A water-mat including liquid and preparing some weirs and some orifices in the baggy mat is used for prevention of bedsores, which improves the body pressure dispersion of patients by controlling the flow of internal liquid. The water-mat has been developed to use for supine position, however, some patients lie by half side-lying position. So we developed a new water-mat for half side-lying position, then measured maximum body pressure of three young and three old people to inspect the effectiveness of it. Gatch up angle for a new water-mat of the half side-lying position was 0, 10, 20 and 30 degrees. From the experimental results using a mattress with the new water-mat, it was shown that the new water-mat has an obvious effect on dispersion of body pressure, and maximum body pressure has decreased by 22% on the average at Gatch up angle 30 degree. In addition, the pressure of the thigh at the time of Gatch up was also decreased.
