Hypoxic challenge assessment in individuals with obstructive sleep apnea

BackgroundThe degree of arterial hypoxemia during air travel in individuals with obstructive sleep apnea (OSA) is not known. The Aerospace Medical Association considers a ground level arterial oxygen tension (PaO2) above 9.3 kPa as safe before air travel.MethodsFifteen subjects with untreated OSA (mean apnea–hypopnea index [AHI] 43/h) and 14 with treated OSA (mean AHI on CPAP 1.9/h) completed an assessment including hypoxic challenge test (HCT). The groups had similar mean age, mean BMI and pre-treatment OSA severity.ResultsFour subjects, all in the untreated group and with resting PaO2 >9.3 kPa and oxygen saturation (SpO2) >95%, had a positive HCT (PaO2 <6.6 kPa and/or SpO2 <85%). The PaO2 at the end of the HCT was significantly correlated with the minimum overnight SpO2 (r = .754, p = .002) but not with the daytime PaO2 and SpO2. Using a cut off value of 65%, the minimum overnight SpO2 had positive and negative predictive values of 57% and 100% respectively.ConclusionsOSA can be an additional risk factor for developing significant arterial hypoxemia during HCT. Baseline PaO2 and SpO2 did not predict arterial hypoxemia during the HCT. Minimum overnight SpO2 <65% may be used as a cut off to advise further assessment. Effective treatment of OSA seems to be the best option before air travel.