Does almitrine bismesylate improve V/Q matching? An animal study.

Pulmonary vascular actions of almitrine bismesylate were studied in ferrets, rats, cats and dogs in conditions which simulated those of patients with hypoxic lung disease. All or part of a lung was made hypoxic or hypoventilated so that affected vessels were constricted. Rats were made chronically hypoxic (10%, O2, normobaric chamber). In vivo and isolated preparations were used. In all preparations and species almitrine bismesylate caused vasoconstriction in normoxia, constriction followed by dilation in hypoxia or hypoventilation. In hypoventilated lung there is ventilation/perfusion mismatching which was not improved by almitrine bismesylate . Ventilatory measurements in chronically hypoxic/hypercapnic rats showed that almitrine bismesylate increased tidal volume but not frequency. It is uncertain whether vascular (Q) or small ventilatory (V) changes are the cause of the improved gas tensions and V/Q matching in patients with chronic obstructive lung disease receiving almitrine bismesylate .