Quantitative evaluation of a novel sensor for measuring muscular tissue flow and gases

Information about muscular tissue flow is important for diagnosing, treating and monitoring patients with tissue ischemia. For this purpose an objective method which is reproducible and continuous is needed. In co-operation with the company Unisense A/S, we have developed a sensor for instantaneous and continuous monitoring of muscle tissue flow in vivo. The method is based on a flexible microsensor which emits and measures minute amounts of inert tracer gases. The objective was to evaluate the capability of the microsensor to measure varying degrees of tissue flow changes and compare these measurements with the 133Xenon Washout Technique for measuring local perfusion rates in skeletal muscle. The Unisense microsensor was tested in the gracilis muscle of six anaesthetized pigs subjected to varying degrees of muscle ischemia. We found that both tissue flow and pO2 declined in synchrony with reduced blood flow to the lower extremities. All the data from the Unisense microsensor show the same trend as the Xenon data and thus confirms that the microsensor can measure changes in tissue flow.