Venous carbon dioxide tensions in chronic obstructive lung disease.

Eighteen patients with severe chronic obstructive lung disease (arterial PCO2 greater than 45 mmHg arterial PCO2 less than 55 mmHg) were studied during a stable period of their disease. Samples of arterial blood and blood from the main pulmonary artery, internal jugular vein, hepatic vein, renal vein and femoral vein were taken by manipulating a Cournand catheter to each of these sites in rapid succession. An estimate of the regional distribution of blood flow was derived from the arterio-venous oxygen content difference of each organ. Expired air was collected into a spirometer. There was a redistribution of blood flow in these patients with chronic lung disease in accord with the observations made by others in the past. Carbon dioxide concentration in the venous blood depends on 1. the blood flow to an organ, and 2. the carbon dioxide production by the organ. The total body CO2 production was within normal limits and there is no reason to suspect any alteration in carbon dioxide production by individual organs in these resting patients. Thus the venous CO2 levels are intimately linked with organ blood flow but even a substantial increase in organ blood flow cannot always compensate for the disorder in the lung. The exact role of CO2 in regulating the peripheral circulation cannot be assessed from this study but they do emphasize the importance of regional blood flow in regulating the concentration of CO2 in the venous blood and presumably in the tissues making up the organ.