Abstract
Continuous monitoring of pump performance is essential and effective for optimal driving of pulsatile type blood pump. For this purpose, real-time measurement of blood volume in a pump (Vb) is necessary. We contrived a practical method for continuous Vb estimation by measuring electrical impedance (Z) in the blood chamber of pump. This method was evaluated with our air-driven diaphragm type pump. Z was measured by charging the alternating current (50kHz, 0.4mA) between two connectors of pump as electrodes. In vitro tests, Z showed maximum value at full-empty state and minimum at full-fill, respectively. The Vb calculated by an exponential equation of Z was linearly related to real Vb (r=0.99). In vivo tests with goats, pump output (Op) estimated by this method was linearly related to Op measured with electromagnetic flow meter, and was effective to evaluate pump performance. For calibration, this method needed only to measure Z at full-fill state. This method was more useful for the trigger system of full-fill full-empty drive than the other system because of direct measurement of Vb. We conclude that this method is practical to estimate pump performance even if implantable type pumps were used, and easily applicable to any kind of pulsatile type pumps.
