ROLE OF HYPOXIA IN DETERMINING PULMONARY VASCULAR RESISTANCE IN INFANTS WITH VENTRICULAR SEPTAL DEFECTS

To evaluate the role of the mild chronic hypoxia present at 5280 feet on pulmonary vascular resistance in subjects with reactive pulmonary hypertension, 43 infants under 2 years of age with ventricular septal defects studied at Denver were compared to 54 infants with ventricular septal defects studied at sea level (Houston). The results indicated that average pulmonary blood flow was approximately twice as great at sea level as compared to 5,280 feet, although pulmonary arterial pressures were similar. Presumably these differences were due to the lower oxygen pressure in Denver. These observations serve to explain the marked responsiveness to tolazoline in the patients with ventricular septal defects studied at Denver compared to those studied at sea level (Houston).