Inflight oxygen saturation decrements in aeromedical evacuation patients

Past studies have shown that patients with severe chronic obstructive pulmonary disease (COPD) may experience oxygen desaturation at the cabin altitudes of pressurized aircraft. Because COPD can be associated in varying degrees with ischemic heart disease (IHD), and because the consequences of hypoxia in such patients can be significant, the ground and altitude pulse oximeter readings of 24 ambulatory aeromedical evacuation patients with known or suspected IHD were recorded. Written, informed consent, as well as smoking history and respiratory spirometry were obtained preflight. Results showed a mean saturation decrease of 5.5 percentage points (95% CI: 4.5-6.4). The mean cabin altitude was 6900 ft (range: 2500-8100). No patients experienced clinical symptoms. Of 24 patients, 3 were given supplemental oxygen when their inflight oximetry readings consistently read below 90%. Saturation decrease did not correlate specifically with age, smoking history, the FEV1/FVC ratio, or the inflight cabin altitude. We conclude that ambulatory aeromedical evacuation patients with known or suspected IHD may demonstrate mild decreases in oxygen saturation which are not readily predicted by age, smoking history, pre-flight spirometry, or inflight cabin altitude. Pulse oximetry compatible with aircraft electrical systems may provide useful inflight monitoring on such patients.