Oxygen transport capacity of the capillary blood within the carotid body.

Local $$\frac{{\Delta P_{O_2 } }}{{\Delta t}}$$ in the carotid body after perfusion stop depends on the oxygen consumption of the tissue and the apparent O solubility coefficient α of the blood. Oxygen consumption of the carotid body tissue can be determined by measuring the local $$\frac{{\Delta P_{O_2 } }}{{\Delta t}}$$ with $$P_{O_2 } $$ needle electrodes after Krebs-Henseleit perfusion. Assuming the same $$\frac{{\Delta P_{O_2 } }}{{\Delta t}}$$ for the blood-perfused carotid body the actual $$P_{O_2 } $$ decrease can be used to estimate the hemoglobin content of the tissue. The influence of hemoglobin is described by the factor α/α. Control values measured in the Krebs-Henseleit-perfused carotid body yielded values of α/α = 0.8 −3. In a series of 11 blood-perfused carotid body preparations with 105 perfusion stops the quotient α/α changed with arterial $$P_{O_2 } $$ values higher than 100 Torr α/α was between 0.8 and 2. This value thus was in the same range as the control values. Below 100 Torr higher values up to 11 were observed. Since a blood-perfused tissue (15 g % Hb) would have an α/α of about 128, we conclude that the carotid body is mainly perfused by plasma, and that with decreasing arterial $$P_{O_2 } $$ more red cells flowed through the carotid body. [ABSTRACT FROM AUTHOR]