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Acetazolamide may prevent some patients with chronic obstructive pulmonary disease (COPD) from suffering altitude-related adverse health effects (ARAHE) when traveling, a randomized controlled trial showed.

In patients with moderate to severe COPD traveling to and staying for 2 days at 3,100 m, ARAHE occurred in 50% of those taking acetazolamide compared with 74% of those taking placebo (HR 0.60, 95% CI 0.40-0.89, P<0.002), reported Konrad Bloch, MD, of the Swiss-Kyrgyz High Altitude Medicine and Research Initiative in Zurich.

All participants randomized in the study used structured self-monitoring (SSM) for symptoms and pulse oximetry, with a positive result for inclusion defined as an SpO₂ of <85% and/or symptoms of acute mountain sickness and/or discomfort.

The number needed to treat was 3.9 (95% CI 2.5-10.5), he said during the European Respiratory Society annual meeting.

Bloch noted that guidance to limit the negative health effects of altitude for COPD patients includes encouraging patients to make a slower ascent to higher altitudes and limiting risks of overexertion.

A previous randomized controlled trial also showed that oxygen treatments at night led to a among COPD patients traveling to 2,048 m, and in this patient population showed that acetazolamide reduced ARAHE when taken before and during stays in areas with higher altitudes.

Bloch explained that the spontaneity of travel and similar situations is often the reason for using SSM, as opposed to a preventive regimen.

"Many patients do not know what they are doing the next day, and therefore they might not have enough time to start preventive treatment," he said. "In addition ... when you apply self-monitoring to limit the preventive treatment to a selective group, you can reduce the amount of the medication considerably -- because only about one-quarter of patients need or will take the medication with a similar number needed to treat."

Looking at SSM-negative patients, 42% experienced ARAHE.

During a Q&A session, Bloch noted that "we found that there were very mild side effects occasionally, consisting of tingling sensations and some poor taste of the medication, but they were not relevant clinically."

For those who did experience some relevant side effects, Bloch explained that they were supported with oxygen therapy, which, in some cases, "relieved their symptoms immediately." Others were brought down to lower altitudes.

Initially, 241 patients with moderate or severe COPD traveled from an elevation of 760 m to a clinic located at 3,100 m by a bus over the course of a few hours. At baseline elevation, patients had a forced expiratory volume in the first second (FEV₁) of 40-80% predicted, an oxygen saturation (SpO₂) of ≥92%, and a partial pressure of carbon dioxide (PaCO₂) of <6 kPa.

Participants utilized SSM techniques four times per day, with 79 patients testing negative and 162 patients testing positive. Of the SSM-positive patients, 76 received acetazolamide 375 mg daily, 81 received placebo, and five were excluded.

A total of 157 patients were included in the final study analysis; 85 were men, and mean age was 59.

Bloch noted that avoidance of high altitudes is not always a possibility when traveling, so assessing multiple elevations in studies is crucial for these patients.

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