PHYSIOLOGIC STUDIES OF PULMONARY EDEMA AT HIGH ALTITUDE

Cardiac catheterization studies have been performed in four patients during acute pulmonary edema at an elevation of 12,300 feet in the central Peruvian Andes.

Pulmonary hypertension, low cardiac output, arterial unsaturation, and low normal pulmonary artery wedge pressures were observed. Oxygen breathing was accompanied by a prompt, marked fall in pulmonary artery pressure and a slight rise in wedge pressure, indicating the presence of anoxic pulmonary arteriolar constriction.

In one patient, pulmonary artery wedge pressures were not elevated during added hypoxia nor during exercise. The blood pressure response to the Valsalva maneuver was normal.

Similar studies were carried out in four subjects after recovery from pulmonary edema. One 9-year-old boy had persisting pulmonary hypertension. None had evidence of underlying cardiac disease. An abnormal rise in pulmonary artery pressure during induced hypoxia was observed in three of four patients.

It is concluded that pulmonary edema at high altitude is a unique form of pulmonary edema produced by hypoxia under certain conditions of exposure at high altitude. Severe pulmonary hypertension due to anoxic pulmonary arteriolar constriction is present. There is no evidence that pulmonary venous constriction and cardiac failure are causative mechanisms.

PULMONARY GAS EXCHANGE DURING INDUCTION OF PULMONARY EDEMA IN ANESTHETIZED DOGS

We examined pulmonary gas exchange in 19 anesthetized dogs during the induction of acute pulmonary edema by intravenous infusion of dextran in saline. We monitored pulmonary capillary pressure by a left atrial catheter, and arterial blood Po2 by an indwelling electrode. PaOO2 remained near normal until just before pulmonary edema was grossly apparent, when it fell precipitously; left atrial pressure mounted to a peak and then declined. The apparent “steady-state” DlCO was reduced as much as 61%, but the dominant cause of hypoxemia was an increased venous admixture (shunt flow) on O2 breathing. Since the shunt was reversible by forcible inflation of the lungs, induced pulmonary edema was probably associated with closure of alveolar units.

pulmonary venous admixture (shunt flow) and diffusing capacity; alveolar closure; arterial blood oxygen; tension in vivo; hypoxemia

Submitted on August 14, 1963