Temperature Regulated Cooling Wheelchair Design and Testing for Pressure Ulcer Prevention

TEMPERATURE REGULATED COOLING WHEELCHAIR DESIGN AND TESTING FOR PRESSURE ULCER PREVENTION

Ali Ersen, Ryan Nguyen, Metin Yavuz Background: Long-term wheelchair users are prone to developing pressure ulcers due complications including reduced mobility, impaired sensations from neurological insults, vascular problems, decreased cognition, and morbid obesity. Pressure ulcers are wounds that results from breakdown of tissue over bony prominences due to localized ischemia caused by constant pressure. The compromised blood circulation along with reduced airflow results in an accumulation of heat in the tissue over the bony prominence that accelerates tissue breakdown. Current ulcer preventing wheelchairs employ thick, foam cushions, which distribute and reduce pressure, but also lead to poor heat distribution contributing to the risk of developing pressure ulcers. Purpose: In this study, we designed a custom-built cushion that circulates chilled water. We measured buttocks surface temperatures and peak pressures around the pelvic bones, with a targeted maximum temperature and pressure of 28°C and 60mmHg, respectively. Method: In this ongoing study, we recruited three subjects who were asked to sit and operate a motorized wheelchair with the aforementioned cushion for 30 minutes. Thermal images of participants buttocks were taken before and after wheelchair use by an Infrared (IR) thermal camera (Flir, T650sc). Temperatures of buttocks (coccyx, right and left thighs proximal to ischial tuberosities), circulating water and ambient were acquired about every second while seated, using digital thermometers (DS18S20) via a microcontroller unit (Arduino Uno). Pressure distribution was captured at the end of the wheelchair use using a pressure mat (Tekscan ConforMat), which was placed on top of the cooling cushion. All study procedures were approved by the institutional review board (IRB) prior to recruitment and testing, and informed consent was obtained from subjects prior to testing. Results: The results indicated that the cooling cushion was capable of cooling tissue from 27.9 to 24.9°C in 30 minutes. The circulating water temperature was 21.8(0.3)°C while ambient temperature was 22.3(0.5)°C. Peak pressure occurred at the right ischial tuberosity in all subjects and was quantified as 92(5)mmHg while average pressure was around 60mmHg. Conclusion: The custom-built cooling cushion maintained temperatures of the buttocks below 28°C, but failed to lower the peak pressure to below 60mmHg. Further modifications such as an additional comfort layer and a longer duration testing of the design are warranted to achieve our goals.