Nifedipine inhibits hypoxic pulmonary vasoconstriction during rest and exercise in patients with chronic obstructive...

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)