The purpose of this study was to investigate the effects of support surface mattresses of different bedbackrest
lifting angles on interface pressures around sacral regions. Ten healthy people (average age 21
± 2.4, 4males) participated in this study. The interface pressure around sacral region was measured in
four types of mattresses with 0, 30, 45 and 70 degrees of bed-backrest lifting angle respectively: a
standard mattress, an iris urethane mattress, an air mattress, and a maxi float mattress. The averages of
interface pressures, maximum interface pressures and area supporting surfaces were measured by the
use of a pressure-sensitive sheet. Those averages with the different bed-backrest lifting angles and the
four types of mattresses were statistically examined by ANOVA. The three types of support surface
mattresses were compared with the standard mattress. The average values of interface pressures of
supporting surface were significantly lower than those of the standard mattress (p < 0.05), and also the
area of supporting surface of support surface mattresses were significantly wider than those of the
standard mattress (p < 0.05). Maximum interface pressures were approximate 100mmHg in all of the
mattresses with bed-backrest 45 and 70 degrees up. The results show that the value of interface
pressure increases as the degree of head up rises in all of the mattresses. This suggests that interface
pressure should be considered while the bed-backrest is lifted up.