Oxygen delivery comparison of two constant-flow masks during flight to 6863 m

Differences in mask design may alter the oxygen flow required to gain similar oxygenation at a particular altitude. The selection of the most efficient mask would be advantageous for general aviation and other applications where oxygen supply is limited.

We compared a basic mask (BAS) without valves or oxygen reservoir bag to a test mask (TST) with three valves and a reservoir designed to deliver up to 80% oxygen for critically ill patients. Randomly assigned parachutists (n = 31) used the masks during a flight with a gradual climb to 6863 m (22,500 ft). The oxygen flow was individually controlled to produce oxygen saturation (SpO2) of 95-97% as determined by pulse oximetry. Oxygen flow and SpO2 were obtained every 305 m (1000 ft).

Baseline age, lung function indices, and SpO2 were comparable for the two groups. Mean in-flight Spo2 values were 95.3 +/- 0.5% for the BAS and 96.2 +/- 1.1 % for the TST, respectively. Above 3965 m (13,000 ft) the TST required significantly less oxygen flow than the BAS to maintain the target SpO2. At 6863 m (22,500 ft), mean oxygen flow was 5.5 +/- 3.5 L x min(-1) for the BAS vs. 3.4 +/- 2.3 L x min(-1) for the TST (p = 0.029). No adverse reactions were reported from either group.

The TST required significantly less oxygen flow compared with the BAS at high altitudes and may, therefore, reduce total oxygen use, resulting in reduced costs and longer oxygen availability during a flight.