Measurement of oxygen saturation in venous blood by dynamic near infrared spectroscopy

A method for the measurement of oxygen saturation in the venous blood, SvO( 2), based on optical measurements of light absorption in the infrared regio n is presented. The method consists of applying relatively low external pre ssure of 25 mm Hg on the forearm, thereby increasing the venous blood volum e in the tissue, and comparing the light absorption before and after the ex ternal pressure application. SvO(2) has been determined from light absorpti on measurements in two wavelengths, before and after the pressure applicati on, using a formula derived for two adjacent wavelengths. The method has be en applied to the hands and fingers of 17 healthy male subjects, using wave lengths of 767 and 811 nm. SaO(2), the oxygen saturation for arterial blood , was also obtained from photoplethysmographic measurements in these two wa velengths (pulse oximetry) using the same formula. The mean (+/-SD) value o f SaO(2) was 94.5%(+/-3.0). The mean Value of SvO(2) was 86.2%(+/-4.1) for the finger and 80.0%(+/-8.2) for the hand. These SvO(2) values are reasonab le for the finger and the hand where arterio-venous anastomoses exist. The method enables the measurement of SvO, in the limbs, a parameter which is r elated to tissue blood flow and oxygen consumption. (C) 2000 society of Pho to-Optical instrumentation Engineers. [S1083-3668(00)01102-3].