The role of hydrogen ion concentration in the regulation of pulmonary arterial pressure. Observations in a patient with hypoventilation and obesity.

THE PULMONARY circulation has been the subject of many studies since the original measurement of pulmonary arterial pressure by Beutner in 1852.1 Of particular importance were the observations by von Euler and Liljestrand in 1946,2 that the administration of 10 per cent oxygen with 90-per cent nitrogen resulted in a significant rise in pulmonary arterial pressure in the cat. This observation was soon confirmed in man by Motley and associates in 1947.3 In addition, von Euler and Liljestrand demonstrated that the administration of 6.5 per cent carbon dioxide in oxygen increased pulmonary arterial pressure.2 Liljestrand, in 1958,4 reemphasized the importance of hydrogen ion concentration as a chemical stimulus for pulmonary vaso-constriction. Recently, Enson and associates5 have shown the importance of hydrogen ion concentration in the regulation of pulmonary arterial pressure in patients with chronic lung disease. They showed that a decrease in blood hydrogen ion concentration, induced by the administration of trihydroxy aminomethane (THAM), caused pulmonary vasodilatation. Further, Enson and associates5 suggested that a change in pulmonary arterial pressure in response to altered hydrogen ion concentration would only be detectable in the presence of chronic pulmonary disease. We recently have had the opportunity to study a woman with hypoventilation and obesity in whom there was no evidence of intrinsic lung disease.6'0 The following report demonstrates that her blood hydrogen ion concentration played a dominant role in the regulation of her pulmonary arterial pressure. Case Report This 43-year-old white woman was first admitted to the University of Colorado Medical Center on March 19, 1964, with cough and fever, which cleared in 3 days. Review of her history revealed that for the past 2 years she had noted a tendency to fall asleep while sitting in a chair, either reading or watching television. However, her exercise tolerance had been excellent with no signs or symptoms of congestive heart failure. There had been no change in her mental acuity. She had always been overweight, weighing as much as 160 pounds in high school and over 250 pounds for the past 5 years. The physical examination revealed a blood pressure of 140/80 mm. Hg, pulse of 60 beats per minute and regular, and a respiratory rate of 16. The patient was 5 feet 6 inches tall, pleasant and alert, with generalized obesity, weighing 279 pounds. There was some duskiness of her lips and tongue but no definite cyanosis. Examination was otherwise normal. The electrocardiogram …