Chest
Volume 83, Issue 2, February 1983, Pages 203-207
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Effects of Nifedipine on Ventilation/Perfusion Matching in Primary Pulmonary Hypertension

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The effects of nifedipine on hemodynamics and pulmonary gas exchange were investigated in two patients with primary pulmonary hypertension. After 20 mg of the drug taken sublingually, pulmonary and systemic vascular resistances decreased, cardiac output increased, and blood oxygenation was improved. As assessed by the multiple inert gas elimination technique, nifedipine induced a deterioration in ventilation/perfusion ( VA/ Q) relationships consisting in an increased perfusion of units with low VA/ Q. In spite of this negative effect on gas exchange, arterial Po2 increased as a consequence of increased mixed venous Po2 in relation to an augmented cardiac output, and in one patient there was a decrease in the secondary atrial shunt. Both patients were clinically improved by the nifedipine as a long-term treatment.

Section snippets

CASE 1

A 61-year-old woman was admitted with a history of progressively severe exertional dyspnea and fatigue over the preceding ten years. She denied previous use of drugs and had never before had symptoms suggestive of cardiac or pulmonary disease. From three years before admission, exertional dyspnea had become invalidating (walking on level ground) and was accompanied by chest pain and palpitations and on four occasions by syncope. One year before admission, a right heart catheterization showed

DISCUSSION

Dantzker and Bower2 have recently shown by the multiple inert gas elimination technique that VA/ Q relationships in patients with chronic obliterative pulmonary vascular disease (idiopathic or secondary to recurrent pulmonary emboli) are only minimally abnormal, with a mean of 10 percent of cardiac output perfusing units with low VA/ Q. The same authors demonstrated that in such patients reduction of pulmonary vascular tone by an infusion of nitroprusside or

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    Manuscript received May 10; revision accepted August 23.

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