[Value of nifedipine in respiratory failure related to obstructive chronic bronchitis during treatment over 6 months]

We studied the simultaneous effects of nifedipine on the pulmonary circulation and blood gases in 12 patients with pulmonary hypertension secondary to obstructive chronic bronchitis. Measurements were carried out at rest and during stress, initially then one hour after administration of 20 mg of nifedipine sublingually. They were repeated in a similar fashion after a 6-month treatment with 60 mg/day (group II) (30 mg/day in case of intolerance) (group I). The results of the immediate effect of nifedipine are in favor of a passive pulmonary vasodilatation secondary to the systemic vasodilatation. After six months of treatment, the pulmonary vasodilatation persists, but is associated with a decreased motor pressure indicating a more specific and more active pulmonary vasodilating effect of long-term nifedipine, especially during stress; this results in the improvement of the performance of the right ventricle without harmful effect on the blood gases. However, these results should be interpreted with caution on account of the small number of patients, the large interindividual variations and the absence of a reference population.