A programmable pressure control system for coronary flow studies

An electrohydraulic servo valve capable of reproducing phasic physiological pressure and flow waveforms has been designed and constructed. The device has been utilized successfully in canine coronary flow studies. By measuring coronary pressure directly it is possible to reproduce waveform frequency components as high as 50 Hz in the cannulated left circumflex coronary artery when operated in a negative feedback configuration. It may easily be adapted to operate in a pressure- or flow-controlled mode in any vascular bed. The closed-loop frequency response of the servo valve itself is flat to 100 Hz with a natural frequency of 170 Hz. When utilized in the cannulated bed the frequency response is dependent on perfusion circuit and catheter dynamics.