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PubMed2002

General practice-specific care categories: a method to examine the impact of morbidity on general practice workload.

BACKGROUND: Governments are increasing pressure on GPs to provide better services to their patients without giving consideration or due recognition to the impact of those initiatives on their already heavy workload. OBJECTIVE: This pilot study aimed to measure accurately the impact of case mix on general practice workload. METHOD: The general practice-specific care category (GP-SCC) model was developed and applied to a random sample of patients who attended a four-doctor suburban practice four or more times between July 1995 and June 1997. RESULTS: The random sample comprised 245 patients (126 males, 119 females) out of a total practice population of approximately 4000. The mean patient age was 42.7 years (CI 39.6-45.8; range: 0-95). The mean patient consulted 10.70 times (CI 9.62-11.77) and discussed 13.19 health problems (CI 11.74-14.63), which equated to 1.20 problems per consultation (CI 1.17-1.23). The ambulatory case mix concept allowed the development of the GP-SCC model--defined as GP-SCC 1, acute/self-limiting problems and preventive care; GP-SCC 2, primarily chronic health problems; GP-SCC 3, psychological problems in conjunction with up to two other problem categories; and GP-SCC 4, a combination of four or more problem categories. GP-SCC 1 comprised 31.1% of patients (CI 29.1-35.1), accounting for 25.6% of visits (CI 24.0-27.3) and 21.9% of all problems encountered (CI 20.5-23.3); GP-SCC 2 comprised 16.7% of patients (CI 10.6-19.6), accounting for 10.6% of visits (CI 9.5-11.9) and 9.9% of all problems encountered (CI 8.9-11.0); GP-SCC 3 comprised 7.1% of patients (CI 4.4-11.2), accounting for 7.8% of visits (CI 6.8-8.9) and 7.7% of all problems encountered (CI 6.8-8.7); and GP-SCC 4 comprised 42.0% of all patients (CI 35.8-48.2), accounting for 56.0% of all visits (CI 54.2-57.8) and 60.5% of all problems encountered (CI 58.8-62.2). CONCLUSIONS: The GP-SCC model, built on the ambulatory case mix concept, is a useful tool to analyse the morbidity of practice populations, and has a good predictive value in terms of a practice' workload.

Adult↗

PubMed2005

The workload of GPs: patients with psychological and somatic problems compared.

BACKGROUND: GPs state that patients with mental problems make heavy demands on their available time. To what extent these perceived problems correspond with reality needs more investigation. OBJECTIVES: To investigate the effect of patients with psychological or social diagnoses on GP's workload, expressed in time investments. METHODS: Data were derived of a cross-sectional National Survey in General Practice, conducted in The Netherlands in 2000-2002. For a year, all patient contacts with a representative sample of 104 general practices were registered. Patients diagnosed with one or more diagnoses in ICPC (International Classification of Primary Care) chapter 'Psychological' or 'Social' (n = 37,189) were compared to patients with only somatic diagnoses (n = 189,731). A subdivision was made in diagnoses depression, anxiety, sleeping disorders, stress problems, problems related to work or partner and 'other psychological or social problems'. Workload measures are the consultation frequency, number of diagnoses and episodes of illness of the patients involved. RESULTS: Patients in all categories of psychological or social problems had almost twice as many contacts with their general practice as patients with only somatic problems. They received more diagnoses and more episodes of illness were shown. Patients with psychological or social diagnoses also contacted their general practice about their somatic problems more frequently, compared to patients with only somatic problems. CONCLUSION: Patients with psychological or social problems make heavy demands on the GP's workload, for the greater part due to the increase in somatic problems presented.

Adult↗

PubMed1998

The influence of an aging surgical population on the anesthesia workload: a ten-year survey.

UNLABELLED: To assess the evolution of the anesthetic workload related to elderly population (> or = 65 yr) at the University Hospital of Geneva, the total number of anesthesia cases, high-risk patients, and emergency procedures, as well as the total duration of anesthesia and incidence of perianesthetic complications, were retrospectively analyzed over 10 yr. The squared correlation coefficient was used to assess the proportion of variance explained by the linear regression of the absolute and the relative number of events over time. More than 165,000 anesthesia procedures were analyzed, and the data were separated into two groups: the younger population (<65 yr) and the elderly population (> or = 65 yr). From 1985 to 1994, the elderly surgical population grew significantly faster (P < 0.001) than the elderly resident population (from 20.3% to 25.1% versus from 12.5% to 13.6%). Half of the increased number of anesthesia cases during this period were administered to elderly patients. The number of high-risk elderly patients increased by 48.3% (P < 0.0001). The number of emergency procedures in elderly patients increased only until 1991, and a significant decrease in the incidence of perianesthetic complications was observed. Because the mean duration of each procedure remained constant, the increased anesthetic workload in our institution was mainly due to increased geriatric surgical activity. IMPLICATIONS: During a study period of 10 yr, the increased anesthetic workload (defined as the number of anesthesia cases, high-risk patients, emergency procedures, and complication rate) at the University Hospital of Geneva was mainly due to the increased geriatric (patients > or = 65 yr) surgical activity, not to the aging of the resident population.

Age Factors↗

PubMedDate not supplied

Clinical workload decreases the level of aerobic fitness in housestaff physicians.

PURPOSE: To examine the relationship between clinical workload and aerobic fitness. METHODS: Twenty healthy intern and resident volunteers were studied in a cross over manner to compare their aerobic fitness after a 1 month "easy" clinical rotation (ECR) to that after a 1 month "hard" clinical rotation (HCR). The ECR and HCR were prospectively estimated as requiring <60 (ECR) and >70 (HCR) total hours per week of hospital work respectively. Aerobic fitness was determined by directly measuring peak oxygen uptake (peakVO2) during peak cycle exercise testing after each rotation. Clinical workload for the month preceding the exercise test was estimated by documenting the amount of hospital work and sleep lost because of on-call duties. The average weekly amount of effective aerobic training for each rotation was also documented. RESULTS: Trainees had a 206.4 (P = 0.0019, 95% CI 94-318.8) mL/min or 3 mL/kg/min (P = 0.0019, 95% CI 1.5-4.4) improvement of peakVO2 after the ECR compared with the HCR. Trainees averaged 1 (95% CI 0.16-1.81) less hour per week of exercise training, 34.1 more hours per week of hospital work (95% CI 23.0-45.3, P < 0.0001) and lost 19.1 hours more sleep per month (95% CI 11.8-26.4, p < 0.0001) during the HCR compared with the ECR. There was no correlation between changes in peakVO2 and changes in exercise training between the two rotations. CONCLUSION: Clinical workload seems to adversely affect aerobic fitness independent of changes in exercise training. This supports previous less-objective survey data.

Adult↗

PubMed1992

An epidemiological profile of in-patient workload in dermatology.

Trends in admission rates, patterns of readmission, lengths of stay and clinical caseload for in-patient dermatology from 1976 to 1985 are described using data from the Oxford record-linkage study. Age-specific admission rates were considerably higher in people aged 50 years and over than in younger people. Admission rates declined over time in most age-sex groups below the age of 70 years, but increased over time for the over 70s. In dermatology, unlike most other specialties, the length of patients' stay did not decrease substantially over the 10 years. In-patient workload consisted predominantly of leg ulcers, psoriasis, and eczema. This did not change appreciably over time. New out-patients at dermatology clinics rose by 41% from 1976 to 1985, and all out-patient visits rose by 20% during the 10-year period. Because the profile of in-patient workload changed relatively little over time, we speculate that the impact of innovations in dermatological practice has been much greater in the ambulatory setting than in the management of those patients requiring prolonged in-patient care. Future routine measures of workload in dermatology should include demographic and clinical data on out-patients.

Adult↗

PubMed2004

Can a health advocate for homeless families reduce workload for the primary healthcare team? A controlled trial.

The objective of the present study was to determine whether provision of health advocacy for homeless patients would reduce the burden of care for a primary healthcare team. The impact of a health advocacy intervention was assessed in a quasi-experimental, three-armed controlled trial. Homeless patients registering at an inner-city health centre were allocated in alternating periods to health advocacy (with or without outreach registration) or 'usual care' over a total intake period of 3 years. The client group were homeless people in hostels or other temporary accommodation in the Liverpool 8 area of the UK. The majority of participants (n = 400) were women (76%) in their twenties (mean age = 26.6 years). Most (63%) were temporarily housed at either one of the women's refuges or Liverpool City Council family hostels, and all were registered with an inner-city health centre. Data on health service utilisation over a 3-month period was collected for all clients recruited to the study and direct health service costs were measured. Homeless adults who were proactively registered by the health advocate on outreach visits to hostels made significantly less use of health centre resources whilst having more contact with the health advocate than patients who registered at the health centre at a time of need. There was no reduction in health centre workload when the offer of health advocacy was made after registration at the health centre. The additional costs of providing health advocacy were offset by a reduction in demand for health-centre-based care. The results demonstrate that health advocacy can alter the pattern of help-seeking by temporarily homeless adults. The intervention was cost-neutral. The short-term health service workload associated with symptomatic homeless patients requiring medication was not reduced, but outreach health advocacy was used successfully to address psycho-social issues and reduce the workload for primary care staff.

Adolescent↗

PubMed2006

Workload and main activities of consultative ICU nurses: long-term experience in a large teaching hospital in the Netherlands.

BACKGROUND: Early recognition and prompt treatment of deteriorating patients outside the intensive care unit (ICU) improves hospital survival. Over the past decade, consultative services have been implemented in many institutions. This service is frequently performed by ICU nurses, while little information is available on the workload and type of activities these ICU nurses actually perform. METHODS: In 1995, a consultative ICU nurse-driven service was introduced in a large teaching hospital in the Netherlands. In this descriptive study, we determined types of consultation, time consumed per visit, and main interventions during these activities. RESULTS: During the study period, 9144 consultations in 4365 patients were performed. While the number of 'scheduled' visits (visits of patients after discharge from the ICU) was reasonably variable during the study period, the number of 'on demand' visits (visits demanded by non-ICU personnel) increased gradually, especially during the first years. At the end of the observation period, approximately half of the visits were 'on demand' in the non-ICU wards. The mean number of consultations per patient dropped gradually over the whole period, from 4.02 in 1996 to 1.54 in 2004. The total workload was approximately half an hour per day; visits were combined with regular activities of the ICU team. Tracheal suctioning was among the most frequent activities during consultation (approximately 90% of all visits). CONCLUSION: Consultative ICU nurses play a growing role in bridging the gap between the ICU and non-ICU departments in our hospital. Workload is acceptable.

APACHE↗

PubMed2004

Appraised psychological workload, musculoskeletal symptoms, and the mediating effect of fatigue: a structural equation modeling approach.

The aim of the present study was to test two structural models of the relationship between appraised psychological workload and musculoskeletal symptoms from the neck, shoulder, and upper and lower back with different aspects of perceived fatigue as mediating variables. In this cross-sectional study a questionnaire survey was conducted among employees at three Swedish assembly plants (n= 305). The proposed models were tested for one general fatigue dimension--lack of energy--and four specific fatigue dimensions--physical discomfort, physical exertion, lack of motivation, and sleepiness--using structural equation modeling. The results indicate that the role of perceived fatigue in the relationship between appraised workload and musculoskeletal symptoms is different for different aspects of fatigue. The general fatigue dimension, lack of energy, does not mediate the relationship. As regards the specific fatigue dimensions, the relationship is partially mediated by physical discomfort and lack of motivation but not by physical exertion or sleepiness. Appraised psychological workload has a unique effect on musculoskeletal symptoms not mediated by fatigue.

Adult↗

PubMed1991

Audit of workload in gynaecology: analysis of time trends from linked statistics.

OBJECTIVE: To report on trends in workload patterns in gynaecology using linked statistical data. DESIGN: Retrospective analysis of linked abstracts of hospital inpatient and day case records for patients treated in the National Health Service in gynaecology. SETTING: Six health districts in the south of England covered by the Oxford record linkage study. SUBJECTS: Records for hospital admissions to gynaecology (excluding obstetric admissions) from 1975 to 1985. MEASUREMENT AND MAIN RESULTS: Inpatient episodes increased by 23.5% and day case episodes increased by 13.1%. More people treated contributed about 90% and increased readmissions contributed about 10% to the increase in workload. The workload was decreased by strike action in 1975 and 1981-2. Average length of stay decreased substantially and consistently over the 11 years. Emergency readmissions increased annually by an average of 2.7%. Admission rates in 11 groups of surgical procedures accounting for 85% of all gynaecological inpatients are reported, and increases occurred in 10 of the 11 groups. For example, average increases in annual admission rates were 1.0% for sterilization, 1.9% for legal abortion and 8.2% for biopsy of the cervix, the rate for dilatation and curettage decreased by 1.4%. CONCLUSIONS: The increase in admission rates in gynaecology was almost entirely due to increases in numbers of people treated. The rise would have been even greater if the increase in private patients had been considered. The increase may reflect increased expectations on the part of patients and their doctors, advances in technology and increased bed availability due to declining lengths of stay.

England↗

PubMed2002

A new approach to off-line setup corrections: combining safety with minimum workload.

Off-line patient setup correction protocols based on electronic portal images are an effective tool to reduce systematic patient setup errors. Recently, we have introduced the no action level (NAL) protocol which establishes a significant error reduction at a very small workload. However, this protocol did not include an explicit verification of the applied setup corrections. Systematic mistakes in the execution of setup corrections (e.g., a setup correction is always executed in the +X direction whereas a correction in the -X direction was prescribed) may introduce large systematic setup errors (irrespective of the setup protocol) and may seriously impair treatment outcome. We have therefore extended the NAL protocol with a correction verification (COVER) stage, solely aimed at detecting such mistakes. In short, COVER tests the magnitude of the postcorrection setup error in each relevant direction. If these residue errors are below the acceptance threshold T, no more electronic portal images are required and the protocol has finished. If not, the origin of this result should be investigated; if no obvious mistakes are present, the procedure is repeated for one more treatment fraction. If the residue setup errors are confirmed to be larger than T, the entire protocol is restarted. Using both Monte Carlo simulations and analytical calculations, we performed a risk analysis and evaluated the workload for various choices of T. A threshold T = 3 x sigma(r), where sigma(r) is the mean standard deviation of the random setup errors, ensured that (1) COVER introduces only a small additional workload (1.05 measurement per patient, while the absolute minimum is 1.0) and (2) serious correction mistakes are detected with high probability. Even if setup corrections are wrongly applied in each patient (worst case scenario), COVER ensures that the final distribution of systematic errors is not wider than the precorrection distribution of systematic errors; for realistic frequencies of correction mistakes (<< 1 per patient) this distribution becomes much more narrow. The combination of NAL and COVER thus provides a highly efficient as well as safe method to reduce systematic setup errors.

Algorithms↗

PubMed2005

An evaluation of the change in activity and workload arising from diabetic ophthalmology referrals following the introduction of a community based digital retinal photographic screening programme.

AIMS: To determine how the workload of an ophthalmology department changed following the introduction of an organised retinal screening programme. METHODS: Information was collected from the hospital medical record of people with diabetes attending eye clinics over 4 years. The first year was before screening, the next 2 years the first round, and the fourth year the second round. RESULTS: The total number of people with diabetes referred each year over the 4 year period was 853, 954, 974, 1051 consecutively. The number of people with diabetes in the county rose by 1400 per annum. The total number of referrals for an opinion about diabetic retinopathy was 227, 333, 363, 368, for cataract was 64, 57, 77, 93, and for glaucoma was 57, 62, 61, 68. The total number of patients referred for laser treatment over the 4 years was 77, 124, 111, and 63 CONCLUSION: This study suggests that the workload in the eye clinic increases in the first round of screening but in subsequent rounds it does not fall below the pre-screening level, except for laser treatment. This may be partly because of increasing numbers of people with diabetes. With the introduction of a national screening programme, this has significant workload implications for the National Health Service.

Adolescent↗

PubMed1992

Choosing the preventive workload in general practice: practical application of the Coronary Prevention Group guidelines and Dundee coronary risk-disk.

OBJECTIVE: To determine the workload implications for general practice of the Coronary Prevention Group and British Heart Foundation action plan for preventing heart disease. DESIGN: Computer simulation of plan, including calculation of Dundee risk scores, with data from OXCHECK trial. SUBJECTS: 4759 patients aged 35-64 who had health checks during 1989-91. MAIN OUTCOME MEASURE: Effect of using different risk scores as thresholds on workload and coverage of patients at known risk. Thresholds of 6-20 were used for cholesterol screening (nearset) and 4-16 for special care (preset). RESULTS: On the basis of workload a nearset of 8 and preset of 12 would be reasonable. This implies cholesterol measurement in 1794 (37.7%) patients and special care in 1074 (22.6%). However, many patients with single risk factors were not allocated to special care at these thresholds: 11 (37.9%) patients with cholesterol concentrations > or = 10 mmol/l, 21 (33.9%) with systolic pressure > or = 180 mm Hg, and 213 (40.7%) heavy smokers (> 20 cigarettes/day) were missed. The distribution of scores was similar in those at established clinical risk, those with family history of heart disease, and others. CONCLUSION: The guidelines may help to make best use of resources within specific age-sex groups but sound protocols for unifactorial risk assessment and modification remain essential.

Adolescent↗

PubMed2006

The triad of shift work, occupational noise, and physical workload and risk of coronary heart disease.

BACKGROUND: Shift work, noise, and physical workload are very common occupational exposures and they tend to cluster in the same groups of workers. OBJECTIVES: To study the short and long term effects of these exposures on risk of coronary heart disease (CHD) and to estimate the joint effects of these factors. METHODS: The study population in this prospective 13 year follow up study of 1804 middle aged industrially employed men was collected at the first screening for the Helsinki Heart Study. The CHD end points (ICD-9 codes 410-414 and ICD-10 codes I20-I25) were obtained from official Finnish registers. The Finnish job-exposure matrix FINJEM provided information on occupational exposures. Relative risks (RR) of CHD for the exposures were estimated using Cox's proportional hazard models adjusting for classical risk factors of CHD. RESULTS: The RR in the five year follow up for continuous noise combined with impulse noise was 1.28; for shift work it was 1.59, and for physical workload 1.18, while in the 13 year follow up the RRs were 1.58, 1.34, and 1.31, respectively. When adjusted for white-collar/blue-collar status the RRs decreased markedly. The RR in the 13 year follow up for those exposed to two risk factors was close to 1.7 and for those exposed to all three, 1.87. CONCLUSION: Shift work and continuous noise entailed an excess risk for CHD in the shortest follow up with only a few retired workers but a decreasing risk during the longer follow up. For physical workload and impulse noise the trend was opposite: the CHD risk was increasing with increasing follow up time despite increasing numbers of retired workers.

Adult↗

PubMed2004

Impact of alcohol related disease and inpatient workload of gastroenterologists in Scotland.

BACKGROUND: Concern among Scots gastroenterologists about alcohol related illness prompted this inpatient prevalence study during the winter of 2000-01. AIMS: To study gastrenterology inpatient workload due to alcohol-related illness, to determine how much was specialty specific, and if there were regional variations. METHODS: 40 Consultant gastrenterologists throughout Scotland collected data on the prevalence of alcohol related conditions among inpatients under their care on each of three specified days during the winter of 2000/2001. All inpatients under the care of participating consultants on the designated study days were included in the study. Overall return rate was 65%. Patients were categorised as follows; (a) general medical inpatients admitted for reasons other than alcohol related illness (b) general medical inpatients with no gastrointestinal or liver disease, but whose admission to hospital was primarily related to alcohol misuse, (c) gastrointestinal (including liver) inpatients admitted for reasons unrelated to alcohol intake, and with no alcohol related disease, and (d) gastrointestinal inpatients whose admission to hospital resulted from alcohol related disease. Additionally the numbers of patients with (e) decompensated liver disease of all causes, (f) decompensated alcoholic liver disease, and (g) the numbers "blocking" acute beds after initial hospitalisation with an alcohol related illness were collected. RESULTS: Overall, 829 general medical and 538 gastroenterology inpatients were entered in the study; total 1367 (705 male, 662 female). Of these, 25% (337/1367) were admitted because of alcohol related illness: 15% (201/1367) had decompensated alcoholic liver disease. Of 538 gastroenterology inpatients, 238 (44%) had problems related to alcohol and 201 of these (37% of all gastoenterology inpatients) had decompensated alcoholic liver disease. Of 246 inpatients with decompensated liver disease, 82% (201) had alcoholic liver disease. Alcohol related illness was significantly more prevalent among male inpatients in the West of Scotland. 10% of specialist gastroentelogy beds were occupied by patients whose discharge was delayed because of alcohol related problems. CONCLUSION: Most Scottish gastroenterlogists contribute to general medical receiving but their specialist inpatient workload is dominated by treatment of patients with alcohol related disease. (44% in gastroenterology v 12% in general medicine). Inpatients with decompensated alcoholic liver disease form 37% of gastroenterology workload. Alcohol related disease contributes to delayed discharge in acute medical units, especially in gastroenterology wards. There are regional differences in prevalence of alcohol related disease, which is greatest in male inpatients in the West of Scotland. Here, alcoholic liver disease accounts for nearly a decompensated liver disease. The findings point to a need to review the current patterns of acute service provision for alcohol related illnesses, so as to assess and improve both the linical effectiveness and cost effectiveness of care, and to ensure that alternatives to acute hospital admission are available when appropriate. This need should not be neglected while efforts are simultaneously being made to improve the early detection of alcohol abuse and prevent irreversible alcohol related disease.

Alcohol-Related Disorders↗

PubMedDate not supplied

Assessing statistics for the measurement of workload at a genitourinary medicine clinic.

Since January 1985 James Pringle House, the genitourinary medicine (GUM) clinic at London's Middlesex Hospital, has built up an extensive computerized patient database. Yearly statistics relating to 1) individual patients, 2) diagnoses, 3) attendances, and 4) an activity estimator (combining features of attendances and their corresponding diagnoses) are extracted. Each is assessed as a potential tool for quantifying the rising workload associated with the clinic's increased staffing levels and expanded services. Only the activity estimator identifies an upward trend, rising 26.3% from 1985-86 to 1991-92, caused largely by human immunodeficiency virus (HIV) and hepatitis B related attendances. This activity estimator could provide the basis for a workload reporting facility on all GUM computer systems. The 4 statistics exhibit other useful information, including a 21.0% rate of non-attendance (a substantial hidden addition to workload) and a strong allegiance to the clinic from patients residing outside of the local Health Authority region.

Adult↗

PubMed2006

The effect of direct-from-recovery room discharge of laparoscopic cholecystectomy patients on recovery room workload.

Ambulatory laparoscopic cholecystectomy pathways move patients through the hospital without encountering delays caused by congested inpatient bed units. However, redirecting patients to a direct discharge pathway might not be beneficial if recovery capacity is further taxed by additional workload. In this study, we attempt to assess the operational impact on recovery room workload of directly discharging laparoscopic cholecystectomy patients to home. We conducted a retrospective case-control review of recovery room flow sheets to determine recovery room time and effort required for laparoscopic cholecystectomy patients. The study was restricted to patients of a single surgeon to minimize confounds from surgical technique. Fifty-seven case patients (May 1, 2004, through November 30, 2004), all managed with intent to directly discharge from the recovery room, were compared with control patients (n = 81) from the corresponding 6 months in the year before the direct-discharge plan. The times (mean; 95% confidence interval) to meet objective criteria for adequate pain control (3.5 minutes [2.1 to 5.9] versus 4.0 minutes [2.6 to 6.1]) and readiness for discharge from phase 1 recovery (8.1 minutes [4.8 to 13.6] versus 6.1 minutes [4.0 to 9.5]) were not different between the groups. The number and distribution of interventions documented in the recovery process were not different between groups, nor was there a difference in recovery room length of stay (158 minutes [138 to 182] versus 149 minutes [132 to 167]). In our study, recovery room records reveal little if any increased workload associated with the direct-to-home discharge of laparoscopic cholecystectomy patients.

Cholecystectomy, Laparoscopic↗

PubMed1995

Going beyond heart rate: autonomic space and cardiovascular assessment of mental workload.

Psychophysiological assessment of pilot mental workload using heart rate should be augmented with an autonomic space model of cardiovascular function. This model proposes that autonomic nervous system influences on the heart may change with psychological processing in ways that are not evident in heart rate. A method of mental-workload assessment was proposed that used multiple psychophysiological measures of cardiovascular responsivity to derive the underlying sympathetic and parasympathetic information needed to represent the autonomic space for heart rate. Principal-components analysis was used to extract Sympathetic and Parasympathetic components from heart period, residual heart period. respiratory sinus arrhythmia, and Traube-Hering-Mayer wave in three experiments that manipulated perceptual/central processing and physical task demands. This initial evaluation of the method concluded that the autonomic components were valid and that the components had greater diagnosticity, and for some manipulations greater sensitivity, than heart rate. These results support the contention that the Sympathetic and Parasympathetic components provided increased precision for mental-workload assessment.

Adolescent↗

PubMed1995

Role of multiple resources in predicting time-sharing efficiency: evaluation of three workload models in a multiple-task setting.

The goal of our study was to assess the validity of the assumptions underlying three prominent workload models: the Time-Line Analysis and Prediction workload model (Parks & Boucek, 1989), the VACP workload model (Aldrich, Szabo, & Bierbaum, 1989), and the W/INDEX model (North & Riley, 1989). Sixteen subjects flew a low-fidelity flight simulation. Subjects were required to perform a two-axis tracking task, a concurrent visual-monitoring task, and a discrete decision task. The decision task had 16 variations defined by two levels on each of the following dimensions: input modality (visual vs. auditory), processing code (spatial vs. verbal), difficulty (easy vs. hard), and response modality (manual vs. voice). Dual-task costs were found only for the tracking task. The tracking data were then analyzed using two approaches: a traditional analysis of variance (ANOVA) and a correlational analysis of tracking performance versus model predictions. The ANOVA revealed that performance on the tracking task was better when the concurrent decision task was responded to vocally and was easy. Input modality and processing code of the concurrent decision task had no significant effect on tracking performance. The correlational analysis was used to evaluate each of the three models, to determine what features were responsible for improving the models' fit, and to compare their performance with a pure time-line model that makes no multiple-resource assumptions. All three models did a good job of predicting variance between experimental conditions, accounting for between 56% and 84% of the variance in our data and between 10% and 40% of an earlier data set. Different features of each model that affect the fit are then discussed. We conclude that it is important for models to retain a multiple-resource coding, although the best features of that coding remain to be determined. Coding tasks by their demand level appears to be less critical.

Adolescent↗