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Hypoxia, Hyperbaric Oxygen and Hypothermia: Some Experimental and Clinical Studies
Get PDFThis thesis contains details of a series of studies in which the interrelationship of hyperbaric oxygen, hypothermia and tissue hypoxia has been examined. The data derive from both experimental and clinical observations. The early experimental studies were designed to examine the pathophysiological changes occurring in animals subjected to various generalised hypoxic insults with a view to subsequent investigation of the effects of hyperbaric oxygen and hypothermia. The limitations of both techniques were revealed in later experimental and clinical studies. These investigations, however, were by no means entirely negative and yielded much information which proved to be of value in the management of a number of clinical conditions with an hypoxic basis, e.g., cardiac arrest, shock, severe anaemia, fat embolism and accidental hypothermia. The introductory chapter includes a summary of the mechanisms of oxygen transport from the lungs to the tissues followed by a brief description of the principal physiological and biochemical disturbances associated with hypoxia. A review of the subjects of hyperbaric oxygen and hypothermia serves as an introduction to more detailed discussion in later chapters. The ability of hyperbaric oxygen to increase oxygen storage capacity in the body was demonstrated by means of respiratory arrest in the anaesthetised dog. In the presence of a normally functioning circulation asphyxia was tolerated for periods of over 20 minutes after breathing oxygen at two atmospheres absolute (2 ATA). In the presence of an arrested circulation the equivalent period was eight minutes - representing only a modest increase on the duration of safe circulatory arrest attainable at normal atmospheric pressure. The combination of hyperbaric oxygen (2 ATA) and moderate hypothermia (2
