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International Journal of Nursing Studies 46 (2009) 317–325 www.elsevier.com/ijns

Effects of two hospital bed design features on physical demands and usability during brake engagement and patient transportation: A repeated measures experimental study Sunwook Kim a, Linsey M. Barker a, Bochen Jia a, Michael J. Agnew a, Maury A. Nussbaum a,b,* a

Department of Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA 24061, United States b School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA 24061, United States Received 28 July 2008; received in revised form 6 October 2008; accepted 9 October 2008

Abstract Background: Work-related musculoskeletal disorders (WMSDs) are prevalent among healthcare workers worldwide. While existing research has focused on patient-handling techniques during activities which require direct patient contact (e.g., patient transfer), nursing tasks also involve other patient-handling activities, such as engaging bed brakes and transporting patients in beds, which could render healthcare workers at risk of developing WMSDs. Objectives: Effectiveness of hospital bed design features (brake pedal location and steering-assistance) was evaluated in terms of physical demands and usability during brake engagement and patient transportation tasks. Design: Two laboratory-based studies were conducted. In simulated brake engagement tasks, three brake pedal locations (headend vs. foot-end vs. side of a bed) and two hands conditions (hands-free vs. hands-occupied) were manipulated. Additionally, both in-room and corridor patient transportation tasks were simulated, in which activation of steering-assistance features (5th wheel and/or front wheel caster lock) and two patient masses were manipulated. Participants: Nine novice participants were recruited from the local student population and community for each study. Methods: During brake engagement, trunk flexion angle, task completion time, and questionnaires were used to quantify postural comfort and usability. For patient transportation, dependent measures were hand forces and questionnaire responses. Results: Brake pedal locations and steering-assistance features in hospital beds had significant effects on physical demands and usability during brake engagement and patient transportation tasks. Specifically, a brake pedal at the head-end of a bed increased trunk flexion by 74–224% and completion time by 53–74%, compared to other pedal locations. Participants reported greater overall perceived difficulty and less postural comfort with the brake pedal at the head-end. During in-room transportation, participants generally reported ‘‘Neither Low nor High’’ physical demands with the 5th wheel activated, compared to ‘‘Moderately High’’ physical demands when the 5th wheel was deactivated. Corridor transportation was similarly reported to be easier when a steering-assistance feature (the 5th wheel or front caster lock) was activated. Conclusions: Braking and steering-assistance features of hospital beds can have important effects on task efficiency and physical demands placed on healthcare workers. Selection of specific designs may thus be able to improve productivity and contribute to a reduction in WMSDs risk among healthcare workers. # 2008 Elsevier Ltd. All rights reserved. Keywords: Ergonomics; Hospital beds; Medical device design; Physical demands

* Corresponding author. E-mail address: [email protected] (M.A. Nussbaum). 0020-7489/$ – see front matter # 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijnurstu.2008.10.005

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What is already known about this topic?  Work-related musculoskeletal disorders are prevalent among healthcare workers.  Design features of a hospital bed can affect physical demands placed on healthcare workers. What this paper adds  Brake pedal locations on a hospital bed have important effects on physical demands and usability.  Though steering-assistance features can reduce physical demands, these demands are still high and may expose healthcare workers to an elevated risk for work-related musculoskeletal disorders during patient transportation.  Evidence that considering ergonomics principles in the design of medical devices, specifically hospital beds, can reduce physical demands and improve usability. 1. Introduction Work-related musculoskeletal disorders (WMSDs) remain prevalent in healthcare workers, as reported by the Bureau of Labor Statistics (BLS, 2006, 2007). In 2006, healthcare workers in the United States experienced one of the highest incidence rates of WMSDs (293 per 10,000 workers) requiring a total of 27,590 days away from work. Internationally, healthcare workers have been recognized as a high-risk occupational group with high incidence rates of various WMSDs (Engkvist, 2008; Pheasant and Stubbs, 1992). Within this occupational domain, manual patient handling has been acknowledged as one of the major risk factors for WMSDs at the low back and/or the shoulder region (Ando et al., 2000; Marras et al., 1999; Waters et al., 2006). Several existing studies have focused on patienthandling techniques and assistive devices that are intended to reduce the low back loads placed on healthcare workers (Marras et al., 1999; McGill and Kavcic, 2005; Zhuang et al., 1999). However, daily duties of healthcare workers include several tasks other than patient handling (e.g., admitting emergency patients, positioning the bed, transporting patients in bed, etc.) that are also physically demanding and potentially associated with the development of WMSDs (Ando et al., 2000; Sherehiy et al., 2004). In addition to relatively high rates of WMSDs, the healthcare industry is facing challenges, such as worker shortages, increased competition for reimbursement and resources, and increased costs for providing care (Aikien, 2001; Aikien et al., 2002; McKinley, 2005). These challenges have led to changes in healthcare work environments, such as extended work hours for healthcare workers, and an increased focus on efficiency of practice and usability of medical technologies (Aikien, 2001; Aikien et al., 2002; Martin et al., 2008; Page, 2004; Trinkoff et al., 2006a). Healthcare workers are expected to interface frequently with hospital beds during their work tasks. Thus, the designs of

hospital beds should incorporate features that enable healthcare workers to work efficiently and at an acceptable workload during their daily routine. Recent research has emphasized the consideration of ergonomics in the design of medical devices, such as hospital beds, in order to improve safety and health for both patients and healthcare workers in healthcare settings (Martin et al., 2008). A few studies have examined design factors of hospital beds (i.e., dimension, weight and wheel arrangement), and noted that such design factors can yield positive effects on physical demands (Petza¨ll et al., 1995, 2001; Petza¨ll and Petza¨ll, 2003). Accordingly, hospital bed manufacturers have incorporated different design features into hospital beds, such as varying brake pedal locations and steering-assistance features (i.e., a retractable 5th wheel and front caster lock). The 5th wheel (an extra wheel located centrally under the bed frame) and front caster lock (a switchable lock attached to the front wheels of the bed) are intended to prevent drifting of a bed during patient transportation. These bed design features are intended to reduce physical demands during brake engagement and inbed patient transportation tasks, both in a patient room and in a hospital corridor. However, the ergonomic benefits and usability of these design features have not been assessed. The purpose of this study was to evaluate the effectiveness of these types of bed design features (i.e., alternative brake pedal locations and a retractable 5th wheel) on the usability and physical demands during brake engagement and patient transportation tasks. Two commercially available hospital beds (midrange medical/surgical) with different brake pedal locations and steering-assistance features were tested in simulated hospital environments. Subjective responses, performance, and measures of biomechanical load were used to assess the usability and physical demands associated with these varying design features. It was hypothesized that the design features incorporated in these hospital beds would have important effects in terms of physical demand and usability during relevant nursing tasks.

2. Methods Separate laboratory-based studied were conducted for the brake engagement and the in-bed patient transportation tasks. For the brake engagement task, nine participants (six males and three females) were recruited from the local student population and community through advertisements. Mean (SD) age, body mass, and stature of participants were 31.8 (4.4) years, 67.4 (12.2) kg, and 172.3 (8.8) cm, respectively. For the transportation task, nine participants (seven males and two females) were recruited, with respective mean (SD) age, body mass, and stature of 32 (4.2) years, 67.4 (12.2) kg, and 171.8 (9) cm. Inclusion criteria were that participants be physically active and have had no selfreported injuries or illnesses within the past year. They also reported having no prior experience with nursing tasks. All

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participants gave informed consent after a demonstration of experimental protocols, and the experimental procedures were approved by the Virginia Tech Institutional Review Board. 2.1. Experimental design and procedures 2.1.1. Brake engagement task Three different brake pedal locations and two hand conditions were evaluated with two hospital beds, namely Beds A and B (bed specifications are given in Table 1). The brake pedal locations included designs with the brake located at the head-end (BrakeHead) or foot-end (BrakeFoot) of Bed A, as well as one with the brake centrally located at the side of Bed B (BrakeSide). These brake positions are illustrated in Fig. 1. Both hands-free and hands-occupied conditions were studied. For the latter, participants were asked to engage the brake while holding a light-weight foam pad in front of their body using both arms, which simulated Table 1 Specifications of the beds.

Mass Length Width with side rails down Wheelbase Wheel track width Steering-assistance feature Brake pedal location

Bed A

Bed B

191 kg 254 cm 102 cm 155 cm 62 cm Front caster lock Head-end and foot-end

214 kg 240 cm 99 cm 178 cm 62.5 cm 5th wheel Side

Wheelbase is the distance between the front and rear swivel axes of the wheels. Wheel track width is the distance between the two front (or the rear) swivel axes.

Fig. 1. Illustration of three brake pedal locations and side rail configurations (A, side rails in the up position; B, side rails in the down position). The brake engagement task was performed with the side rails down. The subscripts head, foot and side represent brakes located at the head-end, foot-end, and side of a bed, respectively. Note that Bed A included both BrakeHead and BrakeFoot whereas Bed B included only BrakeSide.

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the postural restrictions involved when healthcare workers carry materials (supplies, charts, patients) during brake engagement. During all brake engagement trials, participants initially stood approximately 2.5 m away from the brake and all four side rails were placed in the down position. Then, participants were instructed to walk across a simulated hospital room and fully engage the brake at a self-selected ‘quick but comfortable’ pace. They were allowed to use either foot for brake engagement, and raise a side rail as needed. A set of 10 replications of brake engagement was conducted in each of six conditions (three brake  two hand). After each set, participants completed a four-item questionnaire, designed to assess opinions regarding and reactions to the brake system in terms of usability and postural demands. All questions were responded to with five-point scales with verbal anchors related to either level of agreement with the item, level of satisfaction, or perception of a level from low to high. For example, participants were asked to respond to the question ‘‘I would rate my level of confidence in using the brake system as’’ using the following ordered verbal anchors: ‘‘Low’’, ‘‘Moderately Low’’, ‘‘Neither Low nor High’’, ‘‘Moderately High’’, to ‘‘High’’. Presentation order of the three brake pedal locations was counterbalanced, and the order of the two hand conditions was randomized within each brake pedal location. Trunk posture was measured using passive retro-reflective markers that were sampled at 60 Hz using a motion capture system (VICON 524, Lake Forest, CA). A cluster of four markers was placed on the skin midway between the palpated processes of the 7th cervical (C7) and the 8th thoracic (T8) vertebrae. Trunk anatomical markers (incisura jugularis, xiphoid process, C7 and T8) were initially referenced to this cluster, and were reconstructed for each trial (Challis, 1994) after marker position data were smoothed (using a low-pass filter with a cut-off frequency of 3 Hz in order to remove high frequency noise). Task completion time was recorded, using a stopwatch, from the start of walking to full brake engagement. 2.1.2. In-bed patient transportation task—in-room and corridor For in-room transportation, two steering conditions and two patient mass conditions were tested. The steering conditions included the 5th wheel either activated (Bed B + 5th) or deactivated with Bed B (Bed B 5th). The patient mass condition had two levels: 5th percentile female (50 kg) and 95th percentile male body mass (121 kg), with percentiles obtained from McDowell et al. (2005). These two conditions were simulated by distributing weights over the bed surface. Participants were instructed to pull/push the bed along an L-shaped pathway, which represented pulling the bed out of (pulling-out phase), or pushing the bed into (pushing-in phase), a patient room (Fig. 2A). A mock bedside table was also placed beside the initial bed position, and participants were asked not to hit the table. During the in-room

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For corridor transportation, three steering conditions and two patient mass conditions were evaluated. The steering conditions included the front caster lock activated with Bed A (Bed A + CL), which is recommended by the bed manufacturer, as well as the 5th wheel either activated (Bed B + 5th) or deactivated (Bed B 5th) with Bed B. Patient mass conditions were the same as for in-room transportation. Participants were asked to transport the bed along a specified pathway in a corridor, which consisted of a straight path and left/right turns (Fig. 2B). After arriving at the end of the pathway, participants turned the bed around and transported the bed back to the start position. Participants were instructed to transport the bed at a fast but comfortable pace, and to avoid hitting anything in the hallway. Further, they were allowed to practice until they felt confident with the given condition. The order of steering conditions was counterbalanced, and patient mass conditions were randomized within each steering condition. After completing each of six conditions (three steering  two patient mass), participants completed a five-item questionnaire with five-point response scales related to usability of the bed and perceived physical demands during two phases (the turning and the pushing) of the task. 2.2. Data reduction and statistical analyses

Fig. 2. Illustrations of in-room and corridor transportation tasks. (A) L-shaped pathway and the experimental setup for in-room transportation. (B) Specified 41-m (134.5 ft) long and 2.5-m (8.2 ft) wide pathway for corridor transportation.

trials, triaxial forces exerted on the bed frame by the hands were collected at 1080 Hz using two force transducers, or load cells (AMTI MC3A-6, Watertown, MA). The load cells were attached to the end frame of a bed at a height of 89 cm, equivalent to the vertical position of grips on the headboard. Further, each load cell was covered by a 3 cm thick and 10 cm long square plastic grip with rounded edges on which participants were asked to push or pull. The presentation order of steering conditions was counterbalanced, and patient mass conditions were randomized within each steering condition. Participants completed three replications in each of four conditions (two steering  two patient mass). After each condition, participants completed a six-item questionnaire with five-point response scales, regarding usability of the bed and perceived physical demands during the following four phases of the task: the initiating movement, the turning, the pushing, and the pulling of the bed.

For the brake engagement task, the maximum trunk flexion angle from the upright posture was calculated from the marker data (Wu et al., 2005), and used as an indicator of the biomechanical demands on the low back. For the in-room transportation task, the 95th percentile (peak) resultant hand forces from the two load cells were used to quantify physical demand, and were extracted from the force data recorded for the pulling-out and the pushing-in phases of the transportation task. This percentile was used as an indicator of maximal demands, rather than the overall maximum, to minimize influences of noise. For the brake engagement task, separate analyses of variance (ANOVA) were performed on each of the direct measurements (trunk flexion angle and task completion time) and indirect measures (questionnaire responses) in order to determine main and interaction effects of brake pedal location and hand condition. Preliminary analysis indicated that learning effects occurred, but were minimal after 6–7 trials, so a mean of the last three replications (i.e., trials 8–10) was included in subsequent analyses. For transportation tasks, separate ANOVAs were performed on the peak resultant hand forces (only during in-room transportation) and questionnaire responses in order to determine main and interaction effects of steering condition and patient mass condition. Significant effects were followed by post hoc pairwise comparisons (Tukey’s HSD or Student’s t). For parametric statistical analyses, trunk flexion angles and task completion time were log-transformed (though summary statistics are given in original units), and questionnaire responses were assumed to have interval scale properties.

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Fig. 3. Effects of brake pedal location and hand condition on task completion times. Significant differences between brake pedal locations are indicated by asterisk (*), and error bars indicate standard deviations.

Statistical significance was accepted at the level of p < .05, and statistical analyses were performed using JMP7.0 (SAS Institute Inc., Cary, NC). All summary data are presented as means (SD).

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compared to 39 (35)8 and 21 (8)8 for BrakeFoot and BrakeSide, respectively. Further, brake pedal location [F (2,40) = 40.51, p < .0001] and hand condition [F (1,40) = 7.65, p = .0085] both had significant effects on task completion time (Fig. 3). The BrakeHead condition increased completion times by 53– 74% compared to either BrakeFoot and BrakeSide, and the hands-occupied condition did so by 7–12% compared to the hands-free condition. Brake pedal location and hand condition also had significant effects on several perceptual responses (Fig. 4), including perceived overall difficulty [pedal location: F (2,40) = 7.44, p = .0018; hand condition: F (1,40) = 13.17, p = .0008], whole body postural comfort [pedal location: F (2,40) = 5.06, p = .011; hand condition: F (1,40) = 7.69, p = .0084], and confidence in using the brake system [pedal location: F (2,40) = 6.10, p = .0049; hand condition: F (1,40) = 7.61, p = .0087]. Participants generally reported that the BrakeHead was more difficult than the BrakeFoot and BrakeSide, and they felt more confident with the BrakeSide. Participants also rated whole body postural comfort as being neutral using the BrakeHead and moderately comfortable using the BrakeFoot and BrakeSide. Lastly, participants reported that they perceived more difficulty, higher discomfort, and less confidence when using a brake system in the hands-occupied condition. 3.2. Patient transportation task

3. Results 3.1. Brake engagement task Brake pedal location had a significant effect on trunk flexion angle [F (2,40) = 23.11, p < .0001]. In the BrakeHead condition, maximum trunk flexion angle was 68 (27)8,

For in-room transportation, peak hand forces of 163.22 (67.5) N during the pulling-out phase and 259.96 (69.39) N during the pushing-in phase were found. Peak hand forces were not significantly affected by either steering condition [pulling-out: F (1,24) = .76, p = .39; pushing-in: F (1,24) = .47, p = .50] or patient mass condition (pulling-out: F (1,24) = .43,

Fig. 4. Effects of brake pedal location and hand condition on questionnaire responses. Significant differences between brake pedal locations are indicated by asterisk (*), and error bars indicate standard deviations.

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Fig. 5. Effects of steering and patient mass conditions on questionnaire responses related to overall physical demands during in-room transportation. Significant main effects were found on each of the questionnaire responses; i.e., initiating, turning, pushing and pulling. Error bars indicate standard deviations. Note that Bed B + 5th and Bed B 5th denote conditions with the 5th wheel activated and deactivated, respectively.

p = .52; pushing-in: F (1,24) = 3.87, p = .061). However, the steering and the patient mass conditions had significant effects on perceived overall physical demands (Fig. 5) when initiating the movement [steering condition: F (1,24) = 6.8, p < .016; mass condition: F (1,24) = 10.15, p = .004], when turning the bed [steering condition: F (1,24) = 36.64, p < .0001; mass condition: F (1,24) = 13.19, p = .0013], when pushing the bed [steering condition: F (1,24) = 27.77, p < .0001; mass condition: F (1,24) = 5.49, p = .028], and

when pulling the bed [steering condition: F (1,24) = 31.76, p < .0001; mass condition: F (1,24) = 31.76 p < .0001]. Participants generally reported lower physical demands when the 5th wheel was activated (Fig. 5). The heavy patient mass condition yielded larger overall perceived physical demands than the light patient mass condition. In addition, participants indicated ‘‘Moderately High’’ confidence in controlling bed movements in the Bed B + 5th condition, compared to ‘‘Neither Low nor High’’

Fig. 6. Effects of steering and patient mass conditions on questionnaire responses related to overall physical demands during corridor transportation. Significant differences between steering conditions are indicated by asterisk (*), and error bars indicate standard deviations. Note that Bed A + CL denotes the front caster lock activated with Bed A.

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confidence in the Bed B 5th condition [steering condition: F (1,24) = 4.50, p = .044]. For corridor transportation, the steering and the patient mass conditions had significant effects on most of the questionnaire items related to overall physical demands (Fig. 6). Specifically, participants indicated that the 5th wheel activated and the front caster lock activated conditions were easier during corridor transportation than the 5th wheel deactivated condition [F (2,40) = 40.64, p < .0001]. Physical demands were perceived to be higher in the 5th wheel deactivated condition than in the other conditions during bed pushing [steering condition: F (2,40) = 19.08, p = .0001; mass condition: F (1,40) = 5.82, p = .021] and turning [steering condition: F (2,40) = 21.81, p = .0001; mass condition: F (1,40) = 6.58, p = .014]. Further, participants indicated their level of confidence in controlling the bed as ‘‘Neither High nor Low’’ in the 5th wheel deactivated condition, and ‘‘Moderately High’’ in the 5th wheel activated and the front caster lock activated condition, though this effect was not significant [F(2,40) = 1.97, p = .15].

4. Discussion The objective of this study was to determine the effects of bed design features on physical demands and usability within the context of brake engagement and transportation tasks. Specifically, two design features (brake pedal location and steering-assistance features) were evaluated using midrange medical/surgical beds. Brake pedal location was found to influence exposure to risk factors for low back disorders (i.e. trunk flexion magnitude and duration) and work efficiency (task completion time), as well as participants’ perceptions related to postural comfort and usability. Use of steering-assistance features (the 5th wheel and front caster lock) further reduced perceived physical demands during the corridor transportation task. Thus, these findings suggest that considering ergonomics principles in the design of hospital beds can reduce physical demands and enhance usability. Substantial (and potentially risk-inducing) levels of spinal loads are expected to be imposed on healthcare workers during patient transportation, based on the masses of the hospital beds and patients (Table 1). Using a detailed biomechanical model of the spine, Hoozemans et al. (2004) reported that two-handed pushing or pulling of a 135 kg cart (with the hands at the hip level) resulting in estimated lumbo-sacral compressive forces exceed the 3400 N limit recommended by NIOSH (NIOSH, 1994). Similarly, Resnick and Chaffin (1995) estimated with a simplified biomechanical model that pushing cart loads over 225 kg caused lumbo-sacral compressive forces to exceed the recommended NIOSH limit. In addition, a major determinant of physical loads on the spine and the shoulder is the joint moment (or torque), and this moment is primarily determined by individual anthropometry, posture, and hand forces (Chaffin et al., 2006; De Looze et al., 2000). More

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information, such as participants’ postures, would thus be required for an accurate estimation of joint moments, yet our findings suggest that high physical demands and increased risk of musculoskeletal injuries potentially exist even if a steering-assistance feature is activated during patient transportation tasks. Accessibility of the brake pedals affected task completion times (Fig. 3) and trunk flexion angles. From observing the participants, and from their informal feedback, it was evident that the fully lowered side rails can obstruct the brake pedals. Depending on the brake pedal location, participants were required to raise the side rails in order to locate and engage the brake. In this study, the brake pedal located at the head-end of the bed (BrakeHead) was most obstructed by the side rails (Fig. 1), which resulted in the significantly larger trunk flexion angle (688) and the longer task completion time (5.48 s), compared to the other brake pedal locations (trunk flexion angle: 21–398; task completion time: 3.34–3.64 s). Trunk flexion magnitude and duration are generally acknowledged as risk factors for low back disorders (e.g., Bernard, 1997; Norman et al., 1998; Punnett et al., 1991). Further, in a study by Engels et al. (1996), nurses in four Dutch nursing homes reported that the most troublesome physical variables associated with their work included working in awkward postures (47%) and stooping (34%). It can thus be concluded that poor accessibility of brake pedals, due to their location on the bed, may increase the risk of a low back disorder among healthcare workers resulting from repetitive brake engagement tasks. Steering-assistance features (5th wheel and front caster lock) have the potential to reduce physical demands during in-room and/or corridor transportation scenarios. Relatively lower perceived physical demands (‘‘Neither Low nor High’’ or ‘‘Moderately Low’’) were reported with steering-assistance features (the Bed B + 5th and/or the Bed A + CL condition; Figs. 4 and 5), compared to ‘‘Moderately High’’ perceived physical demands without the steering-assistance feature. Though no practical difference in the peak hand forces was found when the 5th wheel was activated during in-room transportation, a cross-sectional study on working nurses revealed that perceived physical demands were associated with reported WMSDs among nurses (Trinkoff et al., 2003). In addition, work by Petza¨ll and Petza¨ll (2003) suggested that the steering-assistance features can prevent drifting of the other wheels during pushing the bed, and that the use of a two-wheel central axle (comparable to the 5th wheel) could provide additional support for the bed and patient masses and act as a pivot point during turning, which may explain the lower perceived physical demands with steering-assistance features activated. Accordingly, the steering-assistance features may reduce risk of low back disorders during in-bed patient transportation tasks. The fact that healthcare workers often work extended schedules exceeding 40 h/week (Burke, 2003; Josten et al., 2003; Rogers et al., 2004; Trinkoff et al., 2006b) could

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imply that healthcare workers are cumulatively exposed to risk-inducing levels of physical demands while interacting with hospital beds during their work tasks, such as brake engagement and patient transportation. This may explain results of previous studies which indicate that patient handling-based training programs or other reactive interventions alone are unlikely to be successful in reducing WMSDs (e.g., Hignett, 2003; Nelson et al., 2006). However, in other industries, such as construction, it has been demonstrated that explicit consideration of safety (and potentially ergonomics) in early design phases of a system can be more proactive, and thereby can be more effective in improving worker safety (Gambatese, 1998; Hecker and Gambatese, 2003). Thus, it follows that the development of medical devices (e.g., hospital beds) should incorporate ergonomic principles while taking into account the daily tasks of healthcare workers and organizational characteristics, such as extended work hours. Such proactive consideration of ergonomics in the design of medical devices could contribute to effectively reducing the risk for developing WMSDs in healthcare workers. There are a few limitations within this study which should be acknowledged. First, the participants had no prior experience related to patient transportation and brake engagement tasks. Their performance levels and perceived physical demands during the tasks may thus not characterize more experienced healthcare workers. However, participants were given an opportunity to practice all tasks in order to minimize learning effects. Second, the participants spanned a limited range of anthropometry, and were somewhat young compared to the average age of the healthcare workforce. However, a within-subject experimental design was employed for both tasks, so that the effects of the design features would not be largely confounded by individual differences (e.g., body size, experience) but could differ in magnitude. The results were found to be relatively consistent across the participants, which suggests generality of the effects of the design features. Nonetheless, to more comprehensively understand the effects of the design features, the study needs to be replicated on actual healthcare workers with an increased number of participants. Lastly, due to constraints in the laboratory equipment, participants were only allowed to push/pull on the load cells attached to the end of the bed during in-room transportation. They were not able to steer the bed using the sides of the bed frame. Thus, these results may only reflect the physical demands and usability of the bed in certain healthcare scenarios, and may not be generalizable for more complex healthcare work environments. In conclusion, the design features of hospital beds (brake pedal location and steering-assistance features) can have important effects on task efficiency and physical demands placed on healthcare workers, but these design features need to be implemented with consideration of how healthcare workers interact with hospital beds during their daily work. Given that use of a hospital bed is essential in diverse

healthcare work environments, design features of these beds should be developed with consideration of their potential impact on exposures of healthcare workers risks of musculoskeletal disorders. To that end, further ergonomic assessments should be performed regarding the effectiveness of bed design features in more realistic work environments and with actual health care workers, in order to enhance the usability of hospital beds and reduce the likelihood of injuries among healthcare workers.

Role of the funding source This research was financially supported by a North American Bed Manufacturer. The company loaned the two hospital beds and provided information on healthcare workers’ daily activities using a hospital bed. However, the company had minimal involvement in study design, and no involvement in data analysis and interpretation, or decision for publication.

Conflict of interest We affirm that all authors have no financial or personal relationships with other persons or organizations that might have inappropriately influenced our work presented herein.

Ethical approval The experimental procedures and ethics were approved by the Virginia Tech Institutional Review Board.

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