Dr. Nareg Roubinian of the University of California, San Francisco and colleagues came to this conclusion after an observational study of patients who were passengers on regular airline flights.
Dr. Roubinian told Reuters Health by email, “We found that hypoxemia occurred commonly during flight, especially in longer flights and in individuals who had used oxygen in the past.”
The researchers note that the Federal Aviation Administration requires that cabin pressure during flight be maintained at or below that at 8000 feet. Even the modest levels of hypoxemia experienced during flight could result in further elevation of pulmonary artery pressures.
To investigate, the team prospectively studied 34 patients with pre-arranged travel plans. Around one-third of them reported being evaluated for flight safety by their treating physician. More than a third reported prior use of oxygen during air travel.
They were supplied with a fingertip pulse oximeter and a handheld analogue altimeter and instructed in their use.
They performed 10 sets of recordings of SpO2, heart rate, and cabin pressure during different stages of their flights from pre-boarding to final descent and arrival at the destination.
The median flight duration was 3.6 hours. The mean cabin pressure at cruising altitude was equivalent to that at 6456 feet above sea level but ranged as high as 8600 feet.
The median drop in Sp02 from sea level to cruising altitude was 4.9% but fell by as much as 15.8%. Nine of the volunteers (26.6%) experienced oxygen desaturation with a minimum SpO2 of 74%. Seven had a history of home oxygen use.[10end]
Nine of the subjects used oxygen during the flight and 2 of this group experienced desaturations.
Thirteen (38%) experienced symptoms during flight but only 5 of these subjects also had desaturations. There was no significant association between clinical variables and desaturation.
Oxygen desaturations were associated with cabin pressures equivalent to those beyond 6000 feet. The lowest reported oxygen saturations occurred after ambulation at cruising altitude. Median flight duration was also longer in those with desaturation (4.0 versus 2.5 hours).
Given the potential risks, the researchers recommend that all such patients “consult with their physician prior to air travel.” Those with a history of oxygen use, including nocturnal use should be evaluated for supplemental in-flight oxygen as should all traveling on flights lasting more than 2.5 hours.
Dr. Roubinian added that “We hope this study will generate further study and discussion of air travel in individuals with pulmonary hypertension and increase awareness of the challenges that many individuals face.”