A volume sensor for a pneumatically driven LVAD.

The volume sensor has proven to be a valuable tool in the operation and characterization of our pneumatically driven LVAD. It compensates for the decoupling between driver and LVAD that occurs in pneumatically actuated LVADs due to gas compressibility. Uses to which we have put the volume sensor represent only a small fraction of the potential applications. Additional uses contemplated include: Use as an alternate or backup for the R-wave detection network currently used to achieve synchronization with the natural heart. This could be done by starting the LVAD ejection phase when the filling flow rate drops below a given threshold, indicating that the left ventricle has finished filling the LVAD. Use for feedback for closed loop control of plate motion. Such control could reduce actuation delays without overdriving the LVAD. Use as a diagnostic tool to aid in the study of the LVAD and its interaction with the cardiovascular system. When used in conjunction with information on left ventricular, aortic, and drive pressures, it is possible to determine the resistance, inertia and compliant characteristics of the major elements of the LVAD and the vascular system to which it is joined.