Nifedipine inhibits hypoxic pulmonary vasoconstriction during rest and exercise in patients with chronic obstructive pulmonary disease. A controlled double-blind study.

: To determine whether nifedipine reduces pulmonary artery pressure and pulmonary vascular resistance index during rest and exercise in patients with hypoxic pulmonary hypertension, we studied 6 clinically stable patients using a randomized, double-blind, crossover design. While patients were hypoxic, nifedipine significantly lowered mean pulmonary artery pressure during rest from (mean +/- SEM) 38 +/- 2 mmHg with placebo to 35 +/- 3 mmHg with nifedipine (p less than 0.01) and during exercise from 63 +/- 4 mmHg with placebo to 51 +/- 3 with nifedipine (p less than 0.01). During hypoxia nifedipine reduced pulmonary vascular resistance index during rest by 27% from 7.84 +/- 0.5 units with placebo to 5.71 +/- 0.6 units with nifedipine (p less than 0.02) and during exercise by 44% from 7.84 +/- 1 units with placebo to 4.37 +/- 1 units with nifedipine (p less than 0.001). Nifedipine when added to low flow oxygen reduced pulmonary vascular resistance index during rest by 16% from 6.15 +/- 0.8 units with oxygen to 5.14 +/- 0.5 units with oxygen plus nifedipine (p less than 0.007) and during exercise by 27% from 5.9 +/- 0.9 units with oxygen to 4.3 +/- 0.7 units with oxygen plus nifedipine (p less than 0.005). On room air nifedipine decreased PaO2 during rest by only 4 +/- 1 mmHg and did not decrease exercise PaO2. During oxygen therapy nifedipine decreased PaO2 during rest by 12 +/- 4 mmHg and during exercise by 8 +/- 3 mmHg. Nifedipine therapy, however, substantially increased oxygen delivery during rest and exercise.(ABSTRACT TRUNCATED AT 250 WORDS)