A non invasive optical oximetry in humans: preliminary data

In order to evaluate the oxygen saturation of hemoglobin in living tissues we use a new experimental instrument: the optical oximeter (LOX). The LOX uses 2 LEDs, like the pulse oximeter (PO). One LED operates at 670 nm (Hb absorption), the other one operates at 830 nm, i.e., near the isosbestic point for which Hb and HbO2 show the same extinction. The oxygen saturation of Hb can be expressed as a linear function of the ratio of the absorption coefficients at the wavelengths of the 2 LEDs. Indeed the LOX is based on diffused reflectance measurements and not on light transmission such as the POs. We studied in standard conditions 10 healthy volunteer subjects (6 M, 4 F aged 40 +/- 4 years) non smokers. We used TO (Combi Sensor) at the subclavicular standard area and at the right ankle, PO with the probe always at 2nd finger of the right hand and LOX at right wrist and at right ankle. We obtained a significant relationship between values of TO, PO and LOX (p < 0.01). Our preliminary data suggest that this could be a new methodology to evaluate tissular oxygenation, also exploring living tissues several centimeters deep.