Improvement in ventilation-perfusion relationships by almitrine in patients with chronic obstructive pulmonary...

Although the respiratory stimulant effects of almitrine bismesylate (AB) via an action on the peripheral chemoreceptors have been demonstrated, the mechanism of its intrapulmonary action has not yet been elucidated. In order to abolish the stimulation of ventilation, observed in studies on spontaneously breathing patients, an investigation of patients suffering from severe COPD under constant mechanical ventilation, with FIO2 = 0.21, during the weaning period was carried out. Eighteen patients were randomly divided into 2 groups (9 receiving 1.5 mg/kg AB and 9 receiving placebo). The ventilatory and hemodynamic variables, blood and alveolar gases, and the VA/Q ratio distributions using the multiple inert gas technique were collected before treatment with drug or placebo, as well as 90 and 180 min afterwards. The PaO2 was found to be raised 90 min after AB administration (+57 +/- 3.9 mm Hg, p less than 0.01) and remained above the baseline value at 180 min (+5.4 +/- 4.6 mm Hg, p less than 0.01). Compared with those in the placebo group, these increases were significant (p less than 0.01). A slight decrease in PaCO2 but similar in the 2 groups was observed despite constant ventilation. The hemodynamic data were the same for the 2 groups. The changes in overall criteria of the distributions (mean VA/Q and SD) were small. The main finding was a decrease in the percentage of the perfusion flowing through the true shunt and the underventilated areas after AB treatment. In the control group, the blood flow percentage in the true shunt and low VA/Q units was either stable or increased.(ABSTRACT TRUNCATED AT 250 WORDS)