Development of a Wheelchair Seat Cushion with Site-Specific Temperature Control for Pressure Ulcer Prevention

Pressure ulcers are prevalent and costly, particularly for individuals with impaired mobility and sensation. They are primarily caused by high pressure near bony prominences. Multiple other factors include shear force, friction, temperature, and moisture. Recent research at the University of Pittsburgh was conducted on local cooling effects with respect to skin blood flow. A reduction of skin temperature to 25°C provided a significant benefit to local tissue in healthy controls and subjects with spinal cord injuries. This concurs with prior animal studies which demonstrated reductions in breakdown at lower interface temperatures. Pressure ulcers have been historically managed by providing support surfaces, such as wheelchair seat cushions, to redistribute pressure at the body interface. Few practical interventions exist to control temperature at this interface; most employ passive cooling methods, which are limited by their inability to modulate applied cooling in response to changes in microenvironment. This study's goal was to develop tightly controlled, local cooling elements for integration into a pressure-redistributing support surface. A holistic view of temperature control methods in an iterative design process was taken. Features, benchmarks, and design specifications were generated using available information from the literature. Idea generation and subsequent evaluation led to the modification of a multi-cell air cushion capable of controlling temperature in specific high risk areas. Proof of concept experiments were conducted with respect to interface cooling to a target temperature, redistribution of pressure, and heat and water vapor transmission. The design delivered local cooling over hour-long trials on able-bodied test subjects. No significant difference in skin temperature (p>0.16) was found after 15 minutes of cooling from our target temperature (25°C). The modified cushion showed similar (p=0.79) peak pressure index values when compared to the same cushion design without the cooling elements. A thermodynamic rigid cushion loading indenter mimicked the environmental conditions of the body on our prototype for 3-hour duration tests. Significantly lower temperatures were observed after 1 hour of cooling (p