Harnessing Dermal Blood Flow Thermoregulation for Mitigating Skin Heating Effects in Transcutaneous Energy Transfer Systems for Wirelessly Energizing Heart Pumps

Mohammad Karim1, Antonio Bosnjak1, James McLaughlin1, Paul Crawford2, David McEneaney3, Omar Escalona1
1Ulster University, 2Paul Crawford Veterinary Services, 3Cardiovascular Research Unit, Craigavon Area Hospital


Introduction This work focuses on developing transcutaneous energy transfer systems (TETS) to power wirelessly the next generation of artificial heart pumps, particularly left-ventricular assist devices (LVADs). This work aims to understand the blood perfusion factors to mitigate thermal damage of the subcutaneous tissue. For this, we emulated the heating effects due to power losses in both continuous and pulsed heating waveform protocols.

Methods A Radiofrequency Power Loss Emulator (RFPLE) was developed to conduct a study on the cutaneous blood circulation cooling effects in the porcine model at various power loss levels, independently of the wireless power supply coupling method being used and their associated inefficiency, thus, enabling analysis and modelling of the skin tissue thermal profile data under a wide range of power loss levels while on-pulse-transmission (50W-700W), on-pulse durations (30ms-480ms) and blood perfused cooling off-time durations (5s-120s). In-silico modelling enabled knowledge-mined characterisation of sub-cutaneous blood circulation cooling factors. Both conventional continuous and pulsed transmission protocols were implemented to assess the heating coefficient from the temperature data of the subcutaneous heating element, for the living-model and in the cadaver-model of 6 porcine cases.

Results The estimated heating coefficient in the living-model measurement, both in pulsed and continuous power transmission heating losses, varied from 1.56x(10-3)±(10-6)°C/s and 7.71x(10-4)±(10-6)°C/s, respectively. The heating coefficient under no-blood-circulation (cadaver) conditions, was at least an order of magnitude higher and varied from 2.22x(10-3)±(10-6)°C/s to 3.14x(10-3)±(10-6)°C/s. Moreover, the heating loss in the continuous transmission is about 2°C higher, or more, than the pulsed transmission. Histological analyses of in-vivo and cadaver models studies confirmed tissue damage occurring in the cadaver measurements due to no blood perfusion.

Conclusion We have characterised blood flow cooling factors and proposed methods for harnessing this important capacity using a novel power-loss emulation system for designing safe high-power TETS with mitigated dermal tissue heating effects.