Effects of bed height on the biomechanics of hospital bed entry and egress

BACKGROUND: Although a significant proportion of patient falls in hospitals occur in the vicinity of the hospital bed, little is known about the contribution of bed height to fall risk. OBJECTIVE: To compare lower extremity joint torques and angles during hospital bed entry and egress at two bed heights. METHODS: Twelve adults (age >55) were purposively selected and had variety of strength and mobility limitations. Biomechanical data for this pilot study were collected with three digital video cameras and processed to obtain estimates for joint torques and included angles. RESULTS: At the low bed height, hip torque for bed entry was significantly higher, and hip, knee, and ankle flexion angles were significantly smaller. The absence of significant differences in knee and ankle torques were the result of a compensation strategy that shifts the center of mass forward by flexing the torso during low bed ingress. Torque data from the egress motion were similar, however 50% of participants were unable to rise from the low bed without assistance. CONCLUSIONS: Healthcare providers should be aware that low bed heights pose safety risks to the population for which they were designed-elderly persons at high risk for falling.