Permanent pulmonary arterial hypertension is a standard part of the prognosis for patients with chronic respiratory insufficiency. As a decrease of pulmonary arterial hypoxic vasoconstriction may be obtained by calcium antagonists, we studied the effects of nifedipine (10 mg sublingually) in 10 patients with chronic repsiratory insufficiency without acute respiratory failure. Our results show that maximal expiratory air flow was not altered. The pulmonary antihypertensive action of this drug, which is less effective than oxygen breathing at low concentration, was associated with a constant decrease of arterial oxygen partial pressure; the oxygen transport was not sustained for everey patient. This result suggests that considerable caution should be exercised in using this drug for the treatment of pulmonary arterial hypertension in patients with chronic respiratory insufficiency without acute failure.
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