Thermal Safety and Usability of a High Powered TET System

Abstract

Heart disease is the leading cause of death in the US and other western countries. Those at end stage heart failure, beyond drug and surgical interventions, have two treatment options. Heart transplants suffer from a serious lack ofavailable donors. Mechanical heart pumps such as left ventricular assist devices (LVADs) can be manufactured in high numbers, but they also have some issues. They use a percutaneous (through the skin) driveline cable to deliver electrical power. Infections at the driveline site are a major cause of morbidity.Transcutaneous energy transfer (TET) can deliver the power wirelessly across the skin, eliminating the driveline and associated risks. Barriers to adoption of TET systems for LVADs are temperature safety concerns and dfficulties inaligning implanted and external power transfer coils. This thesis presents the quantifcation of the operating temperature of a TET system and demonstrates a new TET coil alignment system.This work is focused on using the body to dissipate the heat generated by a TET coil. If the body can dissipate all of the heat generated, then the system will operate safely without imposing restrictions on the user relating to the environment or clothing. Participants were recruited for a study to measure the temperature of the primary coil on the skin. The study showed that the temperature of the coil was below 39°C and easily within regulatory limits of 41°C when delivering 10 W of power to the LVAD.The coil alignment system utilises auxiliary detector coils to sense the magnetic field of a nearby secondary coil and provide information about how the alignment can be improved. The coil alignment system was tested and shown to be accurate within 1 mm of lateral separation, for a 54 mm diameter coil. In a simple trial, users were able to align the primary coil above the skin with a secondary coil hidden under the skin in less than 15 seconds.This thesis has addressed two of the major concerns of TET systems for highpower implantable devices, and is supportive of the adoption of a TET system for powering an LVAD.