The Dewey monitor: Pulse oximetry can independently detect hypoxia in a rebreather diver.
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Rebreather diving has one of the highest fatality rates per man hour of any diving activity in the world. The leading cause of death is hypoxia, typically from equipment or procedural failures. Hypoxia causes very few symptoms prior to causing loss of consciousness. Additionally, since the electronics responsible for controlling oxygen levels in rebreathers often control their alarm systems, frequently divers do not receive any external warnings. This study investigated the use of a forehead pulse oximeter as an independent warning device in the event of rebreather failure. Ten test subjects (seven male, three female, median age 29, range 26-35) exercised at a targeted rate of 2 L/minute oxygen consumption while on a non-functional rebreather breathing loop (mean consumption achieved 2.09 ± 0.36 L/minute). Each subject was tested both at the surface and at pressurized depth of 77 fsw (starting pO₂=0.7 atm). The data show that a pulse oximeter could be used to provide an Mk 16 rebreather diver with a minimum mean of 49 seconds (± 17 seconds SD) of warning time after a noticeable change in blood oxygen saturation (SpO₂ ≤ 95%) but before any risk of loss of consciousness (calculated SpO₂ ≤ 80%), so that the diver may take mitigating actions. No statistical difference in warning time was found between the tests at surface and at 77 fsw (P=0.46).
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Associate Professor of Anesthesiology
Dr Freiberger works on the translation of basic science research on reactive oxygen species signaling into clinical practice involving hyperbaric oxygen (HBO). He has performed animal experiments in the use of HBO for ischemic preconditioning and he is currently funded to conduct a randomized controlled trial of the use of HBO for the treatment of bisphosphonate-induced osteonecrosis of the jaw. The mechanisms of action for HBO in the treatment of: diabetic wounds, bony and soft tissue rad
Professor of Anesthesiology
Research interests include the study of cardiorespiratory function in humans exposed to environmental conditions ranging from 200 feet of seawater depth to high altitude, gas exchange during diving, the pathophysiology of high altitude pulmonary edema, the effect of anesthesia and postoperative analgesia on pulmonary function and monitoring of tissue oxygenation. Ongoing human studies include the use of fractals to study breathing patterns during environmental and perioperative stress, mechanism
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