Measurement of venous oxyhaemoglobin saturation in the adult human forearm by near infrared spectroscopy with venous occlusion.

Measurement of the oxygenation of the peripheral tissues provides useful information about tissue perfusion. A method is described for the measurement of peripheral venous oxyhaemaglobin saturation (SvO2) in the adult forearm by a noninvasive technique, near infrared spectroscopy (NIRS) with venous occlusion. A series of studies is performed on healthy adults to compare measurements of forearm SvO2 made by NIRS with measurements of superficial venous SvO2 made by co-oximetry, and to study the effect of different optode spacings. There is a significant correlation between forearm SvO2 measured by NIRS and SvO2 of superficial venous blood measured by co-oximetry (n = 19, r = 0.7, p < 0.0001). Higher values for SvO2 were obtained using a 2.5 cm spacing than with a 4 cm spacing (mean difference = 4.1% (95% CI 1.4%-6.8%) n = 16). This difference is likely to have been due to a more superficial volume of tissue being studied with the closer optode spacing. Peripheral SvO2 can be measured non-invasively using NIRS with venous occlusion. It may prove to be a useful method to study circulatory disturbances.