Hypoxic challenge assessment in individuals with obstructive sleep apnea.
BACKGROUND
The 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.


METHODS
Fifteen 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.


RESULTS
Four 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.


CONCLUSIONS
OSA 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.
Respiratory Support and Sleep Centre, Papworth Hospital NHS Foundation Trust, Papworth Everard, Cambridge CB23 3RE, UK.
Masood
M
Ali
Ian E
IE
Smith
Atul
A
Gulati
John M
JM
Shneerson
D000328:Adult; D000368:Aged; D000401:Aircraft; D000531:Altitude; D002245:Carbon Dioxide / Q000097:blood; D002248:Carbon Monoxide / Q000097:blood; D045422:Continuous Positive Airway Pressure; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011237:Predictive Value of Tests; D012307:Risk Factors; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000453:epidemiology / Q000503:physiopathology / Q000628:therapy; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology / Q000503:physiopathology / Q000628:therapy; D014195:Travel
D002245:Carbon Dioxide; D002248:Carbon Monoxide; D010100:Oxygen