Risk factors for low back pain, and patient-handling capacity of nursing personnel

Journal of Safety Research, Vol. 25, No. 3, pp. 135-145, 1994 Copyright Q 1994 National Safety Council and Elsevier Science Ltd Printed in the USA. Allrights reserved 0022-4375/94 $6.00+.OO

0022-4375(94)00009-3

Risk Factors for Low Back Pain, and PatientHandling Capacity of Nursing Personnel Yung-Hui

Lee and Wen-Ko

Chiou

Nursing personnel have a relatively high prevalence of low back pain (LBI?). The l-year prevalence of LBP was found to be 69.7% in a study of 3,159 young nurses (mean age 24.8) in Taiwan. Risk factors for LBP, through forward stepwise logistic regression, were identified as lifting heavy objects, work experience, age, and sitting habits. The analysis showed a significant adjusted odds ratio of 2.81 (95% confidence interval = 1.88, 4.20), indicating that with each increase in the “lifting heavy objects” risk factor there was a 2.81-fold increased risk of LBP when effects of work experience, sitting habits, and age were held constant in the analysis. Matching the job demands to a person’s physical characteristics is an effective method of reducing the risk involved in a manual patient-handling task. The psychophysically determined patienthandling strength of nurses was 47 kg (104 lbs), and the strength was highest when bed-height was set at the iliac crest height (90.7 cm) of the nurses.

INTRODUCTION Occupational low back pain (LBP) costs U.S. industry between $4.5 and $38 billion per year (Andersson, Pope, Frymoyer, & Snook, 1990). According to Jensen (1987), nursing personnel are just as likely to sustain a Yung-Hui Lee, PhD, is an associate professor at National Taiwan Institute of Technology, Department of Industrial Management. Wen-Ko Chiou, MSc, is a doctoral candidate at National Taiwan Institute of Technology, Department of Industrial Management. This research was supported by National Science of Council Grant in R.O.C. (NSC 81-0415-E-182A-01). and a Grant from Chang Gung Memorial Hospital (NMRP 163). The authors thank Judy Perry for her editorial assistance and the Nursing Directors and staff of the Chang Gung Memorial Hospital, whose participation was invaluable to the success of this effort.

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back injury as construction laborers, rubbish collectors, and warehouse workers. Among these occupations, nursing personnel have a relatively higher prevalence of LBP (Buckle, 1987), which contributes to the increased cost of job training, insurance, retirement, recovery, and job assignment (Volinn, Koevering, & Loeser, 1991). One study showed that 18% of nursing personnel stopped working because of LBP (Videman et al., 1984). In another study, 3.5% of nursing personnel quit mainly because of LBP, and another 0.8% claimed that LBP was the only reason for quitting (Buckle, 1987). The etiologic risk factors responsible for LBP in nursing personnel have been the topic of much research. Many of the major factors that have been identified are postural in 135

nature, including: heavy physical work; lifting and forceful movements; frequent bending and twisting; static work postures; and repetitive work (Buckle, 1987). Age effects were discussed in a study by Videman et al. (1984). In other poor-posture task-specific and nurses’ LBP-related studies, high levels of biomechanical stress from patient lifting and transferring tasks were identified (Gagnon, Sicard, & Sirois, 1986; Stubbs, Buckle, Hudos, Rivers, & Worringham, 1983). Non-patienttransfer activities that might also be strenuous and hazardous to the spine were discussed by Harber et al. (1987). It appeared that the problem of LBP and occupation has a multivariate nature, that is, no one factor can be uniquely said to “cause” back pain (Baty & Stubbs, 1987). Therefore, a multifactorial investigation would seem to be required to present the confounding factors before any meaningful LBP-related risk factors for nursing personnel could be identified. The majority of nursing personnel’s LBPrelated risk factors were identified based on research conducted in the United States and Europe, with data obtained from the Caucasian population. Research efforts have been limited concerning the LBP of other populations, such as work forces in developing countries. The first objective of this paper is to report the results of a multivariate analysis of LBPrelated risk factors for nurses in Taiwan (R.O.C.). The analysis was based on responses from a survey using self-administered questionnaires. In the study, the precipitating factors for LBP were identified from a group of 17 candidates. The relationships were obtained by using the procedure of forward stepwise logistic regression analysis. The results were compared to those from the westem studies. Bell, Dalgity, Fennell, and Aitken (1979) concluded that since manual lifting is the most common method of patient handling, then priority should be given to a detailed investigation of the problem of this task. Garg, Owen, Beller, and Banaag (1991) conducted a static biomechanical evaluation of the patient-transferring tasks using five manual techniques and three hoist assisted techniques. The study showed that pulling techniques, as compared to lifting the patient, 136

required significantly lower hand forces and produced significantly lower erector spinae and compressive forces at the L5/Sl disc. Subjects’ perceived stress ratings also supported this finding. Durnin and Passmore (1967) reported an energy expenditure rate of 272 watts for bedside nursing, which is comparable with moderate industrial work. Despite the information available conceming the biomechanical and physiological stresses imposed by handling postures, little data are available on the abilities of nurses to handle the loads imposed by patient-handling tasks. Stubbs et al. (1983) indicated strong evidence that strength demands in nursing are poorly matched by nurses’ strength. The second objective of this study is, therefore, to determine the maximum acceptable capacity in patient-handling tasks (MAPH). The determination of MAPH was accomplished using a psychophysical approach. Furthermore, patient-handling tasks are usually performed with beds set at different heights. But do beds of different heights affect nurses’ MAPH? If so, how much will they be affected? This is also a concern of this study. METHODS

Analysis of Risk Factors of LBP Questionnaire. The questionnaire contained the factors known in the literature for their contribution to LBP for nursing personnel. There were questions of sociodemographic information, knowledge of low back health care, daily habits of posture, and a selfdescription of LBP l-year prevalence. The sociodemographic information included age, education, marital status, stature, body weight, work experience, department, and position (Buckle, 1987; Magora, 1970; Stubbs et al., 1983; Videman et al., 1984). There were 27 pairs of questions concerning nurses’ knowledge of and habits of LBPrelated postures: standing, walking, sitting, sleeping, and working (Deyo, 1986; Evans & Kagan, 1986; Millard, 1989; Roland & Morris, 1983; Tait, Pollard, Margolis, Duckro, & Krause, 1988). The description of LBP included experience of LBP in the last Journal of Safety Research

year (Stubbs et al., 1983), subjective rating of perceived pain, and the precipitating factor of lifting heavy objects. Figure 1 illustrates the concept structure of the LBP-related risk factors in the questionnaire. Subjects. All 3,212 subjects of this study were nursing personnel, female, and working in any of the four branches of Chung-Gung Memorial Hospital in the cities of Kee-Lung, Taipei, Linko, and Kau Hsiung. Before collecting the information for the study, questionnaire orientation meetings were held. Head nurses were asked to distribute the questionnaires to nurses in all departments. The questionnaires were returned to the researcher through the office in the hospital after 2 weeks. There were 3,193 questionnaires returned (99.4%), and after excluding the 34 invalid copies, 3,159 copies of the questionnaire were available for analysis.

Statistical analysis. Continuous, categorical, and ordinal data were coded from the questionnaire. Continuous data consisted of questions about age, stature, body weight, and work experience. The knowledge of low back health care was scored using 1 point for correct answers of “agree” or “disagree,” and zero points were given to answers of “I don’t know” or no response. As a result, we obtained five knowledge scores (subscores) of standing, walking, sitting, sleeping, and working, which were the mean of the scores of related questions. In addition, a total knowledge score was obtained for each subject by calculating the mean of all five subscores. An answer of “yes” was coded as 1 and “no” was coded as 2 for the question “Have you had any LBP in the past year?’ (Hosmer & Lemeshow, 1989). The same code method was used for the question “Do you have to lift heavy objects in your work?”

FIGURE 1 ADJUSTED CHI-SQUARE VALUES OF UNIVARL4TE LOGISTIC REGRESSION BETWEEN l-YEAR PREVALENCE OF LOWER BACK PAIN AND THE 17 INDEPENDENT VARIABLES. *sIGNIFICANT FOR P < 0.05. “SIGNllTCANT FOR P < 0.01

l.ls

One-year Prevalence

0.97

1

1.25

2.02 1.81

2.54

12.81

I [ Knowledge

l

=

2.96

1 1

lark

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Each of the 27 questions for daily posture habits was scored using a Likert-type 5-point scale. Thus, we obtained habit scores of standing, walking, sitting, sleeping, working, and a total habit score. They were data of ordinal type. Data of continuous and ordinal types were dichotomized at median levels to construct two-by-two tables, contrasting the relation: ships between all three types of data (continuous, categorical, and ordinal) with the yes/no occurrence of LBP (LBP group vs. non-LBP group) in the last year for all subjects. As a result, 17 two-by-two tables were constructed. Variables were initially examined for differences in frequencies between categories. Differentially distributed variables were further screened for univariate associations with l-year prevalence of LBP through simple logistic regressions. Variables related to LBP at the 5% level of significance were then examined with a forward stepwise logistic regression within each category and then across categories (Harrell, 1988). To evaluate the reliability of the questionnaire, the Kuder-Richardson 20 coefficient (Kuder & Richardson, 1937) was calculated for categorical data of knowledge score and its subscores. The Cronbach’s alpha coefficient was calculated for ordinal data of habit score and its subscores. The validity of the results of the questionnaire was justified by examining the interrelationships of the knowledge and habit scores and their subscores using Pearson correlation coefficients. It was assumed that these scores were intended to measure the practice of habit and knowledge and were likely to lead to healthy backs. Measuring of the MAPH Subjects. Twenty-four female nursing personnel were recruited for the experiment. All subjects had at least 1 year experience in patient handling. The subjects went through a physical examination to ensure that they suffered from no musculoskeletal disorders. In the meantime, they were instructed to refrain from eating, smoking, or having any alcoholic or carbonated drinks one hour before the experiment. In order to make sure that every 138

subject understood the objectives and method of the research, an orientation was given using audio-tape recordings and slide-shows. In addition, all subjects went through a familiarization program. The purpose of this program is not to increase subjects’ physical strength, but to familiarize them with the experimental procedure and psychophysical weight adjustment process. The familiarization program consisted of three 2-hour sessions (one session per day). Subjects determined their MAPH using the psychophysical approach at different bed-heights during each session. Simulate patient-handling task. In the case of patient handling, the shape of the load is awkward for lifting because the human body cannot be considered as a compact mass and is without convenient handholds (Garg et al., 1991). In the simulated patient-handling experiment, a hard plastic dummy was used as the object of handling. Its body was covered with gauze to make its exterior smoother and more flexible. Its was 172 cm in height and 35 kg (77 lbs) in weight. The dummy had an empty interior that pieces of lead weight could be placed inside to change its weights from 35 to 62 kg (77-137 lbs). The lead weights were cut into different sizes and weights so that subjects had no idea of how much weight they added or took-out. Figure 2 illustrates the experimental set up. The simulated patient-handling tasks were composed of four operations that were most frequently observed in nurses’ daily work. The operations were: (a) horizontally lifting the dummy to the bed-side; and turning the dummy (b) from a supine position to lying on its side, (c) from lying on the side to lying with face down, (d) from lying with face down to lying on the side, and (e) from lying on the side to a supine position. Handling techniques were demonstrated by an experienced nurse with emphasis on the safe postures of handling. The techniques were videotaped and shown to all subjects in the orientation program. The subjects followed “psychophysical directions” in adjusting the weights of the dummy when performing the simulated patient-handling task. They were asked to adjust the weight of the dummy so that the Journal of Safety Research

FIGURE 2 THE EXPERIMENTAL

load was the maximum that they could handle without becoming tired, out of breath, overheated, and without excessive strain or discomfort. Subjects were encouraged to adjust the weight as many times as possible. After the test, the subjects rated their perceived exertion (RPE) levels on all parts of body. It took approximate 35 minutes to establish each information point. Pheasant (1987) suggested that a 86.5 cm bed-height when lifting patients (95th percentile of knuckle height). The bed-height levels examined in the study were 70 cm, 80 cm, and iliac crest height. A complete randomized block design was adopted in the experiment, where bed-height is considered a factor, and every subject is seen as a block. There is a total of 72 data entries on handling capacity (3 bed-heights x 24 subjects); every subject underwent handling tasks at three different bed-heights and the test orders were randomly arranged to fulfill the random standard. Every subject underwent only one handling task each day in order to prevent any possible reaction resulting from fatigue. Fall 1994Nolume 25LVumber 3

SET-UP

RESULTS

AND DISCUSSION

LBP-Related Risk Factors Descriptive statistics of the 3,159 nursing personnel’s age, stature, body weight, and work experience are shown in Table 1. Among the subjects, 89.8% were registered nurses, 6% were nursing assistants, and 4.2% were head nurses (including supervisors and directors). The frequency and percentage of other sociodemographic variables are also shown in Table 1. Internal consistency estimates were calculated to evaluate the reliability of the questionnaire. Kuder-Richardson 20 coefficient ranged from 0.42 to 0.76 for knowledge score and its subscores (Table 2). Cronbach’s alpha coefficient ranged from 0.51 to 0.92 for habit score and its subscores. A reliability test was also done on a group of 30 randomly selected nurses; the 2-week test-retest reliability ranged from 0.72 to 0.94. The subscores from the habit and knowledge scores significantly correlated (p < 0.01) with the total habit and 139

TABLE 1 BASIC INFORMATION ON SOCIODEMOGRAPHIC VARIABIXS (N=3,159)

So&demographic Age(year)

IN THE NURSES OF THIS STUDY

Meanf SD (or Frequency)

Variables

25.2+

........................................................

................................................. 2. Nemo.. ................................................. 3. General Poskion: ........................................ I, Nursing Assistant. 2. Registered Nurse .............................................. 3. HeadNurse Education: .............................................. I. HighSchool .......................................... 2. Two-yearcollege ................................................ 3. University Ma&al Status: I. Married .................................................. 2. Single ...................................................

..........................................

Test-retest reliability: 1. Knowledgescale ._._......,................._... Habitscale..................................... 2. 3. LBP

17-53 142-181 33-75 O-28 11.9 12.6

377 396 2386

75.5

188 2801 130

6.0 89.0 4.2

708 2341 36

22.9 75.9 1.2

561 2591

17.8 82.2

However, special attention needs to be paid to the high prevalence of LBP in the group of subjects whose mean age was only 24.8 years old (SD = 3.6) and whose mean work experience was only 3.2 years (SD = 2.5). A logistic regression analysis using 17 precipitating factors as the predictor variable was completed to determine their univariate relationship with the risk of LBP. Variables of lifting heavy objects, age, work experience, work knowledge, work habits, and sitting habits were found to be statistically significant at 5% level (or 1% level) with l-year prevalence of LBP. The adjusted chi-square values are presented in Figure 1. The results showed that the more and the heavier the object lifted, the older the nurse, the longer the work experience, the poorer the knowledge of working

TABLE 2 TIIE RELIABILITY EXPRESSION OF INVESTIGATED

Internal consistency: I. Knowledge scale’ 2. HabR scale*’

3.9

158.5 f 4.7 49.9 f 5.5 3.9 f 3.6

Stature(cm) ...................................................... ................................................... Bodyweight .............................................. Worlcexperience(year) Department: I. I.C.U. ...................................................

knowledge score. The Pearson correlation coefficients are presented in Table 3. The results indicated that these scores measured the practice of habit and knowledge. The mean of the l-year prevalence of LBP in nursing personnel of this study was 69.7%. Nursing is often cited as a particularly stressful occupation because nurses need to meet the demands of the patients immediately at any time. Stubbs et al. (1983) reported that back pain, 78% of which involved the lower part of the back, accounted for 16.2% of sick leave in British National Health Service nurses. This study adopted an “operating” definition of LBP similar to Stubbs et al. The results are consistent with those described above, which implicated that the hazards of work in the nursing industry deserve increasing attention.

Range (or %)

VARIABLES

Total

Stand

Walk

Sii

Sleep

Work

(N=3,159) 0.76 0.91

0.61 0.70

0.42 0.61

0.57 0.69

0.46 0.51

0.69 0.92

0.84 0.96

0.74 0.64

0.80 0.92

0.72 0.75

0.85 0.94

(n=30) 0.79 0.87 0.92

* The Kuder-Richardson 20 coefficient ** The Cronbach’s alpha coefficient

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Journal of Safery Research

TABLE 3 THE VALIDITY EXPRESSION OF INVESTIGATED

I

I

0.13’ 0.06

Habti(total) ................................................. Knowledge (total) ............................................ Stand ..................................................... Walk ...................................................... Sit ........................................................ Sleep ...................................................... work ...................................................... * The Pearson correlation coefficient, Significant for p
LBP

VARIABLES

Habit

Knowledge

0.15’ 0.64” O.TI” 0.57” 0.66” 0.72”

0.56” 0.63” 0.66” 0.34” 0.70”

significant for p c 0.01.

**

postures, the poorer the work habits, and the poorer the sitting habits, the higher the l-year prevalence of LBP. The final data analysis procedure used forward stepwise logistic regression to assess the effects of the six significant variables. The forward stepwise logistic regression included four variables: lifting heavy objects, work experience, sitting-habits, and age. No other variables met the 5% level of significance for entry (see Table 4). The resulting model yielded a chi-square of 86.47 with 4 degrees of freedom (p < O.OOl), with the proportion of log-likelihood explained by the model (R2) equal to 0.38. The identified risk factors could be used as a valuable source of material in the enhancement of the quality of LBP-related ergonomic training programs for nurses. In this study of multivariate analysis of risk factors for nurses’ LBP, lifting heavy objects was identified as the most etiologic one. Several investigations have found a strong relationship between handling patients and occupational LBP; among all factors, the transferring of patients done in hospitals has already been identified as capable of causing occupational LBP (Garg et al., 1991; Harber et al., 1985; St. Vincent & Tellier,

1989; Stubbs et al., 1983; Videman et al., 1984). The analysis showed a significant adjusted odds ratio of 2.81 (95% confidence interval = 1.88, 4.20), indicating that with each increase in the “lifting heavy objects” risk factor, there was a 2.81-fold increased risk of LBP when effects of work experience, sitting habits, and age were held constant in the analysis. Age effects on LBP have been studied by a number of researchers (Buckle, 1987; Stubbs et al., 1983) although the results are generally confounded by grade of LBP and nursing speciality. In this study, the mean age of nurses of the LBP group was 25.6 years old (SD = 4.6), which is a statistically significant (p < 0.01) difference, and older than that of the non-LBP group (20.9 years old, SD = 1.8). Since, the non-LBP group was younger, age could be the primary reason for any differences between the groups. However, the subjects in this study were young nurses, therefore, the conclusion that age is associated with LBP is not totally conclusive. In fact, the epidemiological data in this study supported that both age and length of work experience are associated with LBP. Our study showed that controlling for other specified variables, the odds of having a

TABLE 4 STEPWISE JBGISTIC REGRESSION FOR RISK FACTORS OF LBP

95%Confidence Risk Factors Lifting heavy objects Worltexperience.............. %-habits Age........................

Beta coefficient

Adjusted Odds ratio

Standard error

1.0332 0.8478 0.7562 0.6713

2.81 2.33 2.13 1.96

0.2051 0.2166 0.1938 0.1827

interval (Cl) 1.88420” 1.53-3.57” 1.46-3.11” 1.37-2.80’

*Significant for p < 0.05. ** Significant for p CO.01

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141

nurse with LBP were significantly more likely when the age ratio (adjusted odds ratio of 1.96, between 95% confidence interval of 1.37 and 2.80) increased and when the work experience ratio (adjusted odds ratio of 2.33, between 95% confidence intervals of 1.53 and 3.57) increased. Data from Buckle (1987) show that LBP tends to begin in the third decade of life and reaches maximal frequency during middle age. It tends to be less frequent in the elderly. It seems that an independent assessment of risk factors and careful interpretation is necessary because multifactors of age and work experience may be confounding. The data does not support the notion that lack of experience is associated with the risk of LBP in this study. However, the effects of poor work knowledge, work habits, and sitting habits were identified in the univariate analysis of LBP. Among all, sitting habits was considered a primary factor in the forward stepwise logistic regression with a significant adjusted odds ratio of 2.13, between 95% confidence intervals of 1.46 and 3.11. In the study, nurses with higher knowledge scores of low back health care were not necessarily classified as being at lower risk for LBP attack (a non-LBP group). Additional study to identify the task-specific poor-posture could be useful in the enhancement of our understanding of the cause of LBP. Jobs that require workers to sustain a particular posture for pro-

SUELJECTS’ANTHROPOMETRK

Measurement

longed periods may be associated with musculoskeletal problems related to those postures. Jobs demanding long periods of immobility, either standing or sitting, have been shown to cause muscle fatigue and to have ill effects upon discs (Magora, 1972; Rowe, 1983). The result indicated that training to increase correct knowledge of working and sitting postures may be effective in reducing the prevalence of LBP. The MAPH For the 24 subjects who completed the study, the mean age was 22.6 years (SD = 2.4), mean body weight was 52.2 kg (115 Ibs; SD = 5.5), mean stature was 157.7 cm (SD = 4.7), and mean iliac crest height was 90.7 cm (SD= 3.8). Subjects’ anthropometric characteristics are presented in Table 5. The isometric and isoinertial strengths of subjects are also listed in the table. The isometric strength tests were the arm strength, shoulder strength, back strength, leg strength, and composite strength (Ayoub, Mital, Asfour, & Bethea, 1980). The isoinertial strength tests, using the six-feet incremental lifting machine, were the six-feet lift, knuckle-shoulder lift, elbow height lift, and knuckle height lift (Jiang, Smith, & Ayoub, 1986). Table 5 shows that subjects’ MAPH at bedheights of 70 cm, 80 cm, and iliac crest height

TABLE 5 CHARACTERISTICS,

Mean .t SD

variable

Age(year) ................................. Body weight (kg) .................................................................. Stature(cm) lliaccrestheight(cm)

....................................

................................................ ...................

...........................................................

Isometric strength. (kg) ...................................................................... Armstrength Shoulderstrength ........................................................ ........... Backstrength strength ....................................................................... Compositestrength

.............................................................

Leg

..............................................................

lsoinertial strength: (kg) ....................................................................... Six-feetlift Knuckle-shoulderlift ................................................................. Elbowheightlift .................................................................... Knuckieheightlift ................................................................... ........................................................................... MAPH(kg) ................................................................ 70cmbed-height ................................................................. 80cmbed-height lliaccrestheight

142

STRENGTH, AND MAPH (x1=24)

....................................................................

22.6 52.2 157.7 90.7

f 2.4 f 5.5 f 4.7 * 3.0

16.9 32.3 39.6 77.8 74.5

f 2.9 +z6.3 f 9.5 f 11.3 * 12.6

16.9 21.4 27.5 33.2 46.6 431 47.6 49.8

f f f f f f f f

3.2 3.6 6.3 6.6 7.9 7.6 8.1 7.9

Journal of Safety Research

were 43.1 kg (95 lbs), 47.6 kg (105 lbs), and 49.8 kg (110 lbs), respectively. The MAPH were significantly affected by the factors of bed-height at 5% levels. The Duncan’s multiple range test indicated that there was no significant difference between MAPH at 80 cm and MAPH at iliac crest height. Subjective rating of perceived exertion indicated that the highest exertion level occurred in the arms in the simulated patient-handling tasks. The subjects’ back was subjected to the greatest exertion levels when handling the dummy on the 70 cm bed-height (p c 0.01). Subjective exertion levels in wrists, arms, shoulders and whole body were all significantly higher at 70 cm bed-height than at other heights (p < 0.05). The psychophysical criterion appears to be an appropriate single criterion to use to determine task specific lifting capacity (Ayoub et al., 1980). In this study, the psychophysical approach was used for subjects to determine their maximum acceptable weight while performing a sequence of five patient-handling operations. As a result, a task specific handling capacity with a mean value of 46.8 kg (103 lbs) was obtained. Hence, a maneuver performed at the side of the bed that required the nurse to support a body weight of 82 kg (18 1 Ibs; 95th percentile male patients, Pheasant, 1987) weight would exert 1.7-fold of nurses’ MAPH. Carlson (1989) indicated that often nursing personnel lift and move patients whose weights range from 37 kg (82 lbs) to over 100 kg (221 lbs), showing that the demands of patient handling might be significantly beyond the handling capacity of nurses. Garg et al. (1991) indicated that the static strength of the 50th percentile of the female population at elbow height was about 20 kg (44 Ibs) and the maximum acceptable weight to the same population at knuckle height, assuming a compact load (box weight = 34 cm), is about 17 kg (38 lbs). In the case of patient handling, the human body cannot be considered a compact mass and quite often a nurse partially supports the weight of a patient. The application of non-task-specific strength values in the study of patient-handling capacity of nurses will be of limited value. The height of the bed has important consequences on the working posture and handling Fall 1994Nolume 2SLVumber 3

capacity of nurses. Depending upon the health condition of the patients, some simple nursing tasks (e.g., measuring blood pressure, intravenous injection, and collecting sputum specimens) at the bed side became an endurance type of operation and generated high static loads on the musculoskeletal system of nurses (Harber et al., 1987). When patient-handling tasks were performed on the bed, the large external load plus the dynamic effect of postural load can seriously add to the risk of back injury. Quite often, the bed was set or adjusted to a height that facilitated the patient’s movements in and out of bed and was not adjusted to a height that enables nurses to perform nursing tasks easily. Pheasant (1986) indicated that, for heavy lifting and handling tasks, a working level somewhere between knuckle height and elbow height is considered acceptable. In this study, when bed-height was set on 70 cm, the nursing personnel had lower psychophysical lifting capacity and higher RPE than that of 80 cm and iliac crest height. Lifting capacity and perceived exertion level do not differ much between 80 cm bedheight and iliac crest height, although the latter is slightly better. According to the study of Chaffrn, Hen-in, and Keyserling (1978), when loads were regulated and did not vary in industry, it appears that strength screening would be a useful adjunct to the preemployment history and physical. The loads in the nursing profession are not regulated and the conditions of lifting vary considerably and cannot be optimized (Mostardi, Noe, Kovacik, & Porterfield, 1992). The application of the MAPH obtained in such occupations would appear to lie not in preemployment screening, but in the maintenance of physical fitness and in efforts to ensure that the effective loads to be lifted do not exceed the capacity of the nurses. SUMMARY

Many observations of general interest can be made from this study, some of these are especially related to the risk factors of LBP of nursing personnel and their patient-handling capacity are pointed out. 143

1. The mean of the l-year prevalence of LBP in nursing personnel of this study was 69.7%. The group of subjects had a mean age of only 24.8 years old (SD = 3.6) and mean work experience was only 3.2 years (SD = 2.5). 2. Risk factors for LBP, through forward stepwise logistic regression, were identified as lifting heavy objects, work experience, age, and sitting habits. The identified risk factors could be used as valuable sources of material in the enhancement of the quality of LBP-related ergonomic training programs for nurses. 3. The maximum acceptable weight of patient handling was 47 kg (104 lbs), which showed that the demands of patient handling might be significantly beyond the handling capacity of nurses (patient weight ranged from 37 to 100 kg). 4. The strength was highest when bed-height was set at the iliac crest height (90.7 cm) of the nurses. The issue of how risk factor of LBP can best be incorporated into ergonomic programs remains unsolved. The results of this study indicated that the psychophysical approach provided reasonable handling-strength measurements and the MAPH was affected by the bed-height. Further research is needed to study bimanual handling strengths and to improve the engineering design of the dummy for estimating MAPH more accurately. REFERENCES Andersson, G. B. J., Pope, M. H., Frymoyer, J. W., & Snook, S. H. (1990). Epidemiology and cost. In M. H. Pope, G. B. J. Andersson, M. K-Frymoyer, & D. B. Chaffin (Eds.), Occupational low back pain (pp. 95-113). St. Louis: M&by. Ayoub, M. M., Mital, A., Asfour, S. S., & Bethea, M. J. (1980). Review, evaluation, and comparison of models for predicting lifting capacity. Human Facrors, 22, 257-269. Baty, D., & Stubbs, D. A. (1987). Postural stress in geriatric nursing. International Journal of Nursing Studies, 24, 339-344. Bell, F., Dalgity, M. E., Fennell, M. J., & Aitken, R. C. B. (1979). Hospital ward patient-lifting tasks, Ergonomics, 22, 1257-1273. Buckle, P. W. (1987). Epidemiological aspects of back pain within the nursing profession. International Journal of Nursing Studies, 24, 319-324.

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Carlson, B. L. (1989). Ergonomic job evaluation of nursing assistance at Rock Country health care nursing home facility. Unpublished master’s thesis, Department of Industrial and System Engineering, University of Wisconsin, Milwaukee, WI. Chaffn, D. B., Henin, G. D., & Keyserling, W. M. (1978). Preemployment strength testing: An updated position. Journal of Occuparional Medicine, 6.403-408. Deyo, R. A. (1986). Comparative validity of the sickness impact profile and shoa scales for fun&onal assessment in low-back pain. Spine, 11,951-954. Dumin, J. V. 6. A., & Passmore. R. (1967). Energy, work and leisure. London: Heinemann. Evans, J. H., & Kagan, A. (1986). The development of a functional rating scale to measure the treatment outcome of chronic spins patients. Spine, 11.277-281. Gagnon. M.. Sicard. C.. & Sirois. J. P. (1986). Evaluation of Forces on the Lumbo-sacral joint and assessment of work and energy transfers in nursing aides lifting patients. Ergonomics, 29.407-421. Garg, A., Owen, B. D., Beller, D., & Banaag, J. (1991). A biomechanical and ergonomic evaluation of patient transferring task: Bed to wheelchair and wheelchair to bed. Ergonomics, 34.289-312. Harber, P., Billet, E., Gutowaki, M., Soohoo, D., Lew, M., & Roman, A. (1985). Occupational low back pain in hospital nurses. Journal of Occupational Medicine, 27, 518-524. Harber, P., Shimozaki, S., Gargner, G., Billet, E.. Vojtecky, M., & Kanim, L. (1987). Importance of nonpatient transfer activities in nursing-related back pain: II. Observational study and implications. Journal of Occupational Medicine, 12,971-974. Harrell,.R. E. (Ed.). (1988). SUGZ supplemenral library user’s guide (Version V). Carv, NC: SAS Institute. Inc. Hosmer, 6. W.,. & Lemeihow, 8. (1989). Applied iogisric regression. New York: John Willey & Sons. Jensen, R. (1987). Disabling back injuries among nursing personnel: Research needs and justifications. Research in Nursing & Health, 10, 29-38. Jiang, B. C., Smith, J. L., & Ayoub, M. M. (1986). Psychophysical modeling of manual material handling capacities using isoinedal strength variables. Human Factors, 28,691-702. Kuder, G. F., & Richardson, M. W. (1937). The theory of estimation of test reliability. Psychomerrika, 2, 151-160. Magora, A. (1970). Investigation of the relation between low back pain and occupation. Industrial Medicine, 39.504-5 10. Magora, A. (1972). Investigation of the relation between low back pain and occupation. 3. Physical requirements: Sitting, standing and weight lifting. Industrial Medicine, 41.5-9. Millard, R. W. (1989). The functional assessment screening questionnaire: Application for evaluating pain-relate2 disability. Archives of Physical Medicine and Rehabili&on, 70.303-307. _ Mostardi,R. A., Noe, D. A., Kovacik, M. W., & Porterfield. J. A. (1992). Isokinetic lifting strength and occupational in-jury: A prospective study. Spine, 17. 189-193. Phe&nt, 3. T: (1986). Bodyspace: Anthropometry, ergonomics and design. London: Taylor SKFrancis. Pheasant, S. T. (1987). Some anthropometric aspects of workstation design. Znrernational Journal of Nursing Studies, 24, 291-298. Roland, M., & Morris, R. (1983). A study of the natural history of back pain, Part I: Development of a reliable

Journal

of Safety Research

and sensitive measure of disability in low-back pain. Spine, 8.141-144. Rowe, M. L. (1983). Backache at work. New York: Perington Press. St-Vincent, M., & Tellier, C. (1989). Training in handling: An evaluation study. Ergonomics, 32.191-210. Stubbs, D., Buckle, P., Hudos, M., Rivers, P., & Worringham, C. (1983). Back pain in the nursing profession: Part 1. Epidemiology and pilot methodology. Ergonomics, 26.755-765.

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Tait, R. C., Pollard, C. A., Margolis, R. B.. Duckro, P. N., & Krause, S. I. (1988). The pain disability index: Psychometric and validity data. Archives of Physicnl Medicine and Rehabilitation, 68.438-441. Videman, T., Nurminer, T., Tola, S., Kuorinka, I., Vanharanta, H., & Troup, J. (1984). Low back pain in nurses and some loading factors of work. Spine, 9,400-404. Volinn, E., Koevering, D., & Loeser, J. D. (1991). Back sprain in industry: The role of socioeconomic factors in chronicity. Spine, 16.542-548.

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