Laser Doppler flow-meter assessment of iontophoretically applied norepinephrine on human finger skin circulation.

A miniaturized technique to administer vasoactive substances iontophoretically into the human finger skin and to continuously assess the resulting reaction of the vessels is described. Cutaneous blood flow is measured with a laser Doppler flow-meter. The technique has been used in 9 healthy volunteers with norepinephrine as test substance. The described method is a convenient way to evaluate the effects of transdermally applied vasoactive substances in a semiquantitative way without risking central effects of the substance to influence the registered blood flow.

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.

Clinical assessment of suspected damage from hand-held vibrating tools.

The case history is still the cornerstone in the clinical assessment of suspected vibration injury. Objective tests to verify the symptoms are needed for legal reasons in insurance cases and for research purposes. The minimum requirement of a test used to obtain objective signs of Raynaud's phenomenon is that patients with vibration-induced white finger be evaluated along with symptom-free, but vibration-exposed, subjects for reference. The measurement of systolic blood pressure in the finger after local finger and general body cooling is a test that has been evaluated in this way, as has restitution of finger temperature after local cooling and ischemia combined with general body heating. If neurological symptoms are present, electroneurographic examination is essential since carpal tunnel syndrome, a treatable condition, is common in vibration-exposed patients. Measurements of vibration and temperature thresholds are complementary examinations. The so-called vibrogram may be a method with which to obtain objective neurological signs of vibration injury, but the test needs further evaluation. Until more is known of the pathophysiological mechanisms behind the disease, the patient's description of his symptoms, combined with a detailed exposure history, will remain essential for a diagnosis of vibration injury--irrespective of the results of the tests used.

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.

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.

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.

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.

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.

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.

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.

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.

Vibration white finger: a follow up study.

To study the course of vibration white finger (VWF) 55 men were re-examined three and a half to six years after the first examination. The patients were interviewed and finger systolic pressure after general body and local finger cooling was measured. The test results at the two examinations were compared. At the follow up examination some patients experienced a subjective improvement of VWF symptoms but not until more than three years had passed after they had stopped working with vibrating tools. To study the effect of diminished cold exposure on subjective symptoms, vibration exposed outdoor workers who changed to unexposed indoor work were studied separately. In this subgroup also improvement was reported only when more than three years has passed after the change of work, indicating that diminished cold exposure is not the primary explanation for the improvement. The cold provocation test, however, showed no tendency towards a diminished reaction of the vessels to cooling. Patients who continue to work with vibrating tools report a subjective increase in symptoms. This subjective impairment was reflected in an increased reaction to cold as measured in the cold provocation test.

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.

Contact eczema produced by a beta-adrenergic blocking agent (alprenolol).

In a pharmaceutical industry, several cases of allergic contact eczema caused by the beta-adrenergic blocking agent alprenolol (Aptin) have appeared. This report deals with 12 men and two women who developed eczema during work with the substance. In 13 of the 14 cases, the induction time for sensitization was less than 1 year. The skin reactions were very florid. After healing they could be reproduced by very small quantities of the substance. In one case, eczema could also be produced after ingestion of Aptin tablets. All the cases were transferred to other work within the factory. An intensive programme was implemented to remove dust from the working areas. Despite this, isolated new cases still appear. Some employees in contact with the substance also experienced mucous membrane symptoms. These symptoms could not be shown to have an allergic aetiology, but were considered to be irritant reactions. Alprenolol must be considered a very strong contact allergen.

Alpha-adrenoceptors in the vessels of human finger skin.

To characterize alpha-adrenoceptors in the blood vessels of finger skin the effects of selective alpha-1 and alpha-2 adrenoceptor agonists and antagonists on skin blood flow were studied in vivo. The vasoactive substances were administered into the skin by iontophoresis and the effects on blood flow were evaluated with a laser-doppler. After blockade of alpha-1 adrenoceptors with doxazosine, the blood flow reduction induced by the alpha-1 selective agonist, phenylephrine, was diminished but not that caused by the alpha-2 selective agonist, B-HT 933. In contrast, after alpha-2 selective blockade by rauwolscine, phenylephrine but not B-HT 933 caused a marked decrease in blood flow. The results are compatible with the concept that postjunctional alpha-adrenoceptors in human finger skin vessels are of both alpha-1 and alpha-2 subtypes.