Abstract
In order to reduce the pain of needle insertion for hemodialysis patients, a regional cooling pad was designed and evaluated on both a polyethylene plate and the forearms of healthy subjects (n=8). The cooling pad was fabricated with a cotton sheet and urea particles of less than 1 mm in diameter, or urea powder. Water to dissolve the urea in a heat
absorption reaction was added at constant rate of 0.5 mL/s using a linear actuator. The subcutaneous tissue thickness of the healthy subjects was measured by echography. The time required to reach a skin temperature of 25 degrees Celsius (t25) and the period during which the skin had a temperature under 25 degrees Celsius (T) were compared. The t25 of the pad with urea particles was 17 seconds, and that of the pad with urea powder was 7 seconds. T was more than 390 seconds. Temperature gradients calculated with subcutaneous tissue thickness showed a positive correlation with heat flux. Initial skin temperature showed a negative correlation with T.
