Abstract: Apparatus employing a non-invasive method for objectively determining in vivo, the rate of oxygen utilization in peripheral tissue by spectral measuring means, containing a light source, a clamp or tourniquet for occluding a segment of blood in the tissue, means for transmitting the light through the isolated segment of blood to pick up the spectral values of the oxyhemoglobin for two selected wavelengths, wherein the rate of reduction of the oxyhemoglobin of the blood as determined at one wavelength is faster that the rate of reduction of the oxyhemoglobin at the other wavelength, means for converting the spectral values individually for the two selected wavelengths into current flow, and means for determining the time-space relationship between the changing spectral values of the two selected wavelengths, from the moment of occlusion.

Abstract: A non-invasive method of objectively determining, in vivo, the rate of oxygen utilization in peripheral tissue by spectral measuring means, which involves isolating a segment of blood in the tissue with a clamp or tourniquet, and obtaining rapid, successive spectral curves of the oxyhemoglobin in the occluded area, to and from selected wavelengths of light, and measuring the time-space relationship between a rapidly moving portion of the spectral curve and a slower moving adjacent portion of the same curve, from the moment of occlusion, to establish a rate of reduction of the oxyhemoglobin in the tissue which is directly correlated to the rate of oxygen utilization.