Performance Assessment of a Humidity Measurement System and Its Use to Evaluate Moisture Characteristics of Wheelchair Cushions at the User-Seat Interface.

Little is known about the changes in moisture that occur at the body-seat interface during sitting. However, as increased moisture can add to the risk of skin damage, we have developed an array of MEMS (Micro-Electro-Mechanical System) humidity sensors to measure at this interface. Sensors were first evaluated against traceable standards, followed by use in a cross-over field test (n = 11; 20 min duration) using different wheelchair cushions (foam and gel). Relative humidity (RH) was measured at the left mid-thigh, right mid-thigh and coccyx. Sensors were shown to be unaffected by loading and showed highly reliable responses to measured changes in humidity, varying little from the traceable standard (<5%). Field-test data, smoothed through a moving average filter, revealed significant differences between the three chosen locations and between the gel and foam cushions. Maximum RH was attained in less than five minutes regardless of cushion material (foam or gel). Importantly, RH does not appear to distribute uniformly over the body-seat interface; suggesting multiple sensor positions would appear essential for effectively monitoring moisture in this interface. Material properties of the cushions appear to have a significant effect on RH characteristics (profile) at the body-seat interface, but not necessarily the time to peak moisture.

Evaluation of the Force Sensing Application pressure mapping system.

Pressure mapping techniques are used in wheelchair and seating services to assess posture and assist in the prevention and treatment of pressure ulcers. The Force Sensitive Application (FSA) pressure mapping systems in Wales have a high clinical use and frequent calibration is required. This project aimed to assess the performance of the systems and develop a calibration strategy. Testing of the systems was spilt into three stages. The pilot stage compared different calibration techniques (manual, automated and with new software) to determine the optimal calibration frequency. The second stage, longer term, was like the pilot stage with the best calibration method tested over 10 weeks. The third test was a simple before-and-after calibration test, conducted to determine the effect of calibration. It was concluded that the calibration process is essential to maintain the reliability of the mats and it was decided that the systems in Wales should be calibrated every 2 months to provide a more consistent output.