Microgenerators for energy autarkic pacemakers and defibrillators: Fact orfiction?

Background: Implantable devices for medical use like permanent pacemakers, defibrillators, and fluid pumps depend on an energy provided by batteries. Unfortunately, the battery usually determines the duration of life of these devices, while technical problems occur infrequent. Device replacement for battery exhaustion requires surgical procedures and account for up to 1/3 of all pacemakers sold. Attempts to provide unlimited power support using r adio transmission, nuclear energy etc. did not gain clinical acceptance. Method: We therefore evaluated the potential role of a micro-generator (des igned for use in wrist watches) to recharge pacemaker batteries. We used th e Epson-Seiko Caliber 5M22 that uses a "Gold-Cap" for energy storage. The m ass of the actuator is 1.6 g and an angle of > 10 degrees is needed to over come friction. Output at a rotor frequency of 200 Hz is 1.8 mWatt To measur e the power provided, various experiments were made with the microgenerator taped to the chest of a normal person working in an office. Range of 11 ex periments over 8 hours each was 0.2 to 3.1 mu Watt (median 0.5 mu Watt). Th erefore, the power generated was 10 to 100 times less than the calculated p ower needed to recharge a typical pacemaker battery. A second type of gener ator (Mondaine, Zurich, Switzerland) with less mechanical parts, available in a "black box" version only, generated not more power. Conclusion: Thus, commercially available, yet not optimized microgenerators provided only between 1 to 10% of the power requirements of a pacemaker. H owever, modifications in design and mainly the orientation and weight of th e actuator to generate more power from the C-forces during walking, would r esult in a more meaningful energy output.