[Effects of oral almitrine on the distribution of VA/Q ratio in chronic obstructive lung diseases (author's transl)]

Abstract

A double blind study of effects of a low dose of almitrine has been performed in patients with severe chronic obstructive lung diseases. Besides hemodynamic and ventilation data, ventilation-perfusion ratio distribution was measured by the inert gas method in order to try to explain the improvement in blood gases caused by this drug. At the dose of 1.5 mg/kg almitrine produces : 1) an increase in ventilation and PaO2, 2) no change in pulmonary vascular resistances compared to a rise on placebo, 3) a drop of 4% in the percentage of cardiac output perfusing low VA/Q lung units with a concomitant increase in lung units with VA/Q ratio between 0.1 and 10, and 4) no significant change in the distribution of ventilation. The change in the distribution of blood flow is one of the causes of the rise in PaO2, but its mechanism is at yet not clear. The present results suggest arterial vasoconstriction in units with very low VA/Q accompanied by diversion of blood flow towards lung units with higher VA/Q ratio.