NIFEDIPINE INHIBITS HYPOXIC PULMONARY VASOCONSTRICTION DURING REST AND EXERCISE IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE - A CONTROLLED DOUBLE-BLIND-STUDY

Abstract

To determine whether nifedipine reduces pulmonary artery pressure and pulmonary vascular resistance index during rest and exercise in patients with hypoxic pulmonary hypertension, 6 clinically stable patients were studied using a randomized, double-blind, crossover design. While patients were hypoxic, nifedipine significantly lowered mean pulmonary artery pressure during rest from (mean .+-. SEM [standard error of the mean]) 38 .+-. 2 mmHg with placebo to 35 .+-. 3 mm Hg with nifedipine (P < 0.01) and during exercise from 63 .+-. 4 mm Hg with placebo to 51 .+-. 3 with nifedipine (P < 0.01). During hypoxia nifedipine reduced pulmonary vascular resistance index during rest by 27% from 7.84 .+-. 0.5 U with placebo to 5.71 .+-. 0.6 U with nifedipine (P < 0.02) and during exercise by 44% from 7.84 .+-. 1 U with placebo to 4.37 .+-. 1 U with nifedipine (P < 0.001). Nifedipine when added to low flow O2 reduced pulmonary vascular resistance index during rest by 16% from 6.15 .+-. 0.8 U with O2 to 5.14 .+-. 0.5 U with O2 plus nifedipine (P < 0.007) and during exercise by 27% from 5.9 .+-. 0.9 U with O2 to 4.3 .+-. 0.7 U with O2 plus nifedipine (P < 0.005). On room air nifedipine decreased by PaO2 [O2 partial pressure] during rest by only 4 .+-. 1 mm Hg and did not decrease exercise PaO2. During O2 therapy nifedipine decreased PaO2 during rest by 12 .+-. 4 mmHg and during exercise by 8 .+-. 3 mm Hg. Nifedipine therapy substantially increased O2 delivery during rest and exercise. Nifedipine acutely lowered pulmonary artery pressure and pulmonary vascular resistance index during rest and exercise in patients with clinically stable chronic obstructive pulmonary disease. Nifedipine may be a useful adjuvant to supplemental O2 in the treatment of hypoxic pulmonary hypertension.