抄録
Microcomputer assisted ventricular loading system has been developed for the study of cardiac function. This computer system was composed of 16 bit cpu (8086), numeric data processor (8087), and 12bit A/D, D/A converter. The instantaneous velocity of the flow out of, or into the ventricle, and its volume were calculated based on the assumed loading model from measured ventricular pressure, and output to the servo-pump system. This one cycle was done in 420 microsecond. The afterload was composed of peripheral vascular resistance, aortic compliance, characteristic impedance, and the inertia of blood, and the preload was of atrial pressure and valvular resistance to simulate the physiological loading state. Additionally coronary perfusion pressure was controlled according to either calculated aortic pressure or keyboard input. The advantages of the microprocessor control are as follows: 1) the change of parameters is real time, 2) the quantitative evaluation, and the reestablishment of some experimental condition are easy and precise, 3) the control mode is flexible and such complex controls are easily performed by software, as to fix stroke volume, peak pressure or external work by adjusting preload despite the changes of afterload. On the other hand, following three problems were recognized for the improvement of frequency response of the servo system: 1) replacement of potentiometer of contact type by a newly developed optical type device, position sensitive detector (PSD) and light-emitting diode (LED), 2) increase in diameter and decrease in length of the connecting tube between the Bellofram cylinder and ventricle, 3) improvement of the low stiffness of the rolling diaphragm of the cylinder.
