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PubMed2005

Prevalence of pharyngeal and laryngeal abnormalities in Thoroughbreds racing in Australia, and their association with performance.

REASONS FOR PERFORMING STUDY: Little information is available regarding the prevalence of abnormalities of the upper airway and their association with performance in the general population of Thoroughbred racehorses. OBJECTIVES: To describe the prevalence of selected abnormalities of the upper airway and their association with performance in Thoroughbred racehorses in Australia. HYPOTHESIS: That abnormalities of the upper airway of Thoroughbred racehorses are associated with poor race performance. METHODS: Rhinolaryngoscopy was performed after racing and presence and characteristics of abnormalities of the larynx and pharynx were recorded in a prospective cross-sectional study of Thoroughbred horses racing in Victoria, Australia. RESULTS: Rhinolaryngoscopy was performed once on each of 744 horses over 35 months. Fifty abnormalities of the upper airway were detected in 47 horses (6.3%, 95% confidence interval [CI] 4.7-83%). Epiglottic entrapment was detected in 7 horses (0.9%, 95% CI 0.4-1.9%) and was significantly (P = 0.015) associated with superior performance. Grade 2 asymmetry (4 grade scale) of the left arytenoid cartilage was detected in 9 horses (1.2%, 95% CI 0.5-2.4%) and was also associated with superior performance (P<0.001). Ulceration or erosion of the mucosa of the axial surface of one or both arytenoids was detected in 18 horses (2.4%, 95% CI 13-3.8%) and was not associated with alterations in exercise performance (P = 0.31). CONCLUSIONS: Epiglottic entrapment, Grade 2 laryngeal asymmetry and mucosal erosions detected in Thoroughbred racehorses were not associated with impaired performance; therefore, surgical correction and concern over laryngeal function in horses with Grade 2 asymmetry may not be necessary in individuals performing to expectation.

Animals↗

PubMed1990

Performance indicators--can you afford not to have them? Royal Children's Hospital--a structured approach.

The thought of performance assessment may send chills through even the most experienced hospital manager. It conjures up the worst facets of negativeness, failure, being 'watched', funding cuts and being 'on trial'. Yet the constructive use of performance indicators is undoubtedly an essential tool to all levels of management within a hospital. Performance indicators are as important to health agencies as they are to B.H.P. Stringent financial restraints, calls from 'shareholders' to demonstrate performance and to be more accountable are placing management under increasing scrutiny. Overseas work points to the use and abuse of indicators, and the difficulty in arriving at appropriate and meaningful performance indicators. A computer search of Australian literature reveals a dearth of papers on the subject of health service performance indicators. Perhaps the cultural norm of reticence towards formal performance appraisal is reflected by this dearth. Within individual agencies, however, performance indicators are being utilised in varying degrees. The Royal Children's Hospital, Melbourne, has compiled a structured set of performance indicators for two purposes--firstly, as a means of monitoring performance on a regular basis, and secondly, as a quality assurance tool. The hospital's chosen indicators cover not only throughput, but attempt to shed some light on efficiency and effectiveness. They are designed to highlight areas/trends which diverge from the 'norm', which act as warning signals to investigate further. Whilst some measures relate specifically to the activities and objectives of the Royal Children's Hospital, many are sufficiently general to the hospital field to be worth considering by any hospital interested in a more structured, formal review of its performance. It may also be possible to obtain many of the measures shown without necessarily having in place extensive/comprehensive computer information systems. Introduction of measures may therefore be undertaken progressively.

Australia↗

PubMed1994

Predicting oxygenator clinical performance from laboratory in-vitro testing.

Knowledge and predictability of oxygenator performance is vital to safe and effective conduct of cardiopulmonary bypass. The determination of oxygenator performance in the laboratory, however, is carried out under a strict set of conditions established by the Association for the Advancement of Medical Instrumentation (AAMI). This performance data is of limited value in the clinical setting where the perfusionist generally operates outside this set of parameters. This study (1) reports the laboratory performance characteristics of a hollow fiber membrane oxygenator (Sorin Monolyth), (2) uses this data to develop a model to predict performance under a wide range of clinical conditions, (3) compares predicted performance with clinical data collected at two open heart centers, and (4) reviews the complexities of comparing laboratory and clinical performance. An in-vitro "oxygenator-deoxygenator" circuit was utilized to determine O2 and CO2 gas exchange, blood path pressure drop, and heat exchanger efficiency at a variety of blood and gas flows, under standard (AAMI) blood inlet conditions: [table: see text] This laboratory performance data was compared to hospital and computer modeling data. Simple numerical comparison and analysis of variance of regression coefficients over groups indicated that some clinical parameters of performance (oxygen transfer and coefficient of heat exchange) were not predicted with the laboratory data. It is concluded that the laboratory performance data determined under strict controlled conditions may be of limited value in predicting clinical performance unless modeled to allow for variances in operating conditions.

Analysis of Variance↗

PubMedDate not supplied

[Neurocognitive subtypes of schizophrenia according to performance at verbal fluency tasks].

UNLABELLED: There is a general agreement that schizophrenia is an heterogeneous disorder and cognitive performances could be an interesting feature in order to allow a better description of specific subtypes. The aim of this study was: 1) to describe clinical and neuropsychological performances of 45 DSM IV schizophrenic patients divided in two groups according to their performances in verbal fluency task; 2) to compare each group with the performances of healthy subjects matched for sex, age and education. METHOD: The differentiation criteria was the total number of words generated during 3 formal and 3 semantic fluency tasks. Data were analysed using a disjoint clustering procedure with Euclidean distance. A two cluster solution was considered optimal. Cluster S1 includes 21 schizophrenic subjects defined as low performer (range: 40-83, mean 66.7). Cluster S2 includes 24 schizophrenic subjects (range: 87-158, mean 102.8). All schizophrenic patients were clinically evaluated with SANS, SAPS and a psychosocial aptitude rating scale (PARS). Patients and controls were assessed with the following battery: verbal fluency, Trail making test A & B, Stroop test, Brown Peterson paradigm for evaluation of working memory. RESULTS: Patients with low verbal fluency had significantly higher scores at the SANS and PARS. Furthermore, the low performers (cluster S1) were differentiated from those with better performances (cluster S2) by significantly poorer results in all neuropsychological tests. Comparison with healthy subjects indicated that cluster S1 patients also had significantly poorer results in all neuropsychological tests. Relative to their 24 controls cluster S2 patients performances was lower in all measures excepted in one subscore of the Stroop test and in the number of cluster produced. This later result could indicate that some capacities for willed intention were preserved in this group and that the alteration in verbal fluency performances were better explained by impairment of the other cognitive processes. DISCUSSION: These findings point out that: 1) use of performance in cognitive executive task such as verbal fluency is a possible criteria in order to separate different types of schizophrenic patients; 2) in the two groups of schizophrenic subjects, various processes defects underline cognitive performances indicating the presence of different neurobiological dysfunctioning.

Adult↗

PubMed2003

How often do neuroradiologists perform sonography of the carotid arteries? A survey of academic and nonacademic radiology practices, with implications for fellowship training.

BACKGROUND AND PURPOSE: Debate in the neuroradiology community surrounds the amount of formal training in sonography of the carotid arteries that should be provided to fellows. This study was designed to assess current practice patterns at both academic and nonacademic practices regarding the performance of carotid sonography. METHODS: A neurovascular radiology survey was sent to all 102 program directors of neuroradiology fellowships in the United States and Canada (academic practices). The survey was also sent to 146 randomly selected senior members of the ASNR (three per state, except one each for Alaska and Vermont) who were not affiliated with fellowship programs (nonacademic practices). RESULTS: Fifty-seven surveys from academic practices and 70 surveys from nonacademic practices were returned. Radiologists at academic practices performed approximately 42% of studies (general radiologists or sonography specialists, 36%; neuroradiologists, 5%; cardiovascular radiologists, 1%). Nonradiologists performed approximately 58% of studies (vascular surgeons, 47%; neurologists, 10%; cardiologists, 1%; neurosurgeons, <1%). Neuroradiologists performed carotid sonography at 11% (6/57) of academic practices. On average, radiologists at nonacademic practices performed approximately 62% of studies (general radiologists or sonography specialists, 38%; neuroradiologists, 15%; cardiovascular radiologists, 9%). Nonradiologists performed approximately 38% of studies (vascular surgeons, 25%; neurologists, 6%; cardiologists or internists, 6%). Neuroradiologists performed carotid sonography at 53% (37/70) of nonacademic practices. CONCLUSION: At most academic practices, neuroradiologists do not perform sonography of the carotid arteries. This may explain the reluctance of some fellowships to provide formal training in this technique. In contrast, although neuroradiologists perform carotid sonography at a majority of the nonacademic practices, the percentage of studies that they perform is small; moreover, neuroradiologists perform far fewer studies than do general radiologists or sonography specialists.

Canada↗

PubMed2003

Endovascular interventional neuroradiologic procedures: who is performing them, how often, and where? A survey of academic and nonacademic radiology practices.

BACKGROUND AND PURPOSE: In this report, the authors assess practice patterns at both academic and nonacademic centers regarding the treatment of aneurysms with Guglielmi detachable coils (GDCs), thrombolysis of the carotid-vertebral arteries, and stent placement with angioplasty of the carotid arteries. METHODS: A neurovascular radiology survey was sent to 102 directors of neuroradiology fellowship programs in the United States and Canada ("academic centers"). The survey was also sent to senior members of the American Society of Neuroradiology (three per state) who were not affiliated with fellowship programs ("nonacademic centers"). RESULTS: Fifty-seven surveys from academic practices and 70 surveys from nonacademic practices were returned. A total of 4361 procedures (2283 GDC; 949 thrombolysis; 1129 stent placement) were performed; 84% were performed at academic centers and 16% at nonacademic centers. Ninety percent of GDC, 71% of thrombolysis, and 82% of stent placement procedures were performed at academic centers. Seven academic and three nonacademic centers performed 48% of all GDC procedures; eight academic and four nonacademic centers performed 45% of all thrombolysis procedures; eight academic centers performed 50% of all stent placement procedures. A total of 544/4361 (12%) procedures were performed by nonradiologists. At academic centers, 14% of procedures were performed by nonradiologists; participation by nonradiologists was greatest for carotid stent placement (24% of procedures). At nonacademic centers, only 5% of procedures were performed by nonradiologists. CONCLUSION: According to this survey, most endovascular interventional neuroradiologic procedures are performed at academic centers; given the survey population, this study likely identifies the lower limit of participation by nonradiologists (12%). Performance of these procedures is concentrated in relatively few centers, and these data raise questions about the overall use of intraarterial thrombolytic therapy for acute infarction.

Academic Medical Centers↗

PubMed1998

Assessing the performance of community systems for children.

OBJECTIVE: To present a framework for measuring the quality of community systems for children, based on key attributes of systems performance for children's services. We present a research agenda for refining the model, evaluating indicators across the performance domains identified, developing normative standards for performance, and assessing the empirical basis for performance criteria. PRINCIPAL FINDINGS: Systems performance can be measured. A systems approach to evaluating community systems for children needs to incorporate the multilevel service delivery networks, programs, and systems of care for children. A model of community systems performance for children includes key dimensions of structure, financing, and accountability. Attributes within these dimensions serve as indicators that communities can use to evaluate systems quality. Performance standards can be based on the evidence from field demonstrations as well as from normative assessments. RECOMMENDATIONS: The model of community systems performance should be refined and developed using empirical findings of analyses of children's systems. A set of indicators that capture vital aspects of performance and that are relevant, scientifically valid, and feasible should be developed and tested in field studies. Once indicators are evaluated for use in performance monitoring, communities will be able to implement performance monitoring.

Child↗

PubMed2003

Psychomotor skills assessment in practicing surgeons experienced in performing advanced laparoscopic procedures.

BACKGROUND: Minimally invasive surgery (MIS) has introduced a new and unique set of psychomotor skills for a surgeon to acquire and master. Although assessment technologies have been proposed, precise and objective psychomotor skills assessment of surgeons performing laparoscopic procedures has not been detailed. STUDY DESIGN: Two hundred ten surgeons attending the 2001 annual meeting of the American College of Surgeons in New Orleans who reported having completed more than 50 laparoscopic procedures participated. Subjects were required to complete one box-trainer laparoscopic cutting task and a similar virtual reality task. These tasks were specifically designed to test only psychomotor and not cognitive skills. Both tasks were completed twice. Performance of tasks was assessed and analyzed. Demographic and laparoscopic experience data were also collected. RESULTS: Complete data were available on 195 surgeons. In this group, surgeons performed the box-trainer task better with their dominant hand (p < 0.0001) and there was a strong and statistically significant correlation between trials (r = 0.47 - 0.64, p < 0.0001). After transforming raw data to z-scores (mean = 0 and SD = 1) it was shown that between 2% and 12% of surgeons performed more than two standard deviations from the mean. Some surgeons' performance was 20 standard deviations from the mean. Minimally Invasive Surgical Trainer Virtual Reality metrics demonstrated high measurement consistency as assessed by coefficient alpha (alpha = 0.849). CONCLUSIONS: Objective assessment of laparoscopic psychomotor skills is now possible. Surgeons who had performed more than 50 laparoscopic procedures showed considerable variability in their performance on a simple laparoscopic and virtual reality task. Approximately 10% of surgeons tested performed the task significantly worse than the group's average performance. Studies such as this may form the methodology for establishing criteria levels and performance objectives in objective assessment of the technical skills component of determining surgical competence.

Adult↗

PubMed2026

Effects of Blood Flow Restriction Training at Different Levels of Arterial Occlusion Pressure on Body Composition and Athletic Performance in Youth Soccer Players: A Randomized Controlled Trial.

This study aimed to investigate the effects of low-load blood flow restriction training (BFRT) performed at different levels of arterial occlusion pressure (AOP) on body composition, maximal strength, and athletic performance in youth soccer players. Twenty-four male youth soccer players were randomly assigned to 40% AOP group, 60% AOP group, or control group. Participants in the BFRT groups performed lower-limb resistance training at 30% of one-repetition maximum (1RM) under the corresponding pressure conditions, whereas the control group trained without BFR. Training was conducted three times per week for six weeks. Body composition, back squat 1RM, countermovement jump (CMJ), T-test, and 30-m sprint performance were assessed before and after the intervention. Results showed that lower-limb muscle mass increased significantly in both the 40% AOP group (mean change = 0.55 kg, 95% CI: 0.13 to 0.97 kg, P = 0.010) and the 60% AOP group (mean change = 0.83 kg, 95% CI: 0.37 to 1.29 kg, P < 0.001), with the 60% AOP group showing significantly greater gains than the control group (between-group difference = 1.48 kg, 95% CI: 0.40 to 2.56 kg, P = 0.008). Back squat 1RM improved significantly in both the 40% AOP group (mean change = 6.50 kg, 95% CI: 3.90 to 9.10 kg, P < 0.001) and the 60% AOP group (mean change = 9.25 kg, 95% CI: 6.75 to 11.75 kg, P < 0.001), with the 60% AOP group demonstrating superior strength gains compared with the 40% AOP group (between-group difference = 2.94 kg, 95% CI: 0.20 to 5.68 kg, P = 0.048). CMJ height and T-test performance improved significantly in both the 40% AOP group (CMJ: mean change = 2.07 cm, 95% CI: 0.80 to 3.34 cm, P = 0.002; T-test: mean change = -0.23 s, 95% CI: -0.35 to -0.11 s, P = 0.001) and the 60% AOP group (CMJ: mean change = 2.65 cm, 95% CI: 1.00 to 4.30 cm, P = 0.003; T-test: mean change = -0.26 s, 95% CI: -0.38 to -0.14 s, P < 0.001), with no significant differences between the two BFRT groups (all P > 0.05). No significant changes were observed in 30-m sprint performance across groups (all P > 0.05). This study showed that six weeks of low-load (30% 1RM) blood flow restriction training performed at both 40% and 60% AOP was associated with improvements in lower-limb muscle mass, squat strength, and selected aspects of athletic performance in youth soccer players, compared with low-load training without BFR. While both pressure levels elicited comparable improvements in CMJ and agility performance, training at 60% AOP was associated with greater adaptations in lower-limb muscle mass and squat strength, with no additional benefits observed for 30-m sprint performance.

Humans↗

PubMed1993

Alpha frequency, cognitive load and memory performance.

EEG-signals were recorded from subjects as they performed a modified version of Schneider's and Shiffrin's memory search paradigm. The hypothesis was tested whether individual (centre of gravity) alpha frequency, termed IAF, is related to memory performance and/or attentional demands. The results show that memory performance exerts the strongest effect on IAF. As compared to a resting period, the difference in IAF between age-matched good and bad memory performers reached a maximum when subjects were actually retrieving information from their memory. During retrieval, the IAF of good performers is 1.25 Hz higher than for bad performers. Attentional and task demands also tend to reduce IAF, but as compared to memory performance-to a much lesser degree. The results of amplitude analyses demonstrate further that during retrieval, alpha desynchronization is more pronounced for bad performers than for good performers. Taken together, the results indicate that a decrease in IAF is always related to a drop in performance.

Adult↗

PubMed1995

Improvement in performance of a delayed matching-to-sample task by monkeys following ABT-418: a novel cholinergic channel activator for memory enhancement.

ABT-418, a newly characterized centrally acting cholinergic channel activator (ChCA), was evaluated for its ability to improve performance in a delayed matching-to-sample (DMTS) task by mature macaques well trained in the task. Previous studies in rodents have indicated that ABT-418 shares the memory/cognitive enhancing actions of nicotine, but without many of nicotine's dose-limiting side effects. As DMTS provides a measure both of general cognitive function (the matching concept) and of recent memory, it was hypothesized that some doses of ABT-418 would enhance the monkeys' ability to correctly perform the DMTS task. Intramuscular administration of ABT-418 significantly enhanced DMTS performance at low (2-32.4 nmol/kg) doses. In fact, the drug was slightly more potent that nicotine in this regard, and all eight animals tested in this study exhibited enhanced performance at one or more doses. ABT-418 produced the greatest improvement in DMTS performance at the longest delay interval. In animals repeatedly tested with their individualized "Best Dose", DMTS performance increased on average by 10.1 +/- 3.5 percentage points correct, which was equivalent to an increase of 16.2% over baseline performance. ABT-418 did not significantly affect response times, i.e., latencies to make a choice between stimuli, or latencies to initiate new trials. Whereas nicotine enhanced DMTS performance both on the day of administration and on the following day (in the absence of drug), ABT-418-induced enhanced performance was detected only on the day of administration. Finally, single daily administration of the individualized best dose in three monkeys over a period of 8 days generally maintained enhancement of DMTS performance. Thus, the data were not consistent with the development of significant tolerance to the drug's mnemonic actions. In contrast to nicotine, no overt toxicity or side effects to acute or repeated administration of the drug were noted. Thus, ABT-418 represents a prototype of a new class of nicotinic agonists designed for the potential treatment of human dementias having a low profile of toxicity.

Animals↗

PubMed2004

Learning curves and impact of psychomotor training on performance in simulated colonoscopy: a randomized trial using a virtual reality endoscopy trainer.

BACKGROUND: The aim of this study was to analyze the learning curve for the GI Mentor II endoscope trainer and to determine whether psychomotor training can contribute to an improvement in the performance of virtual colonoscopy. METHODS: To analyze the learning curve, 28 subjects were divided into three groups on the basis of their experience with gastrointestinal (GI) endoscopy: experienced surgeons (group 1, performed > 200 endoscopic procedures, (n = 8)) residents (group 2, performed < 50 endoscopic procedures, (n = 10)); and medical students (group 3, never performed GI endoscopy, (n = 10)). The participants were tested on the GI Mentor II virtual reality simulator 10 consecutive times. Assessment of the learning curve was based on the following three parameters: time used, number of punctured balloons, and number of wall collisions. In the second part of the study, 20 subjects who had never performed GI endoscopy were included. After performing a virtual colonoscopy, they were randomized to a group that received psychomotor training and a control group. Finally, all subjects performed a virtual colonoscopy. Assessment of endoscopic skills during the colonoscopy was based on nine parameters dealing with psychomotor skills. RESULTS: The learning curve for time expended reached a plateau after the second repetition for group 1 (Friedman's test, p < 0.05), after the fifth repetition for group 2 (p < 0.05), and after the seventh repetition for group 3 (p < 0.05). Experienced surgeons did not improve their scores for regarding number of balloons punctured or number of wall collisions (p > 0.05), indicating the absence of a learning curve for these parameters. Group 2 improved their scores up to the fourth and fifth repetitions, respectively (p < 0.05), and group 3 up to the fifth and seventh repetitions, respectively (p < 0.05). Experienced surgeons achieved the best performance, followed by group 2 and then group 3. The surgeons who had received psychomotor training performed the second virtual colonoscopy significantly faster than the control group (Mann-Whitney test, p < 0.001) and made significantly greater improvement in all other parameters as well. CONCLUSIONS: There were different learning curves for surgeons depending on their endoscopic background. The familiarization rate on the simulator was proportional to the endoscopic experience of the surgeons. Psychomotor training had a significant effect on the performance of a simulated colonoscopy.

Clinical Competence↗

PubMed2005

Assessing team performance in the operating room: development and use of a "black-box" recorder and other tools for the intraoperative environment.

BACKGROUND: The objective of this research was to develop a digital system to archive the complete operative environment along with the assessment tools for analysis of this data, allowing prospective studies of operative performance, intraoperative errors, team performance, and communication. Ability to study this environment will yield new insights, allowing design of systems to avoid preventable errors that contribute to perioperative complications. STUDY DESIGN: A multitrack, synchronized, digital audio-visual recording system (RATE tool) was developed to monitor intraoperative performance, including software to synchronize data and allow assignment of independent observational scores. Cases were scored for technical performance, participants' situational awareness (knowledge of critical information), and their comfort and satisfaction with the conduct of the procedure. RESULTS: Laparoscopic cholecystectomy (n = 10) was studied. Technical performance of the RATE tool was excellent. The RATE tool allowed real time, multitrack data collection of all aspects of the operative environment, while permitting digital recording of the objective assessment data in a time synchronized and annotated fashion during the procedure. The mean technical performance score was 73% +/- 28% of maximum (perfect) performance. Situational awareness varied widely among team members, with the attending surgeon typically the only team member having comprehensive knowledge of critical case information. CONCLUSIONS: The RATE tool allows prospective analysis of performance measures such as technical judgments, team performance, and communication patterns, offers the opportunity to conduct prospective intraoperative studies of human performance, and allows for postoperative discussion, review, and teaching. This study also suggests that gaps in situational awareness might be an underappreciated source of operative adverse events. Future uses of this system will aid teaching, failure or adverse event analysis, and intervention research.

Cholecystectomy, Laparoscopic↗

PubMed2004

Human performance breakdowns are rarely accidents: they are usually very poor choices with disastrous results.

When human error is involved in the error chain of accidents in complex systems, the causes of the errors are very seldom the result of: a random slip, one inadvertent oversight, a single unintended action, one mis-perceived event, simple mal-performance of a complex action, or a poor training program for the human operators. Invariably, the cause of the break down is in a very poor conscious choice by someone from the operator back through system designer, the supervision, management and leadership through the entire organization. Usually the operator bears the burden of the blame and is either rebuked, retrained or replaced. In systems such as commercial aviation, complex manufacturing systems, power plants, process control systems, information-processing systems and communications networks, the replacement or retraining of individuals or even classes of individuals usually does not result in any long-term improvement of the safety or effectiveness of the system. What is needed is a system that identifies the reasons why the operators made the errors. Further a system is needed that can recommend what can be done to improve the future performance within the system. The professional performance analysis system (PPAS) has been developed and applied to more than 50 major aircraft accidents in the past 30 years. The PPAS is a direct outgrowth of the human performance analysis system developed by Robert Mager over 45 years ago. The PPAS system is applied after a complete and unbiased definition and description of the events of the accident or incident has been developed by the teams of accident investigation and accident reconstruction professionals. The PPAS then uses a systematic protocol and algorithm to determine the reasons as to why the humans committed the errors or why they performed at subnormal performance levels. This process is based on quantitative behavioral science principles and findings that have been demonstrated valid for many generations. The PPAS looks at five attributes of human performance to identify the factors that can be changed to improve performance in the future. The result is a series of objective definitions of changes that have been demonstrated to be the attributes that influence human performance. The PPAS provides a tool to the analyst, who lacks sophistication or experience in quantitative behavioral sciences, to arrive at recommendations that are based on validated human performance principles.

Accidents, Aviation↗

PubMed2000

Combined eye activity measures accurately estimate changes in sustained visual task performance.

Five concurrent eye activity measures were used to model fatigue-related changes in performance during a visual compensatory tracking task. Nine participants demonstrated considerable variations in performance level during two 53-min testing sessions in which continuous video-based eye activity measures were obtained. Using a trackball, participants were required to maneuver a target disk (destabilized by pseudorandom wind forces) within the center of an annulus on a CRT display. Mean tracking performance as a function of time across 18 sessions demonstrated a monotonic increase in error from 0 to 11 min, and a performance plateau thereafter. Individual performance fluctuated widely around this trend - with an average root mean square (RMS) error of 2.3 disk radii. For each participant, moving estimates of blink duration and frequency, fixation dwell time and frequency, and mean pupil diameter were analyzed using non-linear regression and artificial neural network techniques. Individual models were derived using eye and performance data from one session and cross-validated on data from a second session run on a different day. A general regression model (based only on fixation dwell time and frequency) trained on data from both sessions from all participants produced a correlation of estimated to actual tracking performance of R=0.68 and an RMS error of 1.55 (S. D.=0.26) disk radii. Individual non-linear regression models containing a general linear model term produced the cross-session correlations of estimated to actual tracking performance of R=0.67. Individualized neural network models derived from the data of both experimental sessions produced the lowest RMS error (mean=1.23 disk radii, S.D.=0.13) and highest correlation (R=0.82) between eye activity-based estimates and actual tracking performance. Results suggest that information from multiple eye measures may be combined to produce accurate individualized real-time estimates of sub-minute scale performance changes during sustained tasks.

Adult↗

PubMed2003

Modeling the effects of functional performance and post-transplant comorbidities on health-related quality of life after heart transplantation.

BACKGROUND: Health-related quality of life and functional performance are important outcome measures following heart transplantation. This study investigates the impact of pre-transplant functional performance and post-transplant rejection episodes, obesity and osteopenia on post-transplant health-related quality of life and functional performance. METHODS: Functional performance and health-related quality of life were measured in 70 adult heart transplant recipients. A composite health-related quality of life outcome measure was computed via principal component analysis. Iterative, multiple regression-based path analysis was used to develop an integrated model of variables that affect post-transplant functional performance and health-related quality of life. RESULTS: Functional performance, as measured by the Karnofsky scale, improved markedly during the first 6 months post-transplant and was then sustained for up to 3 years. Rejection Grade > or =2 was negatively associated with health-related quality of life, measured by Short Form-36 and reversed Psychosocial Adjustment to Illness Scale scores. Patients with osteopenia had lower Short Form-36 physical scores and obese patients had lower functional performance. Path analysis demonstrated a negative direct effect of obesity (beta = - 0.28, p < 0.05) on post-transplant functional performance. Post-transplant functional performance had a positive direct effect on the health-related quality of life composite score (beta = 0.48, p < 0.001), and prior rejection episodes grade > or =2 had a negative direct effect on this measure (beta = -0.29, p < 0.05). Either directly or through effects mediated by functional performance, moderate-to-severe rejection, obesity and osteopenia negatively impact health-related quality of life. These findings indicate that efforts should be made to devise immunosuppressive regimens that reduce the incidence of acute rejection, weight gain and osteopenia after heart transplantation.

Bone Diseases, Metabolic↗

PubMed1999

Level of automation effects on performance, situation awareness and workload in a dynamic control task.

Various levels of automation (LOA) designating the degree of human operator and computer control were explored within the context of a dynamic control task as a means of improving overall human/machine performance. Automated systems have traditionally been explored as binary function allocations; either the human or the machine is assigned to a given task. More recently, intermediary levels of automation have been discussed as a means of maintaining operator involvement in system performance, leading to improvements in situation awareness and reductions in out-of-the-loop performance problems. A LOA taxonomy applicable to a wide range of psychomotor and cognitive tasks is presented here. The taxonomy comprises various schemes of generic control system function allocations. The functions allocated to a human operator and/or computer included monitoring displays, generating processing options, selecting an 'optimal' option and implementing that option. The impact of the LOA taxonomy was assessed within a dynamic and complex cognitive control task by measuring its effect on human/system performance, situation awareness and workload. Thirty subjects performed simulation trials involving various levels of automation. Several automation failures occurred and out-of-the-loop performance decrements were assessed. Results suggest that, in terms of performance, human operators benefit most from automation of the implementation portion of the task, but only under normal operating conditions; in contrast, removal of the operator from task implementation is detrimental to performance recovery if the automated system fails. Joint human/system option generation significantly degraded performance in comparison to human or automated option generation alone. Lower operator workload and higher situation awareness were observed under automation of the decision making portion of the task (i.e. selection of options), although human/system performance was only slightly improved. The implications of these findings for the design of automated systems are discussed.

Adult↗

PubMed1999

Executive function in depression: the role of performance strategies in aiding depressed and non-depressed participants.

OBJECTIVES: Depression has been found to be associated with dysfunction in executive processes, whereas relatively automatic processes are thought to remain intact. Failure to generate or implement adequate performance strategies has been postulated in depressed participants. The present study investigated spontaneous strategy usage in depressed and control participants, and the effectiveness of providing a hint about performance strategies. METHODS: Unipolar depressed participants were compared with matched healthy controls on three tasks sensitive to executive function: memory for categorised words, response suppression, and multiple scheduling. Participants in each group were randomly allocated to strategy aid and no strategy aid conditions. Those in the strategy aid condition were given a hint about the use of an appropriate performance strategy for each task, in addition to the standard instructions given to those in the no strategy aid condition. RESULTS: Depressed participants performed worse than controls on each of the three tasks, and were found to use appropriate performance strategies less often. Provision of strategy hints increased the use of performance strategies in two of the three tasks, memory for categorised words, and response suppression, but did not significantly improve overall performance for either group. CONCLUSIONS: The findings were consistent with the view that depressed participants fail to use appropriate performance strategies spontaneously to the same extent as controls. However, provision of information alone does not seem to be an adequate means of enhancing performance. The role of performance strategies in cognitive impairment in depression is discussed, both in terms of initiating use of such strategies and carrying these out efficiently.

Adult↗