Acetazolamide helps patients with COPD reach new peaks

Acetazolamide helps to reduce the chances of altitude-related adverse health effects (ARAHE) in patients with chronic obstructive pulmonary disease (COPD) in a study reported at ERS.

ARAHE occurred in 50 percent of patients taking acetazolamide vs 74 percent of those taking placebo (hazard ratio [HR], 0.60, 95 percent confidence interval [CI], 0.40-0.89; p<0.002) among patients with moderate-to-severe COPD traveling to and staying at an altitude of 3,100 metres for two days.

The number needed to treat was 3.9 (95 percent CI, 2.5-10.5) to prevent one ARAHE, reported Dr Konrad Bloch from the Swiss-Kyrgyz High Altitude Medicine and Research Initiative in Zurich, Switzerland at ERS 2023.

Symptoms worsen at high altitude

Air pressure drops as altitude increases. The effects of increased altitude and the associated hypobaric features can result in hypoxia in people with respiratory problems, particularly those with COPD. Their symptoms could get worse even if stable at low altitudes.

In fact, in a study in Norway, 25 percent of patients with COPD developed hypoxia-related symptoms in flight. [Respir Med 2011;105:50–56]

In the current study, participants traveled for hours by bus to a clinic 3,100 metres high, from an elevation of 760 metres. At baseline elevation, they had a forced expiratory volume in the first second (FEV₁) of 40–80 percent predicted, an oxygen saturation (SpO₂) of ≥92 percent, and a partial pressure of carbon dioxide (PaCO₂) of <6 kPa.

They used structured self-monitoring of their symptoms, together with pulse oximetry. SpO₂ was <85 percent, with symptoms of acute mountain sickness and/or discomfort.

Patients were given acetazolamide 375 mg daily or placebo. “There were mild side effects with treatment, consisting of tingling sensations and poor taste of the medication, but they were not relevant clinically,” reported Bloch. Those who experienced side effects were supported with oxygen therapy, which helped to address the symptoms in some patients. Others were brought down to lower altitudes.

How to reduce ARAHE

Bloch said it is not always feasible to avoid high altitudes when traveling, hence assessing multiple elevations in studies is crucial for COPD patients.

“Guidance to limit the negative health effects of altitude in COPD patients includes encouraging patients to make a slower ascent to higher altitudes and limiting risks of overexertion,” advised Bloch.

He added that the spontaneity of travel and similar situations is often the reason for using structured self-monitoring, 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,” Bloch said. “When you apply self-monitoring to limit preventive treatment to a selective group, the amount of medication can be reduced considerably because only about one-quarter of patients need or will take the medication, with a similar number needed to treat.”