The accuracy and spatial resolution of the measurement of tissue oxygen removal rate

An analysis is presented of factors determining the accuracy and spatial resolution of a method for the estimation of oxygen removal rate in tissues using a multi-cathode electrode placed on the tissue surface. The effect of oxygen consumption by the cathodes is shown to be small for 25-micrometer diameter cathodes, but covering the tissue surface with a thin oxygen oxygen-permeable plastic film can introduce a systematic error into the estimate of removal rate, the size of which depends upon the oxygen diffusion coefficient and solubility in the plastic compared with those in the tissue. Spatial resolution is shown to be adequate for distinguishing changes in removal rate over distances of a few hundred microns, and the averaging of removal rate in the direction normal to the tissue surface is weighted heavily towards the superficial tissue layer.