Effect of acetazolamide on pulmonary vascular haemodynamics in patients with COPD going to altitude: a randomised, placebocontrolled, double-blind trial

Background COPD may predispose to symptomatic pulmonary hypertension at high altitude. We investigated haemodynamic changes in lowlanders with COPD ascending to 3100 m and evaluated whether preventive acetazolamide treatment would attenuate the altitude-induced increase in pulmonary artery pressure (PAP). Methods In this randomised, placebo-controlled, double-blind, parallel-group trial, patients with COPD Global Initiative for Chronic Obstructive Lung Disease grades 2-3 who were living < 800 m and had peripheral oxygen saturation (SpO2) > 92% and arterial carbon dioxide tension < 6 kPa were randomised to receive either acetazolamide (125-250 mg center dot day(-1)) or placebo capsules, starting 24 h before ascent from 760 m and during a 2-day stay at 3100 m. Echocardiography, pulse oximetry and clinical assessments were performed at 760 m and after the first night at 3100 m. Primary outcome was PAP assessed by tricuspid regurgitation pressure gradient (TRPG). Results 112 patients (68% men, mean +/- SD age 59 +/- 8 years, forced expiratory volume in 1 s (FEV1) 61 +/- 12% pred, SpO 2 95 +/- 2%) were included. Mean +/- SD TRPG increased from 22 +/- 7 to 30 +/- 10 mmHg in 54 patients allocated to placebo and from 20 +/- 5 to 24 +/- 7 mmHg in 58 patients allocated to acetazolamide (both p < 0.05) resulting in a mean (95% CI) treatment effect of -5 (-9 to -1) mmHg ( p=0.015). In patients assigned to placebo at 760/3100 m, mean +/- SD SpO 2 was 95 +/- 2%/88 +/- 3%; in the acetazolamide group, the respective values were 94 +/- 2%/90 +/- 3% (both p < 0.05), resulting in a treatment effect of +2 (1 to 3)% ( p=0.001). Conclusions In lowlanders with COPD travelling to 3100 m, preventive acetazolamide treatment attenuated the altitude-induced rise in PAP and improved oxygenation.