Physical model-based indirect measurements of blood pressure and flow using a centrifugal pump

This article describes a technique offering indirect measurements of pump p ressure differential and flow with certain accuracy independent of changes in blood viscosity. This technique is based on noninvasive measurements of the motor current and rotation speed using the physical model equations of the centrifugal pump system, Blood viscosity included in the coefficients o f the dynamic equations is first estimated, and then substitution of the es timated viscosity into the steady equations of the model provides pump flow and pressure differential. In vitro tests using a Capiox pump showed a suf ficient linear correlation between actual values and their estimates for pr essure differential and pump flow. An in vivo test using a 45 kg sheep show ed that the proposed algorithm needs robustness for the convergence of esti mates of viscosity. An overall evaluation, however, of the developed algori thm/model showed indications of success in terms of efficient computation a nd modeling.