PRESSURE CONTROL SYSTEM FOR CARDIAC ASSIST DEVICE

A control system for an inflatable chamber operably positionable with respect to an aorta of a patient monitors an actual flow duration time for inflating and/or deflating the inflatable chamber with a predetermined volume of pressurized fluid and compares the actual flow duration time to a target flow duration time. The system controls the fluid pressure in a high pressure reservoir, and/or in a vacuum reservoir, based on the results of the comparison. If the actual time for inflation is too short compared to the target time, the fluid pressure in the high pressure reservoir is reduced. If the actual time for inflation is too long compared with the target time, the fluid pressure in the high pressure reservoir is increased. If the actual time for deflation is too short compared to the target time, the vacuum in the vacuum reservoir is decreased. If the actual time for deflation is too long compared with the target time, the vacuum in the vacuum reservoir is increased. The incremental step change in fluid pressure within either reservoir can be controlled within predetermined minimum and maximum values, and/or based on the magnitude of the difference between the actual and target time intervals. The change in fluid pressure within either reservoir can be controlled by the system manipulating a control valve, or varying the speed of the compressor, or any combination of the two, until the new calculated value is reached within the reservoir.