The effect of temperature on the oxygen equilibrium curve of human blood.

The oxygen affinity of human blood was measured with the micro blood film technique over six-degree temperature intervals from 13 to 43 degrees C. Results are expressed both as standard curves at pH 7.4 and for conditions of constant carbon dioxide content. P50 (7.4) values found were 5.8, 8.3, 13.2, 19.7, 26.9 and 33.7 Torr at 13, 19, 25, 31, 37 and 43 degrees C, respectively. The shape of the blood oxygen equilibrium curve was invariant with temperature. The measured CO2-Bohr coefficient (delta log P50/delta pH) ranged from -0.46 to -0.51 and was not temperature dependent. P50 data for 7.4 followed a van't Hoff isochore with a slope, delta log P50/delta (1/T K), of -2350 degrees and an apparent enthalpy per mol of oxygen bound of -8.2 kcal/mol. Temperature dependence of blood oxygen affinity expressed for conditions of constant carbon dioxide content exceeds that of the standard curve. New data are used to calculate the temperature dependence of blood oxygen tension at constant total gas content as a function of initial PO2 and saturation.