Improving Sleep and Oxygen Saturation in a Crew-Rest Compartment Mock-up with Oxygen Enrichment

Kurzfassung

Introduction: Adequate crew recovery on long-haul flights is critically important. Previous data of our group suggests that sleep in a crew rest compartment mock-up (CRC) under conditions equivalent to an airliner cabin at cruising altitude is impaired and leads to a reduction of blood oxygen saturation (SpO2). To identify possible causes for this interaction of sleep and SpO2 under hypobaric conditions we conducted a set of experiments altering overall ambient pressure (pA) and partial pressure of oxygen (pO2) independently by oxygen enrichment of the atmosphere inside the CRC. Methods: We used a specially furnished pressure chamber to realistically simulate the atmospheric conditions, confinement and noise inside an airliner. 12 healthy volunteers (6 females, age 26.2 years ± 5.1 SD) slept 3 nights in the CRC with different compositions of the atmosphere: 1. flight condition (pA and pO2 equivalent to a cabin altitude of 8.000 ft), 2. ground condition (pA and pO2 analog to local ground level) and 3. oxygen enrichment (pA corresponding to flight condition and pO2 to ground condition). Participants were blind to the test condition and given a 4-h sleep opportunity each night (0:00-4:00am). Polysomnographic data and SpO2 were recorded. Results: Sleep parameters improved significantly between flight condition and oxygen enrichment. Sleep onset latency was reduced from (mean±SE) 17 ± 5 to 13 ± 2 Minutes (p<0.0001), sleep period time (SPT) prolonged from 218 ± 3 as compared to 227 ± 3 Minutes (p<0.01), and sleep efficiency increased from 83.9% ± 2.3 to 89.9% ± 1.7 (p<0.01). SpO2 during SPT increased from 88.3% ± 0.5 to 96.4% ± 0.3 (p<0.0001). Whereas participants experienced hypoxia (SpO2<90%) during 70% of SPT under flight condition, they were protected against it during oxygen enrichment. Neither the sleep parameters nor SpO2 differed significantly between oxygen enrichment and ground condition. Conclusion: Sleep impairment under flight condition seems to be caused by the decrease of pO2 and not by the reduced pA. Oxygen enrichment of the cabin atmosphere may be an effective countermeasure against sleep impairment and sleep induced hypoxia.