CHARACTERISTICS OF MIXED VENOUS OXYGEN-SATURATION AND PHYSICAL-ACTIVITY AS PARAMETERS FOR ARTIFICIAL-HEART CONTROL

Mixed venous oxygen saturation (SvO(2)) and physical activity (PhyAc) are practical candidates as parameters of total artificial heart (TAH) control because SvO(2) can be measured through a transparent blood pu mp housing with infrared rays and PhyAc can be calculated from signals of an accelerometer used for rate response pacemakers. Although the m ethods for measurement of the parameters have already been developed, characteristics of these parameters for TAH control, such as during ex ercise, are still unclear and were examined in this study. SvO(2), car diac output (CO), and PhyAc were measured as parameters. Multi-stage t readmill exercise tests were performed. Difference values (DVs) from t he value at the start of exercise showed better correlation than did a bsolute values. Correlation coefficients between DV in CO and DV in Sv O(2) and between DV in CO and PhyAc were high at -0.82 and 0.72, while the time constants for the change of SvO(2) and CO to the PhyAc chang e were 26 and 32 sec. Although the correlation coefficient between the CO and SvO(2) was higher than that between CO and PhyAc, PhyAc respon ded more quickly to the speed change compared with the response of SvO (2) and CO. It was concluded that SvO(2) and PhyAc were useful paramet ers with different characteristics for TAH control during exercise.