Integrated Experimental-Computational Analysis of Sacral Soft Tissue Stresses During Patient Migration in Bed

Background: Head of bed elevation (HOB) is a common hospital practice causing the patient’s body to slide down in bed due to gravity, a phenomenon termed ‘migration in bed’ (MIB). This migration effect likely results in tissue shearing between the sacrum and the support, which increases the risk for pressure injuries. A new migration reduction technology (MRT) has been introduced by which the head section of the bedframe and bed surface are extended in unison as the HOB elevates. Although MRT has been shown to reduce MIB, the effect of reducing MIB on tissue shear during HOB elevation has not been evaluated.

Methods: We analyzed relationships between MIB and resulting sacral soft tissue stresses by combining motion analysis and three-dimensional finite element modelling of the buttocks. Migration data were collected for 10 subjects, lying supine on two bedframe types with and without MRT, and at HOB elevations of 45°/65°. Migration data were used as displacement boundary conditions for the modelling to calculate tissue stress exposures.

Results: MIB values for the conventional bed were 1.75-times and 1.6-times greater than those for the MRT bed, for elevations of 45° and 65°, respectively (p<0.001). The modeling revealed that the farther the MIB, the greater the tissue stress exposures. Internal stresses were 1.8-fold greater than respective skin stresses.

Conclusion: Our results, based on the novel integrated experimental-computational method, point to clear biomechanical benefits in minimizing MIB using MRT.