The Influence of Hydrogen Ion Concentration and Hypoxia on the Pulmonary Circulation*

Abstract

The effects of alkalizing solutions on pulmonary hemodynamics were studied in 16 patients with chronic pulmonary disease. In these patients the rise in blood pH was associated with a fall or with no change in pulmonary artery pressures despite increases in pulmonary blood flow and volume. Furthermore, in the presence of a rising blood pH, severe hypoxia was not associated with a pressor response in the pulmonary artery. These observations suggest that a decrease in H-ion concentration is associated with pulmonary vasodilatation. The relationship between pulmonary artery mean pressure, arterial oxygen saturation, and H ion concentration was submitted to statistical analysis in 43 patients with chronic pulmonary disease. Pulmonary artery mean pressure was found to correlate with both oxygen saturation and hydro-gen ion concentration to a significantly higher degree than with either of the latter 2 variables considered singly. At low concentrations of H-ion (high pH), pulmonary artery mean pressure is relatively in-sensitive to hypoxia as manifested by arterial O2 saturation, while at high H-ion concentrations (low pH) pressure is extremely sensitive to hypoxia.. The mechanism whereby H-ion concentration influences the pressor response to hypoxia is not clearly defined at present.