Fig. 6.

Production of carbon dioxide (CO₂) and its relationship with cardiac output (CO). All produced CO₂ easily diffuses and dissolves in blood. Transport from tissues to the venous blood does not restrict clearance from tissues. All produced CO₂ always gets to the venous blood without accumulation in the tissues, and its concentration in the veins depends only on venous return. Higher CO leads to smaller venous CO₂ concentration and smaller arteriovenous difference. Lower CO leads to slower flow through capillaries and the entire CO₂ production is dissolved in smaller venous blood volume, known as the “stagnation phenomenon”. This is why there is higher amount of CO₂ dissolved in venous blood and higher arteriovenous difference. The same applies to reduced capillary net (despite normal CO) when CO₂ from areas with damaged net is drained by remaining capillaries leading inevitably to high CO₂ concentration. HCO₃⁻, bicarbonate