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PubMed1997

Basic Treatment Equivalent (BTE): a new measure of linear accelerator workload.

The measurement of linear accelerator workload in radiation oncology departments is usually based on the number of fields treated per unit time. However, this approach ignores variations in treatment complexity. This prospective study, was designed to measure treatment workload directly, taking into account the variations in complexity of different treatment techniques. From this, a model was to be developed, which would be simple to apply and reproducible, both within and between radiation oncology departments in Australasia. It would provide a realistic basis for assessing treatment costs and enable the comparison of patient throughput between departments. This paper describes the derivation of the model. Over a 4-week period in the Radiation Oncology Department of Westmead Hospital, all fractions of radiotherapy were timed. The data collected included: tumour site; treatment intent; number of fields; number of wedges, compensators and shielding blocks; fraction number; patient age; performance status; and need for general anaesthesia. Multivariate modelling was performed to identify factors that significantly affected fraction duration, so that these could be used to develop a model of resource utilization. The durations of 2371 fractions were measured in 219 patients. Seventy-five per cent of fractions were given with radical intent. The factors found to influence fraction duration on multivariate modelling were: number of fields; number of shielding blocks; first treatment fraction; need for anaesthesia; and performance status. The number of wedges and compensators were also found to be significant but were not included in the model in order to maintain simplicity. This was felt to be necessary if the model is to be applied to the widest possible variety of machines. A model of resources utilization called 'Basic Treatment Equivalent' (BTE) was derived, which incorporated these factors. When tested at Westmead Hospital, this model accurately reflected the predicted BTE value over a further 1-week study period. This model of linear accelerator use, which incorporates complexity has been derived and evaluated in one radiation oncology department. This requires further prospective testing before its widespread use. The model appears to reflect linear accelerator workload better than previous measures. An Australasian study to validate the model further will be undertaken. If adopted, this model has implications for comparative workload reports, diagnostic-related groups, waiting list calculations, and patient scheduling.

Efficiency↗

PubMed2000

Behavioural implications of alarm mistrust as a function of task workload.

The research was conducted to investigate the effect of increasing primary task and alarm workload on alarm mistrust as reflected by alarm and primary task performances. A total of 126 undergraduate students performed a complex psychomotor task battery three times, with the number of concurrent tasks increasing each time. During their performance, the students were required to react to an alarm system (including visual and auditory components) of questionable reliability. Depending on the group to which participants were assigned, the alarm presentation rate constituted a low-, medium- or high-workload condition. Alarm response data (times, frequencies, accuracies) and primary task data (tracking error) were analyzed to assess performance differences as a function of primary and secondary task workload levels. Results generally supported the hypotheses: increasing primary task and alarm task workload degraded alarm response performance. Also, response frequencies supported earlier research suggesting that participants 'probability match' their response rates to alarm system reliability. The results are discussed with regard to the cry-wolf effect, attention theory and alarm system design.

Analysis of Variance↗

PubMed1993

Heart rate as a psychophysiological measure for in-flight workload assessment.

The need to assess pilot workload during flight has become of increasing importance over the past decade--both in combat aircraft where workload can be excessive, and in civil transport aircraft where underload may occur. Subjective reporting in some form has been the long and well established method for assessing workload in the 'real world'. but because subjective opinions are vulnerable to bias and to preconceived notions, an additional measure can be of considerable value on occasions. Of the available psychophysiological variables, recording pilots' heart rates appears to be the most useful. This paper discusses the choice of this measure and presents examples from several studies in which workload was assessed in flight.

Aircraft↗

PubMed1994

Physical, mental, emotional, and subjective workload components in train drivers.

This study, using 12 train drivers on a high speed track and 11 drivers on a mountain track, tried to differentiate between the physical, emotional, mental, and subjective workload components imposed on the drivers during work. With the simultaneous recording and on-line analysis of heart rate and physical activity, the emotional component in terms of the so-called additional heart rate was separated from the physical component. Mental workload was calculated by the heart rate variability and by shifts in the T-wave amplitude of the ECG. Speed of the train, mode of driving, and stress of the situation were rated by two observers who accompanied the drivers in the cabin. During speeds up to 100 km/h as compared to standstills no heart rate changes occurred, but with speeds from 100 km/h up to 200 km/h heart rate decreased indicating a monotony effect. However, heart rate variability, and T-wave amplitude indicated higher mental load during driving in most speed categories. Starting the train and coming to a halt showed greater emotional workload as compared to moving. Observer ratings of stress and subjective ratings of stress by the drivers revealed several discrepancies. Discrepancies were also seen between workload as indicated by the physiological parameters, and corresponding stress ratings by the observers or by the drivers.

Heart Rate↗

PubMed1996

An experimental evaluation of instantaneous self-assessment as a measure of workload.

Instantaneous self-assessment (ISA) is a technique that has been developed as a measure of workload to provide immediate subjective ratings of work demands during the performance of primary work tasks such as air traffic control. This paper reports a study that compared the results of ISA with those gathered from other established workload evaluation techniques; subjective ratings collected at the end of the task, mean heart rate and heart rate variability, and error in the primary task of tracking. ISA ratings were found to be correlated significantly with the post-task ratings of workload, heart rate variability, and task performance. Generally each of the techniques was sensitive to variations in task difficulty. However, performance on the primary tracking task was found to be poorer during periods when ISA responses were required, regardless of whether they were spoken or manual responses. This finding suggests that the usefulness of the technique is limited in comparison to less intrusive measures of workload.

Adolescent↗

PubMed1996

Housestaff experience, workload, and test ordering in a neonatal intensive care unit.

BACKGROUND: Little is known of how the inexperience or the clinical workload of housestaff affects the decisions they make in the neonatal intensive care unit (NICU). The authors hypothesized that less experienced interns would order more tests per infant than more experienced residents, especially under conditions of heavy workload. METHOD: The NICU at the University of Kentucky A. B. Chandler Medical Center has either an intern or a resident on call by himself or herself at night, a natural setting to compare test ordering by interns and residents. The authors counted the numbers of X rays, analyses of arterial blood gases (ABGs), and electrolyte determinations ordered by the house officers on call for 321 infants from July through November 1993. Data for nine interns and seven residents were compared using multivariate linear regression. RESULTS: When workload became heavier (about five NICU patients), the interns increased their ordering of ABGs per infant to a significantly greater degree than did the residents (p = .01), with the difference being even greater on weekends when the housestaff were under less supervision (p = .004). CONCLUSION: As workload becomes greater in the NICU, interns order more ABGs per infant than do more experienced residents, especially when the interns are less supervised.

Academic Medical Centers↗

PubMed1998

The effect at one teaching hospital of interns' workloads on the satisfaction of their patients.

PURPOSE: To explore whether the amount of workload of first-year residents (interns) affects the satisfaction of their patients. METHOD: The authors collected data from January through May 1995 for 145 patients admitted to Lexinton Veterans Affairs Medical Center with the primary diagnosis of chronic obstructive pulmonary disease (COPD) or congestive heart failure (CHF). Workload was measured as the number of other patients for whom the intern had primary responsibility on the day of the studied patient's admission. A questionnaire measured the patients' satisfaction on the day of discharge. The authors analyzed the data using Pearson correlation and multiple linear regression. RESULTS: For the 89 patients with COPD (controlling for patient age, severity of illness, and sex of intern), greater workloads for their interns was a significant predictor of decreased patients' satisfaction (p = .001). No association was found for the 56 patients with CHF. CONCLUSION: Interns' workloads on the day their patients are admitted can influence their patients' subsequent satisfaction.

APACHE↗

PubMed1999

Pulmonary vascular resistance of horses decreases with moderate exercise and remains unchanged as workload is increased to maximal exercise.

This study was carried out to examine changes in pulmonary vascular resistance (PVR) induced by moderate and strenuous exercise; the objective being to understand why pulmonary artery blood pressure of exercising horses increases progressively as work intensity increases. Pulmonary arterial and wedge pressures (referenced at the point of the left shoulder) were determined simultaneously with cardiac output in 2 groups of healthy, sound, exercise-trained horses. Horses in Group 1 (n = 8) were studied at rest and during exercise performed at 8 and 13 m/s; the latter workload eliciting maximal heart rate (mean +/- s.e. 212 +/- 3 beats/min). Horses in Group 2 (n = 7 Thoroughbreds) were studied at rest and during galloping at 14.5 m/s on 5% uphill grade, a workload which elicited maximal heart rate (217 +/- 3 beats/min) and could not be sustained for > 90 s. Pulmonary vascular resistance was calculated by dividing pulmonary perfusion pressure gradient (i.e. mean pulmonary arterial pressure minus mean pulmonary wedge pressure) with cardiac output. Pulmonary arterial and wedge pressures, pulmonary perfusion pressure gradient and cardiac output increased significantly (P < 0.05) with exercise in both groups. There were no differences in PVR between the 2 groups of horses at rest. In Group 1 horses PVR decreased significantly (P < 0.05) with exercise at 8 m/s, but further pulmonary vasodilation did not occur as workload increased to 13 m/s. During exercise at 14.5 m/s on 5% grade, PVR of Group 2 horses also decreased significantly and was not different from values for 8 or 13 m/s in Group 1 horses. It is concluded that PVR reaches its nadir during moderate exercise, presumably due to upper limit of recruitment and distension having been reached. Therefore, in accordance with Ohm's law (P alpha Q x PVR), in going to higher workloads pulmonary blood flow (Q) remained the sole determinant of the rise in pulmonary arterial blood pressure (P). Our data also indicate that pulmonary artery wedge pressure is another variable that is important in determining the absolute value of pulmonary arterial blood pressure.

Animals↗

PubMed1999

Who calls 999 and why? A survey of the emergency workload of the London Ambulance Service.

BACKGROUND: In 1996-97 there were 623,000 emergency (999) calls made to the London Ambulance Service (LAS) and this represents a 30% increase over the previous five years. The reasons for this increase, which is also observed nationally, remain unknown. It has been suggested that some callers may be using the 999 service "inappropriately" but no data are available from the ambulance service. OBJECTIVE: To describe the workload of the emergency ambulance service in London with specific reference to the nature and characteristics of 999 calls, to determine who dials 999 and why, and to establish the number and types of calls that could most appropriately be dealt with by other agencies. DESIGN: A one week census of all emergency calls responded to by the LAS. SETTING: Sixty eight LAS stations. METHODS: Collation of all routine LAS incident forms (LA4) including the classification of the crews' free text description of the incident. This was supplemented by a detailed workload questionnaire for 25% of calls. RESULTS: There were 10,921 calls responded to from 29 April to 5 May 1996. The census showed that the daily number of calls was highest on Saturday and lowest on Wednesday with about half being made during normal general practitioner (GP) working hours. Half of all calls were for women and one third were for people aged > or = 65. Accidents were the commonest type of incident (24%). The remainder comprised various medical conditions such as respiratory, cardiac, and obstetric problems. In 1.5% of calls there was no illness, injury, or assistance required and 5% were for "general assistance" and mostly concerned people aged > or = 65. The workload survey indicated that two thirds of incidents occurred at home and 70% of callers had not tried to contact a GP before dialing 999. In the professional opinion of the responding crew, 60% of calls required a 999 response, with the remainder thought more appropriately dealt with by other services such as primary care, psychiatric services, and social services. CONCLUSIONS: This study suggests that while the majority of 999 calls were "appropriate", part of the 999 workload could be dealt with by other services. More research is required to clarify why people contact the 999 service for non-emergency incidents and also to establish the views of GPs and other agencies as to the role and function of the IAS.

Emergency Medical Service Communication Systems↗

PubMed1993

A survey of workload measurement systems: the occupational therapy manager's perspective.

Interest in measuring workload for budget specific purposes has increased in recent years as health care managers are being forced to cope with the demands of cost containment and fiscal accountability. This paper reports on a survey of senior occupational therapy managers of Ontario facilities accredited by the Canadian Association of Occupational Therapists (CAOT). Respondents were surveyed on their experiences with, and attitudes toward, occupational therapy workload measurement systems and the ability of these systems to assist in management activities. The survey found that most departments were using the National Hospital Productivity Improvement Program (NHPIP) system. Seventy eight percent of managers indicated they were somewhat or very satisfied with the system, but 60% also indicated that it did not adequately meet all of their management needs. In terms of desirable features of a revised workload system, 87% of managers reported wanting a system based on diagnostic or case mix group recording. Client variables (91%), physical and psychosocial aspects of client care (89%) and therapist variables (85%) were also rated as important factors to address in developing new workload systems.

Attitude of Health Personnel↗

PubMed1994

Responding to workload measurement needs.

Workload measurement is a way of capturing and recording the time and/or activities of personnel in the performance of their health care duties. The traditional focus of workload systems in occupational therapy has been on resource allocation, activity tracking and long range planning. The systems are not organized to link with other institutional, financial and management tools to identify and cost client and programme resource use. The position taken in this paper is that occupational therapy workload measurement systems must be expanded to meet these new managerial responsibilities. Occupational therapists must be able to prospectively predict their workload to accommodate the move towards case costing and programme management. The paper also provides information from a national survey which indicates that there is support from the field for this position.

Canada↗

PubMed1998

Context effects in subjective mental workload ratings.

The impact of performance context on subjective mental workload ratings was assessed with the Subjective Workload Assessment Technique (SWAT) and the NASA Task Load Index (TLX). In Experiment 1, a strong context effect was demonstrated. A low range of task difficulty produced considerably higher ratings on a common set of difficulty levels than did a high range of task difficulty. In Experiment 2, increasing the participants' range of experiences during practice eliminated the context effect. We recommend that methods for standardizing context, such as providing experience with the complete difficulty range, be developed for subjective mental workload evaluations. Actual or potential applications of this research include providing methodologies for controlling context effects in practical assessments of mental workload to increase the validity of subjective measures.

Adult↗

PubMed1991

[Evaluation of workload in middle-aged steel workers by measuring urinary excretion of catecholamines and cortisol].

To evaluate physical and mental workload in middle-aged workers, urinary excretion of catecholamines and cortisol and self-reported scores of fatigue, stress and arousal in middle-aged steel workers were compared with those in young steel workers. Noradrenaline excretion in daytime of the day-off was higher in middle-aged workers than that in young workers. In the work days, noradrenaline excretion during working hours increased in both age groups when compared with that in the day-off. The work-related increase in noradrenaline excretion was more evident in the middle-aged group than in the young group. Adrenaline excretion during working hours was greater in the middle-aged group than that in the young group, whereas the adrenaline value in the day-off was almost the same in the two age-groups. Age-difference was hardly observed in dopamine and cortisol excretion. These findings suggest that the workload in middle-aged workers was greater than that in young workers. However, self-reported scores of fatigue and stress in middle-aged workers were less than those in young workers, suggesting inconsistency between subjective score of workload and urinary levels of catecholamines. These age-related differences in urinary levels of noradrenaline and adrenaline were not so obvious in workers engaged in automated and mechanized work (vigilance task) when compared to workers engaged in less automated and less mechanized work. It is considered that factory automation might reduce the workload in middle-aged workers.

Adult↗

PubMed1997

Factors influencing mental workload indexes.

Several findings of the author's own mental workload research are reviewed. Especially, factors, except task demand, influencing mental workload indexes are discussed. First, an experiment using the National Aeronautics and Space Administration Task Load Index (NASA TLX) is reviewed and the effects of a prior task load on a subsequent subjective workload are described. In a physiological measures section, the low reliability of the heart rate variability (HRV) parameters when the subjects' respiration pattern are highly irregular, and the existence of low sweat respondent, although perspiration seems to be sensitive to the workload, are indicated. Furthermore, results of the task specific physiological responses and of a HRV parameter affected by the individual characteristics, like type A behavior pattern, are shown. Discrepancy between autonomic nervous system activity measures may be solvable by introducing a new concept of autonomic space (synergism of sympathetic and parasympathetic nervous system). Finally, the need for strategies of data management concerning the individual differences is emphasized.

Autonomic Nervous System↗

PubMed1998

Frequency of patients' consulting in general practice and workload generated by frequent attenders: comparisons between practices.

BACKGROUND: Patients who attend frequently may present a problem for general practitioners (GPs) in several ways. The frequency of patients' consulting, comparisons between practices, and the effect of frequent consulting on the clinical workload have not been quantified previously. AIMS: To examine the distribution of the number of consultations per patient in four general practices. To estimate the clinical workload generated by frequent attenders. To model the data to demonstrate the contribution of age, sex, and practice on the likelihood of attending frequently. METHOD: Analysis and modelling of a validated data set of date records of consultations collected routinely over a 41-month period from four practices in and around Leeds, representing 44,146 patients and 470,712 consultations. RESULTS: A minority of patients consulted with extreme frequency. All practices had similar distributions but varied with respect to the numbers of frequent attenders, and the frequencies of their consulting. The most frequent 1% of attenders accounted for 6% of all consultations, and the most frequent 3% for 15% of all consultations. Females and older people were more likely to be frequent attenders. CONCLUSION: Frequent attenders have an important effect on GPs clinical workload. Between one in six and one in seven consultations are with the top 3% of attenders. Further research is needed to explain the behaviour underpinning frequent attendance in order to identify appropriate management strategies; such strategies could have an important effect on clinical workload.

Adolescent↗

PubMed1986

Hormonal responses to a graded mental workload.

Three mental arithmetic tests of graded difficulty were presented to eight young male volunteers on consecutive days. The effort compensation patterns were investigated using urinary catecholamines and salivary cortisol. A significant increase in adrenaline excretion was found in response to all three tests. Urinary adrenaline was partially graded according to the level of difficulty of the tests. The response patterns to mental workload also included a significantly lower noradrenaline/adrenaline ratio and a higher adrenaline/dopamine ratio after the tests. No significant increase was found after the tests for noradrenaline and dopamine. Changes in salivary cortisol concentration during the tests were graded with respect to test difficulty between the easiest and both of the more difficult tests. Salivary cortisol concentration changes are proposed as the basis for field observations involving mental workload. It is concluded that mental workload causes distinguishable effort compensation patterns and that under certain conditions urinary adrenaline and salivary cortisol allow one to distinguish different mental workload levels.

Adult↗

PubMed1990

Driver workload during differing driving maneuvers.

Motorcycle-automobile accidents occur predominantly when the car driver turns left across the motorcyclist's right-of-way. Efforts to decrease this specific collision configuration, through an increase in motorcycle conspicuity, have concentrated on the physical characteristics of the motorcycle and its rider. The work reported here examines the behavior of car drivers during different driving sequences, in particular during left-turn maneuvers. An experiment is reported that used simultaneous video-taping of the driver and the forward-looking scene. Subjects followed a preset on-road course and were observed for head movements to determine the possibility of structural interference eye-blink frequency, probe-response time, and probe response error, as measures of cognitive or mental workload. In addition, the subjects completed two major subjective workload evaluations as reflections of effort directed to different components of the driving task. Results indicated that there were significant increases in head movements and mental workload during turn sequences compared to straight driving. This result of higher driver workload may be responsible for increasing the potential for detection failure. Such a propensity is also fostered by the higher structural interference that may be expected during turns. Failures to observe during turning sequences have differing outcomes depending on the presence of opposing traffic, as during the left turn, compared with the absence of such opposition, as occurs in the right turn. Also, the less conspicuous the oncoming vehicle in the left turn scenario, the higher the probability of detection failure. At the present time the least conspicuous powered vehicle is the motorcycle.

Accidents, Traffic↗

PubMed1990

Eye movement indices of mental workload.

Four investigations were carried out to assess the feasibility of using eye movement measures as indices of mental workload. In the first experiment, saccadic extent was measured during free viewing while subjects performed low, moderate and high complexity, auditory tone counting as the workload tasks. The range of saccadic extent decreased significantly as tone counting complexity (workload) was increased. In the second experiment the range of spontaneous saccades was measured under three levels of counting complexity with a visual task that did not require fixation or tracking. The results indicated that the extent of saccadic eye movements was significantly restricted as counting complexity increased. In the third experiment, the effects of practice were examined and decreased saccadic range under high tone counting complexity was observed even when significant increases in performance occurred with practice. Finally, in experiment 4, the first experiment was repeated with additional optokinetic stimulation and the saccadic range was again observed to decrease with tone counting complexity. The results indicated that the extent of spontaneous and elicited eye movements was significantly restricted as counting complexity increased. We conclude that this measure may provide a valuable index of mental workload.

Adult↗