Risk indicators for reported over-exertion back injuries among female nursing personnel.

We conducted a case-referent study to identify and quantify work-related and non-work-related risk indicators for reported over-exertion back injuries among nursing personnel. The source population was all nursing personnel employed in the Stockholm County hospitals during a 32-month period. The 240 cases and 614 referents completed questionnaires about occupation, type of clinic, working hours, shift work, patient transfers, perceived exertion, back pain, prior back injury, job strain, body mass index (BMI), smoking, immigrant status, physical training, and self-rated fitness. The highest relative risks (RR) were observed for work-related factors: working at an orthopedic clinic (RR = 5.2; 95% CI = 2.7-10.2), > or =1 patient transfer/shift (RR = 2.7; 95% CI = 1.6-4.5), and working full-time (RR = 2.4; 95% CI = 1.6-3.6). Training in the use of transfer devices, and regular use of transfer devices, reduced the relative risk from patient transfer. Among the non-work-related factors, only body mass index > or =25 kg/m2 and immigrant status was associated with a slight increase in relative risk.

The accident process preceding overexertion back injuries in nursing personnel. PROSA study group.

OBJECTIVES: This prospective dynamic-population-based study investigated factors involved in the accident process preceding overexertion back injuries among nursing personnel. METHODS: The study covered all reported occupational overexertion back injuries due to accidents among of the approximately 24 500 nurses in the Stockholm County hospitals during 1 year. It was assumed that several factors interact in the accident process. Detailed information was obtained for each injury by interviews with the injured nurse and head nurse. Risks in the physical environment were identified using an ergonomic checklist. RESULTS: During the study 136 overexertion back injuries were reported. Of the 130 nurses participating in the study, 125 had been injured in connection with patient work. Cluster analysis yielded 6 clusters and their pattern of contributing factors. The most frequent injury occurred during patient transfer in the bed or to or from the bed, without the use of transfer devices, when the patient suddenly lost his or her balance or resisted during the transfer and the nurse had to make a sudden movement. However, there were physical conditions, such as shortcomings in the physical work environment or a lack of a transfer device, that compelled the nurses to perform the tasks under unsafe conditions. CONCLUSIONS: The clusters showed a complexity of different kinds of accidents and indicated that the measures for preventing accidents, or for blocking an accident process once started, have to be of different kinds and placed at several different levels in the organization of a workplace.

Computer mouse position as a determinant of posture, muscular load and perceived exertion.

OBJECTIVES: This study concerned the influence of 6 positions of the computer mouse on the work table on posture, muscular load, and perceived exertion during text editing. METHODS: An optoelectronic 3-dimensional motion analysis system was used to register the postures of 10 men and 10 women using video display units. Muscular load was also registered (with electromyography), as was perceived exertion (with rating scales). RESULTS: A neutral posture with a relaxed and supported arm showed the least perceived exertion, and the electromyographic results showed low activity in both trapezius muscles in this position. Short operators (all women) showed a numerically higher activity in the 4 examined muscles than the tall operators (all men, except 1). This finding could be related to lower muscle force among women and to anthropometric differences, which also influence biomechanic load moments. Narrow-shouldered operators (8 women and 1 man) and short operators worked with larger outward rotation and abduction of the shoulder in a position of the mouse lateral to the keyboard than the broad-shouldered (7 men and 2 women) and tall operators did. Arm support markedly reduced muscle load in the neck-shoulder region among the operators. CONCLUSIONS: The operators using video display units in this study preferred to use the mouse on a table in a close to relaxed, neutral posture of the arm in combination with arm support. Short and narrow-shouldered operators worked in more strenuous postures of the arm when the mouse was located lateral to the keyboard.

Evaluation of perceived and self-reported manual forces exerted in occupational materials handling.

The main objective of the study was to evaluate the ability of workers to reproduce simulated manual work forces correctly and to quantify these forces in Newtons (N) by means of self-reports. Fourteen male and 14 female workers participated in the study. Three experiments were carried out. In the first experiment, the ability to reproduce the magnitudes of simulated manual forces occurring in daily work and to estimate these forces in Newtons was tested. A specially designed force-measuring device was used for this purpose. In the second experiment, the subjects estimated the weights of five boxes ranging from 1 to 30 kg. In the third experiment, the subjects were asked to produce five predetermined push and pull forces ranging in magnitude from 10 to 300 N on to the handle of the force-measuring device. The ability to reproduce the magnitudes of manual forces when simulating four familiar work tasks was good (the intraclass correlation coefficients ranged from 0.75 to 0.95). The ability to quantify these forces in Newtons was not as good (the product moment correlation coefficients ranged from 0.21 to 0.69). When the subjects estimated the weights of boxes they underestimated the weights. When they produced predetermined push and pull forces they exerted higher forces than expected when low force levels were requested and lower forces when high force levels were requested. However, the forces were correctly ranked. In summary, simulation of the manual push/pull forces used in familiar work tasks seemed to offer sufficient reproducibility to be worth testing for validity. Self-reports, used without previous training or without known 'reference forces', seemed to be very rough when the aim was to estimate in kg or Newtons. However, the fact that individuals could rank the forces correctly opens a potential for refinement of self-reports as a method for quantifying manual forces in objective terms, e.g. kg or Newtons.

An interview technique for recording work postures in epidemiological studies. Music-Norrtälje Study Group.

BACKGROUND: The aim of the study was to present and evaluate a work-task-oriented interview technique focusing on the placement of the hands relative to the body and assessing per cent time spent in five standard work postures during a working day. METHODS: The reproducibility of estimated time spent in each work posture was tested by the test-retest method in 32 subjects; 16 were interviewed by the same interviewer and 16 were interviewed by another one at the retest. The validity concerning estimated time spent in th five standard work postures was tested in relation to observations in 58 male blue-collar workers. The mean registration (assessment) time was 6 hours and 15 minutes. RESULTS: No evident differences in the reproducibility depending on same or different interviewers at test and retest could be observed. The linear relationship between times estimated by the interview and by observations was high for four of the work postures: 'sitting' (r = 0.86), 'standing with hands above shoulder level' (r = 0.87), 'between shoulder and knuckle level' (r = 0.75), and 'below knuckle level' (r = 0.93). When the work posture 'standing with hands between shoulder and knuckle level' was divided into 'hands fixed' (r = 0.62) and 'hands not fixed' (r = 0.50) the correlations were weak. Current musculoskeletal complaints did not influence the accuracy of the estimations. CONCLUSIONS: The present task-oriented interview technique may be the best available method to estimate these work postures in a way that requires few resources compared to observations and technical measurements.

HARBO, a simple computer-aided observation method for recording work postures.

OBJECTIVES: The aim of the study was to present an observation method focusing on the positions of the hands relative to the body and to evaluate whether this simple observation technique gives a reliable estimate of the total time spent in each of five work postures during one workday. METHODS: In the first part of the study the interobserver reliability of the observation method was tested with eight blue-collar workers. In the second part the observed time spent with work above the shoulder level was tested in relation to an upper-arm position analyzer, and observed time spent in work below knuckle level was tested in relation to a trunk flexion analyzer, both with 72 blue-collar workers. RESULTS: The interobserver reliability for full-day registrations was high. The intraclass correlation coefficients ranged from 0.99 to 1.00. The observed duration of work with hands above shoulder level correlated well with the measured duration of pronounced arm elevation (> 75 degrees). The product moment correlation coefficient was 0.97. The observed duration of work with hands below knuckle level correlated well with the measured duration of pronounced trunk flexion angles (> 40 degrees). The product moment correlation coefficient was 0.98. CONCLUSION: The present observation method, designed to make postural observations continuously for several hours, is easy to learn and seems reliable.

Interview protocols and ergonomics checklist for analysing overexertion back accidents among nursing personnel.

No documented strategy, including preventive strategies, for systematic investigation of overexertion back accidents among nursing personnel has yet been published. One aim of the present study was to develop standardized instruments for the systematic investigation of back accidents among nursing personnel in order to develop preventive strategies. Another aim was to produce a screening tool that could easily be used for identifying potential overexertion back accident hazards. Two structured interview protocols were developed, one for the injured person and one for the supervisor. An ergonomics checklist was designed for the most important spaces according to accident statistics: patient's room, corridor, toilet, and also one for 'other space', eg X-ray and treatment rooms. The instruments were developed by frequent discussions and adjustments in a task force of researchers and occupational health personnel. The protocols were tested in two steps before a final version was established. The construct validity and interobserver reliability of the checklist were tested by ten ergonomists, who checked a patient's room, a toilet and a corridor with some known hazards. The constructed validity agreement was 90% in 19 of 26 items in the checklist. The interobserver reliability had the same figures as the validity for all items in the checklist. The interview protocols and checklist appear to be suitable for systematic investigation of overexertion back accidents.

Nerve conduction in the hands of vibration exposed workers.

Symptoms of peripheral neuropathy in the hands are common among workers using vibrating tools. The mechanism for this and its relation to carpal tunnel syndrome (CTS) was studied in workers exposed to vibration at their workplace (17), along with a control group of healthy construction workers with heavy manual work but without vibration exposure (10). Patients with uni- or bilateral CTS (11) and a group of healthy volunteers without manual work (9) were included for comparison. Median nerve conduction velocities were measured both over the carpal tunnel and in a more distal segment. Vibration exposed workers had similar conduction velocities to unexposed construction workers. The subgroup of vibration exposed patients with symptoms from the hands had normal conduction in the ulnar nerve but demonstrated a decrease in median nerve conduction comparable (but less pronounced) with the CTS group. On a group basis these results indicated that the median nerve is most vulnerable for hand-arm vibrations. However, the conduction defects were not pronounced enough to diagnose CTS in most individual cases.

Sensory perception in the hands of dentists.

The difference between the dominant and nondominant hands in the perception of vibration, temperature, and heat pain was compared between 26 dentists with long-term exposure to high-frequency vibration and 18 with short-term exposure. The dentists with long-term exposure had larger vibration threshold differences than those with short-term exposure, both for digit II (exposed to high-frequency vibration) and for digit V (unexposed), whereas the temperature and pain thresholds were similar. The former group had neurological symptoms in the dominant hand more often than the latter. Vibration threshold differences of exposed digit II and unexposed digit V were higher for the symptomatic dentists than for the symptom-free dentists. Since the exposed and unexposed fingers were similarly affected, the neurological symptoms in the dominant hand of dentists with long-term exposure seem to have some other etiology than high-frequency vibration.

Neural regulation of vascular tone and cold induced vasoconstriction in human finger skin.

Finger skin blood flow was measured by a laser Doppler during control conditions, after neural blockade at the finger base by prilocaine and after localized anaesthesia of the skin by lidocaine introduced iontophoretically into the finger skin. Vasoconstriction was achieved by local cooling of the finger and by iontophoretic administration of norepinephrine during the described three conditions. Compared to the control condition, blood flow increased after nerve block at the finger base but even more after local skin anaesthesia. This additional increase in blood flow after local application of lidocaine indicates that finger skin vascular tone is partly dependent on local reflexes. Vasoconstriction on local cooling was preserved after nerve blockade at the finger base but inhibited after local skin anaesthesia by iontophoresis of lidocaine. This inhibition was not due to paralysis of the vessel wall since vasoconstriction to norepinephrine was preserved. Thus, vasoconstriction in response to local cooling is mediated by local reflexes.

Symptoms of the neck and upper extremities in dentists.

Symptoms of the neck, shoulders, arms, and hands of 99 dentists and a reference group of 100 pharmacists were studied by means of a telephone interview. Forty-four percent of the dentists and 26% of the pharmacists reported symptoms of the neck [relative risk (RR) 2.1, 95% confidence interval (95% CI) 1.4-3.1]. Symptoms of the shoulder were reported by 51% of the dentists and 23% of the pharmacists (RR 2.2, 95% CI 1.5-3.3). Musculoskeletal symptoms in the forearm were present almost exclusively in the dentists (12 versus 1%). Numbness and paresthesia were more common among the dentists than among the referents (RR 4.2, 95% CI 2.3-7.7). Unilateral Raynaud's phenomenon in the dominant hand occurred in six dentists and one pharmacist. The high frequency of symptoms from the neck, shoulders, and upper extremities of the dentists was probably related to their difficult work positions with cervical flexion and rotation, abducted arms, and repetitive precision-demanding handgrips.

Long-term follow up of workers exposed to solvents.

Long term occupational exposure to organic solvents may cause adverse effects to the central nervous system. This collaborative study between six Swedish departments of occupational medicine examines the overall prognosis in terms of working capacity, symptoms, and psychometric test performance for individuals occupationally exposed to organic solvents. After re-analyses of the data from an initial clinical investigation of 111 men, the subjects were divided into two subgroups: one group of 65 with symptoms but no impairment on the tests and one group of 46 with toxic encephalopathy (symptoms and test impairment). At least five years after the initial examination the subjects were asked to attend a re-examination that included a structured medical interview and a psychometric investigation. The results indicate that effects on the central nervous system persist even when exposure has ceased. In the group of 46 more men had stopped working and were receiving sickness or early retirement pensions. This group also had reduced activity levels with regard to everyday life, leisure activities, and education or training and more neuropsychiatric symptoms. There was no support for the view that a solvent induced toxic encephalopathy is a progressive disease comparable with presenile dementia such as Alzheimer's disease or Pick's disease. If a worker was removed from exposure when he presented symptoms without signs of impairment in intellectual function recovery was seen in most cases.

Alpha 2-adrenoceptor inhibition in patients with vibration white fingers.

In healthy subjects the physiological vasoconstriction to local cooling has been linked to sympathetic adrenoceptors of the alpha2-subtype. The present study was designed to determine if the vasoconstriction in response to local cooling in patients suffering from vibration white fingers can be diminished by alpha2-adrenoceptor inhibition. Six men with vibration white fingers, verified in a cold provocation test, were examined. To study the effect of local skin cooling blood flow was measured with laser doppler technique on the dorsum of dig. II or III. The temperature of the laser doppler probe was regulated by Peltier elements. Temperature could be lowered from 30 degrees C to 20 degrees C within 30s. Measurements were performed before and after local inhibition of the alpha2-adrenoceptors. This was achieved by the introduction of the selective alpha2-adrenoceptor inhibitor, rauwolscine, into the finger skin by iontophoresis. During control conditions local cooling consistently resulted in a marked vasoconstriction. Inhibition of the alpha2-adrenoceptors by rauwolscine completely abolished this effect. The present data indicate that substances inhibiting alpha2-adrenoceptors may be of therapeutic value in patients with vibration white fingers.

Adrenoceptors in Raynaud's disease.

Experiments were designed to study adrenoceptor function in subjects with Raynaud's disease. Sympathetic agonists and antagonists were administered into the finger skin by iontophoresis, and the resulting change in local skin blood flow was evaluated by laser Doppler technique. The effects of norepinephrine (NE, stimulating alpha 1- and alpha 2-adrenoceptors), phenylephrine (stimulating alpha 1-adrenoceptors) were studied in 12 women with Raynaud's disease and in 12 healthy controls. Controls and cases showed a similar consistent vasoconstriction to NE and B-HT 933. All control subjects showed a vasoconstriction to phenylephrine. In contrast, the Raynaud subjects demonstrated a weaker vasoconstriction or even a vasodilation, especially to low concentrations of the drug. After blockade of the alpha 1-adrenoceptors by doxazosin in the controls, phenylephrine mimicked the reaction in Raynaud subjects. beta-Adrenoceptor agonists (isoprenaline and terbutaline) had no effect on finger blood flow in the examined finger skin area in either control or Raynaud subjects. We suggest that Raynaud's disease is characterized by a defect in alpha 1-adrenoceptor function.

Correspondence between neurological symptoms and outcome of quantitative sensory testing in the hand-arm vibration syndrome.

To evaluate neurological symptoms in the vibration syndrome, 55 patients with vascular and neurological symptoms in the hand who had been exposed to vibration were examined. Their exposure to vibration was estimated and neurological vascular symptoms were evaluated according to symptom scales. Temperature thresholds were measured on the right thenar eminence and on the distal volar aspect of the second and third fingers held together on both sides. Vibration thresholds were measured dorsally on the second and fifth metacarpal bones and on the second and fifth fingers proximal to the nail roots. Subjects with advanced neurological symptoms had higher temperature and vibration thresholds than subjects with less advanced symptoms. No such relation was found between vascular symptoms and the outcome of sensory testing. Thus neurological but not vascular symptoms are reflected by the outcome of quantitative sensory testing. In subjects with advanced neurological symptoms the tests gave a high proportion of abnormal results, indicating that these tests may be used for the diagnosis of vibration syndrome on an individual basis. Patients with advanced vascular and neurological symptoms had higher exposure dose scores than patients with less advanced symptoms, indicating a dose response relation between vibration "dose" and neurological and vascular symptoms.

Nifedipine and alpha-adrenoceptor function in human finger skin vessels.

Experiments were designed to study the effect of the calcium entry blocker nifedipine on contractions evoked by alpha-adrenoceptor activation in human finger skin vessels and to show whether nifedipine could prevent the vasoconstriction induced by local cooling. Vasoconstriction of finger skin vessels was evoked with phenylephrine (a preferential alpha 1-adrenoceptor agonist), B-HT933 (a preferential alpha 2-adrenoceptor agonist) and by local cooling. The alpha-adrenoceptor agonists were administered into the skin by iotophoresis and local cooling was produced with a Peltier element. Nifedipine significantly attenuated the vasoconstrictor responses both to alpha 1- and alpha 2-adrenoceptor stimulation, the effect on alpha 2-mediated responses being more pronounced. It had no effect on the vasoconstriction induced by local cooling of finger skin.

Effect of tobacco use on vibration white finger disease.

In a cohort of 245 men with vibration white finger disease, the effects of tobacco use on the symptoms of the disease and the results of a cold provocation test were studied. The tobacco habits of 111 patients were confirmed by measurement of nicotine and cotinine in plasma. In a subgroup the cold provocation test was repeated after nicotine absorption according to individual habits. Patients with advanced disease as measured on a symptom scale were found to use tobacco more often and to have higher cotinine levels than patients with less advanced disease. Pathologic test results were found more frequently among users of tobacco than among nonusers. Habitual use of tobacco seems to aggravate the symptoms of vibration white finger disease and to result in an increased reactivity in a cold provocation test.