Comparing Draw Sheets: Low Back and Hand Forces when Boosting a Patient up in Bed

Work-related injuries, including musculoskeletal disorders, are prevalent in healthcare workers (Daynard et al., 2001; Nelson & Baptiste, 2004). The physically demanding nature of patient-handling tasks often leads to these injuries, especially among nursing aids, orderlies, and attendants. According to the Bureau of Labor Statistics [BLS] (2019), more than 57,000 nurses and CNAs reported work-related injuries requiring days away from work in 2018 alone, up from a decade ago despite advances in safe patient handling education and materials. Low back injuries are consistently the most frequent injury in this population. Low back injuries have even caused many of these healthcare workers to consider leaving the profession due to pain that impacts their quality of life (Rice et al., 2011). Methods for reducing forces placed on healthcare workers’ bodies must be continually developed and evaluated.

It has been shown that traditional manual patient handling techniques frequently exceed recommended lifting limits for hand force (35 pounds), low back compression (6300 N for a one-time event, 3400 N for repetitive actions), and shear (1000 N for a one-time event, 500 N for repetitive actions) forces, and have contributed to the current rate of injury among healthcare workers (Menzel et al., 2007; Waters et al., 2006). In contrast, safe patient handling techniques, such as mechanical lifts and friction-reducing draw sheets, have decreased the risk of musculoskeletal injuries for healthcare workers (Menzel et al., 2007; Nelson & Baptiste, 2004; Waters et al., 2006). There is a disconnect between emerging evidence against traditional manual patient handling in favor of safe patient handling and what is taught in occupational therapy curricula (Frost & Barkley, 2012). Thus, researchers must continue to add to the evidence for safe patient handling, as there is a need for more health-related disciplines to shift their standards of practice from traditional manual patient handling to safe patient handling (Frost & Barkley, 2012; Slusser et al., 2012).

Many studies focus on methods for bringing low back and hand forces under the recommended limits during patient handling tasks (Bartnik & Rice, 2013; Hwang et al., 2019; Larson et al., 2018; Larson & Rice, 2015; McGill & Kavcic, 2005; McGill et al., 1998; Waters et al., 1993; Wiggermann et al., 2020). These studies have shown there are still risks as high forces at the lower back and the hands are seen even when using friction-reducing materials. However, the materials and methods of these studies often do not include contemporary devices available for performing patient-handling tasks, such as air-assisted draw sheets.

One of the most common patient-handling tasks is boosting a patient up in bed. This task and others place high levels of force on the lower back. There have been various strategies for reducing the amount of stress placed on healthcare workers' bodies, such as adjusting bed height or angle, which may or may not be implemented by healthcare workers when handling patient tasks (Kanaskie & Snyder, 2018).

Air-assisted devices can potentially reduce low back and hand forces to the recommended limits (Nelson et al., 2004). Studies that include these air-assisted devices either use subjective outcome measures based on the perceptions of the participants (Baptiste et al., 2006; Nelson et al., 2004) or do not use healthcare workers (Lloyd & Baptiste, 2006). One had participants perform various sliding and boosting tasks with research assistants acting as patients to examine the effectiveness of various transfer devices (Hwang et al., 2019). However, since it used only one hand gauge for this bimanual task, the reported force data are likely underestimated, and there are no low back force data. The current study compares healthcare workers’ low back and calculated hand forces during a boosting task when using different friction-reducing devices with a simulated dependent patient. Specifically, it was hypothesized that the AirPal® patient positioning device would require lower peak low back force at the L4-L5 and L5-S1 joints when sliding a patient up in bed than would the Skil-Care™ Super-Sling 4-Handle Transfer Sling, which likewise would require less low back force compared a typical cotton draw sheet.

Methods

This study was a cross-sectional crossover design. Subject recruitment for healthcare workers occurred at inpatient units at hospitals and skilled nursing facilities in and around the greater Provo, UT, USA area. Recruitment took place by word of mouth, and flyers were posted in the previously described facilities. Participants were screened using inclusion/exclusion criteria. Inclusion criteria were healthcare workers between the ages of 18–65; nurses, certified nursing assistants, occupational therapists, occupational therapy assistants, physical therapists, and physical therapy assistants who were currently working in inpatient hospital, acute hospital, or skilled nursing settings and who engage in patient handling tasks consistently throughout the workday as part of their job. Pregnancy was the exclusion criterion. Participants read and signed a printed informed consent form and asked questions regarding anything related to the study and/or the consent form, approved by the Institutional Review Board of Brigham Young University (IRB Protocol # F19017) . Participants were assigned a number so that all study data could be de-identified.

A total of 35 healthcare workers (15 men, 20 women; age range = 18-63 years old; average age = 37.2± 2.21 years) participated in this study. This included 11 occupational therapists, one occupational therapy assistant, 10 physical therapists, three physical therapy assistants, four nurses, and six certified nursing assistants. Together, the participants averaged just over nine years of experience (± 1.63), ranging from six months to 35 years in their respective roles. Based on the data by Larson et al. (2018), this sample size was expected to be sufficient to determine a difference in peak low back forces required to complete the boosting task with the three different types of draw sheets using an α = .05, and a β = .8 (Larson et al., 2018).

A ten-camera Oqus motion capture system (Qualisys, Göteborg, Sweden) was used to collect motion data at 100 Hz. Two force plates were used to collect ground reaction forces at 400 Hz. Nineteen reflective markers used for measuring joint angles were placed as recommended by C-Motion with slight modification (C-motion, 2010) for use in the 3-Dimensional Static Strength Prediction Program (University of Michigan, Ann Arbor, MI):

To complete the boosting task, the participant placed one foot on each force plate initially, then on the count of three, slid the “patient” (research assistant, n = 1) approximately six inches up in the hospital bed using one of the three draw sheets based on the results of randomization. The “patient” was a 202-pound female who acted as a dependent patient for all boosting tasks. A trained occupational therapist (n = 1) was on the other side of the hospital bed to make the “patient’s” movement symmetrical. This was performed three times.

The order of device presentation was randomized. The three devices included a standard cotton sheet, an AirPal® patient transfer system device (short), and a Skil-Care™ Super-Sling 4-Handles Transfer Sling, as depicted in Figure 1 and Figure 2. Participants completed a series of nine transfers, three with each device at the maximal bed height. Motion and force plate data were filtered using a low-pass Butterworth filter with a 10 Hz cutoff frequency. The moment of peak hand force was found, and this single frame was used for further analysis. Custom MATLAB code was used to compute planar angles and estimate hand forces as specified by 3DSSPP. It was then processed by 3DSSPP, which gave specific information regarding peak L4-L5 and L5-S1 compression and shear joint forces. The average of the three boosts was taken for each sheet type, followed by a comparison of peak forces. Low back compression and shear forces during the three conditions were analyzed using a one-way ANOVA followed by a Tukey test for pairwise comparisons.

Figure 1. Draw Sheets Used in this Study. Top: Cotton; Middle: Skil-Care™; Bottom: AirPal®

Figure 2. AirPal® Air Supply

Results

There were significant differences in low back forces when comparing the boosting task with the three different types of friction-reducing devices. The comparison showed the AirPal® reducing low back forces most effectively compared to the cotton sheet and the Skil-Care™. Surprisingly, the Skil-Care™ had the greatest peak low back and was not statistically different from the cotton sheet. The specific results of the comparisons can be found in Table 1. There were also significant differences in hand forces when comparing the different categories consistent with the differences in low back forces, such that the AirPal® was the best performing and the Skil-Care™ had the highest force, as seen in Table 2. The air-assisted device was the best-performing device, effectively reducing most low back and hand forces by up to 34% compared to the other devices.

Table 1. Various Peak Low Back Forces Between Sheet Types

* indicates a significant difference between the sheet types.

Table 2. Peak Hand Force Between Sheet Types

* indicates a significant difference between the sheet types.

Discussion

This study aimed to assess which of three patient repositioning devices had the most effect on reducing low back and hand forces. The results show that the AirPal® was the most effective of the devices tested in this study for achieving that goal. The results of the current study confirmed the findings of a similar project by Larson et al. (2018). They found that the only effective reduction in force with a simple friction-reducing sheet compared to a cotton sheet occurred when the friction-reducing sheet was doubled up on itself, creating a double layer of friction-reducing material that can slide against itself instead of sliding against the cotton sheet. The device used here, the Skil-Care™, is not of sufficient size to be doubled up for the boosting task. These results are also consistent with those of Hwang et al. (2019), who found that a simple friction-reducing draw sheet did not produce hand force differences compared to a cotton sheet. That said, direct comparisons between these studies are difficult due to the different patient handling tasks performed (lateral transfer (Hwang et al., 2019) vs. boosting (the current study). In addition, they only used a force gauge in one hand, which gives an incomplete picture of the overall force for these patient-handling tasks. Lastly, they used “patients” with less mass than the “patient” in the current study, which is less representative of typical inpatients.

Wiggerman et al. (2020) also observed low back forces during patient-handling tasks. Their study systematically used “patients” of three different weights to assess the effectiveness of various patient-handling materials. They also showed that there was not a significant difference between low back forces when boosting up a patient in bed when comparing a typical cotton draw sheet to a simple friction-reducing device, but that there were significant differences between an air-assisted device and the others with the lightest category of “patient.” Interestingly, they found more pronounced differences in hand forces between the devices as “patient” weight increased. This study used a bed height of the “knuckle height of the caregiver or higher,” which may be a lower-than-optimal position.

The lack of difference between the cotton sheet and the Skil-Care™ in the current study is a concern. The Skil-Care™ purports to be a friction-reducing device (Skil-Care Corporation, 2013) but does not seem to perform its primary function, as evidenced by the high low back and hand forces when used per manufacturer recommendations. This suggests that using the Skil-Care device still greatly stresses healthcare workers’ bodies.

Even with this best-performing device, the AirPal®, the average hand force was above the recommended lifting limit of 35 pounds. The lowest hand force recorded was 37 pounds, averaging 54.9 pounds using the AirPal®. This shows that while it is better to use than the other devices in this research study, it is still not enough to bring the force under the recommended limit. Thus, it still places healthcare workers at risk of musculoskeletal injury due to regular patient handling tasks that are a required part of the job.

Multiple factors are at play in the decision-making process when healthcare workers are considering which materials to use during patient-handling tasks. The most prohibitive factor is the cost of air-assisted devices. Prices vary by supplier, but an air supply and a reusable transfer pad can cost thousands of dollars (Baptiste et al., 2006), a sizeable investment per patient. Another factor is the time it takes for healthcare workers to place the equipment under the patient when, in most cases, there is already a cotton sheet under them. These factors together tend to make administrators and frontline workers balk at using the equipment when they do not see the value. The value can become apparent when the knowledge of the effectiveness of air-assisted devices becomes common.

Limitations

All the preliminary and main study participants lived in the greater Provo, Utah area, so the results cannot be generalized to a greater population as there may be educational differences in healthcare education in different regions. There was only one healthy, young individual who acted as a patient. This was important as a control factor to make direct comparisons between other factors, but this individual was atypical of a general patient population. Actual patients tend to be sickly, older, and less cooperative. This research assistant also only represents one height and weight. In contrast, genuine patients are much more varied and have individualized differences that can affect patient handling technique and experience for the caregiver.

Proper boosting should be undertaken with healthcare workers of the same approximate height. Therefore, the height difference between participants and the consistent assistant helping with the boosting task can be considered a limitation. There were occasionally stark height differences between them. This limitation was necessary as a control factor to make accurate comparisons.

Another limitation of this study was the relatively small sample size. However, the power analysis indicated this was a sufficient sample size, and the number of participants was consistent with other studies of this type.

Future Research and Implications

With new technology coming out frequently, it is essential to continue to test all purported friction-reducing devices and observe how they compare to materials already available and how they compare to each other. It is also crucial for companies that manufacture and sell these materials to test them before their distribution to ensure the efficacy of their products. This will continue to inform healthcare workers about the best methods for reducing the risk of work-related musculoskeletal injury.

Incorporating multiple patient-handling techniques and comparing low back forces between them is also warranted. Techniques like simply bending the patient’s legs and putting their feet on the bed before the boosting task to placing the bed at a decline before the boost. It would also be important to study the tradeoff between low back force and shoulder force during these patient-handling tasks to see if healthcare workers place themselves at greater risk of shoulder injury and vice versa by lowering the force at the lower back.

Another future study could incorporate inclining the bed with the air-assisted device and seeing if there is an angle where the air overcomes the friction of the bed and allows the patient to slide freely to the edge of the bed, as this would be a safety concern. This idea would necessitate very controlled conditions with healthy individuals to prevent injury.

Conclusion

Nurses and other healthcare workers are at risk for injury during patient handling. Injuries impact a substantial number of healthcare workers yearly and contribute to the shortage of healthcare workers at the bedside. Identifying ways to reduce the risk of injury during patient handling is imperative for healthcare workers and patients. Using assistive technologies may help to reduce the incidence of injury. Still, more research must be done to identify the best available technology and its feasibility at the bedside.

Acknowledgements
Thanks to Lauren Adams and Spencer Peterson for contributing their time and expertise to data collection during this project. Also, a thank you to AirPal® for loaning the air-assisted device used throughout this study.

Authors

Robert E. Larson, OTR, Ph.D.
Email: rolarson@ttuhsc.edu
ORCID ID:

Robert E. Larson earned his PhD from BYU where he worked with the other authors on this paper. Prior to that, he earned his occupational therapy doctorate degree from the University of Toledo where he also picked up a keen interest in safe patient handling. He has published multiple articles in this area and is eager to continue in this line of research.

Dustin A. Bruening, Ph.D
Email: dabruening@byu.edu
ORCID ID:

Dustin A. Bruening graduated with a PhD from the University of Delaware and has extensive training in biomechanics research, which was especially important when laying the foundation for the current project when delving into the procedures for collecting and processing data.

Sarah T. Ridge, Ph.D.
Email: sarah_ridge@byu.edu
ORCID ID:

Sarah T. Ridge earned her PhD from the University of Delaware in biomechanics and had keen input into several foundational aspects of the current study. She directly influenced the formation of this project by giving insight into the processing and interpretation of the data.

Wayne Johnson, Ph.D., PT
Email: wayne_johnson@byu.edu
ORCID ID:

Wayne Johnson earned his PhD from Brigham Young University and his Physical Therapy degree from the University of Alabama at Birmingham. He has worked extensively researching and teaching about the back and spine and has clinical experience in a variety of settings.

Ulrike H. Mitchell, Ph.D., PT
Email: rike@byu.edu
ORCID ID:

Ulrike H. Mitchell earned her PhD from Brigham Young University and her first Physical Therapy degree from Krankengymnasikschule Hessisch Lichtenau in Germany. She has taught topics related to the spine for many years and has published some innovative MRI based studies regarding the low back and traction in the past.