1. Almitrine at a low dose of 100 mg orally significantly raises Pao2 and lowers Paco2 in patients with chronic obstructive pulmonary disease, compared with placebo, when they were breathing air or 28% oxygen.
2. The estimated ideal alveolar — arterial Po2 difference was less after almitrine compared with placebo, when patients were breathing either air or 28% oxygen.
3. After almitrine overall ventilation breathing air increased by 10% but this did not reach statistical significance. During 28% oxygen breathing almitrine hardly altered overall ventilation but the inspiratory duty cycle (Ti/Ttot.) decreased and mean inspiratory flow rate (VT/Ti) increased compared with placebo. These changes were significant on a paired t-test (P<0.05).
4. Changes in both volume and pattern of breathing may explain the improved gas exchange in the lung after almitrine.