EFFECT OF NIFEDIPINE ON PHYSIOLOGICAL SHUNTING AND OXYGENATION IN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

PURPOSE: To assess changes in physiologic shunting and oxygenation fol lowing short-term treatment with nifedipine in patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease. PATI ENTS AND METHODS. Changes in pulmonary vascular pressure, pulmonary va scular resistance, venous admixture, and systemic arterial oxygen tens ion following sublingual administration of 20 mg of nifedipine were st udied 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 expi ratory flow rate of 112 (SD 27) L/min (mean 22.2 [SD 12.2]% of predict ed value), mean forced expiratory volume in 1 second (FEV1) of 0.84 (S D 0.23) L (mean 31.2 [SD 8.5]% of predicted value), mean FEV1/forced v ital capacity ratio of 31.6 (SD 4.5), and mean carbon monoxide diffusi ng capacity of 6.8 (SD 1.96) mmol/min/kPa. RESULTS: There was a signif icant decrease in mean pulmonary vascular resistance (562 to 371 dyne sec.CM-5) and a significant reduction in the mean pulmonary arterial p ressure (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 decreas ed from 5.8 (SD 1.3) kPa to 4.5 (SD 0.8) kPa at 60 minutes following d rug administration (p < 0.001). CONCLUSION: The role of nifedipine in the treatment of pulmonary hypertension secondary to chronic bronchiti s may be limited because of its deleterious effect on venous admixture .