IN VIVO PERFORMANCE EVALUATION OF THE FEEDBACK TRANSCUTANEOUS ENERGY TRANSMISSION SYSTEM (FTETS) FOR AUTOMATIC VOLTAGE REGULATION

Abstract

In vivo performance of the feedback transcutaneous energy transmission system (FTETs) has been evaluated through several animal experiments with implant of the total artificial heart (TAH). Improvements to current status of the FTETs development o automatic voltage regulation are reported. The FTETs based on magnetic induction has the external primary and implanted secondary coils. External part is composed of a Class E inverter, and driven by center frequency of 390 kHz. For automatic voltage regulation, a feedback controller only on external part was proposed. This controller tunes center frequency by detecting a resonant voltage of Class E inverter reflecting internal output voltage. Therefore, the implanted coil could be miniaturized to improve implantability, and its diamete and weight be reduced to 39 mm. 13 grams, respectively. Maximum delivered efficiency increased to 90 % at 70 W. The TAH system with FTETs was implanted in the body of about 53 kg sheep three times. In vivo results for total 10 days showed that the measured dc/dc efficiency was average 80.1 % at load with 13 W power, corresponding to cardiac output of 5–6 L/min and AoP of 90–120 mmHg. A relative frequency range of only 10 % on a center frequency was sufficient to regulate the output voltage at 37 V for both load resistances, 5 ohm to infinity, and skin thickness, 5 to 20 mm. The temperature rise around the implanted coil was kept below 2 °C. The developed FTETs system showed good in vivo results and could supply a stable electrical power to the TAH without a decline in pump performance.