Effect of nifedipine on physiologic shunting and oxygenation in chronic obstructive pulmonary disease

purpose: To assess changes in physiologic shunting and oxygenation following short-term treatment with nifedipine in patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease. patients and methods: Changes in pulmonary vascular pressure, pulmonary vascular resistance, venous admixture, and systemic arterial oxygen tension following sublingual administration of 20 mg of nifedipine were studied in 18 patients (13 men, 5 women; mean age of 59.7 [SD 7.2] years) using Swan-Ganz catheterization. These patients had a mean peak expiratory flow rate of 112 (SD 27) L/min (mean 22.2 [SD 12.2]% of predicted value), mean forced expiratory volume in 1 second (FEV 1) of 0.84 (SD 0.23) L (mean 31.2 [SD 8.5]% of predicted value), mean FEV 1/forced vital capacity ratio of 31.6 (SD 4.5), and mean carbon monoxide diffusing capacity of 6.8 (SD 1.96) mmol/min/kPa. results: There was a significant decrease in mean pulmonary vascular resistance (562 to 371 dyne sec.cm −5) and a significant reduction in the mean pulmonary arterial pressure (mean 32.8 to 23.6 mm Hg). Pulmonary venous admixture, however, increased significantly from the baseline mean of 44.6% (SD 16.1) to a mean of 56% (SD 15.6), and the mean arterial oxygen tension decreased from 5.8 (SD 1.3) kPa to 4.5 (SD 0.8) kPa at 60 minutes following drug administration (p < 0.001). conclusion: The role of nifedipine in the treatment of pulmonary hypertension secondary to chronic bronchitis may be limited because of its deleterious effect on venous admixture.