A large population study to assess the magnitude of prenatal programming in dairy cattle.

The performance of an adult dairy cow may be influenced by events that occur before her birth. The present study investigated potential effects of 2 prenatal groups of factors, Assisted Reproductive Techniques (ART) and maternal characteristics (e.g., dam parity), on offspring performance during their first lactation, in populations of 2 dairy cow breeds: French Holstein and Montbéliarde. The different ART studied included the type of semen (conventional or X-sorted) used for Artificial Insemination (AI) and the technology of conception used (AI, embryo transfer, or in vitro fertilization). Three maternal characteristics were considered: (1) the dam age at first calving, (2) dam parity number, and (3) indicators of dam udder health during gestation (somatic cell score and events of clinical mastitis). First, we investigated whether heifer survival from 3d to 18 mo old was associated with any of the prenatal factors considered. We then estimated the associations of these prenatal factors with 8 traits of commercial interest: (1) stature, (2-4) milk, fat, and protein yields, (5) somatic cell score, (6) clinical mastitis, and (7-8) heifer and cow conception rate, all measured on genotyped cows. Linear models were used for this study with the prenatal factors as covariates in the model, and for the 8 traits, phenotypes were adjusted for their corresponding genomic estimated breeding value. The results indicated that the survival rate of heifers born from embryo transfer was significantly higher than that of heifers born from AI (probably due to preferential management practices), while the other prenatal factors did not explain differences in heifer survival. Among the Montbéliarde cows born from AI, those born from X-sorted semen showed a lightly but significantly lower milk yield than those born without X-sorting of the semen (-52 kg of milk in the first lactation). Among the Holstein cows, those born from embryo transfer presented significantly lower milk performance than cows born from AI. Regarding the maternal characteristics, none or very weak associations were found between the dam age at first calving and the offspring performance in both breeds. Dam parity, on the other hand, was associated with offspring performance for milk, fat, and protein yield in both breeds, however not in the same direction. In the Holstein breed, an increase in dam parity was favorable for offspring performance for milk, fat, and protein yield, whereas in the Montbéliarde breed, an increase in dam parity was associated with lower milk and protein yield and no association was found for fat yield. The udder health of the dam during gestation was not or only weakly associated with the traits studied in the offspring. Although some significant associations were identified due to the large sample size, the effects were modest, typically less than 1% of the phenotypic mean, and were not consistently observed across the 2 breeds.

Determination of immunoglobulin concentrations and genetic parameters for colostrum and calf serum in Charolais animals.

Colostrum samples from 366 Charolais primiparous cows, as well as serum from their calves at 24 to 48 h of age, were collected to gain an overview of the situation regarding passive immune transfer in beef cattle, from both the phenotypic and genetic points of view. All samples were analyzed to quantify their G1 immunoglobulins by radial immunodiffusion (RID) and their IgG, IgA, and IgM using ELISA. The average concentrations obtained in colostrum were 84 mg/mL for RID-IgG1, and 158 mg/mL, 4.5 mg/mL and 10.8 mg/mL for ELISA-IgG, -IgA, and -IgM, respectively. The corresponding values in calf serum were 19.9, 30.6, 1.0, and 1.9 mg/mL. Apart from the general environmental effect (farm-year combination and laboratory conditions), the characteristics of the dams tested did not reveal any influence on colostrum immunoglobulin concentrations. Calving difficulty, as well as the birth weight and sex of calves, were found to be associated with serum concentrations in some cases. Heritability estimates were low to moderate, with the highest being for RID-IgG1 in colostrum (h2 = 0.28, standard error = 0.14) and serum (h2 = 0.36, standard error = 0.18). Phenotypic correlations among the different immunoglobulins were generally positive or null, and none of the genetic correlations were significant due to large standard errors. The phenotypic correlation between dam colostrum and calf serum values was 0.2 for RID-IgG1 and null for the 3 ELISA measurements. The correlation between RID-IgG1 and ELISA-IgG was, unexpectedly, null for colostrum and 0.4 for serum. Increased RID-IgG1 levels in calf serum were associated with improved survival, as well as better early growth and fewer health problems. These results thus showed that despite generally higher concentrations in beef than in dairy cattle, passive transfer was unsuccessful in a considerable number of calves. This should be brought to the attention of breeders to avoid negative effects on survival and subsequent performance. The heritability estimates were encouraging; however, obtaining phenotypes on a large scale constitutes a real limitation regarding these traits.

Minimizing the duration of laser Doppler flowmetry recordings while maintaining wavelet analysis quality: A methodological study.

Recording oscillations in cutaneous blood perfusion using laser Doppler flowmetry (LDF) is of common use in clinical research, due, mainly, to its non-invasive nature. Detailed information about the vascular tone in different frequency bands and the related physiologic compartment can be inferred from wavelet analysis (WA) of an LDF signal. However, little is known about the minimal recording duration required to generate a proper representation of the frequency content of such signals. To address this question, the three lowest frequency bands (i.e. myogenic, neurogenic and endothelial) of the LDF wavelet power spectrum were studied to define the shortest recording duration needed to perform a quality WA. Sixty-five healthy participants were included for 20 min of basal LDF recording on forearm and dorsum of the foot. Recordings were short cut every minute and compared to the 20-min reference recording that is generally used in the literature. Our results indicate that minimum 10 min recordings are required for analysis of myogenic events, whatever the anatomical site. On the forearm, LDF recordings lengths should be at least 15 min and 10 min for the neurogenic and endothelial bands, respectively. On the foot, 13 min of LDF recording is required to assess neurogenic and endothelial bands. Depending on the aim of any given study involving healthy subjects, LDF recordings need to last at least 15 min on forearm and 13 min on the foot to maintain a quality WA on low-frequency bands.

QT interval measurement and correction in patients with atrial flutter: a pilot study.

BACKGROUND AND PURPOSE: Measurement of QT intervals during atrial flutter (AFL) is relevant to monitor the safety of drug delivery. Our aim is to compare QT and QTc intervals in AFL patients before and after catheter ablation in order to validate QT measurement during AFL. METHODS: 25 patients suffering from AFL underwent catheter ablation; 9 were in sinus rhythm and 16 were in AFL at the time of the procedure. Holter ECGs were continuously recorded before, during and after the procedure. In AFL signals, flutter waves were subtracted using a previously-validated deconvolution-based method. Fridericia's QTc was computed before and after ablation after hysteresis reduction. RESULTS: Comparing QTc values obtained before and after ablation showed that (1) the intervention did not significantly affect QTc, and (2) the QTc during AFL was concordant with the QTc value in sinus rhythm. CONCLUSION: QTc can be reliably measured in patients with AFL using flutter wave subtraction and hysteresis reduction.

Vascular reactivity at rest and during exercise in middle-aged obese men: effects of short-term, low-intensity, exercise training.

OBJECTIVE: Although increased blood flow (BF) in exercising muscles is thought to be impaired in obese subjects and may contribute to physical inactivity, data are scarce in this regard and the involvement of endothelium dysfunction remains partly hypothetical. METHODS: A total of 16 middle-aged obese men (body mass index, BMI ≥ 30 kg m(-2)) and 16 normal-weight men (BMI<25 kg m(-2)), matched for age, were recruited. We used ultrasonography to compare intima-media thickness (IMT) and distensibility of the carotid artery, flow-mediated dilation (FMD), nitrate-dependent dilation (NDD) and peak BF during post-ischemic hyperemia in the brachial artery (a conduit artery), and leg BF during knee-extensor exercise (indicative of resistance vessel function) in obese and in normal-weight men. In addition, 10 obese men participated in an 8 week individualized low-intensity training program. RESULTS: Compared with normal-weight men, obese men had higher carotid IMT (0.50 ± 0.01 vs 0.62 ± 0.04 mm, P < 0.05) but lower carotid distensibility (0.26 ± 0.03 vs 0.11 ± 0.03 mm Hg(-1) 10(-2), P < 0.05), FMD (5.7 ± 0.4 vs 3.3 ± 0.5%, P < 0.05) and peak BF during post-ischemic hyperemia (398 ± 52 vs 229 ± 24%, P < 0.05), despite similar maximal shear rate, without NDD differences. Lower limb BF (ml min(-1) 100 g(-1)) increased significantly from rest to maximal exercise in both groups with lower values in obese men (at peak power, 36.9 ± 1.6 vs 31.5+2.2 ml min(-1) 100 g(-1), P < 0.05). Exercise training normalized carotid distensibility (0.14 ± 0.04 before vs 0.23 ± 0.03 mm Hg(-1) 10(-2) after training, P = 0.09) and FMD (2.7 ± 0.4 before vs 4.8 ± 0.5% after training, P < 0.05), but did not improve brachial post-ischemic peak BF or exercising leg BF. CONCLUSIONS: In obese men, conduit and resistance vessel reactivity is depressed, but a short-term low-intensity exercise training improves distensibility and endothelium dependent vasodilation in the large conduit artery, but not post ischemic or exercise muscle BF.

Abnormal vascular reactivity at rest and exercise in obese boys.

BACKGROUND: Obese children exhibit vascular disorders at rest depending on their pubertal status, degree of obesity, and level of insulin resistance. However, data regarding their vascular function during exercise remain scarce. The aims of the present study were to evaluate vascular morphology and function at rest, and lower limb blood flow during exercise, in prepubertal boys with mild-to-moderate obesity and in lean controls. MATERIALS AND METHODS: Twelve moderately obese prepubertal boys [Body Mass Index (BMI: 23.9+/-2.6 kg m(-2))] and thirteen controls (BMI:17.4+/-1.8 kg m(-2)), matched for age (mean age: 11.6+/-0.6 years) were recruited. We measured carotid intima-media thickness (IMT) and wall compliance and incremental elastic modulus, resting brachial flow-mediated dilation (FMD) and nitrate-dependent dilation (NDD), lower limb blood flow during local knee-extensor incremental and maximal exercise, body fat content (DEXA), blood pressure, blood lipids, insulin and glucose. RESULTS: Compared to lean controls, obese boys had greater IMT (0.47+/-0.06 vs. 0.42+/-0.03 mm, P<0.05) but lower FMD (4.6+/-2.8 vs. 8.8+/-3.2%, P<0.01) in spite of similar maximal shear rate, without NDD differences. Lower limb blood flow (mL min(-1).100 g(-1)) increased significantly from rest to maximal exercise in both groups, although obese children reached lower values than lean counterparts whatever the exercise intensity. CONCLUSIONS: Mild-to-moderate obesity in prepubertal boys without insulin resistance is associated with impaired endothelial function and blunted muscle perfusion response to local dynamic exercise without alteration of vascular smooth muscle reactivity.

Genetic analysis of calf health in Charolais beef cattle.

The objective of this study was to investigate the factors that influence calf health and survival in Charolais cattle. Data from 2,740 calves, originating from 16 French farms and observed from birth until 30 d of age, were analyzed using models that took account of direct genetic, maternal genetic, and common environmental effects. Both direct and maternal genetic parameters were estimated for birth weight (BW), calving ease (CE), neonatal vitality (NV), survival at 30 d (Surv), and umbilical infection and diarrhea at different ages (0 to 5 d: Umb1 and Diar1; 6 to 20 d: Umb2 and Diar2; and 21 to 30 d: Umb3 and Diar3). The heritability values for direct and maternal genetic effects were, 0.026 (SE = 0.027) and 0.096 (SE = 0.042) for Surv, 0.280 (SE = 0.063) and 0.063 (SE = 0.038) for BW, 0.129 (SE = 0.041) and 0 for CE, 0.073 (SE = 0.035) and 0 for NV, 0.071 (SE = 0.038) and 0.017 (SE = 0.026) for Umb1, 0 and 0.082 (SE = 0.029) for Umb2, 0 and 0.044 (SE = 0.030) for Diar1, 0.016 (SE = 0.022) and 0.012 (SE = 0.026) for Diar2, and 0.016 (SE = 0.028) and 0 for Diar3, respectively. Significant genetic variability in beef cattle was thus revealed for five calf health traits: NV, Surv, Diar1, Umb1, and Umb2. In addition, for three traits (Surv, Diar1, and Umb2), maternal genetic effects clearly contributed more to health performance than direct genetic effects. Estimates of genetic correlation between traits varied markedly (from 0 to 1 in absolute values) depending on the traits in question, the age for a given trait, and the type (direct or maternal) of the genetic effects considered. These results suggest that not all health traits in Charolais cattle can be improved simultaneously, and breeders will therefore have to prioritize certain traits of interest in their breeding objectives. Overall, our results demonstrate the potential utility of collecting and integrating data on calf diseases, NV and survival in future beef cattle breeding programs. To ensure appropriate biological and genetic evaluations of calf health performance, it is important to accurately describe the phenotypes for diarrhea and umbilical infections (in terms of age ranges) and account for maternal genetic and common environmental effects that explain calf health performance traits. Further investigation and improved data collection are now necessary to maximize the efficiency of breeding schemes designed to simultaneously improve production and health traits.

Corticosteroid-induced osteoporosis in children: outcome after two-year follow-up, risk factors, densitometric predictive cut-off values for vertebral fractures.

OBJECTIVE: To identify factors that contribute to a decreased Z score of volumetric spine bone mineral density (ZvSBMD) and the development of vertebral fractures (VF) in children receiving chronic systemic corticosteroid therapy (SCT); to describe their outcome after 2 years, and to define predictive threshold values for ZvSBMD for VF. METHODS: Fifty-five children on SCT for >or= 6 months were prospectively followed for 2 years. In children with a ZvSBMD > -1.5, we prescribed preventive measures for osteoporosis and densitometry annually. In children with ZvSBMD

Development and implementation of a participative intervention to improve the psychosocial work environment and mental health in an acute care hospital.

OBJECTIVES: To describe the development and implementation phases of a participative intervention aimed at reducing four theory grounded and empirically supported adverse psychosocial work factors (high psychological demands, low decision latitude, low social support, and low reward), and their mental health effects. METHODS: The intervention was realised among 500 care providers in an acute care hospital. A prior risk evaluation was performed, using a quantitative approach, to determine the prevalence of adverse psychosocial work factors and of psychological distress in the hospital compared to an appropriate reference population. In addition, a qualitative approach included observation in the care units, interviews with key informants, and collaborative work with an intervention team (IT) including all stakeholders. RESULTS: The prior risk evaluation showed a high prevalence of adverse psychosocial factors and psychological distress among care providers compared to a representative sample of workers from the general population. Psychosocial variables at work associated with psychological distress in the prior risk evaluation were high psychological demands (prevalence ratio (PR) = 2.27), low social support from supervisors and co-workers (PR = 1.35), low reward (PR = 2.92), and effort-reward imbalance (PR = 2.65). These results showed the empirical relevance of an intervention on the four selected adverse psychosocial factors among care providers. Qualitative methods permitted the identification of 56 adverse conditions and of their solutions. Targets of intervention were related to team work and team spirit, staffing processes, work organisation, training, communication, and ergonomy. CONCLUSION: This study adds to the scarce literature describing the development and implementation of preventive intervention aimed at reducing psychosocial factors at work and their health effects. Even if adverse conditions in the psychosocial environment and solutions identified in this study may be specific to the healthcare sector, the intervention process used (participative problem solving) appears highly exportable to other work organisations.

Effectiveness of a participative intervention on psychosocial work factors to prevent mental health problems in a hospital setting.

OBJECTIVES: To assess the effectiveness of a workplace intervention aimed at reducing adverse psychosocial work factors (psychological demands, decision latitude, social support, and effort-reward imbalance) and mental health problems among care providers. METHODS: A quasi-experimental design with a control group was used. Pre-intervention (71% response rate), and one-year post-intervention measures (69% response rate) were collected by telephone interviews. RESULTS: One year after the intervention, there was a reduction of several adverse psychosocial factors in the experimental group, whereas no such reduction was found in the control group. However, there was a significant deterioration of decision latitude and social support from supervisors in both experimental and control groups. There was also a significant reduction in sleeping problems and work related burnout in the experimental hospital, whereas only sleeping problems decreased in the control group while both client related and personal burnout increased in this hospital. The comparison between the experimental and control groups, after adjusting for pre-intervention measures, showed a significant difference in the means of all psychosocial factors except decision latitude. All other factors were better in the experimental group. CONCLUSION: Results suggest positive effects of the intervention, even though only 12 months have passed since the beginning of the intervention. Follow up at 36 months is necessary to evaluate whether observed effects are maintained over time. In light of these results, we believe that continuing the participative process in the experimental hospital will foster the achievement of a more important reduction of adverse psychosocial factors at work. It is expected that the intensity of the intervention will be directly related to its beneficial effects. Long term effects will however depend on the willingness of management and of staff to appropriate the process of identifying what contributes to adverse psychosocial factors at work and to adopt means to reduce them.

Reproducibility of automated pulse wave velocity measurement during exercise. Running head: pulse wave velocity during exercise.

Pulse wave velocity measurement is used as an index of arterial stiffness. The purpose was to evaluate the reproducibility of pulse wave velocity measurement at rest, during exercise and recovery from exercise, using an automated device. Twelve healthy young adults (mean age 22.0 +/- 3.1 yrs) underwent an upright submaximal cycle test on two separate occasions, one week apart. Pulse wave velocity, systolic and diastolic blood pressures and heart rate were assessed at rest, during the last 2 min of exercise and 10 min later. Pulse wave velocity was measured on the upper limb and the forearm by the cross-correlation function of photoplethysmography and Doppler signals. Brachial artery pulse wave velocity was calculated from upper limb and forearm pulse wave velocities. No significant difference was found on duplicate measurements of heart rate, systolic and diastolic blood pressures at rest, during exercise and recovery, showing that pulse wave velocity was measured under similar conditions. Coefficient of variation for upper limb and forearm pulse wave velocities ranged from 2.9 to 5.9% at rest and during recovery, and were respectively 2.9% and 8.3% during exercise. However, coefficient of variation for brachial pulse wave velocity was 7.7 and 10.3% at rest, 15.7% during exercise, and 5.8% during recovery. During exercise, pulse wave velocity measurements were satisfying, but indirect assessment of brachial artery pulse wave velocity showed poor reproducibility. Thus, upper limb and forearm pulse wave velocities may be used during exercise to assess the effect of training or drugs on arterial wall mechanical properties.

Effects of dietary polyphenols on metabolic syndrome features in humans: a systematic review.

Dietary polyphenols constitute a large family of bioactive substances potential beneficial effect on metabolic syndrome (MetS). This review summarizes the results of clinical studies on patients with MetS involving the chronic supplementation of a polyphenol-rich diet, foods, extracts or with single phenolics on the features of MetS (obesity, dyslipidemia, blood pressure and glycaemia) and associated complications (oxidative stress and inflammation). Polyphenols were shown to be efficient, especially at higher doses, and there were no specific foods or extracts able to alleviate all the features of MetS. Green tea, however, significantly reduced body mass index and waist circumference and improved lipid metabolism. Cocoa supplementation reduced blood pressure and blood glucose. Soy isoflavones, citrus products, hesperidin and quercetin improved lipid metabolism, whereas cinnamon reduced blood glucose. In numerous clinical studies, antioxidative and anti-inflammatory effects were not significant after polyphenol supplementation in patients with MetS. However, some trials pointed towards an improvement of endothelial function in patients supplemented with cocoa, anthocyanin-rich berries, hesperidin or resveratrol. Therefore, diets rich in polyphenols, such as the Mediterranean diet, which promote the consumption of diverse polyphenol-rich products could be an effective nutritional strategy to improve the health of patients with MetS. © 2016 The Authors. Obesity Reviews published by John Wiley & Sons Ltd on behalf of World Obesity.

Irregular dynamics of excitation in biologic and mathematical models of cardiac cells.

Excitation and impulse propagation in cardiac tissues are dependent on the heart rate and can occur in extremely complex patterns. In this chapter we present the results of Purkinje fiber experiments and of computer simulations using an ionic (Beeler & Reuter) model for the ventricular cell. We have studied the global rate-dependent behavior of cardiac cells through a systematic analysis of their response to single as well as repetitive depolarizing stimuli, and determined the role of nonlinearity in the mechanism(s) of their behaviors. To this end, we devised an analytical difference equation model of cardiac cell excitation which could be used to predict simple as well as chaotic behavior of both the Purkinje fiber and the Beeler & Reuter cell, depending on the stimulation rate. Both experimental and modeling results suggest that the presence of supernormal recovery in cell excitability establishes sufficient nonlinearity so that, during repetitive stimulation, the dynamics of cell response may be regular and predictable when the stimulus magnitude is either very small or very large, or they may be chaotic and very unpredictable when the stimulus magnitude is intermediate. The overall results suggest that the application of nonlinear systems theory to electrophysiology may have importance in the understanding of cardiac rhythm and conduction disturbances, and may have clinical implications as well.

Piecework, repetitive work and medicine use in the clothing industry.

This study was designed to examine the potential effects of severe time constraints on workers' health. Medicine use is considered to be an indicator of non-specific morbidity that is worthy of interest in industrial health research when it is possible to compare workers who share the same culture and socio-economic characteristics, but are submitted to different work conditions. In the clothing industry, our hypotheses were that (1) piecework paid operators would have a higher percentage of medicine users than the hourly paid and (2) operators who did repetitive work would have a higher percentage of medicine users than those who did non-repetitive work. Women selected into the study were between the ages of 45 and 70, natives of Canada, spoke French and lived in the metropolitan region of Montreal. The occupational data came from the files of The Ladies' Clothing Joint Commission. They encompass the 30-year period 1956-85. Data on socio-economic characteristics, smoking status and medicine use of the 800 respondents were obtained by questionnaires administered by specially trained nurses. Among currently employed women, the probability of using stomach medication was higher for pieceworkers than among women who received an hourly wage: OR = 2.57 (1.19-3.96). The probability was also higher for women who did repetitive work than for women who did non-repetitive work: OR = 2.43 (1.26-3.60).

Synchronization and symmetry-breaking bifurcations in constructive networks of coupled chaotic oscillators.

The spatiotemporal dynamics of networks based on a ring of coupled oscillators with regular shortcuts beyond the nearest-neighbor couplings is studied by using master stability equations and numerical simulations. The generic criterion for dynamic synchronization has been extended to arbitrary network topologies with zero row-sum. The symmetry-breaking oscillation patterns that resulted from the Hopf bifurcation from synchronous states are analyzed by the symmetry group theory.

Disability among female garment workers. A comparison with a national sample.

An indicator of permanent disability was used to measure the chronic health problems associated with garment work. The study population comprised 800 female sewing-machine operators employed in the Quebec garment industry between 1976 and 1985. The workers were identified from public agency records. Their disability status was obtained in a personal interview. The disability prevalence of these workers was compared to national disability data of women employed in clerical work, services, and manufacturing industries. The garment workers who had left employment had an increased prevalence of severe disability (in comparison with that of workers who had left other types of employment) and an increased prevalence of moderate and slight disability. Currently employed garment workers had an increased prevalence of moderate and slight disability when compared with workers currently employed in other occupations. The risk ratios remained similarly elevated when the data were adjusted for age and smoking status.

Effect of duration of employment in piecework on severe disability among female garment workers.

This study measured the association between duration of employment in piecework and the prevalence of severe disability among 533 Quebec female garment workers who left employment between 1976 and 1985. Yearly information regarding occupational characteristics was available from a public agency for the 30-year period 1956-1985. Information on disability status was collected in a personal interview. Duration of employment in piecework was associated with the prevalence of severe disability. A multivariate analysis found that the association was independent of age, smoking habits, education, type of task and total length of employment. Workers who spent 5-9, 10-14, 15-19, and greater than or equal to 20 years in piecework had an increased prevalence of severe disability in comparison with the base-line category of 0-4 years. The adjusted risk ratios were 2.2 [95% confidence interval (95% CI) 1.0-4.6], 3.3 (95% CI 1.5-6.9), 3.6 (95% CI 1.5-8.4), and 2.3 (95% CI 0.8-6.6), respectively. The association was particularly strong for disability due to musculoskeletal problems and disability due to cardiovascular disorders although small numbers were involved.

Model study of the spread of electrotonic potential in cardiac tissue.

This model study describes the electrotonic response of a cable model of cardiac tissue stimulated at one point. The stimulus is applied intracellularly in the form of a 2 ms pulse of current of near threshold amplitude. The attenuation of the electrotonic potential with distance and its mode of propagation along the cable are compared for equivalent passive, continuous and discontinuous cables. The three structures have the same basic physical and electrical characteristic and they differ either with respect to being active or passive or to the presence or absence of intercellular gap junctions. In the continuous cable a just subthreshold stimulus produces a local active response which propagates more slowly and is attenuated less rapidly with distance than in a passive cable. The spatial decrement of the local response in a discontinuous cable is faster than in a continuous cable of equal average resistivity. It is suggested that the larger time constant of the foot of the action potential observed in the longitudinal direction in cardiac muscle could be due in part to the electrotonic spread of the local response from the site of stimulation.

[Study of the reproducibility of cardiac output measurement during exercise in pre-pubertal children by doppler echocardiography and CO2 inhalation]. / Etude de la reproductibilité de la mesure du débit cardiaque à l'exercice chez l'enfant prépubère par échocardiographie doppler et par réinhalation de CO2.

Non-invasive measurement of the cardiac output is essential in investigations of healthy children. However, the data concerning the reproducibility of the measurements are very limited. The aim of this study was to assess the reproducibility of the measurement of cardiac output during exercise by Doppler echocardiography and reinhalation of CO2 (extrapolation method). Fourteen pre-pubertal children underwent two similar tests at increasingly intense levels of exercise. The cardiac output was measured at rest and during the last minute of each stepwise increment of exercise. The results show no difference between the cardiac outputs of the two tests, whichever method was used and at all levels of exercise. They also demonstrate a better reproducibility of cardiac output measurement by Doppler echocardiography (coefficient of variation: 7.5% at rest and 5.2% at maximal effort) compared with reinhalation of CO2 (coefficient of variation: 16.8% at rest and 11.7% at maximal effort). Both methods showed better reproducibility on exercise, resulting from smaller variations in heart rate and stroke volume on effort than at rest. The authors conclude that Doppler echocardiography is very accurate and its simplicity makes it the method of choice in pre-pubertal children for measuring cardiac output during exercise.

[Absence from work as an indicator of health: significance, measures and conditions for use]. / L'absence du travail comme indicateur de santé: signification, mesures et conditions d'utilisation.

This paper discusses the use of absence from work for health reasons and particularly absence of long duration as a non specific morbidity indicator in studies of occupational health. Until now, absence has been neglected by occupational health researchers because of methodological problems. The aim of this paper is to show when and how this indicator may be appropriately used. First, absence is discussed in the context of non specific morbidity. Secondly, different conceptions of and approaches to absence are reviewed with a special accent on absence for health reasons. Finally, methodological precautions for the use of the indicator in epidemiological studies are emphasized.