A biomechanical and ergonomic evaluation of patient transferring tasks: bed to wheelchair and wheelchair to bed.

A laboratory study was conducted in an effort to reduce back stress for nursing personnel while performing the patient handling tasks of transferring the patient from bed to wheelchair and wheelchair to bed. These patient handling tasks were studied using five manual techniques and three hoist-assisted techniques. The manual techniques involved one-person and two-person transfers. One manual technique involved a two-person lift of the patient under the arms; the others used a rocking and pulling action and included the use of assistive devices (a gait belt using a two-person transfer, a walking belt with handles using a one-person and a two-person transfer, and a patient handling sling with cutout areas to allow for a hand grip (Medesign) for a one-person transfer). The three mechanical hoists were Hoyer, Trans-Aid and Ambulift. Six female nursing students with prior patient transfer experience served both as nurses and as passive patients. Static biomechanical evaluation showed that pulling techniques, as compared to lifting the patient, required significantly lower hand forces and produced significantly lower erector spinae and compressive forces at the L5/S1 disc (P greater than or equal to 0.01). Shear force, trunk moments and the percentage of females who were capable of performing the transfers (based on static strength simulation) also favoured pulling methods. Perceived stress ratings for the shoulder, upper back, lower back and whole body were lower for pulling methods than those for lifting the patient (P less than or equal to 0.01). Patients found the pulling techniques, with the exception of when using the gait belt, felt more comfortable and more secure than the lifting method (P less than or equal to 0.01). However, a number of subjects believed that the patient handling sling (Medesign) and the walking belt with one person making the transfer would not work for those patients who could not bear weight and those who were heavy, contracted or combative. A walking belt with two persons was the preferred manual method. Two out of three hoists (Hoyer lift and Trans-Aid) were perceived by the nurses to be as physically stressful as manual methods. Patients found these two hoists to be more uncomfortable and felt less secure than with three of the five manual methods (one- and two-person walking belts and Medesign). Ambulift was found to be the least stressful, the most comfortable, and the most secure among all eight methods. Pulling techniques and hoists took significantly longer amounts of time to make the transfer than manually lifting the patient (P less than or equal to 0.01). The two-person walking belt using a pulling technique and Ambulift are recommended for transferring patients from bed to wheelchair and wheelchair to bed. A large-scale field study is needed to verify these recommendations.     

Prevention of back injuries in healthcare workers

A laboratory study was conducted to evaluate five different manual techniques (two-person lifting; rocking and pulling the patient using a gait belt with two persons; walking belt with handles with one and two persons; and a patient handling sling with cutouts with one person) for transferring patients from wheelchair to toilet and toilet to wheelchair. In addition, three different mechanical hoists (H, T and A) were studied for transferring patients from toilet to wheelchair. Six female nursing students with prior patient transfer experience served both as nurses and passive patients.

The mean trunk flexion moments, erector spinae muscle forces and compressive forces for the four manual pulling methods ranged from 93 to 133 Nm, 1861 to 2653 N and 1974 to 2745 N, respectively, as compared to about 200 Nm, 4100 N and 4800 N for two-person manual lifting. Manual lifting was perceived to be the most stressful by the nurses and the least comfortable and secure by the patients. Hoist A was perceived to be the least stressful and the most comfortable and secure. Hoists H and T were perceived to be more stressful, less comfortable and less secure than the walking belt.

An intervention study was conducted in two units of a nursing home (140 beds and 57 NAs) to determine the effectiveness of ergonomic changes. Nursing assistants (NAs) in the two units of the nursing home were trained in the use of selected devices and shower rooms and toilets were modified. The mean acceptability rates for walking belt and hoist A were 81% and 87%, respectively. The reported incidence and severity rates for back injuries over 13 months decreased from 83 to 43 and from 634 to 0, respectively, after the intervention. Nursing assistants perceived their job as “very light” after the intervention as compared to between “somewhat hard” and “hard” before intervention.     

Patient handling with and without slings: an analysis of the risk of injury to the lumbar spine

Health professionals handling patients are known to be at risk of sustaining work related low back injuries. It is not known whether the use of lifting slings reduces the risk of injury to the lumbar spine for patient handlers. This study used kinematic variables and subjective ratings of body part stress and lifter preference as measures of relative risk for three two-person techniques for carrying a patient from one chair to another chair. The techniques used no slings, one and two slings respectively. Twenty-two nurses performed five trials each of the three techniques. Kinematic measures of angular displacement, velocity and acceleration were obtained using the lumbar motion monitor and visual analogue scales were used to obtain measures of body part stress for seven body parts. Angular displacement, velocity and acceleration were significantly greater (p < 0.05) in the frontal, sagittal and transverse planes for the no sling technique compared to techniques using slings. Comparatively small yet significant differences between techniques using slings were recorded for sagittal flexion and rotation. There was no significant difference between one and two sling techniques for other dependent variables. Mean total body stress rating was higher for the no sling technique and all subjects indicated that their first preference was for slings. Although all three measures of risk rated the no sling technique as carrying a higher level of risk than the techniques using slings. No single measure adequately captured all aspects of relative risk. The elimination of manual patient handling is thought to be the best option for the reduction of work related back injuries in patient handlers. Where resources or technology are not yet adequate to provide practical alternatives and where the use of manual technique for a seat to seat task is unavoidable, the use of patient handling slings will reduce the risk.     

Spine loading and trunk kinematics during team lifting

Two-person or team lifting is a popular method for handling materials under awkward or heavy lifting conditions. While many guidelines and standards address safe lifting limits for individual lifting, there are no such limits for team lifting, and these lifts are poorly understood. The literature associated with team lifting offers some interesting paradoxes. Many studies have indicated that people lift less per individual under team conditions compared with one-person lifting. Yet, at least one study has reported an increase in team-lifting capacity when subjects were height-matched. The current study explored the spine loading characteristics of one- and two-person lifting teams when subjects lifted under several sagittally symmetric and asymmetric conditions. Spine compression was lower for two person lifts for a given weight, while lifting in sagittally symmetric conditions whereas lateral shear became much greater for two-person lifts under asymmetric lifting conditions. This study has linked these changes to differences in trunk kinematic patterns adopted during one- versus two-person lifting.     

Spine loading and trunk kinematics during team lifting

Two-person or team lifting is a popular method for handling materials under awkward or heavy lifting conditions. While many guidelines and standards address safe lifting limits for individual lifting, there are no such limits for team lifting, and these lifts are poorly understood. The literature associated with team lifting offers some interesting paradoxes. Many studies have indicated that people lift less per individual under team conditions compared with one-person lifting. Yet, at least one study has reported an increase in team-lifting capacity when subjects were height-matched. The current study explored the spine loading characteristics of one- and two-person lifting teams when subjects lifted under several sagittally symmetric and asymmetric conditions. Spine compression was lower for two person lifts for a given weight, while lifting in sagittally symmetric conditions whereas lateral shear became much greater for two-person lifts under asymmetric lifting conditions. This study has linked these changes to differences in trunk kinematic patterns adopted during one- versus two-person lifting.     

The handling of patients on geriatric wards. A challenge for on-the-job training

Patient lifting habits were studied on seven geriatric wards in five hospitals. The methods used were workplace analysis, questionnaire and video analysis of lifts. Mechanical hoists were regularly used only on the ward that had well organised on-the-job-training. The reasons given for not using the hoist (lack of space or time, etc) were similar on this and the other wards where hoists were used irregularly. Lifting with hoists is slower than without aids, but the total extra time needed for their use is only 3-6% of the 8-hour work shift. Stooped and twisted trunk positions occurred less often when lifting aids were used than without an aid. However, some nurses worked in bad spine-loading positions, even when using lifting aids. To eliminate these postures from nursing work, more attention should be paid to working postures during the organised training of patient handling.     

An evaluation of patient lifting techniques

Abstract

In the present laboratory study five two-person manual lifting techniques were evaluated as to the amount of physical exertion required of the nurses. Ten female volunteers served as nurses; two healthy volunteers (weight: 55 kg and 75 kg) served as passive patients. The working postures and motions were recorded on videotape. The data thus obtained were used in a anatomical-biomechanical analysis. The perceived exertion by the nurses was measured as well. In almost all situations the compressive forces on the nurse's spine exceeded their acceptable limit of 3425 N. Differences between the lifting techniques were most obvious when the 55 kg patient was lifted. Ratings of the perceived exertion (RPE scores) were higher in symmetrical handling than in asymmetrical handling. The three techniques using asymmetrical hand positions produced less subjective stress. RPE scores and rotation of the back were negatively correlated. Rotating the back when moving a patient from one side to the other seems to ease the task. On the whole, the results of the biomechanical evaluation are in line with the subjective perception of the nurses. In both instances the barrow lift appeared to be the most strenuous one; the Australian lift resulted in low compressive forces and a moderate level of perceived exertion     

Ergonomic evaluation of slide boards used by home care aides to assist client transfers

Home care aides risk musculoskeletal injury because they lift and move clients; the body weight of most adults exceeds the NIOSH recommended limit for lifting. Methods to reduce manual patient lifting in institutional settings are often technically or economically infeasible in home care. Our goal was to identify suitable, safe, low-technology transfer devices for home care use. Sixteen experienced home care aides performed client transfers from wheelchair to bed (upward) and bed to wheelchair (downward) in a simulated home care environment (laboratory), using four different slide boards and by hand without a device. Aides’ hand forces were measured during client transfers; aides also evaluated usability of each board. Hand forces exerted while using slide boards were mostly lower than in manual transfer, and forces were lower in downward versus upward transfers. Aides judged a board with a sliding mechanism easier to use than boards without a sliding mechanism.

Practitioner Summary: This paper provides quantitative biomechanical measurements showing that slide boards reduced the hand forces needed by home care aides to transfer clients from bed to wheel chair and vice versa, compared to manual lifting. Using a semi-quantitative usability survey, aides identified boards with a sliding mechanism easiest to use.     

Symmetry of the elbow kinematics during racing wheelchair propulsion

The purpose of this study was to establish whether bilateral symmetry exists during wheelchair propulsion in the elbow movement pattern of trained wheelchair racers. Seven endurance-trained wheelchair racers volunteered to participate in the study. Each subject was recorded by two-dimensional video analysis while pushing on a single-roller wheelchair ergometer at 14 mph (6.58 ms^-1) in their own racing wheelchair. The range of elbow flexion, elbow orientation and selected timing parameters including cycle time and time spent in contact with the handrim (propulsion phase) were obtained from both left and right sides. Wilcoxon Matched-Pairs Signed-Ranks tests determined the differences between the left and right sagittal plane images of wheelchair propulsion. Furthermore, the Bland-Altman method determined the agreement between the left and right sagittal plane images. The results indicated that the propulsion phase, elbow height and elbow angular displacement characteristics were not significantly different between right and left sides. The right elbow was higher than the left during the recovery phase, but the magnitude of this difference was only 0.03 m (N.S). Factors associated with chair design and the athlete's posture may have contributed to the small differences noted between left and right sides. In conclusion, the results appear to suggest that the assumption of bilateral symmetry of the elbow movement pattern during wheelchair propulsion is valid for the group. However, it is important to note that asymmetries exist in individuals and further research is warranted.     

Reducing back stress to nursing personnel: an ergonomic intervention in a nursing home.

A prospective epidemiologic study was conducted in two units (140 beds and 57 nursing assistants) of a nursing home to demonstrate the efficacy of an ergonomic intervention strategy to reduce back stress to nursing personnel. The total programme involved the following: determining patient handling tasks perceived to be most stressful by the nursing assistants (NAs); performing an ergonomic evaluation of these tasks; and conducting a laboratory study to select patient transferring devices perceived to produce less physical stress than existing manual patient-handling methods. The intervention phase included training NAs in the use of these devices, modifying toilets and shower rooms, and applying techniques to patient care. Immediately after completing the intervention programme, a post-intervention analysis (which lasted eight months in unit 1 and four months in unit 2) was performed. A biomechanical evaluation of the physical demands required to perform stressful patient-handling tasks showed that the mean compressive force on the L5/S1 disc, the mean hand force required to make a transfer, and the strength requirements (expressed as percentage female population capable) were 1964 N, 122 N, and 83% after intervention as compared to 4751 N, 312 N, and 41% before intervention. Subjectively, the mean rating of perceived exertion was less than 'very light' after intervention as compared to between 'somewhat hard' and 'hard' before intervention. Overall, the mean acceptability rates for the walking belt and the mechanical hoist were 81% and 87% for patient transfers. The incidence rate for back injuries prior to the intervention, 83 per 200,000 work-hours, decreased to 47 per 200,000 work-hours after the intervention. There were no injuries resulting in lost or restricted work days during the last four months of the post-intervention. It is concluded that an appropriate ergonomic intervention programme offers great promise in reducing physical stress and risk of low-back pain to nursing personnel. However, large-scale studies in different nursing homes are needed to confirm the above findings.     

Psychophysical assessment of assistive devices for transferring patients/residents

This article reports the psychophysical assessment of nine battery-powered lifts, a sliding board, a walking belt, and a baseline manual method for transferring nursing home patients/residents from a bed to a chair. A separate article reports the biomechanical evaluation of the same task and devices. The objectives of the psychophysical assessment were to investigate the effects of resident-transferring methods on the psychophysical stress to nursing assistants performing the transferring task, and to identify transfer methods that could reduce the psychophysical stress reported by nursing assistants. Nine nursing assistants served as test subjects. Two elderly persons participated as residents. The results indicated that the psychophysical stresses on nursing assistants were significantly lower when performing resident transfers with some of the assistive devices than when performing transfers with the baseline manual transfer method. The nursing assistants generally preferred the basket-sling lift and stand-up lift to other methods. The residents' comfort and security ratings indicated the comfort and security with most of the assistive devices were greater than or equal to the baseline manual method. Most of the comments of the nursing assistants and residents on the assistive devices were favourable.     

Analysis of hand pressures related to wheelchair rim sizes and upper-limb movement

Hand pressure is important in wheelchair design as it is directly related to the comfort or injury of the patients/sportsmen using the wheelchair. However, little research has been done on hand pressure during wheelchair propelling. This study aimed to measure hand pressures and joint movements in the upper limb with the different size of wheelchair rims during manual propulsion. Nine healthy adult subjects participated in the study, and they were required to perform wheelchair propelling at their self-comfortable way. A specific mat of pressure sensors was used to measure the hand pressure of the palm and a motion capture system to capture the movements at the shoulder and elbow. The results showed that under the condition of the speeds between 0.7–1.7 m/s, the mean hand pressures were ranged between 180 and 200 kPa on the palm; the ranges of motion were from 30° to 70° at the shoulder and from 15° to 50° at the elbow. The pressure and kinematic data collected provide a set of database available for wheelchair manufacturer, glove designer, clinicians and sports exerciser as reference when they need.Relevance to industryPushing wheelchair usually causes hand uncomfortable or injury. Our study provides the first experimental data of hand pressures associated the joint movements in the upper limbs at different sizes of push-rims. These results are valuable for devising gloves for patients, thus improving the life quality of the patients using wheelchair.     

A Review of: “Human Error in Medicine”, edited by MARILYN SUE BOGNER,Lawrence Erlbaum,Hillsdale (1994), pp. xv + 411, 536-00 (pbk). ISBN 0-8058-1386-1; $79·95 (hbk), ISBN 0-8058-1385-3.

This work investigated maximal voluntary lateral hand pulling force in 18 healthy, habitually active men. Measurements were made in standing at different static angles of lateral trunk flexion, as well as at different constant lifting and lowering velocities. Movement was constrained to the frontal plane, velocity was controlled by an isokinetic dynamometer, pulling force was measured with a strain gauge and overall lateral angular displacement of the trunk by an electrogoniometer. Mean peak pulling force values ranged from 478 to 658 N (static), 291 to 528 N (lifting), and 801 to 911 N (lowering), respectively. The static pulling forces were the highest in flexed positions to the loaded side (10 and 20 trunk angles). In lifting, peak and position-specific pulling force decreased with increasing velocity. Peak lifting force occurred in a flexed trunk position of 7 to 9 to the loaded side. In lowering, pulling forces were significantly higher than during lifting at corresponding velocities and showed less changes with velocity. Peak lowering force occurred at a trunk angle of- 7 to- 11, that is towards the unloaded side. In conclusion, maximal voluntary pulling force in the frontal plane was found to be task dependent. Lowering was accompanied by higher forces and a different velocity and position dependency than lifting which, in addition to the fact that the trunk muscles act predominantly eccentrically during the lowering task, may impose an increased risk of injury.     

Reducing back stress to nursing personnel: an ergonomic intervention in a nursing home

A prospective epidemiologic study was conducted in two units (140 beds and 57 nursing assistants) of a nursing home to demonstrate the efficacy of an ergonomic intervention strategy to reduce back stress to nursing personnel. The total programme involved the following: determining patient handling tasks perceived to be most stressful by the nursing assistants (NAs); performing an ergonomic evaluation of these tasks; and conducting a laboratory study to select patient transferring devices perceived to produce less physical stress than existing manual patient-handling methods. The intervention phase included training NAs in the use of these devices, modifying toilets and shower rooms, and applying techniques to patient care. Immediately after completing the intervention programme, a post-intervention analysis (which lasted eight months in unit 1 and four months in unit 2) was performed.

A biomechanical evaluation of the physical demands required to perform stressful patient-handling tasks showed that the mean compressive force on the L5/S1 disc, the mean hand force required to make a transfer, and the strength requirements (expressed as percentage female population capable) were 1964?N, 122?N, and 83% after intervention as compared to 4751?N, 312?N, and 41% before intervention. Subjectively, the mean rating of perceived exertion was less than ‘very light’ after intervention as compared to between ‘somewhat hard’ and ‘hard’ before intervention. Overall, the mean acceptability rates for the walking belt and the mechanical hoist were 81% and 87% for patient transfers. The incidence rate for back injuries prior to the intervention, 83 per 200 000 work-hours, decreased to 47 per 200 000 work-hours after the intervention. There were no injuries resulting in lost or restricted work days during the last four months of the post-intervention. It is concluded that an appropriate ergonomic intervention programme offers great promise in reducing physical stress and risk of low-back pain to nursing personnel. However, large-scale studies in different nursing homes are needed to confirm the above findings.     

Review paper A comparative study of methods for establishing load handling capabilities

There has been much effort in recent years to quantify manual handling capabilities. Four main techniques have been used to this end; biomechanical modelling; the measurement of intra-abdominal pressure; psychophysics; and metabolic/physiological criteria. The aim of this study was to compare quantitatively the data produced from the first three techniques. The comparisons were limited to bimanual, sagittal plane lifting, which of all manual handling activities has been studied the most comprehensively, except that pushing and pulling data were compared from the psychophysics and intra-abdominal pressure (‘force limits’) databases. It was found that the data from ‘force limits’ proposed weights for bimanual lifting in the sagittal plane are lower than those reported to be psychophysically acceptable except for lifting close to and around the shoulder. The closest agreement between the databases was for lifting from an origin above knuckle height. The ‘force limits’ data were found to propose weights of lift which are at a minimum when lifting with a freestyle posture from the floor whereas the psychophysical technique proposes weights which are at a maximum when lifting from the floor. The psychophysical data were found to generate compressive forces at L5/S1 according to a static sagittal plane biomechanical model about 10% in excess of the NIOSH action limit (NIOSH 1981) when lifting from the floor, although over other lifting ranges the compressive forces were less than the NIOSH action limit. Lifting the (force limits) weights generated compressive forces which were on average 55% less than the AL (range 45 to 60%) when lifting in an erect posture. The data for pushing according to the psychophysical and ‘force limits’ database showed good agreement, but for pulling the ‘force limits’ weights were considerably greater than those selected psych ophysically. The implications of these findings are discussed.     

A comparative study of methods for establishing load handling capabilities

There has been much effort in recent years to quantify manual handling capabilities. Four main techniques have been used to this end; biomechanical modelling; the measurement of intra-abdominal pressure; psychophysics; and metabolic/physiological criteria. The aim of this study was to compare quantitatively the data produced from the first three techniques. The comparisons were limited to bimanual, sagittal plane lifting, which of all manual handling activities has been studied the most comprehensively, except that pushing and pulling data were compared from the psychophysics and intra-abdominal pressure ('force limits') databases. It was found that the data from 'force limits' proposed weights for bimanual lifting in the sagittal plane which [corrected] are lower than those reported to be psychophysically acceptable except for lifting close to and around the shoulder. The closest agreement between the databases was for lifting from an origin above knuckle height. The 'force limits' data were found to propose weights of lift which are at a minimum when lifting with a freestyle posture from the floor whereas the psychophysical technique proposes weights which are at a maximum when lifting from the floor. The psychophysical data were found to generate compressive forces at L5/S1 according to a static sagittal plane biomechanical model about 10% in excess of the NIOSH action limit (NIOSH 1981) when lifting from the floor, although over other lifting ranges the compressive forces were less than the NIOSH action limit. Lifting the 'force limits' weights generated compressive forces which were on average 55% less than AL (range 45 to 60%) when lifting in an erect posture. The data for pushing according to the psychophysical and 'force limits' database showed good agreement, but for pulling the 'force limits' weights were considerably greater than those selected psychophysically. The implications of these findings are discussed.     

Spinal loads during individual and team lifting

The aim of this experiment was to compare lumbar spinal loads during individual and team lifting tasks. Ten healthy male subjects performed individual lifts with a box mass of 15, 20 and 25 kg and two-person team lifts with a box mass of 30, 40 and 50 kg from the floor to standing knuckle height. Boxes instrumented with force transducers were used to measure vertical and horizontal hand forces, whilst sagittal plane segmental kinematics were determined using a video based motion measurement system. Dynamic L4/L5 torques were calculated and used in a single equivalent extensor force model of the lumbar spine to estimate L4/L5 compression and shear forces. A significant reduction in L4/L5 torque and compression force of approximately 20% was found during team lifts compared to individual lifts. Two main reasons for the reduced spinal loads in team lifting compared to individual lifting were identified: (1) the horizontal hand force (i.e. pulling force) was greater in team lifting, and (2) the horizontal position of the hands was closer to the lumbar spine during team lifts. The horizontal hand force and position of the hands had approximately equal contributions in reducing the spinal load during team lifting compared to individual lifting.     

Occupational lifting by nursing aides and warehouse workers

Nursing aides (18 women and six men) at one traditional and one modern geriatric ward, and warehouse workers (16 men) at two different types of warehouse departments were studied during occupational work. The vertical load during manual handling was measured using strain gauges built into wooden shoes. The warehouse workers performed four times as many lifts as the nursing aides and transferred five times as great a mass per unit time. Less than 25% of the lifts were carried out with the load evenly distributed on both feet during both the upward lift and lowering. In the warehouses the lifts were short, while the nursing aides were exposed both to lifts of longer duration and to carrying, as well as a greater frequency of unexpected, sudden and high peak load. The heart rate and oxygen uptake values recorded were relatively low, and both groups utilized approximately 25% of their maximum aerobic power. According to official occupational injury statistics, both warehouse workers and nursing aides belong to risk groups with a high frequency of reported back injuries. However, more injuries are reported by nursing aides than by warehouse workers. Greater muscle strength in male workers may partly explain this difference. Qualitative differences in the design of the lifting work, with more lifts of long duration in awkward work postures, more carrying, more exertion of horizontal forces and a greater frequency of unexpected rapid lifts in the nursing aides may also contribute to the differences in risk of injury between these occupational groups. Considerable differences were found between the two hospital wards as regards lifting frequency, force, duration and the proportion of lifts with an even distribution of load on both feet during upward lift. The lifting work was approximately 50% less in the modern ward, which has easily maneuvered electric overhead hoists, spacious premises and better work organization than in the traditional ward, even though the patient handling needs were equivalent. In the warehouse department at which the wares were stored with easy access, the frequency of lifts with an even distribution of load on both feet was approximately 25%, compared to 7% in the other warehouse department. In conclusion, evaluations of occupational lifting work should include a quantitative assessment of the duration and load distribution of lifting, as well as of postures. Workstation design, technical aids and work organization have a profound effect on the lifting work load even in jobs with equal manual handling demands.     

Biomechanical evaluation of assistive devices for transferring residents.

This is the first of two articles to report a biomechanical evaluation and psychophysical assessment of nine battery-powered lifts, a sliding board, a walking belt, and a baseline manual method for transferring nursing home residents from a bed to a chair. The objectives of the biomechanical evaluation were: (1) to investigate the effects of transfer method and resident weight on the biomechanical stress to nursing assistants performing the transferring task, and (2) to identify resident-transferring methods that could reduce the biomechanical stress to the nursing assistants. Nine nursing assistants served as test subjects; two elderly persons participated as residents. A four-camera motion analysis system, two force platforms, and a three-dimensional biomechanical model were used to measure biomechanical load. The results indicate that transfer method and resident weight affect a nursing assistant's low-back loading. The basket-sling and overhead lift devices significantly reduced the nursing assistants' back-compressive forces during the preparation phase of a resident transfer. In addition, the use of basket-sling, overhead, and stand-up lifts removed about two-thirds of the exposure to low-back stress (lifting activities per transfer) as compared to the baseline manual method. Thus, the use of these devices reduces biomechanical stress, and thereby will decrease the occurrence of resident-handling-related low-back injuries. Furthermore, lifting device maneuvering forces were found to be significantly different and a number of design/use problems were identified with various assistive devices. The second article will detail the psychophysical assessment of the same resident-transferring methods.     

An ergonomic evaluation of nursing assistants' job in a nursing home

Thirty-eight nursing assistants (NAs) in a nursing home ranked and rated 16 different patient handling tasks for perceived stresses to the low back. The nursing assistants were observed for 79 4?h shifts and were videotaped for 14 4?h shifts to describe a typical workday and to determine the number of patient-handling tasks performed per shift, the use of assistive devices, and biomechanical stresses to the low back. In addition, data were collected on nursing assistants' and patients' characteristics.

The top eight ranked tasks included transferring patient from toilet to wheelchair (WC), WC to toilet, WC to bed, bed to WC, bathtub to WC, chairlift to WC, weighing patients and lifting patients up in bed. The mean ratings of perceived exertion for these tasks were between ‘somewhat hard’ and ‘hard’. The estimated compressive force on L5/S1 disc for the 50th percentile patient weight ranged from 3·7 to 4·9 KN. Nursing assistants worked in teams of two and performed 24 patient transfers per 8?h shift by manually lifting and carrying patients. Assistive devices (a hydraulic lift and gait belt) were used less than 2% of the time. Patient safety and comfort, lack of accessibility, physical stresses associated with the devices, lack of skill, increased transfer time, and lack of staffing were some of the reasons for not using these assistive devices. Environmental barriers (such as confined workspaces, an uneven floor surface, lack of adjustability of beds, stationary railings around the toilet, etc.) made the job more difficult. Nursing assistants had a high prevalence of low-back pain and 51 % of nursing assistants visited a health care provider in the last three years for work related low-back pain.