Changes of Blood Gases and Lactic Acid After Exercise in Patients With Rheumatic Heart Disease

Abstract

It has been demonstrated by a number of investigators 1 that changes in the oxygen unsaturation, carbon dioxide combining power, and lactic acid content of the venous blood occur in normal individuals after exercise. These changes seem to bear a definite relation to the amount of work performed. Very slight, or no differences are observed following mild exercise. When the exercise or amount of work performed is increased, greater changes are noted. The changes consist of an increase in the oxygen unsaturation and lactic acid content, and a decrease in the carbon dioxide combining power.

The object of the present study was to determine what changes occurred in the oxygen unsaturation, lactic acid, and carbon dioxide combining power of the venous blood in patients with rheumatic heart disease after performing measured amounts of work. The cases included in this study were children between the ages of twelve and sixteen years, with various valvular and muscular defects caused by the rheumatic infection.

Their response to effort was tested clinically and they were classified according to the Classification of the American Heart Association. 2

The three determinations, oxygen unsaturation, lactic acid content, and carbon dioxide combining power, were made in the same case after the same amount of work in the majority of cases. The oxygen unsaturation was determined at rest and approximately one minute after the exercise was completed, and the lactic acid and carbon dioxide combining power at rest and again four minutes after the exercise. The exercise consisted of climbing thirty feet in forty seconds. In a number of instances the determinations were made after double and triple the amount of work was performed.

The following changes were observed when the work consisted of climbing thirty feet in forty seconds: the 2A cases showed only slight changes, whereas the children classified as 2B showed, with few exceptions, a definite increase in the oxygen unsaturation and lactic acid, and a decrease in the carbon dioxide combining power.