On-line pressure estimation for a left heart assist device

An online pressure-estimation technique for use with a portable pneumatically driven left-heart assist device is described. The online maximum likelihood algorithms are used for the estimation, with the technique based on the use of physical models of the components of the driver and blood-pump system. The technique estimates the inlet and outlet pressures of the blood pump. The directly measured driving air pressure and piston position of the pneumatic actuator are used for the estimation. In vitro and in vivo experiments were made to test the use of the online estimation technique. The results show successful linear correlations between the actual pressures and their estimates. This technique offers the following advantages: accurate pressure information for online control, accessibility to the transducers for recalibration, and noninvasive location of the transducers.