Spectrophotometric studies. XVI. Determination of the oxygen saturation of blood by a simplified technique, applicable to standard equipment.

The metabolism, as measured by oxygen consumption, of organs in situ is being increasingly investigated by the vascular catheterization technique (see Drabkin (3) for pertinent literature). The oxygen consumption is derived from the arteriovenous difference in the oxygen saturation or percentage of oxyhemoglobin (4) of blood entering and leaving the tissue. Such work has pointed to the need of a practical and withal reliable method for the routine analysis of the oxygen saturation of small blood samples (5, 6). Probably the most accurate determination of the percentage of oxyhemoglobin available at present is the direct spectrophotometric method of Drabkin and Schmidt (7), which avoids certain inaccuracies inherent in the standard, indirect gasometric technique employed for many years (8, 9). The extension of optical instrumentation to the analysis of oxygen saturation was made possible by the use of the Drabkin and Austin special cuvette of calibrated 0.007 cm. depth (lo), which had been introduced much earlier for measurements of this type upon whole blood or concentrated hemoglobin solutions unexposed to air. An important advantage of the 0.007 cm. cuvette is that it permits the examination of undiluted blood and thereby circumvents the volumetric measurement of the sample, which remains one of the least accurate steps of analytical