Adaptive full-ejection point detection for automatic control of the electrohydraulic total artificial heart.
An adaptive algorithm to detect full ejection points was developed for the automatic control of the electrohydraulic total artificial heart (EHTAH). To automatically control the EHTAH, systole in each ventricle is completed when a hyper-pressurization spike is detected on the oil side of that ventricle. A problem associated with the method of determining ventricular full ejection under variable afterload pressure is that a fixed level comparison method could fail to provide a normal full ejection condition. To increase system stability, safety, and efficiency, there is a definite need to vary the full ejection trigger level with changes in afterload. In this study, the full ejection trigger level for the current beat was changed based on the estimated afterload derived from the previous beat's pressure waveform. To increase this estimate's accuracy, an adaptive averaging window was used to determine which part of the previous pressure waveform would be used for the afterload estimation. With this enhanced control scheme, mock circulation tests with the EHTAH device demonstrated that estimated afterload tracked actual afterload. This scheme was also used successfully to control the EHTAH device implanted in three chronic calves.
Kim
H C
HC
Department of Biomedical Engineering, Seoul National University, Korea.
Khanwilkar
P S
PS
Long
J W
JW
Olsen
D B
DB
D000818:Animals; D006354:Heart, Artificial; D012984:Software; D013318:Stroke Volume; D013599:Systole