Development of a closed-loop pacemaker controller regulating mixedvenous oxygen saturation level |
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Authors: | Inbar G.F. Heinze R. Hoekstein K.N. Liess H.-D. Stangl K. Wirtzfeld A. |
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Affiliation: | Dept. of Electr., Eng., Technion-Israel Inst. of Technol., Haifa; |
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Abstract: | A simplified model of the CV system is developed where the heart rate (HR) is the controlled input variable, the mixed venous oxygen saturation level (SO2) is the model output, and the work loads are the disturbances. The model relates the SO2 level to the HR and the work through linear relationships, gains, and first-order time constants, and nonlinear relationships, the most important being the nonlinear relation between cardiac output (CO) and heart rate due to the optimal-heart-rate phenomenon. The critical gain is calculated and is shown to be a function of the CO due to the shortening of circulation time delay with increased CO-a stabilizing phenomenon. The step response of the system in open and closed-loop modes to various loads are simulated in the time domain. A proportional-plus-derivative controller which in the simulation increases SO2 from 36% with a 100-W load at constant HR to 57% is described. This is achieved at a cost of increasing HR to 62 to 96 beats/min |
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