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PubMed2004

Response of B-type natriuretic peptide to exercise in hypertensive patients with suspected diastolic heart failure: correlation with cardiac function, hemodynamics, and workload.

BACKGROUND: Diastolic heart failure (DHF) is characterized by dyspnea due to increased left ventricular (LV) filling pressures during stress. We sought the relationship of exercise-induced increases in B-type natriuretic peptide (BNP) to LV filling pressures and parameters of cardiovascular performance in suspected DHF. METHODS: Twenty-six treated hypertensive patients with suspected DHF (exertional dyspnea, LV ejection fraction >50%, and diastolic dysfunction) underwent maximal exercise echocardiography using the Bruce protocol. BNP, transmitral Doppler, and tissue Doppler for systolic (Sa) and early (Ea) and late (Aa) diastolic mitral annular velocities were obtained at rest and peak stress. LV filling pressures were estimated with E/Ea ratios. RESULTS: Resting BNP correlated with resting pulse pressure (r=0.45, P=0.02). Maximal exercise performance (4.6 +/- 2.5min) was limited by dyspnea. Blood pressure increased with exercise (from 143 +/- 19/88 +/- 8 to 191 +/- 22/ 90 +/- 10 mm Hg); 13 patients (50%) had a hypertensive response. Peak exercise BNP correlated with peak transmitral E velocity (r = 0.41, P <.05) and peak heart rate (r = -0.40, P <.05). BNP increased with exercise (from 48 +/- 57 to 74 +/- 97 pg/mL, P =.007), and the increment of BNP with exercise was associated with maximal workload and peak exercise Sa, Ea, and Aa (P <.01 for all). Filling pressures, approximated by lateral E/Ea ratio, increased with exercise (7.7 +/- 2.0 to 10.0 +/- 4.8, P <.01). BNP was higher in patients with possibly elevated filling pressures at peak exercise (E/Ea >10) compared to those with normal pressures (123 +/- 124 vs 45 +/- 71 pg/mL, P =.027). CONCLUSIONS: Augmentation of BNP with exercise in hypertensive patients with suspected DHF is associated with better exercise capacity, LV systolic and diastolic function, and left atrial function. Peak exercise BNP levels may identify exercise-induced elevation of filling pressures in DHF.

Atrial Function, Left↗
PubMed2005

Is it possible to reduce endoscopy workload using age, alarm symptoms and H. pylori as predictors of peptic ulcer and oesophagogastric cancers?

OBJECTIVES: We examined referrals to oesophagogastroduodenoscopy and the impact of demographic and clinical variables to predict major findings (peptic ulcer, cancer) on oesophagogastroduodenoscopy. METHODS: We collected data on 3669 consecutive patients referred for oesophagogastroduodenoscopy. RESULTS: Dyspeptic and reflux symptoms constituted 80% of oesophagogastroduodenoscopy referrals. A major finding was observed in 419 patients (11.4%). The mean age of cancer patients was 72.7 years (95% confidence interval (CI) 70.0-76.5 years) and that of peptic ulcer patients 62.0 years (95% CI 60.5-63.5 years). Independent risk factors for a major finding were age >50 years (odds ratio (OR) 1.62, 95% CI 1.24-2.10), male sex (OR 1.38, 95% CI 1.11-1.72), ulcer-type pain (OR 2.33, 95% CI 1.80-3.02), weight loss (OR 1.70, 95% CI 1.14-2.53), anaemia (OR 1.82, 95% CI 1.38-2.40), bleeding symptoms (OR 3.27, 95% CI 2.26-4.75) and Helicobacter pylori (OR 2.49, 95% CI 2.00-3.11), whereas reflux symptoms were protective (OR 0.73, 95% CI 0.53-1.00). The area under receiver operating characteristic curve of age over 50 years with alarm symptoms to predict major finding was 0.68 (95% CI 0.65-0.71), which positive H. pylori status increased to 0.71 (95% CI 0.69-0.74). Of the major findings, 87.2% were detected in patients with risk factors. Major findings were detected in 15.1% patients with and 8.1% (p < 0.001) without alarm symptoms. CONCLUSIONS: Dyspeptic and reflux symptoms constitute the majority of oesophagogastroduodenoscopy workload. Discriminative power of alarm symptoms even with positive H. pylori status to detect peptic ulcer or cancer was low. Because of their low cancer risk, reflux and dyspeptic patients younger than 50 years can be treated without oesophagogastroduodenoscopy.

Age Factors↗
PubMed2006

Calcium-mediated coupling between mitochondrial substrate dehydrogenation and cardiac workload in single guinea-pig ventricular myocytes.

We measured mitochondrial NADH autofluorescence or Ca(2+) using Rhod-2, simultaneously with cell shortening in isolated guinea-pig ventricular myocytes. When both frequency and amplitude of twitch shortening (work intensity) were increased by raising stimulus frequency in incremental steps from 0.1 to 3.3 Hz, the steady level of NADH signal increased in a frequency-dependent manner. Mitochondrial Ca(2+) also increased with increasing work intensity. Applying Ru360, an inhibitor of mitochondrial Ca(2+) uniporter, largely attenuated the response of both NADH fluorescence and mitochondrial Ca(2+). The increase in mitochondrial Ca(2+) was slow with t(1/2)=~12 s and no obvious cyclic changes were observed in the NADH signal. When a step change from 0.1 to 3.3 Hz stimulation was applied, the NADH signal first decreased to 83% and then increased to 155% of the control level. Upon returning to 0.1 Hz, the NADH signal showed an overshoot before declining to the control level. The biphasic onset time course was well explained by the delayed Ca(2+) activation of the substrate dehydrogenation superimposed on the feedback control of the ATP synthesis, while the offset time course with a delayed deactivation of dehydrogenation. A computer simulation using an oxidative phosphorylation linked to the cardiac excitation contraction model well reconstructed the response of NADH. This model simulation predicts that the activation of substrate dehydrogenation provides ~23% of driving force of the ATP synthesis to meet the increased workload induced by the jump of stimulus from 0.1 to 3.3 Hz, and remaining ~77% is supplied by the feedback control.

Animals↗
PubMed1978

A study of factors affecting laboratory workload.

1. The use of a mathematical modelling technique is described. The factors influencing the day to day variation in laboratory workload were investigated to provide for accurate management forecasts. Analysis by linear stepwise regression showed that a potentially controllable factor the clinician ordering habits, accounted more significantly in this variation than less controllable factors such as admissions, routine and acute, total occupied beds and public holidays. 2. The significant factors remained valid after a review period of one year.

Laboratories↗
PubMed2003

Physiological state model for human ergonomic workload.

Twenty ergonomic tasks were evaluated in which human operators performed mixed static work and dynamic work. Steady-state physiological data are the input into a model as regressor variables, which are then multiplied by the respective regressor coefficients. The resultant physiological state model output is a single response variable that represents the workload. Mixed stepping regression techniques were utilized to calculate the regressor coefficients. Ten physiological state model equations resulted. A lower order equation (with three regressor variables) accounted for 80% of the observed variance. The highest order equation (with ten regressor variables) accounted for 89% of the variance.

Computer Simulation↗
PubMed1999

Slowed cognitive processing and high workload in Parkinson's disease.

It is suggested that cognitive slowing in Parkinson's disease (PD) may be evident on a task with high cognitive load. This hypothesis was tested using a workload design with a progressive increase in task difficulty, on a group of Parkinson patients and normal controls. Using measures of Reaction Time (RT) and Event Related Potentials (ERP), results showed that RT and ERP waveforms increased in line with task difficulty. The RT data was not significantly different between groups but the ERP showed a much reduced P300 in the patient group. These results are indicative of cognitive slowing in PD, at the stage of stimulus evaluation but not for response selection. An interpretation of the literature in terms of reduced activation in relation to cognitive slowing is discussed.

Adult↗
PubMed2005

The effects of a high carbohydrate diet on cortisol and salivary immunoglobulin A (s-IgA) during a period of increase exercise workload amongst Olympic and Ironman triathletes.

The present study observed the effects of a 6-day high carbohydrate (H-CHO) diet on salivary cortisol and IgA during a period of increased exercise workload. Thirty-two competitively trained male triathletes were randomly allocated into a self-selected (SS), or an H-CHO (12 g CHO kgbm (-1) . day (-1)) dietary group. In addition to their training regimes, all subjects performed a 1-hour running exercise bout at 70 % V.O (2max) . d (-1), for six days. Saliva samples were taken pre, immediately post, and morning post-exercise bout on days 1, 4, and 6. The concentrations of s-IgA and cortisol were determined by ELISA assays. There was a significant (p < 0.001) interaction between Group x Time for cortisol, with a marked increase in concentrations occurring in the SS dietary group pre to post exercise, and pre to morning post-exercise (p < 0.01). Conversely, a significant (p = 0.009) Group x Time interaction reflected higher post exercise s-IgA concentrations (p < 0.005) than pre exercise in the H-CHO diet group. Blood glucose concentration decreased pre to post exercise in the SS diet group (p < 0.01), whilst remaining stable in the H-CHO group. It is concluded that the consumption of a high CHO diet throughout a 6-day period of overtraining had a favourable effect on markers of immune activity and thereby reduced the susceptibility of these endurance athletes to upper respiratory tract infection URTI.

Adult↗
PubMed1991

An examination of the hemodynamic and metabolic effects of carteolol during different workloads on a bicycle ergometer.

The influence of 10 mg carteolol/day on the serum concentrations of insulin, C-peptide, glucagon, free fatty acids, adrenaline, noradrenaline, blood glucose, blood lactate levels, on heart rate and systolic blood pressure was investigated during different workloads on a bicycle ergometer in a placebo-controlled randomised double-blind study involving twelve male volunteers. The subjects performed standardized increasing exercises until subjective exhaustion as well as three 40-minute endurance exercises of varying intensity, corresponding to a lactate concentration of 1.0 to 2.0 mmol/l, 2.5 to 3.5 mmol/l and more than 3.5 mmol/l in the region of the anaerobic threshold, each exercise being followed by one rest day. The most important findings are: --the ISA of carteolol is of significance for the influence on the heart rate at rest but plays a minor role with respect to the degree of reduction in the heart rate and blood pressure under exercise; --carteolol exerts a minor influence on the metabolic parameters investigated in this study. This can be partly ascribed to the pronounced ISA of carteolol. In the case of endurance exercises, which lead to blood lactate concentrations of more than 3 mmol/l, the blood glucose levels showed a tendency to decrease. However, this was not statistically significant.

Adult↗
PubMed2003

A study on the student pilot's mental workload due to personality types of both instructor and student.

The main purpose of this paper is to provide the ideal flight crew combination for instructor and student pilots in order to enhance the flight training effects based on Myers Briggs Type Indicator (MBTI) theory. In addition to personality, various levels of flight difficulty are considered in order to investigate their potential interaction effect in terms of student pilots' mental workload measured in heart rate, altitude deviation, NASA-TLX (Task Load Index) and subjective degree of personality harmony. Based on an experiment performed in a real flight situation, we found significant effects of personality combinations in terms of all four outcome measures. Both group C types of instructors and students who are concrete, realistic and have mechanical skills turn out to be the ideal flight crew combination. A structural equation model, fitted to analyse causality among the four response variables, implied that as the heart rate increased, the altitude deviation increased. In addition, as the altitude deviation and personality harmony increased, NASA-TLX increased. The results of this study are expected to provide a theoretical basis for manning the flight crew combinations and thereby enhancing the efficiency of flight training.

Aviation↗
PubMed2004

Distraction from multiple in-vehicle secondary tasks: vehicle performance and mental workload implications.

This study investigates the impact of multiple in-vehicle information systems on the driver. It was undertaken using a high fidelity driving simulator. The participants experienced, paced and unpaced single tasks, multiple secondary tasks and an equal period of 'normal' driving. Results indicate that the interaction with secondary tasks led to significant compensatory speed reductions. Multiple secondary tasks were shown to have a detrimental affect on vehicle performance with significantly reduced headways and increased brake pressure being found. The drivers reported interaction with the multiple in-vehicle systems to significantly impose more subjective mental workload than either a single secondary task or 'normal driving'. The implications of these findings and the need to integrate and manage complex in-vehicle information systems are discussed.

Adolescent↗
PubMed1990

The physical and physiological workload of refuse collectors.

In order to secure a safer and healthy work situation, the heavy physical loads imposed on 23 refuse collectors (aged 26-54) working in the city of Haarlem, in The Netherlands, were studied in a series of three experiments between 1984 and 1987. The aims were respectively (1) to study the load for workers collecting dustbins or polythene bags; (2) to introduce changes to reduce the load to avoid exceeding the overload criteria by individual refuse collectors; and (3) to investigate the effects of interventions to improve the efficiency of refuse collecting. The maximal isometric lifting force (Fmax) and the maximal aerobic power (VO2max) of 23 refuse collectors were measured in the laboratory. Fmax was measured with an isometric dynamometer pulling with one arm from the floor; the mean value was 912 (+/- 127)N. VO2max was measured running on a treadmill; the mean value was 43.3 (+/- 0.8)ml O2 per kg body mass per min. The physical load on the oxygen transport system was measured through work analysis and by a continuous registration of the heart rate over three working days. Criteria for overload were set at a mean external load of 20% Fmax and a mean energy expenditure of 30% VO2max and an energy expenditure of 50% VO2max or more for a maximum of 60 min per day. Replacement of dustbins by polythene bags resulted in a 70% increase in the total amount of refuse collected, an increase in throwing frequency, but a lower mean load per throw, and no significant differences in the mean heart rate over the working day. When polythene bags were used the mean values did not exceed the overload criteria, but 39% of the individual collectors did have a workload that was too high with respect to one of the criteria. In the last experiment the collectors were advised to reduce their work load by (a) lifting no more than two bags at a time; (b) reducing their walking pace; and (c) taking more breaks. Although compliance with the recommendations was good, and the weight lifted and the walking speed decreased, the physiological load remained the same. This may have been caused by a 15% increase in the total amount of refuse that had to be collected at that time.

Adult↗
PubMed1990

Observations of working postures in garages using the Ovako Working posture Analysing System (OWAS) and consequent workload reduction recommendations.

The working postures of mechanics (n = 84) in 42 garages were observed using the Ovako Working posture Analysis System (OWAS). During observation, both working postures and work activities were recorded. A computer program was developed for the data analyses. Using this program it is possible to calculate the working posture load for each work activity and the contribution of a specific activity to the total working posture load. This is a substantial extension of the original OWAS method. Five out of 19 observed postures of the body members were classified as Action Category 2, which suggests they were slightly harmful to the musculoskeletal system and likely to cause discomfort. Of the so-called typical working postures, 31.9% was classified in Action Category 2, suggesting that during a substantial part of the working day typical working postures occur which are at least slightly harmful to the musculoskeletal system. Moreover, those work activities principally causing the workload to fall in OWAS' higher Action Categories were identified. For each of these three work activities an alternative work method was observed. The data show that in all three work activities the use of a vehicle lift reduces the number of poor working postures thereby reducing the load on the musculoskeletal system.

Accidents, Occupational↗
PubMed1998

A comparison of factor analytic methods of obtaining cardiovascular autonomic components for the assessment of mental workload.

The diagnosticity of heart rate for mental workload assessment can be improved with an autonomic space model of sympathetic and parasympathetic nervous system influences on the heart. Methods of deriving autonomic components to estimate the underlying sympathetic and parasympathetic activity needed to identify autonomic modes of control for heart period were examined. Alternative factor extraction and rotation methods were compared using data from a laboratory study that measured the electrocardiogram and impedance cardiogram simultaneously. Principal components analysis with varimax rotation was found to validly estimate the sympathetic and parasympathetic activity when computed on multiple psychophysiological measures obtained from raw EKG data. Use of the method was illustrated with single and dual mental arithmetic and second-order compensatory manual tracking tasks. Different autonomic modes of control were found for divided attention that were not evident in heart period. Uncoupled sympathetic activation was indicated for divided attention when the mental arithmetic tasks were added to the tracking single tasks, but uncoupled parasympathetic inhibition was indicated for divided attention when the tracking tasks were added to the mental arithmetic single tasks.

Adult↗
PubMed1982

Workload, space, and personnel of clinical chemistry laboratories in teaching hospitals.

The resources needed to operate a clinical chemistry laboratory are known only as rough approximations. In order to gather more information about these resources, a 13-page questionnaire was completed by 50 pathology departments of which 38 departments provided adequate information about their clinical chemistry section to permit adequate data analysis. This study provides the results for resource and workload factors, and significant regression analyses among these factors for the whole clinical chemistry section and the subsections of general chemistry, urinalysis, endocrinology, enzymology, lipid analysis, and toxicology. These data provide a basis for evaluating the current needs of clinical chemistry and for making projections for the future.

Chemistry, Clinical↗
PubMed1977

'Workload' and risk of myocardial infarction--a prospective psychosocial analysis.

The study group consisted of 5187 building construction workers aged 41-61 in Greater Stockholm who had all responded to a psychosocial questionnaire and had been in full-time work without long-lasting illness episodes in the year before the study. A factor analysis of about 60 psychosocial variables was performed, and on this basis three indices were formed. The study group was followed for two years in official registers yielding information on morbidity and mortality. The 'workload' index was demonstrated to be significantly associated with subsequent risk of myocardial infarction.

Adult↗
PubMed1997

Rheumatology out-patient workload increases inexorably.

Rheumatology out-patient consultations in the south-west of England from 1 to 30 November 1994 were recorded by standard methods and compared to 1988, 1990, 1991 and 1992. Historical records at one centre provided additional detailed information. There has been an overall increase of 31% in the number of patients seen (30% for follow-up cases, 36% for new referrals), but the mean waiting time for new patient consultations increased from 65 to 108 days. The proportion of new patient consultations with non-arthritic diseases increased by 8.2%, and those with rheumatoid arthritis and polyarthritis decreased by 9.0%. Variation in discharge rates and length of follow-up appointments occurred, but mostly in uncommon diagnostic categories. Referral rates have been rising faster since the introduction of National Health Service reforms than can be accommodated by the increased workload undertaken.

Ambulatory Care↗
PubMedDate not supplied

Dynamic cardiomyoplasty decreases myocardial workload as assessed by tissue tagged MRI.

The effects of dynamic cardiomyoplasty (CMP) on global and regional left ventricular (LV) function in end-stage heart failure still remain unclear. MRI with tissue-tagging is a novel tool for studying intramyocardial motion and mechanics. To date, no studies have attempted to use MRI to simultaneously study global and regional cardiac function in a model of CMP. In this study, we used MRI with tissue-tagging and a custom designed MR compatible muscle stimulating/pressure monitoring system to assess long axis regional strain and displacement variations, as well as changes in global LV function in a model of dynamic cardiomyoplasty. Three dogs underwent rapid ventricular pacing (RVP; 215 BPM) for 10 weeks; after 4 weeks of RVP, a left posterior CMP was performed. After 1 year of dynamic muscle stimulation, the dogs were imaged in a 1.5 T clinical MR scanner. Unstimulated and muscle stimulated tagged long axis images were acquired. Quantitative 2-D regional image analysis was performed by dividing the hearts into three regions: apical, septal, and lateral. Maximum and minimum principal strains (lambda, and lambda2) and displacement (D) were determined and pooled for each region. MR LV pressure-volume (PV) loops were also generated. Muscle stimulation produced a leftward shift of the PV loops in two of the three dogs, and an increase in the peak LV pressure, while stroke volume remained unchanged. With stimulation, lambda1 decreased significantly (p<0.05) in the lateral region, whereas lambda2 increased significantly (p<0.05) in both the lateral and apical regions, indicating a decrease in strain resulting from stimulation. D only increased significantly (p<0.05) in the apical region. The decrease in strain between unassisted and assisted states indicates the heart is performing less work, while maintaining stroke volume and increasing peak LV pressure. These findings demonstrate that the muscle wrap functions as an active assist, decreasing the workload of the heart, while preserving total pump performance.

Animals↗