Design Testing

The following criteria were examined to evaluate the performance of the device during the testing phase of the design process: consistency of the alarms (both visual and auditory), ability of the system to function under various types of pressure-relief exercises, and the ability of the system to adapt to premature sitting during the exercises.

Over 6 hours of in-chair testing in addition to hours of extensive troubleshooting of the microchip in lab was completed to assess quantitatively, and qualitatively the efficacy of each of these criterion. Each trial was defined as one 15-minute timed period followed by a 15-second pressure relief exercise.  An alarm indicated the onset of the pressure-relief exercise and initiated timing when it sensed the patient began performing an acceptable exercise. The timer paused if the patient failed to complete the full 15-second exercise and resumed the alarm until a summation of the full 15 seconds was reached.

Reliability Test

Twenty-five full trials were carried out and all executed correctly. To ensure proper execution under any of the three acceptable exercise conditions, 13 full-pressure relief, 6 left partial--pressure relief, and 6 right partial--pressure relief exercises were completed. Of the 25, 12 trials were tested under the condition that the patient sat down too quickly and was thus signaled to resume the exercise. The summation of intervals that patient required to adequately complete the exercise was recorded. 

The reliability of the Auto-PRT timing is graphed in Figures 8 and 9.  The graphs show the deviation from the ideal value for each of the 25 trials for both the time between pressure-relief exercises (Figure 1) and duration of exercise (Figure 2), respectively. Mean time-interval between exercises was 14.99 ± 0.35 minutes and each pressure relief exercise lasted a mean duration of 15.04 ± 0.54 seconds.
                                     

Figure 2. Alarm signaling completion of exercise sounds at 15 ± 0.34 seconds with 99% confidence

Durability Test

Evaluation to assess the robustness of the device during the testing phase of the design process was based on the device’s resistance to liquids, its performance under both repetitive and severe loading, battery life, and its resilience to deformation under potential user-misuse.

The water-resistant properties of the cover were tested by pouring water over its surface, then checking both the cushion and the interior of the cover itself for leakage. Results show that the cover is resistant to liquid and furthermore that a wet cover does not interfere with the functioning of the device. The waterproof cover also provides a surface that is easy to clean by simply wiping it with a mild cleaning agent.
     

Quality Test

Finally, in the quality assessment, the device will be examined in terms of patient comfort.  A random sampling of individuals will be asked to test the device and report any discomforts.  These subjects will also evaluate the device with respect to ease-of-use.      Culmination of the data from the reliability, durability, and quality tests will determine the success of the design.  It will also provide valuable feedback to direct future research in the area of pressure-relief technology.