Seemingly controlled obesity hypoventilation syndrome can still cause in-flight hypoxemia

By Scott Baltic

NEW YORK (Reuters Health) - People with obesity hypoventilation syndrome (OHS) are at substantial risk of severe hypoxemia during air travel, even if their disease is otherwise well controlled with nocturnal non-invasive ventilation, according to a small UK study.

"I would recommend an assessment at least 6 weeks before the intended air travel to allow some time to make arrangements for interventions like in-flight oxygen if needed," lead author Dr. Masood Ali of Southend University Hospital NHS Foundation Trust in Essex told Reuters Health by email.

Commercial airline flights can cruise at altitudes as high as 38,000 feet, but are required to keep a cabin pressure of no less than the atmospheric pressure at 8,000 feet, Dr. Ali and colleagues write in Respirology, online July 23.

While healthy people can tolerate the lower arterial oxygen tension at this pressure, those with respiratory disease may develop severe hypoxemia.

To investigate, the researchers had 13 OHS patients undergo various assessments, including a hypoxic challenge test that simulates the arterial oxygen desaturation that typically occurs during air travel. All patients had received nocturnal non-invasive ventilation for at least three months prior to the study.

During the hypoxic challenge test, patients breathed a 15% oxygen/85% nitrogen mix for 20 minutes. Seven of the 13 participants tested positive, that is, experienced an arterial oxygen tension <6.6 kPa and/or oxygen saturation <85%, thus meeting criteria for in-flight supplementary oxygen, say the researchers.

Dr. Ali said OHS is often not recognized by physicians. "Although there is significant morbidity associated with OHS, several studies have consistently reported that it is frequently undiagnosed, and treatment is often delayed," he said.

About 10-20% of obese patients with obstructive sleep apnea will also have OHS, with a higher percentage among those with extreme obesity (body mass index of at least 40), according to the American Lung Association.

A conservative estimate is that between one in 300 and one in 600 adults in the general population have OHS, Dr. Norman H. Edelman of the American Lung Association told Reuters Health by email.

Primary care physicians should suspect OHS if an obese patient has sleep apnea, Edelman advised, adding that the initial signs and symptoms of OHS can be subtle, though a throbbing morning headache is common.

SOURCE: http://bit.ly/1v849QN

Respirology 2014.

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