Document Type


Date of Award

Fall 1-31-2004

Degree Name

Master of Science in Occupational Safety and Health Engineering - (M.S.)


Industrial and Manufacturing Engineering

First Advisor

Arijit K. Sengupta

Second Advisor

One-Jang Jeng

Third Advisor

George Hanna Abdou


The incidence of musculoskeletal injuries among healthcare workers has been well documented in the medical and ergonomic literature. The epidemiological evidence demonstrates high injury rate among nurses, nurse's aides, therapists and other medical workers who frequently handle patients. The biomechanical research has shown large compressive forces developed in the lumbar spine performing various patient handling transfers that exceed the National Institute of Occupational Safety and Health's recommended guideline. One of the most strenuous patient handling tasks is transferring the patient from bed to the chair and vice versa.

One of the objectives of this thesis is to design and conduct a laboratory experiment to determine whether six experienced physical therapists and physical therapy assistants can accurately and consistently assess the patient's functional level based on a widely used grading system for a non-dependent patient. An additional objective is to measure the lumbar spinal compression forces during the assisted transfers to investigate whether they pose a risk of injury to the lumbar spine for healthcare workers. In the past, the reliability of this functional grading system and the biomechanical risk of performing assisted transfers has never been evaluated. The hand coupling forces and the therapist's perceived exertion was recorded and analyzed to verify the therapist's accuracy using the grading system on a patient. A small, able-bodied male, posing as a patient, was transferred from bed and from wheelchair using a gait belt.

The therapists were consistent in their grading of the assistance level for the transfer from the bed with an average R2 value of 0.62 and an overall correlation coefficient of 0.95. For the transfers from the wheelchair, the gradings were not well correlated with the respective values of 0.34 and 0.41. This low correlation was attributed to the mismatch between the varying anthropometry of the therapists with respect to the fixed lower height of the wheelchair.

The spinal compression forces at L5/S 1 assessed for one large male therapist and one small female therapist were under the recommended safe level of 3400 N. The maximum spinal compression force was 2100 N using a static biomechanical model. The transfers, under the same experimental conditions, were extrapolated to 50th and 95th percentile bodyweight patients, with and without gait belts. Results revealed that the gait belt transfers continued to remain under the safe lumbar load levels. For larger patients requiring higher levels of assistance, the transfers performed without the gait belt ranged from 3555 to 4143 N, which is over the recommended safe limit. These biomechanical findings should assist healthcare workers in deciding whether to handle patients with manual or mechanical technique.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.