GAS TENSIONS IN CARDIAC LYMPH AS A REFLECTION OF THE INTERSTITIAL SPACE OF THE HEART

The purpose of this study was to determine the feasibility of measurin g partial pressure of oxygen (pO(2)), partial pressure of carbon dioxi de (pCO(2)), and pH in cardiac lymph and to evaluate the relationship of these parameters to comparable measurements in arterial and coronar y sinus blood in the normal heart under various respiratory conditions . In four anesthetized open-chest dogs, the principal cardiac lymphati c as well as the femoral artery and coronary sinus were cannulated. Ve ntilation was varied by changing oxygen concentration, tidal volume, a nd respiratory rate. PO2, pCO(2), and pH were measured in the cardiac lymph, arterial blood, and coronary sinus blood after each change in v entilation. For pH and pCO(2), good correlations were observed between the arterial blood and cardiac lymph, arterial blood and coronary sin us blood, and coronary sinus blood and cardiac lymph. The correlation between the pO(2) measured in the arterial blood and the pO(2) measure d in the cardiac lymph was not as strong, and this may have been relat ed to difficulty achieving a steady state. Gas tensions (pO(2), pCO(2) , and pH) can be measured in cardiac lymph and may provide a window to the interstitial compartment of the heart. This is an additional tool for the laboratory study of ischemia and other forms of heart disease .