Effect of Oxygen Flow on Passenger Face Mask Performance

摘要

The passenger emergency oxygen system presently used onboard USAF transort aircraft is a phase dilution continuous flow system, and is similar to that on commercial aircraft. The mask is certified for emergency use up to 40,000 ft, when provided with an oxygen flow in accord with military specifications (MIL-D-19326F). We have evaluated the effect on arterial hemoglobin saturation (SaO2), of reductions in oxygen flow (below those specified) to the emergency mask; the volunteer subjects were exposed to simulated altitudes of 40, 35, 30 and 25 thousand feet. At reduced oxygen flows to the emergency pasenger mask, SaO2, was: 88 + or - 2.8%, 92 + or - 3.5%, 98 + or - 1.2%, and 97 + or - 1.0%; at 40, 35, 30, and 25 thousand ft respectively. Although halving the oxygen flow to the mask at 25,000 ft and 30,000 ft resulted in acceptable levels of SaO2, reductions in flow--at 35,000 ft and, especially, at 40,000 ft--were not as well tolerated. at 40,000 ft and, to a lesser extent, 35,000 ft, inboard leakage of ambient air around the face and through the anti-suffocation valve seriously compromised SaO2, Because passengers suddenly exposed to a 40,000-ft cabin altitude would undboubtedly suffer from anxiety and would tend to hyperventilate, and because of limitaions inherent in continuous flow oxygen systems, we recommend that oxygen flow to the passenger mask (as specified in MIL-D-19326F) be reduced with great caution. Keywords: Air breathing equivalency; Arterial hemoglobin saturation; Dixie Cupmask; Emergency passenger mask; Hyperventilation; Hypoxia; Loss of consciousness; Steady-state.