Aviat Space Envir Md
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The adverse physiological effects of flight, caused by ascent to altitude and its associated reduction in barometric pressure, have been known since the first manned balloon flights in the 19th century. It soon became apparent that the way to protect the occupant of an aircraft from the effects of ascent to altitude was to enclose either the individual, or the cabin, in a sealed or pressurized environment. ⋯ More recent research findings on the physiological and psycho-physiological effects of mild hypoxia have provided cause for renewed discussion of the "acceptability" of a maximum cabin cruise altitude of 8000 ft; however, we did not find sufficient scientific data to recommend a change in the cabin altitude of transport category aircraft. The Aerospace Medical Association (AsMA) should support further research to evaluate the safety, performance and comfort of occupants at altitudes between 5000 and 10,000 ft.
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Aviat Space Envir Md · Apr 2008
Case ReportsPneumomediastinum diagnosed by chest radiography after centrifuge training.
A retrospective review of the human centrifuge training database in the Republic of Singapore Air Force was carried out for the period 1995-2006. Six cases of pneumomediastinum were reported in aircrew trainees who underwent ab initio human centrifuge training. Only two of the six cases presented with chest discomfort with or without neck pain, with the rest being incidental findings picked up during routine medical examination. ⋯ This is believed to be attributable to over-zealous or incorrect performance of the anti-G straining maneuver in trainees unaccustomed to a high G environment. Trainees subsequently underwent a structured weights training program and centrifuge training profiles were reviewed and revised to allow graduated G training. All affected trainees recovered uneventfully with conservative management, and were able to return to flying training.
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Aviat Space Envir Md · Feb 2008
Trait anxiety and salivary cortisol during free living and military stress.
Accumulating evidence suggests that negative affect is associated with elevated cortisol. Limited research has investigated this association in young, highly functioning, and stress-resilient populations. ⋯ These findings suggest that trait anxiety influences the diurnal cortisol pattern in young, apparently healthy men during free-living conditions, but does not predict the cortisol response to uncontrollable military stress.
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Aviat Space Envir Md · Feb 2008
Profound hypoxemia in pulmonary patients in airline-equivalent hypoxia: roles of VA/Q and shunt.
Airliners at cruise altitudes have cabin pressures of 84.3-75.2 kPa, equivalent to 5000-8000 ft. Supplementary oxygen in flight is generally advised for patients whose ground-level arterial oxygen saturation by pulse oximetry (SpO2) is < 92%. However, some pulmonary patients with values above that threshold nevertheless develop profound in-flight hypoxemia (SpO2 < or = 82%) as cabin pressure falls. This experiment measured the contributions of ventilation-perfusion ratio (VA/Q) and pulmonary shunt to that phenomenon. ⋯ In patients with similar ground-level SpO2, profound hypoxemia was more likely to develop in those with reduced VA/Q (< or = 0.69) as opposed to those with shunts of 20%. Measurement of VA/Q and shunt during hypoxic hypoxia improves prediction of patient need for supplementary oxygen on airline flights.