Mountaineering oxygen mask performance at 4572 m.
BACKGROUND: Supplemental oxygen delivered by mask at high altitude is used to increase arterial oxygen saturation (SaO2) thereby mitigating physiological and cognitive dysfunction secondary to hypoxemia. Historically, mask performance has not been well documented although it may be a critical factor in determining the success of an expedition. METHODS: Three mountaineering masks were used by ten healthy, nonaltitude-acclimatized participants (eight males, two females) to compare ventilatory responses, SaO2, heart rate, and end-tidal gases. Masks tested were: Life Support Engineering Ltd. (LSEL); Zvezda Enterprise (ZE); and a prototype of our own design (Duke). Test conditions were as follows: simulated altitude at 0 and 4572 m (15,000 ft); rest and cycle exercise at 75 W; and supplemental oxygen flow at 0, 1.1 +/- 0.05, and 1.7 +/- 0.06 L x min(-1) (mean +/- SD). Statistical analysis was completed using GLM (SAS software). RESULTS: As there were no differences between the 1.1 and 1.7 L x min(-1) flow rates, the data were pooled. All three masks improved SaO2 with the ZE and Duke masks being more effective during exercise, maintaining mean SaO2 >90%. CONCLUSIONS: All three masks provided at least partial protection of physiological norms during rest and exercise at 4572 m. The ZE and Duke systems offered the best performance. The need for performance evaluation as part of system design is evident as subtle differences in design can significantly affect performance.
Hendricks, DM; Pollock, NW; Natoli, MJ; Vann, RD
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