NEW YORK (Reuters Health) - Results on the hypoxia inhalation test (also known as the hypoxia altitude simulation test) predict how patients with chronic obstructive pulmonary disease (COPD) will respond during air travel, researchers from New Zealand report in the April issue of Chest.

Lead investigator Paul T. Kelly of Christchurch Hospital told Reuters Health, "Air travel will cause significant desaturation in passengers with COPD, which will be worsened by in-flight activity such as visiting the lavatory."

Kelly and his colleagues performed preflight respiratory function tests on 13 volunteers with COPD who were planning to take commercial flights for their own purposes. Physiologic parameters were measured while subjects were airborne, and the hypoxia inhalation tests were done after the flights.

Mean altitude during the flights was 2165 m. Participants did not use oxygen, and no adverse events were recorded. However, oxygen saturation fell from 95% before the flight, to 86% during the flight, and to as low as 78% during onboard activity.

Hypoxia inhalation tests conducted an average of 2 weeks after the flight had similar results, with a mean oxygen saturation value of 84%. Subjects' mean partial pressure of inspired oxygen was significantly higher during the flights than on the hypoxia inhalation tests (113 versus 107 mm Hg), suggesting that oxygen saturation values on the test have the closest correlation with the in-flight values.

"We found that simulating the aircraft environment in the laboratory using a low inspired oxygen gas mix was the best test to predict in-flight response in this group of passengers," Kelly said.

In an accompanying editorial, Dr. Lawrence C. Mohr of the Medical University of Charleston, South Carolina, notes that hypoxia altitude simulation tests are "being used with increasing frequency for the evaluation of cardiopulmonary patients prior to commercial air travel." He calls for more research in order to improve simulations of in-flight environments for specific groups of patients.

Chest 2008;133:839-842,920-926.

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