Venous pressure regulation during pulsatile extracorporeal life support

During the use of pulsatile extracorporeal life support (pulsatile-ECLS), the patient's venous pressure near the inlet venous catheter tip must be monitored to maintain sufficient blood flow and to prevent vein collapse. However, direct measurement of the venous pressure and the estimate of suction using measured blood inflow and prepump pressure are not practical because of setup difficulties during emergency treatments and in cardiovascular operations. In this article, we describe a new method for estimating the venous pressure that can be implemented in the controller of the pulsatile-ECLS system, the T-PLS. It uses real-time measurement of the electric current and actuator motion. The current waveform of the T-PLS is used to determine the outflow amount and the volume remaining in the pulsatile pumps. Previously measured values of the pulsatile-ECLS compliance and the hemodynamic resistance along the inflow path are used to evaluate venous pressure with estimated blood flow. Estimated prepump pressure, inflow, and venous pressure were compared to the measured data in a series of in vitro experiments. The estimated venous pressure was used to avoid vein collapse and to increase the reliability in animal experiments.