A NOVEL ALGORITHM TO CONTINUOUSLY MONITOR CHANGE OF TOTAL PERIPHERAL RESISTANCE USING PERIPHERAL ARTERIAL BLOOD PRESSURE VALUES FOR PREDICTION OF ORTHOSTATIC INTOLERANCE

摘要

This paper introduces and validates a novel algorithm to continuously estimate changes of total peripheral resistance (TPR) by using peripheral arterial blood pressure (ABP) waveforms. TPR is an important cardiovascular index to monitor, because low TPR is believed to be an indicator of astronauts' post-flight orthostatic intolerance. In estimating changes of TPR, our algorithm uses diastolic, rather than systolic, ABP values. The hypothesis is that the diastolic pressure values are less sensitive than systolic values to waveform distortion caused by impulse propagation through the arterial vasculature, suggesting that use of end-diastolic ABP values would increase TPR estimation accuracy. Our algorithm first calculates the Windkessel time constant which governs diastolic decay in the peripheral ABP in such a way that computed and measured ABP waveforms have agreement in diastolic pressure values. Then, TPR, proportional to the Windkessel time constant, is given on a beat-to-beat basis. To validate our algorithm, previously recorded Yorkshire swine data sets were processed and analyzed. An overall root-mean square normalized error of 14.0% was achieved. Our algorithm demonstrated continuous monitoring of TPR changes from peripheral ABP, and has the potential to predict post-flight orthostatic intolerance of astronauts.