Oxygen requirement to reverse altitude-induced hypoxemia with continuous flow and pulsed dose oxygen.

BACKGROUND: Hypoxemia secondary to reduced barometric pressure is a complication of ascent to altitude. We designed a study to compare the reversal of hypobaric hypoxemia at 14,000 ft with continuous flow oxygen from a cylinder and pulsed dose oxygen from a portable concentrator.

METHODS: There were 30 healthy volunteers who were randomized to one of three study groups, placed in an altitude chamber, and ascended to 14,000 ft. There were 10 subjects in each study group. Subjects breathed room air for 10 min to induce hypoxemia. Oxygen was then delivered via a nasal cannula from a cylinder at 1, 2, or 3 lpm of continuous flow for 10 min. The subjects again breathed room air at altitude for 10 min and were then placed on pulsed dose oxygen and titrated to obtain the continuous flow Spo2 equivalent. Spo2, Etco2, RR, HR, Hgb, and tissue oxygenation (Sto2) were continuously recorded.

RESULTS: The 1-lpm group's Spo2 range was 89-99%. The 2-lpm group's Spo2 range was 95-98%, and the 3-lpm group's Spo2 range was 95-99%. The 2-lpm and 3-lpm flows were able to correct hypoxemia in every subject. The mean pulsed dose required to achieve an equivalent Spo2 ranged from 36.8 ml ± 18.9 ml in the 1-lpm arm, and 102.4 ml ± 53.8 in the 3-lpm arm.

CONCLUSIONS: Portable oxygen concentrators using pulsed dose technology corrected hypoxemia in every subject. Oxygen concentrators may be an alternative to liquid oxygen or cylinders for use during aeromedical evacuation.