration oxygen groups of both studies. In the pneumonia study 36/72 (50.0%) vs 11/75 (14.7%) met this endpoint, with a relative risk of 3.4 (95% CI 1.9 to 6.2; P <0.001), and in the asthma study 22/50 (44%) vs 10/53 (18.9%) met this endpoint, with a relative risk of 2.3 (95% CI 1.2 to 4.3; P=0.009). Similarly, a rise in PtCO2 8 mmHg was more common with high concentration oxygen. In the pneumonia study 11/72 (15.3%) vs 2/75 (2.7%) of patients met this endpoint, with a relative risk of 5.7 (95% CI 1.3 to 25.0; P=0.007), and 10/50 (20%) vs 3/53 (5.7%) of asthma patients met this endpoint, with a relative risk of 3.6 (95% CI 1.1 to 12.3; P=0.03). A third study measured the physiological response to 20 minutes of 100% oxygen in chronic severe asthma, with comparison to a group of negative controls (normal subjects) and positive controls (COPD patients). There was a significant rise in PtCO2 of similar magnitude in the asthma and COPD groups compared with the normal controls. The mechanism of the PtCO2 rise was similar in asthma and COPD, with an increase in VD/VT but no change in minute ventilation.
These studies demonstrate than uncontrolled high concentration oxygen has the potential to cause CO2 retention in respiratory diseases other than COPD, and that in asthma the mechanism of hypercapnia is similar to that in AECOPD. In acute asthma and community-acquired pneumonia oxygen should be administered only to those patients with evidence of arterial hypoxaemia in a dose that relieves hypoxaemia without causing hyperoxia, thereby achieving the benefits of oxygen therapy while reducing the potential for harm.
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Morozoff, Edmund Pavel. "Modelling and fuzzy logic control of neonatal oxygen therapy". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq24210.pdf.
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Ruiz, González Rubén. "New strategies in antimicrobial photodynamic therapy and singlet oxygen detection". Doctoral thesis, Universitat Ramon Llull, 2013. http://hdl.handle.net/10803/119556.
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Tres estratègies adreçades a aportar una major perspectiva en el camp de la teràpia fotodinámica antimicrobiana comprenen la primera part de la tesi. En una primera aproximació, sis fotosensibilitzadors catiònics, amb diferent càrrega elèctrica neta i estructura, han estat caracteritzats en dissolució i les seves propietats fotoinactivadores provades contra diferents tipus de microorganismes. En una segona aproximació, conjugats entre un fotosensibilitzador i el pèptid antimicrobià Apidaecina 1b han estat analitzats fotofísica i mecanísticament, i les seves propietats correlacionades amb la seva habilitat fotosensibilitzadora en bacteris. En l'última aproximació, dues proteïnes fluorescents –TagRFP i miniSOG- han estat expressades en E. coli i s'ha estudiat la seva fototoxicitat així com el seu mecanisme d'acció. A més, s'ha reevaluat i estudiat en detall la capacitat de miniSOG per fotosensibilitzar la formació d'oxigen singlet.
En la segona part de la tesi, l'interès s'ha centrat en la detecció d'oxigen singlet. En la primera secció, s'ha avaluat la capacitat de detecció en dissolució d'una nova díada composta per un naftoxazol i una trampa química d'oxigen singlet. En l'última secció, es desenvolupa, prova i discuteix la viabilitat de nanopartícules de poliacrilamida com a plataforma potencial per a la detecció d'oxigen singlet en sistemes intracel•lulars.Tres estrategias destinadas a aportar una mayor perspectiva en el campo de la terapia fotodinámica antimicrobiana componen la primera parte de la tesis. En una primera aproximación, seis fotosensibilizadores catiónicos, con distinta carga eléctrica neta y estructura, han sido caracterizados en disolución y sus propiedades fotoinactivadoras probadas contra diferentes tipos de microorganismos. En una segunda aproximación, conjugados entre un fotosensibilizador y el péptido antimicrobiano Apidaecina 1b han sido analizados fotofísica y mecanísticamente, y sus propiedades correlacionadas con su habilidad fotosensibilizadora en bacterias. En la última aproximación, dos proteínas fluorescentes –TagRFP y miniSOG- han sido expresadas en E. coli y se ha estudiado su fototoxicidad así como su mecanismo de acción. Además, se ha reevaluado y estudiado en detalle la capacidad de miniSOG para fotosensibilizar la formación de oxígeno singlete. En la segunda parte de la tesis, el interés se ha centrado en la detección de oxígeno singlete. En la primera sección, se ha evaluado la capacidad de detección en disolución de una nueva díada compuesta por un naftoxazol y una trampa química de oxígeno singlete. En la última sección, se desarrolla, prueba y discute la viabilidad de nanopartículas de poliacrilamida como plataforma potencial para detección de oxígeno singlete en sistemas intracelulares.
Three strategies addressed to give further scope on to the antimicrobial photodynamic therapy field comprise the first part of the thesis. In a first approach, six cationic photosensitisers varying in the net electrical charge and structure have been characterised in solution and their photoinactivation skills have been tested against different types of microorganisms. In a second approach, conjugates between a photosensitiser and the antimicrobial peptide Apidaecin 1b have been analysed in a photophysical and mechanistic way, and their properties have been correlated with their bacterial photoinactivation ability. In the last approach, two fluorescent proteins –namely TagRFP and miniSOG- have been expressed in E. coli and their phototoxicity has been studied and characterised mechanistically. Moreover, the capacity of miniSOG to photosensitise singlet oxygen formation has been revisited and studied in detail. In the second part of the thesis, focus has been shifted towards singlet oxygen detection. In the first section, the probing ability of a new dyad comprising a naphthoxazole moiety plus a singlet oxygen chemical trap has been evaluated in solution. In the last section, we develop, test, and discuss the feasibility of a polyacrylamide nanoparticle scaffold as a potential platform for singlet oxygen detection in intracellular systems.
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Vudiniabola, Sunia. "Hyperbaric oxygen therapy for the treatment and prevention of osteoradionecrosis /". Title page, contents and summary only, 1997. http://web4.library.adelaide.edu.au/theses/09DM/09dmv986.pdf.
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Germain, Geneviève. "Effect of hyperbaric oxygen therapy on exercise-induced muscle injury". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29504.
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The purpose of this study was to examine the effects of HBO2 therapy on exercise-induced muscle damage. Subjects (n = 16 university student volunteers) were randomly divided into an experimental group that received HBO2 therapy and a control group that did not receive any treatments. HBO2 treatments consisted of 5 sessions of breathing 95% oxygen at 2.5 atm abs for 100 min. Temporary muscle soreness was created using a single-leg eccentric exercise task involving the quadriceps femoris. Over the next 14 days, measurements were obtained on muscle soreness, leg circumference, quadriceps peak torque, quadriceps average power, fatigue and plasma creative kinase. After eccentric exercise, plasma CK levels and perceived muscle soreness were elevated but were not different between HBO2 and control groups. HBO2 therapy did not alter leg circumference, quadriceps peak torque, average power or fatigue compared to the control group. The data indicated that five HBO2 treatments did not speed recovery following eccentric exercise that induced temporary muscle damage.
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Skelton, Deborah. "The effects of hyperbaric oxygen therapy on acute ankle sprains /". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31140.
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This study investigated the effects of hyperbaric oxygen (HBO) therapy on acute ankle injuries and determined if HBO therapy shortened time to recovery, decreased edema and pain, and increased range of motion and strength of the ankle. Subjects were randomly assigned to either an experimental (HBO) group (n = 4) or a control group (n = 4). All subjects received the same standardized physical therapy for lateral ankle sprains at the McGill Sport Medicine Clinic. The HBO group received 5 consecutive HBO treatments at 2.5 ATA for 90 minutes starting within 24 hours post injury. The control group received no HBO treatments. All subjects were evaluated by a physician within 24 hours of injury. All subjects suffered a second-degree lateral ankle sprain. Pain, range of motion, strength, volume displacement, and function were evaluated on the day of injury (Day 1), on Day 6 post injury, and on the day of return to play (Day RTP). There was no significant difference in time to return to play. However, the HBO group (25.5 +/- 11.6 days) did return 31% faster than the control group (36.8 +/- 19.4 days). There were no differences found between groups on the variables. There was a decrease in pain found over time (Day 1 was 57 mm, Day 6 was 18.5 mm, and Day RTP was 7 mm). The results of this study suggest that with treatment of HBO there is no effect on ankle sprains for return to play or improved function.
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Cashman, Lauren E. "Oxygen Therapy in Malawi: Revising Oxygen Concentrator Filtration and Use for Improved function in Low-Resource Hospitals". Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/79132.
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The quality of healthcare in low-resource countries is often limited by the environment, lack of funds, staff availability, electricity availability, and more. In the words of a Malawian physician, medicine can feel like improvisation, wherein one must make due with available resources rather than desired resources. One prevalent problem among low-resource hospitals is the functionality and longevity of medical equipment. A large percentage of all medical equipment in Malawian hospitals is donated, resulting in a wide spectrum of models, necessary spare parts, and functionality. These machines can break quickly due to heavy use prior to donation, missing user and maintenance manuals, and a lack of replacement parts. Thus, finding necessary life-saving equipment in Malawian hospital wards can be a challenge. One such piece of equipment is the oxygen concentrator, necessary for treatment of respiratory disease, use with CPAP machines, and in the administration of surgical anesthesia. This device fills many roles in low-resource hospitals, but in many Malawian hospitals it is the most frequently malfunctioning piece of equipment.
A survey administered to medical personnel and maintenance personnel in hospitals in Malawi’s Central and Southern Regions isolated some common causes of oxygen concentrator malfunction. Prominent among these were poor oxygen concentrator ventilation and the lack of consumable replacement parts such as the intake bacterial filter. A stand made from locally-sourced materials was developed to encourage better oxygen concentrator exhaust and raise the device out of dust and cleaning fluids on ward floors. Intake bacterial filter alternatives were researched, designed, constructed, and tested, manufactured from housing materials and filter media available in Malawi or continental Africa.
A primary source of difficulty for low-resource hospitals is lack of autonomy, requiring aid from affluent nations to supply equipment and consumable materials. This work suggests that sustainable innovations, such as allowing consumables to be produced in-country, can replace aid with development and create more accessible materials to hospital maintenance personnel. Collaboration with material suppliers and engineers in Malawi can provide sustainable designs and systems to help hospitals access the supplies they need to service oxygen concentrators and other equipment.Master of Science
The quality of healthcare in low-resource countries is often limited by the environment, lack of funds, staff availability, electricity availability, and more. In the words of a Malawian physician, medicine can feel like improvisation, wherein one must make due with available resources rather than desired resources. One prevalent problem among low-resource hospitals is the functionality and longevity of medical equipment. A large percentage of all medical equipment in Malawian hospitals is donated, resulting in a wide spectrum of models, necessary spare parts, and functionality. These machines can break quickly due to heavy use prior to donation, missing user and maintenance manuals, and a lack of replacement parts. Thus, finding necessary life-saving equipment in Malawian hospital wards can be a challenge. One such piece of equipment is the oxygen concentrator. This device fills many roles in low-resource hospitals, but in many Malawian hospitals it is the most frequently malfunctioning piece of equipment. A survey was used in hospitals in Malawi’s Central and Southern Regions to collect information on why oxygen concentrators malfunction. Common reported causes of malfunction were oxygen concentrators overheating due to clogged exhaust vents, and the unavailability of necessary disposable filters. A stand made from locally-available materials was developed to improve oxygen concentrator ventilation. Replaceable filter alternatives were researched, designed, constructed, and tested, made from housing materials and filter materials available in Malawi or continental Africa. A primary source of difficulty for low-resource hospitals is dependence on more developed nations for supplies and aid. This work suggests that designing materials from locally-available materials can lessen this dependency and make necessary medical materials more accessible. Collaboration with material suppliers and engineers in Malawi can provide sustainable designs and systems to help hospitals access the supplies they need to service oxygen concentrators and other equipment.
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Lau, Wai-lee Cherry. "Outcomes of COPD patients receiving long term oxygen therapy a retrospective cohort study /". Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23316767.
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Quine, David. "Studies and observations on different kinds of oxygen monitoring, oxygen therapy, and associated morbidities in preterm infants". Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/25105.
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Introduction: Oxygen is ubiquitous, can be life saving, and is one of the most commonly used therapies in neonatal intensive care for the past 60 years. Despite this there is no consensus among neonatologists as to what is the most appropriate way to monitor oxygen, what target level to aim for, and how to change inspired oxygen levels. There may be two or more distinct time periods that can be defined, in the early life of extreme preterm infants who go onto suffer from bronchopulmonary dysplasia (BPD) for which the best oxygen target levels need to be clearly identified. Infants with BPD have difficult early years, often failing to thrive, requiring frequent readmission to hospital for respiratory exacerbations, and having significant chance of other morbidities of prematurity. Yet current definitions of BPD based on the use of oxygen therapy alone give wide variations in the incidence of disease that reflect little more than clinician variation and have little relevance to the severity of any underlying pathology. Objectives: To compare methods of oxygen monitoring, look at how infants oxygen dissociation curves affected oxygen tensions achieved, and see how our reaction to monitors affect oxygen stability. Finally, to measure V/Q and shunt non-invasively in infants with BPD at 36 weeks corrected gestational age and examine whether this would be a useful physiological definition of BPD. Four studies were carried out. Study 1: Aimed to determine whether care based on transcutaneous oxygen tension (TcPO2) or saturation (SpO2) monitoring is associated with less time spent with high oxygen tension and less variability of oxygenation. Care based on Sp02 monitoring was associated with more time spent with high oxygen tension, more time with low oxygen tension, more variability in oxygen tension and more variability in oxygen saturation than care based on TcPO2 monitoring. Within the target ranges studied SpO2 monitoring was associated with significantly more variable oxygenation than TcPO2 monitoring. Study 2: Aimed to describe the range of oxygen tensions likely to be achieved in the first three weeks of life in a population of high risk preterm infants at currently targeted oxygen saturation levels, and to determine whether infants who develop adverse outcome have different haemoglobin oxygen dissociation characteristics than infants who remain well. Study 3: Aimed to see which nurse oxygen adjustment practices influence oxygen stability and degree of adherence to oxygen saturation targets in preterm ventilated infants by separating out the variation in oxygen stability attributable to the condition and behaviour of the baby from that attributable to the nurse oxygen adjustment practices. Variations in oxygen adjustment practices were also related to nursing seniority. After controlling for the intrinsic instability of the infant we found that larger and more frequent changes in FiO2 may contribute to instability of oxygenation. More senior nurses achieved less hyperoxic time and, made smaller oxygen changes. Stability of oxygenation in ventilated preterm infants is influenced by the oxygen adjustment practices of the staff who care for the baby. These are potentially modifiable practices. Study 4: Aimed to quantify the severity of gas exchange impairment in preterm infants with BPD in a graded fashion and to partition this between the contribution made by reduced ventilation/perfusion ratio (VA/Q) and that due to right to left shunt, using non-invasive measurements of PIO2 and SpO2. The predominant gas exchange impairment in BPD is a reduced VA/Q described by the right shift of the SpO2 vs PIO2 relationship. This provides a simpler method for defining BPD that grades disease severity. Summary: In summary this series of studies found that the method by which oxygenation is monitored and the ways that staff adjust oxygen levels have an important influence on the oxygen levels achieved. The overall oxygen affinity of the neonatal blood did not appear to be an important determinant of the risk of adverse outcome. Individual infants vary widely in their stability in terms of oxygenation. The optimal oxygen levels for developing preterm infants remain uncertain and this is the subject of a major prospective international research collaboration (NeOPRoM). Interpretation of the results of the clinical trials of different saturation targets that are currently recruiting will be difficult unless good data on compliance with protocol are gathered. A simple non-invasive measure of gas exchange impairment that might better grade disease severity of BPD has been defined. These studies will help to focus future research, and should assist clinicians in achieving improved compliance to oxygen targets.
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McGavock, Jonathan M. "The effect of hyperbaric oxygen therapy on aerobic performance following fatigue". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0027/MQ50544.pdf.
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Carnochan, Fiona Mary. "The metabolic consequences of inflammation and the effects of oxygen therapy". Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305435.
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Al-Hadi, Hadil. "The effect of Hyperbaric Oxygen Therapy on osteoclast and osteoblast function". Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1614.
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Bone remodelling, the process by which the skeleton adapts to environmental changes, is dependent on the actions of osteoclasts that resorb bone and osteoblasts which make new bone matrix. Aberrant remodelling underpins bone loss in several debilitating skeletal diseases such as osteoporosis, metastatic breast cancer and multiple myeloma. Changes in remodelling activity can also arise as a consequence of therapeutic intervention for instance intravenous bisphosphonate treatment is associated with osteochemonecrosis of the jaw and localised osteoradionecrosis is a common side effect of radiotherapy. Hyperbaric oxygen is often used as an adjunctive therapy in the treatment of these disorders. HBO involves the administration of 100% oxygen at atmospheric pressures greater than one in sealed chambers. The following studies aimed to evaluate the effect of HBO, hyperoxia, and pressure on RANKL-induced osteoclast differentiation and bone resorption from RAW264.7 and human peripheral blood mononuclear cells (PBMC), and osteoblast differentiation in vitro. The study also aimed to further examine the effect of HBO on ex vivo osteoclast formation from peripheral blood monocytes obtained from patients undergoing HBO. Daily exposure to HBO for ninety minutes significantly suppressed osteoclast differentiation and bone resorption in mouse and human monocytes in normoxic and hypoxic conditions in vitro. The suppressive action of HBO on osteoclast formation was associated with a significant reduction in HIF-1α and RANK mRNA expression and HBO also caused a significant reduction in NFATc1 and DC-STAMP expression. This study has for the first time shown that HBO is able to reduce the ability of precursors to form bone resorbing osteoclast. HBO also suppressed the ability of peripheral blood monocytes to develop into RANKL-induced resorptive osteoclasts. In an ex vivo culture system the suppressive effect of HBO was meditated by an action prior to activation of osteoclast differentiation by RANKL and must therefore be an inhibitory effect on the ability of precursors to differentiate along the osteoclastic lineage. HBO also accelerates the rate of osteoblast differentiation and augments early stages of mineralization and has a more pronounced effect than hyperoxia or pressure alone. HBO enhanced bone nodule formation and ALP activity in human osteoblasts. Furthermore HBO promoted the expression of type I collagen and Runx-2 in both normoxic and hypoxic conditions. HBO had a greater effect on these key markers of osteoblast differentiation than hyperoxia or pressure alone. This study suggests that HBO suppresses osteoclast activity and promotes osteoblastic bone formation, which may at least in part mediate its beneficial effects on necrotic bone. This provides evidence supporting the use of HBO as an adjunctive therapy to prevent osteoclast formation in a range of skeletal disorders associated with low oxygen partial pressure. The study also provides further support for the use of HBO in the treatment of skeletal disorders associated with excessive resorption such as osteomyelitis, and also provides a potential mechanism through which short term HBO may help fracture healing.
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Philips, Alyssa. "EFFECTS OF HYPERBARIC OXYGEN ON STAPYLOCOCCUS AUREUS". OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2328.
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Hyperbaric Oxygen Therapy (HBOT) is an old technology which has acquired value in chronic wound care. HBOT is known to promote local and systemic healing effects by improving the oxygenation of the wound tissue. The increased tissue oxygenation hastens removal of the bacterial bioburden, which allows resolution of inflammation and facilitates matrix production, cell division, and ultimately wound closure. Staphylococcus aureus is the most frequently isolated organism from Diabetic Foot Infections (DFI). Therefore, our lab chose to use the treatment paradigm of HBOT to initially look at the single species level as to how HBOT affects S. aureus. DFI are primarily polymicrobial, so the responses of bacterial communities to this therapy were also considered. Previous research focused solely on host response to HBOT, but our pilot testing indicates that HBOT also exhibits a bacterial response. Initial testing with S. aureus indicated that HBOT can create growth defects in bacteria in vitro. In preliminary experiments, our lab discovered that bacterial culture on solid medium is greatly altered under the pressure of hyperbaric oxygen. Normal robust growth and pigmentation are seen in S. aureus cultured in ambient conditions. However, when the same strain is cultured under HBOT conditions, there is a marked decrease in pigmentation and colony size. When other species were exposed to HBOT conditions, growth on solid media was significantly diminished. Interestingly, K. pneumoniae is able to grow normally under HBOT conditions. Normal air mixtures at the increased pressure do not have any discernable effect on bacterial growth, and the limiting effects of oxygen are not seen unless used at the increased pressure. In a broth macrodilution MIC assay, various antibiotics show an increase in susceptibility after exposure to HBOT. Lastly, biofilm formation is altered under HBOT conditions, further supporting a bacterial adjustment to HBOT and an altered mode of growth. In order to better understand the effects of a high pressure high oxygen environment on the bacterial bioburden, this study investigates the effects of HBOT on bacterial species comprising a chronic wound. Primary data has suggested that HBOT increases susceptibility of antibiotics, and can alter bacterial transcription to hinder growth of many organisms. We hypothesize that Hyperbaric Oxygen Therapy affects diabetic foot infections by changing the healing process via transcriptional alteration of bacterial species in the wound. Furthermore, we hypothesize that HBOT alters the efficacy of some antibiotics as well as affecting the biofilm capacity of many bacterial species.
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Bennett, Michael Heywood Prince of Wales Clinical School UNSW. "The evidence basis of diving and hyperbaric medicine - a synthesis of the high level clinical evidence with meta-analysis". Awarded by:University of New South Wales. Prince of Wales Clinical School, 2006. http://handle.unsw.edu.au/1959.4/24243.
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Introduction: Hyperbaric oxygen therapy (HBOT) is the administration of 100% oxygen at pressures greater than 1 atmosphere. One recurrent criticism that has been made of this field is that treatment is based on little or no good clinical evidence. Aims: The primary objective of this thesis is to make a useful response to that criticism. I planned to collate all the available randomised evidence in the fields of diving and hyperbaric medicine, supply a critical appraisal of each paper, and synthesise that evidence in a series of systematic reviews with meta-analysis. I also intended to use a cost analysis of hyperbaric practice in our own facility to inform formal cost-effectiveness analysis using the estimates of effect generated by the individual meta-analyses. Methods: A comprehensive search strategy was used to identify all clinical RCTs involving the administration of hyperbaric breathing mixtures. Each trial was appraised using the software developed by the Oxford Centre for Evidence Based Medicine. Each critical appraisal was loaded onto a searchable web site at www.hboevidence.com. Each diagnostic category identified was considered for inclusion in a Cochrane systematic review and meta-analysis. Results: The database includes 130 critical appraisals covering 173 separate reports. The site has received more than 17,000 hits. There are 12 formal meta-analytical reviews and all have been accepted for publication in the Cochrane Database of Systematic Reviews at the time of writing. These form the basis of this thesis and include late radiation tissue injury, chronic wounds, acute hearing loss and tinnitus, multiple sclerosis and decompression illness. The meta-analyses in this thesis suggest there are several areas where HBOT is associated with improved clinical outcomes and that routine use is probably justified in some areas (e.g. radiation proctitis healing with HBOT: NNT 3, 95%CI 2 to 11). On the other hand, these analyses suggest there is most unlikely to be significant clinical benefit from the application of HBOT to patients currently referred for HBOT (e.g. multiple sclerosis). Conclusions: The randomised evidence for the use of HBOT is now significantly easier to access. Recommendations for therapy and future research directions can be made on the basis of these analyses.
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Jackson, Laura. "Oxygen-regulated gene expression in Escherichia coli and hypoxia-targeted gene therapy". Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414676.
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Al-mzaiel, Anwar J. "Mechanisms by which hyperbaric oxygen therapy may resolve inflammation in chronic wounds". Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1945.
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Hyperbaric oxygen (HBO) therapy is the intermittent inhalation of 100% oxygen at a pressure greater than one atmosphere absolute. It is an effective treatment for various inflammatory conditions, including chronic wounds which are characterized by an excessive influx of neutrophils and their prolonged persistence at the wound site. Neutrophil apoptosis and clearance have been shown to be required for resolution of inflammation. The mechanisms by which HBO aids wound healing are well documented, but its effects on cellular inflammatory response are not well understood particularly with respect to neutrophils. The hypothesis presented in this thesis is that increased oxygenation via HBO assists chronic wound healing by enhancing non-inflammatory neutrophil defences and cell death through apoptosis. An investigation was carried out into the effects of HBO on neutrophil antimicrobial function and apoptosis using differentiated HL-60 cells as an in vitro neutrophil model. The data clearly showed that a single HBO treatment for 90 min caused an increase in the oxidative burst activity of neutrophil-like cells as shown by increased NBT staining, superoxide (cytochrome c reduction) and H2O2 production (Kruskal-Wallis, P < 0.05), and phagocytosis of Staphylococcus aureus. HBO treatment displayed a pro-apoptotic effect, enhancing caspase 3/7 activity both in the presence and absence of a TNF-α stimulus (Kruskal-Wallis, P < 0.05) and causing morphological changes (observed using Giemsa and SYBR® Safe staining) associated with apoptosis. Although no consistent pattern was observed, both hyperoxia and pressure alone seemed to contribute to both the increase in antimicrobial activity and the increase in apoptosis induced by HBO in these neutrophil-like cells (Chapters 4 and 5). HBO-enhanced neutrophil clearance by macrophages was investigated using bovine neutrophils and monocyte-derived macrophages (MDMФ). A single 90 min HBO exposure significantly increased the clearance of fresh and 22 h-aged neutrophils by MDMФ (two-way ANOVA, P < 0.05), suggesting an increase in phosphatidylserine (PS) exposure in apoptotic neutrophils after HBO treatment (Chapter 6). Importantly, a long-term repetitive exposure to HBO in patients with chronic wounds caused a significant decrease in the antioxidant enzyme defence system (one-way repeated measures ANOVA, P < 0.05), plasma TNF-α and IL-1β after 30 HBO sessions, with down regulation of expression of the anti-apoptotic factors, NF-B and Bcl-2 (Chapter 7). These findings may go some way towards explaining the effectiveness of HBO treatment not only for chronic wounds but also for other inflammatory conditions that may be affected by this treatment.
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Kelly, Carol Ann. "Patients' and healthcare professionals' perceptions of oxygen therapy : an interpretative phenomenological analysis". Thesis, Edge Hill University, 2014. http://repository.edgehill.ac.uk/6432/.
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Background: Despite common usage of oxygen as a therapeutic intervention, audit suggests the existence of poor prescribing and administration practices. Contemporary studies and guidelines propose an influencing culture whereby oxygen is given to alleviate breathlessness and to most acute clinical presentations, with disregard for potential drawbacks; but there is no evidence supporting this claim. The problem self-perpetuates as erroneous beliefs are passed to patients, their carers and the general public. Aim: To explore healthcare professionals’ (HCPs) and patients’ perceptions of oxygen therapy. Method: Semi-structured interviews were undertaken with 28 patients and 34 HCPs (including nurses, paramedics, pharmacists and general practitioners). Self-reported beliefs and behaviours were recorded, transcribed verbatim and analysed iteratively using interpretative phenomenological analysis (IPA). Results: Three master themes were identified: oxygen as a panacea, the burden of oxygen, and antecedents to beliefs. Sub-themes under these constants differed between HCPs and patients, but fundamentally both groups viewed oxygen as an innocuous therapy with numerous benefits. Patients used oxygen for breathlessness and as an enabler; they were grateful to the oxygen and accepted it as part of the disease. HCPs used oxygen because it helps patients; it works!; it makes HCPs feel better, and also out of compassion. But oxygen is not benign and a burden is evident, for patients it makes the disease visible and carries associated costs. For HCPs there is an awareness of the dangers and the patients’ burden, which often results in clinical dilemmas and an emotional cost to caring. The study exposed patients’ potential antecedents to beliefs as faith in HCPs and past experiences; for HCPs these were entrenched culture and expectations. Patients appeared not to think about oxygen and understanding was poor. All HCPs believed they had not received enough education specific to oxygen, and an approach of DIY education prevailed. Summary: These findings suggest that a set of fixed beliefs regarding oxygen therapy exist, influenced by several impacting factors. The overwhelming perception that oxygen is a universal remedy presides, but is, at times, contradictory, when benefits are countered by adverse effects of oxygen. These adverse effects, additional to physiological dangers, included psychosocial and emotional costs. This is the first time that perceptions of oxygen therapy have been reported and will be an important contribution to knowledge, supporting strategies to raise awareness of entrenched cultures, influence future educational and research strategies, and inform policy.
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Muhonen, Arja. "Distraction osteogenesis of irradiated rabbit mandible with and without hyperbaric oxygen therapy". Turku : Turun Yliopisto, 2002. http://catalog.hathitrust.org/api/volumes/oclc/50131839.html.
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Mostert, Lelane. "Central oxygen pipeline failure". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86313.
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Thesis (MMed)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Case Report - A case is described of central oxygen pipeline failure that occurred at a large academic hospital and its subsequent implications for managing the situation. Literature review - The literature review undertaken focused on the current state of affairs with regards to anaesthetic staff's knowledge of and preparedness for the management implications of central oxygen pipeline failure. The events I describe below demonstrate a significant deficiency in the staff’s understanding of and training for the crisis, which should be remedied to improve patient safety. Specific measures are suggested in the literature to prevent such incidents and guidelines are available to manage central oxygen pipeline failure. These are reviewed in this study. Recommendations - This study attempts to bring together the most critical aspects that need to be addressed to safely manage similar future incidents. Prevention should include measures to implement clearly stated disaster management plans and increased awareness with regards to the medical gas pipeline system (MGPS), simulation training, efficient alarm systems, personally conducted routine evaluations of equipment and emergency backup systems by anaesthesiologists and effective communication between hospital staff. Careful planning and successful coordination during maintenance and modification of the medical gas pipeline system, using piston-type or air-driven, rather than oxygen-driven, ventilators and optimal design of the hospital bulk oxygen system can contribute to reduce risks. In the event of central oxygen pipeline failure a specific sequence of actions should be taken by the anaesthesiologist and a clear institutional operational policy is described.
AFRIKAANSE OPSOMMING: Gevalsbeskrywing - 'n Geval van sentrale suurstoftoevoerversaking, wat plaasgevind het by 'n groot opleidingshospitaal, word bespreek. Daar word ook gekyk na die praktiese gevolge met betrekking tot die hantering van die situasie. Literatuurstudie - 'n Literatuurstudie is aangepak met die doel om te fokus op die huidige toedrag van sake betreffende narkosepersoneel se kennis en paraatheid in die hantering van sentrale suurstoftoevoerversaking. 'n Wesenlike gebrek aan begrip en opleiding aangaande hierdie onderwerp is geïdentifiseer – areas wat, met die nodige aandag, verbeter kan word ten einde die welstand van pasiënte te verseker. Spesifieke voorkomende maatreëls en hanteringsriglyne word voorgestel deur die literatuur en word gevolglik hersien in hierdie studie. Aanbevelings - Hierdie studie poog om kernaspekte aan te raak ten einde soortgelyke toekomstige voorvalle veilig en optimaal te kan hanteer. Voorkomende maatreëls behels onder meer die daarstelling van duidelik verstaanbare noodplanne, verbeterde bewustheid aangaande die mediese gaspypsisteem, simulasie-opleiding, doeltreffende alarmstelsels, effektiewe kommunikasie tussen hospitaalpersoneel, sowel as narkotiseurs wat self roetine-evaluasies van hul narkosetoebehore en -noodtoerusting uitvoer. Noukeurige beplanning en neweskikking tydens herstelwerk of werk aan die mediese gaspypsisteem, die gebruik van suierventilators (of dan lugaangedrewe in plaas van suurstofaangedrewe ventilators) en die optimale uitleg van 'n hospitaal se suurstoftoevoer, kan bydra om die risiko's te beperk. In die geval van sentrale suurstoftoevoerversaking behoort die narkotiseur stapsgewyse aksie te neem. 'n Duidelike institusionele noodbeleid word ook omskryf.
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Ragàs, Amalrich Xavier. "Singlet Oxygen in Antimicrobial Photodynamic Therapy: Biological effects, Mechanistic Studies and Future Directions". Doctoral thesis, Universitat Ramon Llull, 2010. http://hdl.handle.net/10803/9302.
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En aquesta tèsi s'ha avaluat l'ús de la teràpia fotodinàmica antimicrobiana (APDT) com a alternativa als antibiòtics. Inicialment, s'ha demostrat in vitro i en un model de cremades en ratolins el potencial de les fenotiazines, i més concretament del nou blau de metilè, per inactivar un bacteri resistent a antibiòtics com Acinetobacter baumanii. A més, també s'ha investigat el potencial dels porficens aril catiònics com a agents fotosensibilitzadors per a APDT in vitro i in vivo, inactivant exitosament diferents tipus de bacteris gram positius i negatius, així com fongs. Per altra banda, s'han estudiat les cinètiques de formació i decaïment d'oxigen singlet (1O2) en E. coli mitjançant un espectrofotòmetre ultrasensible a l'infraroig proper amb resolució temporal per sota del microsegon. Els resultats ens permeten profunditzar en el mecanisme de l'APDT, és a dir, en la localització del fotosensibilitzador (PS) en el bacteri i la reactivitat de l'1O2. Per un costat, l'entorn del PS canvia quan la distribució de les càrregues catiòniques varia. Per l'altre, en funció del lloc de formació, l'1O2 reacciona amb l'entorn proper o és capaç d'escapar fora de les cèl·lules.
En tercer lloc, també s'ha estudiat, mitjançant sondes fluorescents i tècniques amb resolució temporal, l'habilitat d'una proteïna fluorescent per produir espècies reactives d'oxigen, actuant com a agents fotosensibilitzadors genèticament codificats. Així, s'ha calculat per primera vegada el rendiment quàntic de formació d'1O2 obtenint un valor similar al del cromòfor sintètic de les GFPs.
Finalment, s'ha investigat mitjançant l'espectrofotòmetre en l'infraroig proper l'efecte plasmó produït per films d'illes de plata sobre l'1O2, demostrant un increment màxim en la luminescència d'1O2 a 1270 nm al voltant de 30 vegades en alguns casos.
En esta tesis se ha evaluado el uso la terapia fotodinámica antimicrobiana (APDT) como alternativa a los antibióticos. Inicialmente, se ha demostrado, in vitro y en un modelo de quemaduras en ratón, el potencial de las fenotiazinas, y más concretamente del nuevo azul de metileno, para inactivar una bacteria resistente a antibióticos como Acinetobacter baumanii. Además, también se ha investigado el potencial de los porficenos aril catiónicos como agentes fotosensibilizadores para APDT in vitro e in vivo, inactivando exitosamente distintos tipos de bacterias gram positivas y negativas, así como hongos.
Por otro lado, se ha estudiado las cinéticas de formación y decaimiento de oxígeno singlete (1O2) en E. coli mediante un espectrofotómetro ultrasensible en el infrarrojo cercano con resolución temporal por debajo del microsegundo. Los resultados nos permiten profundizar en el mecanismo de la APDT, es decir, en la localización del fotosensibilizador (PS) en la bacteria y la reactividad del 1O2. Por un lado, el entorno del PS cambia cuando la distribución de las cargas catiónicas varía. Por otro lado, en función del lugar de formación, el 1O2 reacciona con el entorno cercano o es capaz de escapar fuera de las células.
En tercer lugar, también se ha estudiado, mediante sondas fluorescentes y técnicas con resolución temporal, la habilidad de una proteína fluorescente para producir especies reactivas de oxígeno, actuando pues como agentes fotosensibilizadores genéticamente codificados. Así, se ha calculado por primera vez el rendimiento cuántico de formación de 1O2 mostrando un valor similar al del cromóforo sintético de las GFP.
Finalmente, se ha investigado mediante el espectrofotómetro en el infrarojo cercano el efecto plasmon producido por films de islas de plata sobre 1O2, observando un incremento máximo de la luminiscencia de 1O2 a 1270 nm alrededor de 30 veces en algunos casos.
In this thesis, the use of antimicrobial photodynamic therapy as alternative to antibiotics has been assessed. First, the potential of phenothiazinium dyes, and specifically new methylene blue, to inactivate multidrug-resistant strains has been demonstrated against Acinetobacter baumanii in vitro and in a mouse burn model. In this regard, it also has been investigated the potential of aryl cationic porphycenes as photosensitizing drugs in APDT in vitro and in vivo, successfully inactivating different gram-positive and negative bacteria, and fungal cells.
Second, the kinetics of singlet oxygen (1O2) production and fate in E. coli have been investigated by means of an ultrasensitive near-infrared spectrometer with submicrosecond time resolution. The results allowed us to gain insight into the mechanism of APDT, i.e., the localization of the photosensitiser (PS) in the bacteria and the reactivity of 1O2. On one hand, the microenvironment of the PS changes when the distribution of the cationic charges changes. On the other hand, depending on the site of production, 1O2 reacts with the nearest microenvironment or is able to escape out of the cells.
Third, the ability of fluorescent proteins (GFPs), as genetically-encoded photosensitisers, to produce reactive oxygen species has been studied by means of fluorescent probes and time-resolved techniques. Thus, for the first time, the quantum yield of 1O2 production of some of the studied proteins has been calculated showing a value similar to that of the synthetic GFP chromophore.
Finally, the plasmonic effect of silver island films on 1O2 has been investigated using the near-infrared spectrometer, demonstrating a maximum enhancement of the 1O2 luminescence signal at 1270 nm ca. 30-fold in some cases.
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Lau, Wai-lee Cherry y 劉慧莉. "Outcomes of COPD patients receiving long term oxygen therapy: a retrospective cohort study". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B3197014X.
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Ding, Rui. "Enhanced Singlet Oxygen Production from Metal Nanoparticle Based Hybrid Photosensitizers". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447690607.
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Shi, Shuning. "VEGF-A, VEGF-B and PIGF in mouse oxygen induced retinopathy /". St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17390.pdf.
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Franzen-Korzendorfer, Holly. "Effects of monochromatic infrared energy on transcutaneous oxygen measurements in diabetic subjects with a loss of protective sensation". Diss., NSUWorks, 2006. https://nsuworks.nova.edu/hpd_pt_stuetd/15.
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Moolman, Francis Sean. "Oxygen carriers for a novel bio-artificial liver support system". Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-09092004-162043.
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Thesis Ph. D.)(Chemical Engineering)--University of Pretoria, 2003.Title from opening screen (viewed Oct. 06, 2004). Summaries in English and Afrikaans. Includes bibliographical references (leaves 144-151).
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Liebich, Ingrid. "Hyperbaric oxygen therapy for children with cerebral palsy : Jebsen-Taylor test of hand function". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31117.
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Despite lack of scientific evidence, hyperbaric oxygen therapy (HBO2) has been used as a treatment for children with cerebral palsy (CP). Recently, a multi-centre randomised, double-blind, placebo-controlled trial assessed the efficacy of HBO2 therapy for children with CP. Using the same cohort, the purpose of this study was to examine the effectiveness of HBO2 therapy on hand function using the Jebsen-Taylor test. All children received 40 treatments over a 2-month period. HBO2 treatments were 60 minutes with 100% O2 at 1.75 atmospheres absolute (ATA). Placebo treatments were also 60 minutes with air (21% O2) at 1.3 ATA. Seventy-eight children with CP, aged 3--12 years completed pre and post hand function assessments. Hand function was evaluated using one quantitative measure (time) and three qualitative measures. There were no significant changes between baseline and follow-up tests for any of the measures, although both experimental and control groups improved ( p = 0.08) their total times for the Jebsen test. The HBO2 group improved by 54.5 seconds (8.8%) while the placebo group improved by 47.8 seconds (7.7%). The results indicate that HBO2 therapy did not enhance the hand function of children with CP.
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Askie, Lisa. "A randomised controlled trial of oxygen therapy on growth and development of preterm infants". Connect to full text, 2003. http://hdl.handle.net/2123/599.
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Thesis (Ph. D.)--University of Sydney, 2003.Includes tables and questionnaires. Title from title screen (viewed Apr. 28, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Centre for Perinatal Health Services Research, School of Public Health. Includes bibliography. Also available in print form.
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Askie, Lisa Maree. "A randomised controlled trial of oxygen therapy on growth and development of preterm infants". Thesis, The University of Sydney, 2003. http://hdl.handle.net/2123/599.
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Background: Physiological studies have shown that many preterm infants and infants with chronic lung disease may suffer chronic hypoxaemia, which possibly leads to poor growth and development. Anecdotal reports indicate that there is a drive to increase the oxygen saturation target range to a higher level in these infants due primarily to perceived benefits derived from clinical experience and from uncontrolled observational studies of babies discharged on home oxygen. Objective The BOOST (Benefits Of Oxygen Saturation Targeting) trial is the first randomised trial to assess the long-term benefits and harms of two different oxygen saturation target ranges. Methods: BOOST was a multicentre, double blinded, randomised controlled trial that enrolled 358 infants born at less than 30 weeks� gestation who remained oxygen-dependent at 32 weeks postmenstrual age. They were randomly assigned to target either a functional oxygen saturation range of 91-94% (standard or control group) or 95-98% (higher or treatment group). The primary outcomes were growth and neurodevelopmental measures at 12 months corrected age. Secondary outcomes included length of hospital stay, retinopathy of prematurity, health service utilisation, parental stress, and infant temperament. Results: Prognostic baseline characteristics did not differ between the two groups. Mean birth weight and gestational age of enrolled infants was 917g and 26.5 weeks respectively. The rate of antenatal corticosteroid use was 83%.
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Askie, Lisa Maree. "A randomised controlled trial of oxygen therapy on growth and development of preterm infants". University of Sydney. Public Health, 2003. http://hdl.handle.net/2123/599.
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Background: Physiological studies have shown that many preterm infants and infants with chronic lung disease may suffer chronic hypoxaemia, which possibly leads to poor growth and development. Anecdotal reports indicate that there is a drive to increase the oxygen saturation target range to a higher level in these infants due primarily to perceived benefits derived from clinical experience and from uncontrolled observational studies of babies discharged on home oxygen. Objective The BOOST (Benefits Of Oxygen Saturation Targeting) trial is the first randomised trial to assess the long-term benefits and harms of two different oxygen saturation target ranges. Methods: BOOST was a multicentre, double blinded, randomised controlled trial that enrolled 358 infants born at less than 30 weeks� gestation who remained oxygen-dependent at 32 weeks postmenstrual age. They were randomly assigned to target either a functional oxygen saturation range of 91-94% (standard or control group) or 95-98% (higher or treatment group). The primary outcomes were growth and neurodevelopmental measures at 12 months corrected age. Secondary outcomes included length of hospital stay, retinopathy of prematurity, health service utilisation, parental stress, and infant temperament. Results: Prognostic baseline characteristics did not differ between the two groups. Mean birth weight and gestational age of enrolled infants was 917g and 26.5 weeks respectively. The rate of antenatal corticosteroid use was 83%.
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Smith, David L. "Nocturnal hypoxaemia in cystic fibrosis". Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296267.
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Troy, Lauren Kristie. "Supplemental Oxygen Therapy in Patients with Early Interstitial Lung Disease: Physiological Effects during Exercise and Sleep". Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16400.
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Background and goals: The interstitial lung diseases (ILD) are characterised by inflammation and fibrosis of the lung, resulting in poor gas exchange and restricted lung mechanics. Hypoxaemia during exercise and sleep are frequently observed, impacting on effort tolerance, sleep architecture, quality of life and survival. Intermittent hypoxaemia during exercise and sleep may be important in the development of pulmonary hypertension (PH) in this patient population. Currently in Australia, supplemental oxygen is largely prescribed for ILD patients with severe resting hypoxaemia. In this thesis, we hypothesised that oxygen provided for ILD patients with exercise- or sleep-desaturation would provide significant benefits, with potential for improvement in pulmonary vascular function and markers of oxidative stress. Results: Both significant nocturnal oxygen desaturation (NOD, i.e. 10% or more of total sleep time spent with oxygen saturation below 90%) and sleep disordered breathing (SDB) occurred frequently during sleep in a large unselected ILD population. Significant NOD independently predicted the presence of PH at 6 months, and was the only sleep index to be prognostic of overall and progression-free survival. Supplemental oxygen during sleep for 4 weeks led to a significant improvement in sleep oxygenation and indices of SDB, compared with medical air for the same period. Furthermore, plasma brain natriuretic peptide (BNP), a biomarker of pulmonary vascular dysfunction, was reduced with oxygen use in ILD patients with significant NOD. Oxygen during shuttle walk testing and cardiopulmonary exercise testing (CPET) significantly improved endurance in ILD patients with known exercise-desaturation. During CPET, oxygen attenuated minute ventilation (VE) and reduced the ventilatory equivalent for carbon dioxide (VE/VCO2), a surrogate for PH in this population. A subgroup who did not improve their endurance with oxygen were seen to have higher VE at all stages of exercise, with no reduction during oxygen testing. Right ventricular (RV) function, studied directly during exercise with real-time cardiac magnetic resonance imaging, was significantly depressed in patients, compared with healthy controls. Oxygen enhanced RV contractility in the patient group, with a strong correlation found between the degree of improvement in RV function and the response in endurance time seen during CPET using oxygen. In both the patients with sleep and exercise-desaturation, there was evidence of chronic oxidative stress, with specific correlation between redox indices and pulmonary vascular dysfunction. These markers of oxidative stress were improved with the use of oxygen in the Sleep and Exercise-ILD cohorts. Conclusion: Desaturation during sleep and exercise is associated with the development of PH and reduced overall survival in the ILD population. Supplemental oxygen prevents nocturnal desaturation and sleep–disordered breathing, improves exercise performance, enhances RV function, and reduces the burden of oxidative stress. The amelioration of pulmonary vascular dysfunction with oxygen may impact on the long-term outlook for patients with ILD.
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Smith, Cameron. "Intravenous Administration of Perfluorocarbon Emulsions as a Non-Recompression Therapy for Decompression Sickness". VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/1555.
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Decompression sickness (DCS) results from a sudden decrease in ambient pressure leading to super-saturation of tissues with inert gas and subsequent bubble formation within both tissues and blood. Perfluorocarbons (PFC) are able to dissolve vast amounts of non-polar gases. The administration of intravenous (I.V.) PFC emulsions reduce both morbidity and mortality of DCS, but the mechanism of this protective effect has not yet been demonstrated. Juvenile Dorper cross sheep between 16 and 24 kg (n=31) were anaesthetized and instrumented for physiological monitoring, the administration of I.V. fluids and sampling of arterial and mixed venous blood. Animals were placed in a hyperbaric chamber and compressed to 6.0 atmospheres absolute for 30 minutes, then rapidly decompressed. Upon chamber exit animals were randomly assigned to receive 6cc/kg of either PFC or saline control over 5 minutes beginning immediately after chamber exit. They were also randomized to receive one of 4 breathing gases post-chamber: 100% O2, 80/20 N2/O2, 50/50 HeO2, or 80/20 HeO2. Blood samples were drawn at 5, 10, 15, 30, 60, and 90 minutes to examine whole-body oxygenation. Respiratory gases were monitored and recorded in real-time using mass spectroscopy to examine nitrogen washout. PFC administration increased arterial oxygen content (16.30±0.27 vs. 14.75±0.25 mL/dL, p<0.0001), oxygen delivery (14.83±0.28 vs. 13.44±0.25 mL/minute/kg, p=0.0004), and tissue oxygen consumption (3.37±0.14 vs. 2.76±0.13 mL/minute/kg, p=0.0018) over saline control, but did not increase mixed venous oxygen content (12.45±0.26 vs. 11.74±0.24 mL/dL, p=0.0558) or extraction ratio (0.23±0.012 vs. 0.21±0.011, p=0.1869). PFC administration lowered the plateau of the curve, increasing the amount of nitrogen washout vs. saline control (22.22±1.566 vs. 15.98±1.380 mmHg, p= 0.0074). Breathing 80/20 HeO2 increased the decay constant of the curve, increasing the rate of washout vs. breathing 100% O2 (0.03176±0.001044 vs. 0.03096±0.0009402, p=0.5777). PFC improves whole-body oxygenation after severe DCS and increases the amount of nitrogen washout. Although the effects of both PFC and 80/20 HeO2 breathing were statistically significant the magnitude of the nitrogen washout effect is quite small, and unlikely to be clinically significant. Thus it is likely that the improved oxygenation is responsible for the previously-observed therapeutic effects of PFC in treating DCS.
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Daulton, Donna Lynn. "Using Optimal Control Theory to Optimize the Use of Oxygen Therapy in Chronic Wound Healing". TopSCHOLAR®, 2013. http://digitalcommons.wku.edu/theses/1232.
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Approximately 2 to 3 million people in the United States suffer from chronic wounds, which are defined as wounds that do not heal in 30 days time; an estimated $25 billion per year is spent on their treatment in the United States. In our work, we focused on treating chronic wounds with bacterial infections using hyperbaric and topical oxygen therapies.
We used a mathematical model describing the interaction between bacteria, neutrophils and oxygen. Optimal control theory was then employed to study oxygen treatment strategies with the mathematical model. Existence of a solution was shown for both therapies. Uniqueness was also shown for hyperbaric therapy. We then used a forward-backward sweep method to find numerical solutions for the therapies. We concluded by putting forth ideas for how this problem could progress toward finding applicable treatment strategies.
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Holdsworth, Clark Thomas. "Vascular ATP-sensitive potassium channels impact spatial and temporal oxygen transport: implications for sulphonylurea therapy". Diss., Kansas State University, 2015. http://hdl.handle.net/2097/20562.
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Doctor of PhilosophyDepartment of Anatomy and Physiology
Timothy I. Musch
Matching local muscle O[subscript]2-supply to O[subscript]2-demand during the prodigious exercise-induced metabolic challenge is achieved through coordinated mechanisms of vascular control. The unique sensitivity of ATP-sensitive potassium (K[subscript]ATP) channels to cell metabolism indicates the potential to match energetic demand to peripheral O[subscript]2 transport. The aim of this dissertation was to determine the magnitude and kinetics of the K[subscript]ATP channel contribution to vascular control during exercise in health and heart failure. It was hypothesized that K[subscript]ATP channel inhibition via glibenclamide would, in healthy rats, 1) reduce exercising skeletal muscle blood flow and vascular conductance 2) speed the fall of microvascular O[subscript]2 driving pressure (PO[subscript]2mv; set by the O[subscript]2 delivery-O[subscript]2 utilization ratio) during muscle contractions and 3) in heart failure rats, augment the PO[subscript]2mv undershoot and delay the time to reach the contracting steady-state. A total of 55 male Sprague-Dawley rats were used under control and glibenclamide conditions (5 mg kg[superscript]-1). Hindlimb muscle blood flow (radiolabelled microspheres) was determined at rest (n = 6) or during treadmill exercise (n = 6-8; 20, 40 and 60 m min[superscript]-1, 5% incline). Spinotrapezius muscle PO[subscript]2mv (phosphorescence quenching) was measured in 16 heart failure (coronary artery ligation) and 12 healthy rats and during 180 s of 1-Hz twitch contractions (~6 V). The major effects of glibenclamide were, in healthy rats, 1) a reduction in exercising hindlimb skeletal muscle blood flow with the greatest effect in predominantly oxidative muscle fiber types and at higher running speeds 2) an increased prevalence of the undershoot of PO[subscript]2mv steady-state and doubled time to reach the steady-state and 3) in heart failure rats, a reduced baseline PO[subscript]2mv, an augmented undershoot of the steady-state and time to reach steady-state and a reduction in the mean PO[subscript]2mv during contractions. These data suggest that the K[subscript]ATP channel contributes substantially to exercise-induced hyperemia and may contribute to the slowing of VO[subscript]2 kinetics given the spatial and temporal effects of glibenclamide. The K[subscript]ATP channel-mediated protection against a severe O[subscript]2-delivery to O[subscript]2-utilization mismatch at the onset of contractions raises serious concerns for sulphonylurea treatment in diabetes which is likely to cause perturbations of [metabolite] and compromise exercise tolerance.
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Bauer, Timothy Alan. "Oxygen uptake kinetics in peripheral arterial disease". Diss., Manhattan, Kan. : Kansas State University, 2005. http://hdl.handle.net/2097/125.
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Atilgan, Serdar. "Water Soluble Distyryl-boradiazaindacenes As Efficient Photosensitizers For Photodynamic Therapy". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607601/index.pdf.
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Photodynamic therapy (PDT) is an emerging treatment modality for a range of disease classes, both cancerous and noncancerous. This has brought about an active pursiut of new PDT agents that can be optimized for the unique set of photophysical characteristics that are required for a succesful clinical agent. There are many reported or commercially available photosensitizers, but most have limitations, such as low photostability, or a limited usable range of solvent conditions.
In this study, we introduced a novel class of extended conjugation water soluble boradiazaindacene dyes which are efficient singlet oxygen generators. These sensitizers have strong absorptions in the therapeutic window and have spectacular photoinduced cytotoxicity. In addition, they display no dark toxicity at the active concentrations. With these remarkable properties, they are likely to find applications as promising new reagents for photodynamic therapy.
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Marntell, Stina. "Sedation and dissociative anaesthesia in the horse : physiological and clinical aspects /". Uppsala : Dept. of Large Animal Clinical Sciences, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/v169.pdf.
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Yukruk, Funda. "Water Soluble Green Perylenediimide (pdi) Dyes As Potential Sensitizers For Photodynamic Therapy". Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605693/index.pdf.
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Photodynamic therapy has been established as one of the approaches for the treatment of various malignant tumors. While most of the reagents used for this purpose are porphyrin derivatives, there is a strong motivation for finding novel and better sensitizers.
Perylenediimides are known for their photo- and chemical stability, but they do not have absorptions in the red end of the visible spectrum. However, recently reported green perylenediimides which have dialkylamino substituents on the perylene core, provide an alternative. To that end, we have designed and synthesized novel green perylenediimides with remarkable water solubility at neutral pH and absorption peaks beyond 650 nm. We demonstrated that on red-light excitation, singlet oxygen trap 1,3-diphenyl-iso-benzofuran is rapidly degraded.
We also carried out cell culture experimentsan important parameter to be optimized for practical application as a novel photodynamic therapy agent was the excited dye toxicity to dark toxicity. Our results confirmed that these novel perylenediimides acted as sensitizers generating singlet oxygen and the initial in vitro biological experiments demonstrated their potential utility in photodynamic therapy.
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Durand, Marcus L. "The evaluation of methods for the prospective patient safety hazard analysis of ward-based oxygen therapy". Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4480.
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When even seemingly benign and routine processes fail in healthcare, people sometimes die. The profound effect on the patient’s families and the healthcare staff involved is clear (Vincent and Coulter, 2002), while further consequences are felt by the institution involved, both financially and by damage to reputation. The trend in healthcare for learning through experience of adverse events is no longer a viable philosophy (Department of Health,Sir Ian Carruthers OBE and Pauline Philip, 2006). In order to make progress towards preventative learning, three Prospective Hazard Analysis (PHA) methods used in other industries were evaluated for use in the area of ward based healthcare. Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA) and Hazard and Operability Analysis (HAZOP) were compared to each other in terms of ease of use, information they provide and the manner in which it is presented. Their results were also compared to baseline data produced through empirical research. Oxygen Therapy was used in this research as an example of a common ward based therapy. The resulting analysis listed 186 hazards almost all of which could lead to death, especially if combined. FTA and FMEA provided better system coverage than HAZOP and identified more hazards than were contained in the initial hazard identification method common to both techniques. FMEA and HAZOP needed some modification before use, with HAZOP requiring the most extensive adjustment. FTA has a very useful graphical presentation and was the only method capable of displaying causal linkage, but required that hazards be translated into events for analysis. It was concluded that formal Prospective Hazard Analysis (PHA) was applicable to this area of healthcare and presented added value through a combination of detailed information on possible hazards and accurate risk assessment based on a combination of expert opinion and empirical data. This provides a mechanism for evidence based identification of hazard barriers and safeguards as well as a method for formal communication of results at any stage of an analysis. It may further provide a very valuable vehicle for documented learning through prospective analysis incorporating feedback from previous experience and adverse incidents. The clear definition of systems and processes that form part of these methods provides a valuable opportunity for learning and the enduring capture and dissemination of tacit knowledge that can be continually updated and used for the formulation of strategies for safety and quality improvement.
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O'Neill, Brenda. "The efficacy and use of ambulatory and short burst oxygen therapy in chronic obstructive pulmonary disease". Thesis, University of Ulster, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413826.
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Dost, Zeynep. "Efficient Synthesis Of Novel Near Ir Emitting Distyrylboradiazaindacene Sensitizers For Photodynamic Therapy". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607377/index.pdf.
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Photodynamic therapy (PDT) is a noninvasive method of treating malignant
tumors and age-related macular degeneration. Current practice of PDT is limited to a
few functionalized porphyrins, however these compounds are not considered to be
ideal drugs for use in PDT. Among the limitations, the most prominent is the low
extinction coefficient of porphyrins in the body’
s therapeutic window. Therefore, there is a significant impetus to develop novel and better efficiency sensitizers for use in PDT. Boradiazaindacenes (BODIPY dyes or difluoroboradipyrrines) are well known fluorescent dyes. We discovered novel distyryl-derivatized boradiazaindacene dyes. These dyes have strong absorptions beyond 650nm. In order to transform these novel dyes into potential PDT reagents, bromine substituents were placed and then heavy atom effect was showed. We also demonstrated that on red-light excitation, singlet oxygen trap 1,3-diphenyl-iso-benzofuran is rapidly degraded.
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Kong, Lingkun. "The expression of the VEGF gene in a mouse model of oxygen-induced retinopathy /". [St. Lucia, Qld.], 2000. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16968.pdf.
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Joyce, Lauren Elizabeth. "Ru(II), Os(II), and Rh2(II,II) Complexes as Potential Photodynamic Therapy Agents". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291176129.
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Valentine, Ronan. "Biophysical aspects of photodynamic therapy". Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2471.
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Photodynamic therapy (PDT) is a multimodality cancer treatment available for the palliation or eradication of systemic and cutaneous malignancies. In this thesis, the application of PDT is for the treatment of non-melanoma skin cancer (NMSC). While PDT has a well-documented track record, there are, at this time no significant indicators to suggest the superiority of one treatment regime over the next. The motivation for this work is to provide additional evidence pertaining to PDT treatment variables, and to assist in optimising PDT treatment regimes. One such variable is the treatment light dose. Determining the light dose more accurately would assist in optimising treatment schedules. Furthermore, choice of photosensitiser pro-drug type and application times still lack an evidence base. To address issues concerning treatment parameters, fluorescence spectroscopy – a valuable optical diagnostic technique – was used. Monitoring the in vivo PpIX fluorescence and photobleaching during PDT was employed to provide information pertaining to the progression of treatment. This was demonstrated by performing a clinical study at the Photobiology Unit, Ninewells Hospital and Medical School, Dundee. Two different photosensitiser pro-drugs – either 5-aminolaevulinic acid (ALA) or its methyl ester (MAL) – were investigated and based on the fluorescence and pain data recorded both may be equally suitable for topical PDT. During PDT, surface fluorescence is observed to diminish with time – due to photobleaching – although cancerous cells may continue to be destroyed deep down in the tissue. Therefore, it is difficult to ascertain what is happening at depth in the tumour. This raised the questions; How long after surface PpIX fluorescence has diminished is the PDT treatment still effective and to what depths below the surface is effective treatment provided? In order to address these important questions, a three-dimensional (3D) Monte Carlo radiation transfer (MCRT) model was used to compute the light dose and the ¹O₂ production within a tumour, and the PpIX fluorescence emission from the tumour. An implicit dosimetry approach based on a single parameter – fluorescence photobleaching – was used in order to determine the ¹O₂ generation, which is assumed to be related to tissue damage. Findings from our model recommended administering a larger treatment light dose, advocating an increase in the treatment time after surface PpIX fluorescence has diminished. This increase may ultimately assist in optimising PDT treatment regimes, particularly at depth within tumours.
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Andrasik, Stephen James. "Singlet Oxygen Generation Using New Fluorene-Based Photosensitizers Under One- and Two-Photon Excitation". Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2210.
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Molecular oxygen in its lowest electronically excited state plays an important roll in the field of chemistry. This excited state is often referred to as singlet oxygen and can be generated in a photosensitized process under one- or two-photon excitation of a photosensitizer. It is particularly useful in the field of photodynamic cancer therapy (PDT) where singlet oxygen formation can be used to destroy cancerous tumors. The use of two-photon activated photosensitizers possesses great potential in the field of PDT since near-IR light is used to activate the sensitizer, resulting in deeper penetration of light into biological tissue, less photo-bleaching of the sensitizer, and greatly improved resolution of excitation. The synthesis and photophysical characterization of new fluorene-based photosensitizers for efficient singlet oxygen production were investigated. The spectral properties for singlet oxygen production were measured at room temperature and 77 K. Two-photon absorption (2PA) cross-sections of the fluorene derivatives were measured by the open aperture Z-scan method. The quantum yields of singlet oxygen generation under one- and two-photon excitation ([Phi][sub Delta] and 2PA[Phi][sub Delta], respectively) were determined by the direct measurement of singlet oxygen luminescence at ≈ 1270 nm. The values of [Phi][sub Delta] were independent of excitation wavelength, ranging from 0.6 - 0.9. The singlet oxygen quantum yields under two-photon excitation were 2PA[Phi][sub Delta] ½[Phi][sub Delta, indicating that the two processes exhibited the same mechanism of singlet oxygen production, independent of the mechanism of photon absorption.Ph.D.
Department of Chemistry
Sciences
Chemistry PhD