The development of a continuous blood oxygen saturation measuring and control system

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Virginia Polytechnic Institute and State University

An instrument is described which continuously monitors and controls the blood oxygen saturation at the outlet of a membrane-type oxygenator. A reflection oximeter was developed which employs the ratio of the incident light intensity at two wavelengths to obtain the continuous blood oxygen saturation measurement. The ratio of the intensities of incident light at the two wavelengths is linearly related to the oxygen saturation, provided the reflected light intensities at these two wavelengths are held constant. The continuous oxygen saturation measurement from the oximeter is compared to a preselected oxygen saturation value by the instrument. The difference between the actual and the desired oxygen saturation is used to change the oxygen partial pressure gradient in the oxygenator in such a way that the oxygenator outlet saturation approaches the preselected value. A detailed description of the instrument's design is presented along with data obtained from the instrument's operation.