Background: In this study, a new algorithm was developed for estimating the pump\noutflow of a pneumatic ventricular assist device (p-VAD). The pump outflow estimation\nalgorithm was derived from the ideal gas equation and determined the change in\nblood-sac volume of a p-VAD using two external pressure sensors.\nObjectives: Based on in vitro experiments, the algorithm was revised to consider the\neffects of structural compliance caused by volume changes in an implanted unit, an air\ndriveline, and the pressure difference between the sensors and the implanted unit.\nMethods: In animal experiments, p-VADs were connected to the left ventricles and\nthe descending aorta of three calves (70ââ?¬â??100 kg). Their outflows were estimated using\nthe new algorithm and compared to the results obtained using an ultrasonic blood\nflow meter (UBF) (TS-410, Transonic Systems Inc., Ithaca, NY, USA).\nResults: The estimated and measured values had a Pearsonââ?¬â?¢s correlation coefficient\nof 0.864. The pressure sensors were installed at the external controller and connected\nto the air driveline on the same side as the external actuator, which made the sensors\neasy to manage.
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