Ii. the Carbon Dioxide Absorption Curve and Carbon Dioxide Tension of the Blood in Cardiac Dyspnea

In cardiac dyspnea the carbon dioxide tension of the alveolar air as determined by the Haldane method is lower than normal in comparison with the plasma bicarbonate as measured by means of the Van Slyke pipette (1, 2). The ratio between these two in health and in most pathological conditions has been shown by Van Slyke, Stillman, and Cullen (3), Walker and Frothingham (4), and Peters (1, 5) to be very close, varying from the mean by only 10 per cent. The existence of such a close relation might well be expected in the light of current theories with regard to the physicochemical control of the respiratory mechanism. That this relation should be disturbed in cardiac dyspnea is hardly extraordinary. In the average normal person at rest carbon dioxide content, carbon dioxide tension, and hydrogen ion concentration of arterial and of venous blood all vary within comparatively narrow limits both individually and in relation to one another. Furthermore, the physicochemical regulatory mechanism is so delicately adjusted that changes in any of these factors are reflected in an immediate response on the part of the respiratory mechanism, which produces a compensatory alteration of the alveolar COz. As long as the sensibility of the respiratory center and the mechanical facilities for the exchange of gases between the blood and the air in thelungs remain unaffected, changes in any of these factors are instantly compensated by changes in one or all of the others. If either the