Dynamic Air Exchange Prosthesis: Effects on Heat Transfer and Limb Adherence for Active Lower Limb Amputees
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Lower limb amputees are often dissatisfied with the comfort of their prosthesis. A literature review of 38 selected studies revealed that more than 53% of people with amputation experienced heat and/or perspiration discomfort inside their prostheses. Current prosthetic liners are usually made from silicon, polyurethane or a combination polymer with a fabric outer layer and have thermally insulating properties. Lack of liner breathability and permeability also causes disproportionate amounts of moisture to pool against the skin. A novel new Dynamic Air Exchange (DAE) socket, being evaluated for this study, uses a small vacuum pump and pressure sensor to dynamically maintain a slight vacuum suction in the socket. Air is drawn in through four proximal liner ports, flows distally through a thin sock between the skin and liner, and forces perspiration and water vapor out a port in the prosthesis’ distal locking pin. Analysis includes a computational model to show how heat removal varies in different thermal environments, physical test results from a thermal manikin, and preliminary outcomes from human subject study results (n=2) comparing adherence between the DAE socket and a standard of care (SoC) pin lock socket. The DAE system removes moisture from the socket effectively but has little effect on overall skin temperature. The computational model suggests that cooling rates for current DAE socket airflow are near 3W for 20 °C ambient air and 10% relative humidity. Cooling rates increase to 29W when the flow velocity is increases from 0.03m/s (current DAE) to 0.5m/s under the same external conditions. Effects of varying flow velocity, relative humidity, and inlet air temperature on heat transfer rate are also presented.
- Mechanical engineering