Five Questions for Dr. Jacob Banks, PhD, Principal Engineer, Baxter Ergonomics Lab
It’s good advice that has clinicians’ best interests at heart. After all, it’s well documented that manual patient handling activities are directly associated with musculoskeletal disorders in healthcare workers.1,2,3,4 In the United States, healthcare workers suffer from a high prevalence of musculoskeletal disorders — with nursing assistants and registered nurses ranking second and fifth in terms of prevalence.5
Although it is natural for administrators and ergonomists to encourage clinicians to use mechanical lifts for every lift and transfer, in today’s busy healthcare environments — plagued with staffing shortages — these blanket edicts may prove ineffective.
That’s why a team of researchers at Baxter’s Ergonomics Lab in Batesville, IN, recently conducted a study to measure perceived vs. actual in vivo physical demands during a common caregiver task: bed-to-chair transfers.6 The goals were:
1. Compare perceived exertion and injury risk under a variety of transfer conditions6
2. Suggest an upper limit for patient weight that could be considered safe for manual patient transfers6
Dr. Jacob Banks, PhD, Principal Engineer at Baxter, led the research team. To help understand the study and its results, we asked him five questions.
Knowing that bed-to-chair transfers are frequently performed tasks among healthcare workers, the research team studied five transfer conditions representing various patient masses/assistance levels and techniques:
· Gait belt only (GB_BW)
· Galt belt + 18% of patient body weight offset by overhead support (GB_18%)
· Gait belt + 36% of patient body weight offset by overhead support (GB_36%)
· Slide board + gait belt (SB_BW)
· Slide board + gait belt + 18% of patient body weight offset by overhead support (SB_18%)*
* Note: Slide board + gait belt combination was not studied with 36% of patient body weight offset by overhead support because initial piloting found these conditions to be too effortless.
Left: a healthcare worker transfers the patient from bed to wheelchair using a gait belt and slide board with 18% counterweight (shown suspended in the far left of the photo) condition. Right: full-body thoracolumbar musculoskeletal model used to estimate shoulder torques and lower-back demands. Green arrows represent measured hand force vector. Grey spheres in both panels are motion-tracking markers.
13 healthcare workers (e.g., personal care aides, physical therapists, registered nurses) performed transfers during the study on a patient weighing 140 lbs. An eight-camera optical motion capture system synchronously tracked the healthcare workers’ movements and external forces during all transfer trials. Transfers were performed three times, then healthcare workers rated their perceived exertion on a scale of 0-10.6 In vivo shoulder and lower-back demands were estimated from the recorded data using a musculoskeletal model.6
"It’s important to note that all participants were actual healthcare workers,” points out Dr. Banks. “We wanted them to come into the study with their own patient handling technique and skill, so our results would be applicable to healthcare workers in the field.”
„Transfer condition had a significant effect on all dependent variables (i.e., perceived exertion, hand force, shoulder torque, lower back forces).6 Generally speaking, there was a linear relationship between musculoskeletal forces and the amount of support offered during the transfer.6
Vertical Hand Forces |
|
Gait belt only (GB_BW) |
Most exceeded recommended vertical lifting capacity6,7 |
Galt belt + 18% of patient body weight offset (GB_18%) |
|
Slide board + gait belt (SB_BW) |
Only 29% exceeded recommended vertical lifting capacity6,7 |
Slide board + gait belt + 18% of patient body weight offset (SB_18%) |
|
Gait belt + 36% of patient body weight offset (GB_36%) |
None exceeded recommended vertical lifting capacity6,7 |
To reduce injury risk, the National Institute of Occupational Safety & Health (NIOSH) recommends that a healthcare worker never lift more than 35 lbs (16 kg).7 Most of the gait-belt-only and GB_18% transfers exceeded this recommendation. However, none of the GB_36%, and only 29% of the slide board transfers, exceeded 35 lbs. This suggests that vertical assistance and slide boards can reduce physical demands, but not necessarily below recommended guidelines.
Overall, participants’ ratings of their perceived exertions were low.6 The transfer using a gait belt only was perceived as most arduous — but even that was rated as only “somewhat hard.”6 The significant differences in perceived exertion across transfer conditions corresponded with those of in vivo physical stress.
“Our participants were nurses, personal care aides and physical therapists,” points out Dr. Banks. “People in these roles are familiar with patient handling techniques, and they do a great job of minimizing the load on their bodies. But this study shows us that skill isn’t enough to protect them in most cases. The difference between the physical stresses healthcare workers perceive compared to what they are actually exposed to suggests they might be underestimating their injury risk.”
This exercise predicted that, for a bed-to-wheelchair transfer using only one healthcare worker, a relatively light patient of up to 140 lbs might be safely transferred using only a gait belt.6 This estimate, however, comes with many caveats. For example:
· This estimate is based on a study of only 13 healthcare workers
· Patient sizes, abilities and level of coherence will vary
· Clinician size, ability and skill will vary
Together with some additional methodological limitations, this estimate may ultimately represent a best-case scenario that is not sufficiently conservative for manual transfers with only a gait belt.6
“We know it’s unrealistic to tell healthcare workers to use a mechanical lift every time,” says Dr. Banks. “So while 140 lbs may be an upper limit for manual transfers, we know conditions won’t always be this favorable. We want clinicians to protect themselves as best they can. Bottom line: it is never wrong to use a lift.”
Portions of this data were presented at the 2023 Human Factors Conference in Washington DC.8 The full study will be available later this year. Complete the form to download a digital copy now.
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