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 (FEV1) of 0.84 (SD 0.23) L (mean 31.2 [SD 8.5]% of predicted value), mean FEV1/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.