Randomized, placebo controlled trial evaluating efficacy of acetazolamide in preventing altitude related adverse health effects (ARAHE) in lowlanders with chronic obstructive lung disease travelling from 760 m to 3200 m.

This is a randomized, placebo-controlled, double-blind parallel trial evaluating the efficacy of acetazolamide prophylaxis in reducing the incidence of altitude related adverse health effects (ARAHE) in lowlanders with chronic obstructive pulmonary disease travelling to altitude. Participants living in the Bishkek area, Kyrgyzstan (760m), will be transferred by car within 4h to the Tuja Ashu high altitude clinic (3200 m), and stay there for 2 days. Acetazolamide 375mg/day (or placebo), will be administered before departure at 760 m and during the stay at altitude. Outcomes will be assessed during the stay at 3200 m.

An interim analysis will be carried out when 90 patients will have completed the study or after the first year. The Peto's method will be used to correct the P-values.

Inclusion Criteria:

• Male and female patients, age 18-75 yrs.
• COPD diagnosed according to GOLD, FEV1 40-80% predicted, SpO2 ≥92% at 750 m.
• Born, raised and currently living at low altitude (<800m).
• Written informed consent.

Exclusion Criteria:

• COPD exacerbation, very severe COPD with hypoxemia at low altitude (FEV1/FVC <0.7, FEV1 <40% predicted, oxygen saturation on room air <92% at 750 m).
• Comorbidities such as uncontrolled cardiovascular disease, i.e., unstable systemic arterial hypertension, coronary artery disease; previous stroke; OSA; pneumothorax in the last 2 months.
• Internal, neurologic, rheumatologic or psychiatric disease including current heavy smoking (>20 cigarettes per day)
• Known renal failure or allergy to acetazolamide and other sulfonamides