A review of the use of human factors classification frameworks that identify causal factors for adverse events in the hospital setting.

Various human factors classification frameworks have been used to identified causal factors for clinical adverse events. A systematic review was conducted to identify human factors classification frameworks that identified the causal factors (including human error) of adverse events in a hospital setting. Six electronic databases were searched, identifying 1997 articles and 38 of these met inclusion criteria. Most studies included causal contributing factors as well as error and error type, but the nature of coding varied considerably between studies. The ability of human factors classification frameworks to provide information on specific causal factors for an adverse event enables the focus of preventive attention on areas where improvements are most needed. This review highlighted some areas needing considerable improvement in order to meet this need, including better definition of terms, more emphasis on assessing reliability of coding and greater sophistication in analysis of results of the classification. Practitioner Summary: Human factors classification frameworks can be used to identify causal factors of clinical adverse events. However, this review suggests that existing frameworks are diverse, limited in their identification of the context of human error and have poor reliability when used by different individuals.

Comparison of work related fatal injuries in the United States, Australia, and New Zealand: method and overall findings.

OBJECTIVES: To compare the extent, distribution, and nature of fatal occupational injury in New Zealand, Australia, and the United States. SETTING: Workplaces in New Zealand, Australia, and the United States. METHODS: Data collections based on vital records were used to compare overall rates and distribution of fatal injuries covering the period 1989-92 in Australia and the United States, and 1985-94 in New Zealand. Household labour force data (Australia and the United States) and census data (New Zealand) provided denominator data for calculation of rates. Case definition, case inclusion criteria, and classification of occupation and industry were harmonised across the three datasets. RESULTS: New Zealand had the highest average annual rate (4.9/100,000), Australia an intermediate rate (3.8/100,000), and the United States the lowest rate (3.2/ 100,000) of fatal occupational injury. Much of the difference between countries was accounted for by differences in industry distribution. In each country, male workers, older workers, and those working in agriculture, forestry and fishing, in mining and in construction, were consistently at higher risk. Intentional fatal injury was more common in the United States, being rare in both Australia and New Zealand. This difference is likely to be reflected in the more common incidence of work related fatal injuries for sales workers in the United States compared with Australia and New Zealand. CONCLUSIONS: The present results contrasted with those obtained by a recent study that used published omnibus statistics, both in terms of absolute rates and relative ranking of the three countries. Such differences underscore the importance of using like datasets for international comparisons. The consistency of high risk areas across comparable data from comparable nations provides clear targets for further attention. At this stage, however, it is unclear whether the same specific occupations and/or hazards are contributing to the aggregated industry and occupation group rates reported here.

Developing measures of fatigue using an alcohol comparison to validate the effects of fatigue on performance.

The effects of 28 h of sleep deprivation were compared with varying doses of alcohol up to 0.1% blood alcohol concentration (BAC) in the same subjects. The study was conducted in the laboratory. Twenty long-haul truck drivers and 19 people not employed as professional drivers acted as subjects. Tests were selected that were likely to be affected by fatigue, including simple reaction time, unstable tracking, dual task, Mackworth clock vigilance test, symbol digit coding, visual search, sequential spatial memory and logical reasoning. While performance effects were seen due to alcohol for all tests, sleep deprivation affected performance on most tests, but had no effect on performance on the visual search and logical reasoning tests. Some tests showed evidence of a circadian rhythm effect on performance, in particular, simple reaction time, dual task, Mackworth clock vigilance, and symbol digit coding, but only for response speed and not response accuracy. Drivers were slower but more accurate than controls on the symbol digit test, suggesting that they took a more conservative approach to performance of this test. This study demonstrated which tests are most sensitive to sleep deprivation and fatigue. The study therefore has established a set of tests that can be used in evaluations of fatigue and fatigue countermeasures.

Assessment, re-design and evaluation of changes to the driver's cab in a suburban electric train.

A new type of electric train, called the Tangara, began replacing older trains on the Sydney city and suburban network in 1990. Shortly afterwards, some of the train drivers began reporting pain in the arms while driving the new train. The Ergonomics Unit of Worksafe Australia was then engaged to identify and assess ergonomic problems in the driver's cab. This process included direct observation of drivers at work, distribution of a self-administered questionnaire to all drivers, and analysis of anthropometric problems using a computer-aided design package. The analysis of 193 completed questionnaires and the problems shown by the design study were used in developing an improved design. A mock-up of the modified cab was made and tried out by 134 drivers whose comments led to further changes. The modified design was applied to new production, and existing cabs were modified during major maintenance. By 1996, 96% of the driver's cabs were to the new design. An evaluation of the new design was undertaken using written questionnaires, which were completed by 227 drivers. The results were strongly in favour of the new design, showing the effectiveness of the ergonomic modifications.

Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication.

OBJECTIVES: To compare the relative effects on performance of sleep deprivation and alcohol. METHODS: Performance effects were studied in the same subjects over a period of 28 hours of sleep deprivation and after measured doses of alcohol up to about 0.1% blood alcohol concentration (BAC). There were 39 subjects, 30 employees from the transport industry and nine from the army. RESULTS: After 17-19 hours without sleep, corresponding to 2230 and 0100, performance on some tests was equivalent or worse than that at a BAC of 0.05%. Response speeds were up to 50% slower for some tests and accuracy measures were significantly poorer than at this level of alcohol. After longer periods without sleep, performance reached levels equivalent to the maximum alcohol dose given to subjects (BAC of 0. 1%). CONCLUSIONS: These findings reinforce the evidence that the fatigue of sleep deprivation is an important factor likely to compromise performance of speed and accuracy of the kind needed for safety on the road and in other industrial settings.

Evaluation of an 8 hour versus a 12 hour shift roster on employees at a power station.

Several studies exist that have conducted research into the effects of different shiftwork patterns on the individual, especially regarding 8 and 12 h rosters. The findings of these studies have been largely supportive of longer shifts, however, the effects on work performance are not as clear cut. This study aimed to examine the changeover from an 8 h roster to a 12 h roster in a power station via monitoring on-shift performance, general health and well-being, sleep and mood behaviour, as well as absence and accident data. Results suggest that the domestic and social life of workers was markedly improved under the 12 h roster. Improvements in physical health, sleeping behaviour and mood state of employees were also documented. On-shift performance measures showed an increase in error rates at the end of a 12 h shift. Ways of reducing the risk of error towards the end of a 12 h shift should be explored. The results of this study suggest that 12 h shifts are a valid alternative to 8 h shifts in this particular workplace, although tasks that require error-free activities should not be performed towards the end of a 12 h shift.

The role of physical and psychological factors in occupational low back pain: a prospective cohort study.

OBJECTIVE: To examine risk factors for onset of low back pain (LBP) in healthcare workers. METHODS: Nursing students, during their 3 year training period, and 1 year after training were studied in a prospective cohort study, with repeated self reported measurements of determinants of LBP at 6 monthly intervals for 3 years during training, and after a 12 month interval there was an additional final follow up. RESULTS: During training, increased risk of new episodes of LBP was associated with having had LBP at baseline, with part time work, and with a high score on the general health questionnaire (GHQ). A high GHQ score preceded the onset of LBP, in such a way that a high score at the immediately previous follow up increased risk of LBP at the next follow up. 12 Months after training, a history of recurring LBP during training increased the risk of a new episode as did having obtained work as a nurse. A high GHQ score at this follow up was also associated with a concurrently increased risk. Pre-existing GHQ score, either at the end of training or at baseline, had no effect on risk of LBP 12 months after training. CONCLUSIONS: Other than a history of LBP, pre-existing psychological distress was the only factor found to have a pre-existing influence on new episodes of LBP. Increased levels of psychological distress (as measured by the GHQ) preceded the occurrence of new episodes of pain by only short intervening periods, implying a role for acute distress in the onset of the disorder. This finding suggests that management of the onset of occupational LBP may be improved by management of psychological distress.

The impact of work practices on fatigue in long distance truck drivers.

Twenty seven professional truck drivers completed a 12 hour, 900 km trip under each of three driving regimes-a relay (staged) trip, a working hours regulated one-way (single) trip, and a one-way (flexible) trip with no working hours constraints. The results indicated that none of the driving regimes prevented fatigue and that the pattern of fatigue experienced during the trips appeared to be related to pretrip fatigue levels.

The role of confounding variables in the assessment of neurobehavioural effects of chronic solvent exposure.

An issue in the assessment of toxic effects on neurobehavioural function in occupational or environmental settings is the presence and relative contribution of confounding variables. Factors such as education level and alcohol use are well-known to exert effects on the performance of neurobehavioural tests. In a prospective study of a cohort of vehicle spray painters, measures of neurobehavioural function, demographic characteristics, daily habits including alcohol-use and general health status were taken from the onset of their exposure on four occasions for three full years. This study provided the opportunity to assess the relative contribution of confounding variables and the study factor, solvent exposure, on neurobehavioural function in a study design which limits the heterogeneity of the study sample. In such a design the effects of confounding would expected to be reduced. Multiple linear regression analysis was used with three confounding variables, education level, alcohol use and occupational experience as well as solvent exposure as predictor variables of neurobehavioural test performance. Although the level of solvent exposure was considerably less than the composite threshold limit value for the solvent mixtures encountered, the results indicated that psychomotor performance deteriorated with increasing solvent exposure, but only on the hand steadiness test. The confounding variables showed even greater influences on performance. Education level affected performance on both psychomotor and cognitive tests in the expected direction. Occupational experience also influenced test performance but only for psychomotor tests. With increasing time in the trade, spray painters showed significantly superior performance on reaction time, hand steadiness and visual pursuit tests. Since training in spray painting focuses on psychomotor coordination, this result would be expected. Alcohol use was associated with mixed effects on neurobehavioural function. Painters who reported using greater amounts of alcohol showed significantly poorer performance on the visual test, critical flicker fusion, but better performance on the short term memory and learning measures of the paired associates test so supporting the findings of previous studies of facilitating effects of lower levels of alcohol on memory. These findings reinforce the importance of separating effects due to confounders from effects due to toxic exposures in studies of neurobehavioural function. They emphasise the dilemma of test selection, choosing tests that are sensitive enough to detect effects due to toxic exposure but which are not affected by confounding variables.

Historical overview of computerized behavioral testing of humans in neurotoxicology.

Since the early 1970s, when they became more accessible, computers have been used increasingly for behavior measurement over a wide range of purposes, including the detection of neurotoxic effects. Over these relatively few years, the number of computerized tests in use in neurotoxicology has grown from one or two to around 16 major batteries. The development of computerized tests in neurotoxicology has been influenced by a number of drives or influences. Some of these influences have included the push for computerizing traditional paper-and-pencil tests, the moves to develop a standard or core test battery, the emphasis on culture-free tests, and on the pragmatic screening approach to test selection. Lately, there has been more emphasis on the development of tests with stability and reliability. These influences have made, and are still making, some impact on the directions of test and test battery construction. The nature and degree of impact will be discussed in the context of analyzing the development of computerized behavioral testing to its current state.

Individual serum bile acids in apprentice spray painters in association with solvent exposure.

The effects of exposure to solvents on serum bile acids were investigated by comparing a group of apprentice vehicle spray painters (exposed group) with one of apprentice electricians. Apprentice spray painters from the study were subdivided into high- and low-solvent-exposure groups. Concentrations of individual serum bile acids (SBA) were measured and compared with conventional liver function tests (LFTs). Total, free, glycine- and taurine-conjugated SBA were consistently found to be present at higher levels in the spray painters than in the electricians, even at the beginning of the apprenticeship. Total SBA tended to increase in spray painters with increasing years of exposure during the apprenticeship, but this was significant at only one time point. No rises were observed over the sampling period in electricians. The mean values of individual and total SBA concentrations were all found to be higher in the high-exposure group than in the low-exposure group, with some differences reaching statistical significance. None of the routine liver biochemistry parameters was different between spray painters and electricians. gamma-Glutamyl transferase (GGT) was the only enzyme found to be significantly different between the high- and low-exposure groups, but all values were within the normal range. This study suggests that occupational exposure even to low levels of solvent mixtures results in increases in SBA. The increased SBA may be indicative of a subclinical liver dysfunction. Alternatively, they may reflect solvent exposure only, with the raised levels having no pathologic implication or consequence.

Neurobehavioural test batteries: current status, critical evaluation and new directions.

Neurobehavioural techniques are currently making a contribution to knowledge in toxicology which is being used to set safety limits of exposure to hazards. This, however, puts pressure on researchers in the field to ensure that the methods used are the best and most informative available. A review of the neurobehavioural tests currently in use shows that there are a number of issues that need to be addressed to strengthen and increase their utility. Issues include test selection and the validity, reliability and sensitivity of tests, bias and confounding of measurement in the testing session and problems in interpreting the results.

Analysis of gamma-aminobutyric acidergic synaptic contacts in the thalamic reticular nucleus of the monkey.

Gamma-aminobutyric acidergic (GABAergic) neurons in the thalamic reticular nucleus (TRN) spontaneously generate a synchronous bursting rhythm during slow-wave sleep in most mammals. A previous study at the electron microscopic level in cat anterior TRN has suggested that synchronous bursting activity could result from the large number of presumably GABAergic dendrodendritic synaptic contacts. However, little is known about the synaptology of the monkey thalamic reticular nucleus and whether it contains dendrodendritic contacts. To address this issue, we examined tissue obtained from Macaca fascicularis that was prepared for electron microscopy using postembedding techniques to demonstrate GABA immunoreactivity. Examination of the anterior (motor) and posterior (somatosensory) portions of the TRN disclosed the following: The majority of synaptic contacts (87.5% of 958) were formed by axon terminals showing no GABA immunoreactivity and making asymmetric synaptic contacts on dendrites or cell bodies. A further 6.4% of synaptic contacts was composed of GABA-immunoreactive presynaptic terminals making symmetric contacts with the dendrites of TRN neurons. The majority resembled the pleomorphic vesicle containing F-terminals seen in the dorsal thalamus and known to originate from axons of TRN. A subset or possible second class did not resemble any previously described class of GABA-immunoreactive terminals in the TRN. Both classes of these terminals making symmetric contacts may originate wholly or partially within the nucleus. There was one dendrodendritic synaptic contact and only a small number (3.2%) of axodendritic contacts with synaptic vesicles visible both pre- and postsynaptically. We conclude that dendrodendritic contacts are probably not responsible for the synchronized bursting neuronal activity seen in the slow-wave sleep of monkeys, and that, if TRN neurons are coupled synaptically, the most likely mechanism is through the synapses formed by recurrent axon collaterals of TRN neurons onto TRN dendrites.

Changing the hours of shiftwork: a comparison of 8- and 12-hour shift rosters in a group of computer operators.

Twelve-hour shifts are currently regarded by many workers as one solution to the disruptive effects of shiftwork on health, well-being and lifestyle. Twelve-hour shifts offer larger and more frequent blocks of leisure time than do 8-h shifts. Nevertheless, concern must be addressed about the possible effects of working these additional hours on work quality and productivity and whether they are worked at significant extra cost to the worker. In a study of 75 computer operators, the effect of changing from a predominantly 8 h per shift irregular roster to a 12 h per shift regular roster was investigated. Operators completed a questionnaire covering demographic and health details including the General Health Questionnaire (GHQ), and details about general job satisfaction including the Work Environment Scale (WES). They also completed a 14-day diary of sleeping and eating patterns and mood state at the beginning and end of each shift for the same period. The questionnaires and diaries were completed first under the 8-h shift roster, then again 12 months later after the 12-h shift roster had been worked for 7 months. Work quality, productivity, staff turnover and sickness and other absence data were also collected under the two shift systems. The results showed that changing to the 12-h shift roster produced improvements in health, particularly in psychological health and in reduced feelings of tiredness throughout the work period. The change in working hours was at no cost to feelings of job satisfaction or the worker's perceptions of any particular aspects of the work environment, or to measures of productivity.

Electron microscopic evidence that cortical terminals make direct contact onto cells of the thalamic reticular nucleus in the monkey.

Injections of WGA-HRP were made into somatosensory cortex to determine whether or not the cortex makes monosynaptic connections with neurons of the thalamic reticular nucleus. Two classes of synaptic profiles making asymmetric contacts onto small dendrites were labeled. The first class was small, and contained densely packed vesicles and few mitochondria. The second, larger class contained loosely packed vesicles, several mitochondria, and accounted for approximately one-third of labeled contacts.

A prospective cohort study of the chronic effects of solvent exposure.

The issue of the health effects of long-term exposure to solvents still attracts considerable debate, particularly among regulators and policymakers. This is especially true for studies of neurobehavioral effects. A major reason for this debate is that cross-sectional research designs are almost universally used in this area. Cross-sectional studies suffer from problems of possible confounding by a range of unknown factors and also usually from poor estimates of exposure. This study is an attempt to solve this problem by using an inception cohort design in which the subjects are measured at the beginning of their exposure and then at intervals while their exposure continues. Two hundred first-year apprentice vehicle spray painters were entered into the study within 6 months of beginning their apprenticeship together with a comparison group of 76 first-year apprentice electricians and 49 first-year apprentice metal fabricators. Measures of neurobehavioral function using a test battery based on an information-processing model were made at study entry and will be made annually. In addition apprentice's assessments of their own exposure are being made annually and compared with workplace-exposure assessments. So far measures have been made at the beginning of the second year for the entire cohort and at the beginning of the third year for one-third of the cohort. This paper is a description of the results for this one-third. The results suggest that there were no significant changes in neurobehavioral function in the first 2 years of exposure to solvents. However, the results of workplace monitoring suggest that exposure is considerably below current exposure standards for solvents during this time.

GABAergic regulation of noradrenergic spinal projection neurons of the A5 cell group in the rat: an electron microscopic analysis.

Recent studies have demonstrated an important contribution of the A5 noradrenergic cell group of the rostral medulla in the regulation of nociceptive messages at the level of the spinal cord. These noradrenergic controls parallel those arising from the serotonin-containing neurons of the nucleus raphe magnus. In the present study, we used postembedding immunogold staining to identify GABA-immunoreactive terminals that synapse upon identified spinally projecting noradrenergic neurons of the A5 cell group in the rat. A5 projection neurons were identified by Fluoro-Gold transport from the spinal cord; sections containing retrogradely labelled cells were then immunoreacted for tyrosine hydroxylase (TH) to identify the catecholamine-containing, presumed noradrenergic, neurons. Double-labelled A5 cells were intracellularly filled with Lucifer Yellow (LY) and then the LY was photo-oxidized to an electron-dense product. Seven intracellularly filled TH-immunoreactive projection neurons were studied with postembedding immunocytochemistry. Each A5 neuron received a significant GABA-immunoreactive terminal input. Out of a pooled total of 151 terminal profiles found in apposition to intracellularly labelled somatic and dendritic profiles, 31 (20.5%) were GABA-immunoreactive. The proportion of GABA-immunoreactive terminals that contacted somatic profiles (12/72; 17%) was similar to the proportion that contacted TH-labelled dendritic profiles (19/79; 24%). There was a discernible synaptic specialization in about 50% of the labelled terminals that contacted the TH projection neuron. Both symmetric and asymmetric synaptic specializations were found. Labelled terminals contained round or pleiomorphic vesicles, but not flat vesicles; many also contained dense-core vesicles. Our results indicate that noradrenergic neurons of the A5 cell group, which contribute to both antinociceptive and cardiovascular controls through their projection to the spinal cord, are regulated by local GABAergic, presumably inhibitory, mechanisms. Whether the initiation of A5 neuron activity results from a lifting of tonic GABAergic inhibitory control, as has been proposed for the neurons of the nucleus raphe magnus, remains to be determined.

Fine structure of calcitonin gene-related peptide immunoreactive synaptic contacts in the thalamus of the rat.

Recent studies have shown a prominent calcitonin gene-related peptide immunoreactive (CGRP-ir) pathway extending from the external medial and external lateral para-brachial nuclei to the area surrounding and including the gustatory nuclei in the thalamus, and the cortex and amygdala. The function of the CGRP-ir pathway is not completely understood, but may be involved with the processing of both nociceptive and gustatory information in the thalamus. The purpose of this study was to characterize the nature of the CGRP-ir synaptic contacts in the gustatory nucleus. Electron microscopic examination of CGRP-ir synaptic contacts revealed two classes of CGRP-ir terminals. One class, which was large, formed asymmetric synaptic contacts on dendritic appendages, had many small, round synaptic vesicles, and heavy patches of reaction product which obscured any underlying organelles. Since similar terminals in unstained tissue contained large numbers of dense-cored vesicles, it was concluded that CGRP-ir was contained predominantly in dense-cored vesicles. A second class of CGRP-ir terminals was smaller and made either asymmetric or symmetric synaptic contacts. Both symmetric and asymmetric small terminals contained small, round synaptic vesicles and fewer patches of dense reaction product. Several of the CGRP-ir terminals making symmetric contacts also contained pleomorphic vesicles. There were very few contacts on cell bodies. There were no contacts on other CGRP-ir elements, somal or dendritic, or on axon terminals. None of the CGRP-ir terminal elements were postsynaptic to unlabeled terminals. Axons containing CGRP-ir were primarily unmyelinated, but a few myelinated axons were also seen.

A simple technique for the determination of kappa and lambda immunoglobulin light chain expression by B cells in whole blood.

This article describes the development of a simple technique by which the numbers of surface immunoglobulin expressing cells can be analysed by dual fluorescence flow cytometry in samples of whole blood. We have compared the results obtained using this procedure with those obtained using samples prepared by traditional density gradient centrifugation, and demonstrate an excellent correlation between the two techniques. The method is applicable both to blood samples from normal individuals and from patients with B cell malignancies such as B-CLL and B-NHL. We have also confirmed previous findings that density gradient centrifugation may preferentially deplete certain lymphocyte subsets. This technique offers the following advantages: (i) it is rapid, (ii) it is accurate, (iii) it is reliable, (iv) it is useful in cases of lymphopenia, and (v) it requires only a small volume of blood. It is likely to be applicable to other situations in which the presence of serum factors interfere with antibody staining in whole blood.

A classification system for causes of occupational accidents for use in preventive strategies.

A comprehensive classification system, which allowed operational analysis of the events preceding accidents, was applied to the analysis of information surrounding the occurrence of all traumatic work-related fatalities in Australia in 1982-1984. The coded information included factors immediately antecedent to the accident leading to the fatality and factors removed in time which contributed to the occurrence of the accident. The complex network of events leading up to the accident, their interrelationships, and their relative contribution to causing the accident were examined. The results provide information about the use of accident analysis for the formulation of preventive strategies.