[An adaptive control system of the ventricular assist device with the functions of measurement and analysis].

A personal computer based digital control system for driving the ventricular assist device (VAD) has been developed. Adaptive control, monitoring and analyzing functions are integrated into a software of the personal computer in this system. These functions can operate in parallel with one another because of the multi-interrupt processing used in the software. The system enables the operator to analyze the hemodynamic behavior of the circulatory system simultaneously with VAD pumping and to make on-line use of the result of the analysis in order to improve the driving condition of VAD.

[Synthesis and evaluation of the adaptive control system for the ventricular assist device by using the circulatory system simulator].

An on-line digital simulator using microcomputer system was developed to mimic the hemodynamic behavior of the human circulatory system under ventricular assist device (VAD) pumping. This simulator could calculate the response to the variation of the cardiac function or the driving mode of VAD in the real-time fashion. This simulator was used as the mock controlled object to evaluate and improve the algorithm of an adaptive controller of the drive unit for VAD. The adaptive one-step ahead controller was introduced as the precompensator for the PI-controller, which decides the outflow volume from VAD in order to follow up the reference flow value by changing the systolic duration. It was confirmed that the proposed adaptive control system improved the response speed of the VAD driving system automatically according to the variation of the controlled object.

Early endoscopic features of stomach cancer and its mode of growth.

To establish the earliest sign of stomach cancer in endoscopy and to reveal the subsequent morphologic changes of the lesion, we studied retrospectively 41 cases of stomach cancer. The eariest sign consisted of redness, small polypoid lesions, flat mucosa with slight unevenness and small depressed lesions. There was no clear correlation between the observation period and the size of cancer lesion in cases of early stomach cancer. In cases of advanced cancer, however, the observation period correlated with the size of cancer lesion to a certain extent, and the correlation between the area of cancer (Y cm2) and the observation period (X months) gave a linear equation of Y = 0.68X-3.13.