Variability of oxygen affinity of normal blood: an automated method of measurement.

Oxygen equilibrium curves of 48 healthy adult subjects have been measured by the method of Rossi-Bernardi et al. (Clin. Chem. 21: 1747, 1975), in which H2O2 is gradually added to a sample of deoxygenated blood that contains an excess of catalase. The mean P50 for nonsmokers was 26.9 Torr and the distribution of values was slightly skewed to the right (range 24.2--29.9 Torr). The method differs from others previously available in that pH, PCO2, and HCO3-- are constant during oxygenation. The system for control of the experiment and data collection and processing has been automated by the use of a microprocessor so that the equilibrium curve can be obtained quickly, reproducibly, and relatively simply. With the aid of a digital computer, the parameters of the generalized Adair equation can also be estimated.