Effects of bed height on the biomechanics of hospital bed entry and egress.

BACKGROUND: Although a significant proportion of patient falls in hospitals occur in the vicinity of the hospital bed, little is known about the contribution of bed height to fall risk. OBJECTIVE: To compare lower extremity joint torques and angles during hospital bed entry and egress at two bed heights. METHODS: Twelve adults (age > 55) were purposively selected and had variety of strength and mobility limitations. Biomechanical data for this pilot study were collected with three digital video cameras and processed to obtain estimates for joint torques and included angles. RESULTS: At the low bed height, hip torque for bed entry was significantly higher, and hip, knee, and ankle flexion angles were significantly smaller. The absence of significant differences in knee and ankle torques were the result of a compensation strategy that shifts the center of mass forward by flexing the torso during low bed ingress. Torque data from the egress motion were similar, however 50% of participants were unable to rise from the low bed without assistance. CONCLUSIONS: Healthcare providers should be aware that low bed heights pose safety risks to the population for which they were designed-elderly persons at high risk for falling.

The effect of ergonomic laparoscopic tool handle design on performance and efficiency.

BACKGROUND: Many factors can affect a surgeon's performance in the operating room; these may include surgeon comfort, ergonomics of tool handle design, and fatigue. A laparoscopic tool handle designed with ergonomic considerations (pistol grip) was tested against a current market tool with a traditional pinch grip handle. The goal of this study is to quantify the impact ergonomic design considerations which have on surgeon performance. We hypothesized that there will be measurable differences between the efficiency while performing FLS surgical trainer tasks when using both tool handle designs in three categories: time to completion, technical skill, and subjective user ratings. METHODS: The pistol grip incorporates an ergonomic interface intended to reduce contact stress points on the hand and fingers, promote a more neutral operating wrist posture, and reduce hand tremor and fatigue. The traditional pinch grip is a laparoscopic tool developed by Stryker Inc. widely used during minimal invasive surgery. Twenty-three (13 M, 10 F) participants with no existing upper extremity musculoskeletal disorders or experience performing laparoscopic procedures were selected to perform in this study. During a training session prior to testing, participants performed practice trials in a SAGES FLS trainer with both tools. During data collection, participants performed three evaluation tasks using both handle designs (order was randomized, and each trial completed three times). The tasks consisted of FLS peg transfer, cutting, and suturing tasks. RESULTS: Feedback from test participants indicated that they significantly preferred the ergonomic pistol grip in every category (p < 0.05); most notably, participants experienced greater degrees of discomfort in their hands after using the pinch grip tool. Furthermore, participants completed cutting and peg transfer tasks in a shorter time duration (p < 0.05) with the pistol grip than with the pinch grip design; there was no significant difference between completion times for the suturing task. Finally, there was no significant interaction between tool type and errors made during trials. CONCLUSIONS: There was a significant preference for as well as lower pain experienced during use of the pistol grip tool as seen from the survey feedback. Both evaluation tasks (cutting and peg transfer) were also completed significantly faster with the pistol grip tool. Finally, due to the high degree of variability in the error data, it was not possible to draw any meaningful conclusions about the effect of tool design on the number or degree of errors made.

The effect of lifting speed on cumulative and peak biomechanical loading for symmetric lifting tasks.

BACKGROUND: To determine the influence of lifting speed and type on peak and cumulative back compressive force (BCF) and shoulder moment (SM) loads during symmetric lifting. Another aim of the study was to compare static and dynamic lifting models. METHODS: Ten male participants performed a floor-to-shoulder, floor-to-waist, and waist-to-shoulder lift at three different speeds [slow (0.34 m/s), medium (0.44 m/s), and fast (0.64 m/s)], and with two different loads [light (2.25 kg) and heavy (9 kg)]. Two-dimensional kinematics and kinetics were determined. A three-way repeated measures analysis of variance was used to calculate peak and cumulative loading of BCF and SM for light and heavy loads. RESULTS: Peak BCF was significantly different between slow and fast lifting speeds (p < 0.001), with a mean difference of 20% between fast and slow lifts. The cumulative loading of BCF and SM was significantly different between fast and slow lifting speeds (p < 0.001), with mean differences ≥80%. CONCLUSION: Based on peak values, BCF is highest for fast speeds, but the BCF cumulative loading is highest for slow speeds, with the largest difference between fast and slow lifts. This may imply that a slow lifting speed is at least as hazardous as a fast lifting speed. It is important to consider the duration of lift when determining risks for back and shoulder injuries due to lifting and that peak values alone are likely not sufficient.

Prediction of peak back compressive forces as a function of lifting speed and compressive forces at lift origin and destination - a pilot study.

OBJECTIVES: To determine the feasibility of predicting static and dynamic peak back-compressive forces based on (1) static back compressive force values at the lift origin and destination and (2) lifting speed. METHODS: Ten male subjects performed symmetric mid-sagittal floor-to-shoulder, floor-to-waist, and waist-to-shoulder lifts at three different speeds (slow, medium, and fast), and with two different loads (light and heavy). Two-dimensional kinematics and kinetics were captured. Linear regression analyses were used to develop prediction equations, the amount of predictability, and significance for static and dynamic peak back-compressive forces based on a static origin and destination average (SODA) back-compressive force. RESULTS: Static and dynamic peak back-compressive forces were highly predicted by the SODA, with R(2) values ranging from 0.830 to 0.947. Slopes were significantly different between slow and fast lifting speeds (p < 0.05) for the dynamic peak prediction equations. The slope of the regression line for static prediction was significantly greater than one with a significant positive intercept value. CONCLUSION: SODA under-predict both static and dynamic peak back-compressive force values. Peak values are highly predictable and could be readily determined using back-compressive force assessments at the origin and destination of a lifting task. This could be valuable for enhancing job design and analysis in the workplace and for large-scale studies where a full analysis of each lifting task is not feasible.

A revised back compressive force estimation model for ergonomic evaluation of lifting tasks.

Occupational back pain and injury are common and costly issues. Biomechanical models are often used to quantify job risk by estimating back muscle forces. In general, the most accurate models are also the most complex, creating demand for models that are both straightforward and accurate. An existing, basic hand-calculation back compressive force estimation model (HCBCF v1.0) was revised in two iterations to reduce the error induced by original simplifying assumptions. Lifting tasks (n=6000) from observational data were used to compare the HCBCF models with the University of Michigan 3D Static Strength Prediction Program (3DSSPP) The greatest r(2) (0.97) between the HCBCF v1.2 and the 3DSSPP was achieved with gender-specific equations designed to account for differences between males and females and a more detailed estimation of torso flexion angle and upper body mass center location. This gender-specific back compression and risk estimation model is a relatively simple alternative to computer-based back compressive force models. In addition the hand-calculation can be used as a general survey tool to determine which jobs should be analyzed with more sophisticated computer-based models.

Development of a carpal tunnel syndrome screening method using structured interviews and vibrotactile testing.

Carpal tunnel syndrome (CTS) is a debilitating and expensive health problem. An inexpensive screening method that would differentiate between people who do not have CTS and those that may have CTS would be useful. The screening methodology investigated here had two phases: a structured interview and provocative vibrotactile testing (VT). The control group (n = 36) was composed of asymptomatic college students and faculty, the case group was composed of patients currently visiting an occupational medicine clinic for symptoms consistent with CTS. The case group was subdivided into positive and negative for nerve conduction latency, NCL+ (n = 21) and NCL- (n = 13), respectively. Using a scored, structured interview, 33 of the controls and none of the symptomatic cases were identified as non-CTS. The results from the provocative flexion VT indicated that if the difference between the age corrected baseline and the threshold at 15 minutes is 15 microm or more, the subject was likely to be NCL+ (odds ratio 12.6, 95% CI 3.8 to 41.8). Further research may improve this screening methodology to not only determine whether or not a person has CTS, but also to determine the level of median nerve impingement or damage.

Effects of prolonged wrist flexion on transmission of sensory information in carpal tunnel syndrome.

UNLABELLED: Carpal tunnel syndrome presents a constellation of symptoms which include discomfort (eg, pain, paraesthesia) and diminished sense of touch. This exploratory study simultaneously measured changes in tactile threshold and discomfort ratings during prolonged wrist flexion in symptomatic patients from a rehabilitation clinic and from a control population. Prolonged (15 min) wrist flexion significantly increased tactile threshold and discomfort ratings above baseline levels in both symptomatic and control populations. Sixty-two percent of the symptomatic sample was found to have abnormal conduction latency. Tactile threshold in symptomatic subjects with normal conduction latency (n = 13) did not differ significantly from control subjects (n = 36) at baseline but showed significant elevation during wrist flexion. In contrast, subjects with abnormal conduction latency (n = 21) exhibited significant elevation relative to control subjects at baseline and throughout wrist flexion as well as a slower recovery after flexion. Conduction latency correlated with baseline (r = .52, P < .0001) and 15-min (r = .67, P < .0001) tactile threshold for the entire subject population, as well as 15-min threshold (r = .53, P = .013) for the subpopulation with abnormal conduction latency. At 2.5 min after flexion, correlation was significant for whole (r = .64, P < .0001) and abnormal conduction latency (r = .58, P = .0063) samples. Regression slope of tactile threshold versus conduction latency was significantly greater than zero and did not differ significantly from linearity. The study demonstrates that increases in mechanosensory threshold and discomfort ratings during prolonged wrist flexion are more profound (and recovery less rapid) in patients with electrophysiologic evidence of injury. PERSPECTIVE: This study demonstrates a provocative procedure that enhances the symptoms of carpal tunnel syndrome. This measure may help clinicians discriminate median nerve compression from other types of peripheral nerve injury and help researchers investigate the impact of mechanical stress, tissue compression, and vascular stasis on compression-related neuropathy.

Job level risk assessment using task level ACGIH hand activity level TLV scores: a pilot study.

Existing upper extremity musculoskeletal disorder analytical tools are primarily intended for single or mono-task jobs. However, many jobs contain more than 1 task and some include job rotation. This case/control study investigates methods of modifying an existing tool, the American Conference of Governmental Industrial Hygienists (ACGIH) Hand Activity Level (HAL) Threshold Limit Value (TLV), to assess the upper extremity risk of multi-task jobs. Various methods of combining the task differences and ratios into a job level assessment were explored. Two methods returned significant odds ratios, (p < .05) of 18.0 (95% CI 1.8-172) and 12.0 (95% CI 1.2-120). These results indicate that a modified ACGIH HAL TLV may provide insight into the work-related risk of multi-task jobs. Further research is needed to optimize this process.

Job level risk assessment using task level strain index scores: a pilot study.

This paper explores 2 methods of modifying the Strain Index (SI) to assess the ergonomic risk of multi-task jobs. Twenty-eight automotive jobs (15 cases and 13 controls) were studied. The first method is based on the maximum task SI score, and the second method is modeled on the NIOSH Composite Lifting Index (CLI) algorithm, named cumulative assessment of risk to the distal upper extremity (CARD). Significant odds ratios of 11 (CI 1.7-69) and 24 (CI 2.4-240) were obtained using the modified maximum task and CARD, respectively. This indicates that modification of the SI may be useful in determining the risk of distal upper extremity injury associated with a multi-task job.

High-risk head and neck movements at high G and interventions to reduce associated neck injury.

BACKGROUND: Neck injuries are a significant concern for aviators of high performance aircraft. A recent comprehensive technical report on cervical spinal injury associated with exposure to sustained acceleration, from NATO's Research and Technology Organization, recommended delineating the neck muscles used by aviators in this flying environment and developing improved neck muscle strengthening programs in an attempt to reduce such injuries. METHODS: A review of current literature was conducted in the fields of biomechanics, ergonomics, orthopedics, neurology, neurosurgery, rehabilitative medicine, and aerospace medicine. An objective description is provided of the muscles involved in specific head and neck movements, and those movements that are associated with a greater risk of injury during high-G sorties. The intensity and duration of force exposures common to high performance aircraft sorties, the effects of seat-back angle on these exposures, and the types and mechanisms of neck injury reported in this environment are also described. RESULTS: Primary, secondary, and tertiary preventive interventions are introduced with the goal of providing unit-level flight surgeons an approach to reducing neck injury and promoting prompt, safe return to flying of aviators with identified neck injury. A central component of these interventions is a "specific" and "intensive" neck muscle training regimen, as described in the medical literature. CONCLUSION: Increased axial compressive force and unique biomechanics combine to make neck injury likely in high performance aviators. The application of some proposed intervention strategies may reduce the occurrence of these injuries.

Evaluation and quantification of manual materials handling risk factors.

This study investigated the ability of the Revised NIOSH Lifting Equation (RNLE) to measure the risk of low back injury as verified by employee health outcomes. In addition, several basic risk factors and combinations of risk factors presumed related to low back disorders were explored. The RNLE was modified to allow analysis of one-handed and two-handed, asymmetric lifts. Predictive performance was not changed. Simplifying the RNLE by removing several variables did not significantly reduce the RNLE's predictive performance. These modifications to the RNLE show promise for increasing both the usability and utility of the RNLE.

An analysis of VDT monitor placement and daily hours of use for female bifocal users.

A population of 72 bifocal wearers was studied to determine the relationship between VDT (video display terminal) placement for those who reported musculoskeletal pain and those who did not. The mean hours worked was 50.4 minutes (p=0.003) greater for those who reported head/neck pain versus those who did not and 48.6 minutes (p=0.004) greater for those who reported shoulder/arm pain that those who did not. There was no statistically significant difference between the means of monitor height, distance, or angle for those who reported pain symptoms versus those who did not. This study indicates that, self reported pain symptoms are correlated with hours of VDT work and that there appears to be a threshold at approximately five hours for pain symptoms among bifocal wearers. No such correlation can be made for monitor placement

An ergonomic comparison between mechanical and manual patient transfer techniques.

Multiple studies have concluded that manual patient transfer and repositioning techniques are a significant cause of low back injuries. The objective of this study was to compare the low back stresses resulting from the use of two different mechanical patient transfer assist devices with the use of traditional manual transfer techniques. The mechanical transfer systems used were the Barton Patient Transfer System and a Sling-Suspension Lift similar to a "Hoyer Lift". The back compressive forces derived using the Michigan 3D Static Strength Model (Version 4.0) and electromyography (EMG) of the muscles of the low back were compared. This study found that the mechanical assist devices placed less stress on the low back and were more desirable to use than the traditional manual techniques. The Barton System was found to be, in general, less hazardous and more preferred than the Sling Suspension Lift.

An exploratory study of nurse bag use by home visiting nurses.

Although the bag of the home care nurse is functional and historical, there is limited information in the literature about its use and nurses' preferences. This study analyzes how the bag is used, and examines comfort issues and preferences nurses have for this valuable tool. Implications for design and features are gained from this research as well as specific features to seek when choosing this important ergonomic tool.