Characterizing the Compressive Force at L5/S1 During Patient Transfer From Bed to Wheelchair

Abstract

The peak compressive forces at L5/S1 during patient transfers have been estimated. However, no study has considered the actual patient body weight that caregivers had to handle during transfers. We developed a simple kinematic model of lifting to address this limitation. Fifteen prospective health care providers transferred a 70-kg individual who mimicked a patient (“patient”) from bed to wheelchair. Trials were acquired with the patient donning (weighted) and doffing (unweighted) a 5-kg weight belt. Trials were also acquired with and without knee assistance and a mechanical lift. During trials, kinematics and kinetics of transfers were recorded to estimate the peak compressive force at L5/S1 using static equilibrium equations. The peak compressive force was associated with the transfer method (P < .0005), and the compressive force was 68% lower in lift-assisted than manual transfer (2230 [SD = 433] N vs 6875 [SD = 2307] N). However, the peak compressive force was not associated with knee assistance, nor with a change in the patient body weight. Our results inform that mechanical loading exceeding the National Institute for Occupational Safety and Health safety criterion occurs during patient transfers, confirming a high risk of lower back injuries in caregivers. However, the risk can be mitigated with the use of a mechanical lift.