Further Observations on the Effect of Hydrogen Ion on the Pulmonary Circulation

Abstract

The effects of an acutely induced and modest increase in blood hydrogen-ion concentration on pulmonary hemodynamics were studied in 15 patients with obstructive lung disease. Pulmonary arterial pressure rose when the blood hydrogen-ion concentration increased; this change was greater when the arterial oxyhemoglobin saturation was lower than 91%. The pressor response was independent of change in cardiac output, pulmonary blood volume, and left veno-atrial pressure and is ascribed to pulmonary arterial vaso-constriction. Increased concentration of hydrogen ion is a factor in the production of pulmonary hypertension in patients with chronic obstructive pulmonary disease. Since infusion of acid produced a marked increase in ventilation, the effects of voluntary hyperventilation on pulmonary hemodynamics were studied in three patients with similar pulmonary diseases. In these subjects pulmonary arterial pressure fell as ventilation was increased by a degree comparable to that which occurred during the infusion of acid.