DELETERIOUS EFFECT OF NIFEDIPINE ON PULMONARY GAS-EXCHANGE IN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

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Abstract
Nifedipine was given, 20 mg sublingually, to 6 patients with pulmonary hypertension secondary to advanced chronic obstructive pulmonary disease, and its effects on hemodynamics, blood gases, lung mechanics and the distribution of ventilation-perfusion ratios (.ovrhdot.VA/.ovrhdot.Q) were investigated. Systemic vasodilation was obtained, with a reduction in mean systemic arterial pressure and in systemic vascular resistance by 16 and 36%, respectively. Cardiac index increased by 29%. Pulmonary vascular resistance decreased by 28%, without changes in pulmonary arterial mean pressures. Arterial PO2 [partial pressure of O2] decreased from 52 .+-. 4 to 47 .+-. 3 mm Hg (P < 0.001). A deterioration in .ovrhdot.VA/.ovrhdot.Q matching could be demonstrated, with a redistribution of blood flow into the lungs by a diversion of 20% of total blood flow from units with normal .ovrhdot.VA/.ovrhdot.Q, between 0.23 to 3.0, to hypoxic units with low .ovrhdot.VA/.ovrhdot.Q from 0.19-0.009. These changes might be explained by a partial inhibition of hypoxic pulmonary vasoconstriction.

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