A rapid micro method for obtaining oxygen equilibrium curves on whole blood

A method for recording complete dynamic oxygen equilibrium curves (O2EC) from microliter samples of whole blood is described. The blood sample is compressed into a thin film between two 6-micron thick Teflon membranes in order to promote rapid gas exchange with gas volume surrounding the membranes. Oxygen tension of the gas volume around the blood film is charged at a controlled rate from zero to ca. 100 Torr by a specially designated gas-exchanging cuvette. Saturation of red cell hemoglobin in the film is measured by dual-wavelength spectrophotometry using Soret wavelengths of 430-453 nm. Gas volume oxygen tension is measured with a Teflon membrane covered oxygen cathode. Full saturation is secured by introducing an oxygen mixture whose PO2 exceeds 650 Torr. A single O2EC can be run in about 4 min at 37 degrees; multiple O2EC can be recorded from the same blood film. Each curve is run isocapnically at a preselected carbon dioxide tension. Blood film pH is calculated from the CO2 partial pressure and an independently determined buffer line. Data are presented to show that normal standard curve for man as determined with this blood-film method and those determined by other methods are equivalent.