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Biomedical subjects

T Reybrouck

Publications and source records attributed to T Reybrouck.

At least 19 recordsLinked to original sources
PubMed1999

Gender differences in the oxygen transport system during maximal exercise in hypertensive subjects.

STUDY OBJECTIVES: To analyze gender differences in the oxygen transport system at peak exercise with particular emphasis on the difference in systemic arteriovenous oxygen extraction and in mixed venous oxygen saturation. PATIENTS AND METHODS: Cardiopulmonary graded exercise testing and hemodynamic assessment were performed on a cycle ergometer in 64 hypertensive patients (32 female and 32 male) varying in age from 23 to 64 years. Female and male patients were matched for age and BP. MEASUREMENTS AND RESULTS: Peak oxygen uptake was significantly lower in women than in men, and when expressed in absolute units (L/min: -39%) and when normalized for body mass (mL/min/kg: -33%) or statistically adjusted for height and weight (-29%). This resulted essentially from a significantly lower cardiac output in women, both when expressed in absolute units and when adjusted for body size. At the peripheral level, female patients had a lower arteriovenous oxygen content difference at peak exercise, which resulted from a lower hemoglobin concentration and the inability to decrease mixed venous oxygen saturation to the same level as in men. CONCLUSION: The lower peak oxygen uptake of women results from both central and peripheral factors. The significantly higher value for mixed venous oxygen saturation, which contributes to the lower arteriovenous oxygen difference of women, could result from their smaller muscle mass, lower capillary density, and lower oxidative potential.

Adult↗
PubMed1998

Ventilatory inefficiency for carbon dioxide during exercise in patients with pulmonary hypertension.

The purpose of this study was to analyse the ventilatory efficiency for carbon dioxide (CO2) in the assessment of exercise tolerance in patients with pulmonary hypertension. Two groups of patients were studied. One group consisted of 37 patients with normal pulmonary artery pressure who underwent surgical closure of a left-to-right shunt. Another group was composed of 10 patients with pulmonary hypertension. Both patient groups were compared with the mean value of an age-matched pool of normal control subjects. Aerobic exercise performance was assessed by determination of the ventilatory threshold. The ventilatory efficiency for CO2 was assessed by calculating the slope of ventilation over carbon dioxide below the ventilatory threshold. The slope of ventilation vs. carbon dioxide output in patients with pulmonary hypertension (48 +/- 12) was steeper than the slope (31.3 +/- 7.0) in patients with normal pulmonary artery pressure (P < 0.05). Significant correlations (P < 0.05) were found between the pulmonary artery pressure and the slope of pulmonary ventilation over carbon dioxide (r = 0.92) and also with the physiological dead space-tidal volume ratio at maximal exercise (r = 0.55). This was associated with a severe reduction in exercise performance in patients with pulmonary hypertension, whereas in patients with normal pulmonary artery pressure it was only slightly below the lower limit of normal. These results demonstrate that patients with pulmonary hypertension have an inefficient ventilatory response to metabolically produced CO2 during exercise, which severely limits exercise tolerance.

Adolescent↗
PubMed1998

Tilt training: a new treatment for recurrent neurocardiogenic syncope and severe orthostatic intolerance.

Medical treatment of neurocardiogenic syncope is insufficient in many cases. We have observed a therapeutic effect of repeated head-up tilt testing. Therefore, we have started a program of tilt training for heavily symptomatic patients. After hospital admission, they were tilted daily (60 degrees inclination) until syncope, or until a duration of 45-90 minutes (90 sessions in 13 patients). The mean tilt tolerance, at the first diagnostic head-up tilt table test, was 22.3 minutes (st. dev. 10.9). Before hospital discharge, 12/13 patients could sustain the full duration of tilt table testing without any symptom. In one patient syncope persisted. The patients were instructed to continue a program of daily tilt training at home, by standing against a wall for 30 minutes, one or two times per day. This resulted in a complete disappearance of syncope in all 13 patients. Orthostatic intolerance and the excessive autonomic reflex activity of neurocardiogenic syncope can be remedied by a program of continued tilt training, without the administration of drugs.

Adult↗
PubMed1997

Assessment of cardiorespiratory exercise function in obese children and adolescents by body mass-independent parameters.

The parameters used to assess aerobic exercise function by gas exchange are usually adjusted for body mass and are expressed as millilitres per minute per kilogram. In the case of obese children this could lead to overcorrection with an underestimation of their exercise capacity. The purpose of the present study was to assess cardiorespiratory exercise function in obese subjects using body mass-independent parameters. As both carbon dioxide output (VCO2) and oxygen uptake (VO2) are usually corrected for body mass, the slope of VCO2 versus VO2 can be considered to be independent of body mass. This slope was calculated below the ventilatory threshold (S1) and above the ventilatory threshold (S3). Exercise tests were performed on a treadmill and respiratory gas exchange was measured breath-by-breath. A group of 29 obese children [mean age 11 (SD 2.5) years] were compared to 16 normal controls of the same age range [mean age 10.8 (SD 2.2); P > 0.05]. The patients were overweight by 36 (SD 17.9)% and had a body mass index of 25.0 (SD 3.8). The results showed that S3 in the obese subjects was significantly steeper compared to the normal controls [1.30 (SD 0.20) vs 1.10 (SD 0.20); P < 0.05]. The steepest values for S3 were found in the subjects with the highest degree of obesity. This method has some limitations, since in a large proportion of the patients (48%) no ventilatory threshold could be detected, which is prerequisite for calculation of these slopes. The latter was already suppressed at the onset of exercise in 21% of the sample or could not be detected because of breathing irregularity in 27%. It is suggested from this study that cardiorespiratory exercise function in obese children is reduced, especially when assessed by parameters of aerobic exercise which cancel the confounding effect of body mass.

Adolescent↗
PubMed1996

Prognostic significance of peak oxygen uptake in hypertension.

The aim of this study was to investigate the prognostic value of cardiopulmonary fitness in hypertension. From 1972 to 1982 oxygen uptake and heart rate were recorded during an exercise test to exhaustion in 216 patients (143 men). Their outcome was ascertained in 1994. During 3,411 patient years of follow-up, 53 patients suffered at least one fatal or nonfatal cardiovascular event and 25 patients died. After adjustment for age, gender, and weight, the relative hazard rates (RHR; Cox regression) of peak oxygen uptake (l.min-1) amounted to 0.44 (P = 0.01) for the first occurring cardiovascular events and 0.35 (P = 0.05) for all-cause mortality. These RHR remained significant after additional adjustment for traditional cardiovascular risk factors (RHR = 0.45 and 0.28, respectively; P < 0.05). Heart rate at 50 W did not predict outcome after adjustment for age and gender (P = 0.94 and 0.14, respectively), nor after additional adjustment for heart rate at rest (P = 0.86 and 0.61, respectively). In conclusion, a lower peak oxygen uptake, but not a higher submaximal heart rate, is significantly and independently associated with a higher incidence of cardiovascular events and a higher total mortality in hypertensive patients.

Cardiovascular Diseases↗
PubMed1996

Dynamics of respiratory gas exchange during exercise after correction of congenital heart disease.

In pediatric exercise testing, conventional measures of aerobic exercise function such as maximal O2 uptake or the ventilatory anaerobic threshold (VAT) use only one value for the assessment of exercise capacity. We studied a more comprehensive approach to evaluate aerobic exercise function by analyzing the steepness of the slope of CO2 production (VCO2) vs. VO2 above the VAT (S3). This was calculated in 32 patients operated on for congenital heart disease [16 for transposition of the great arteries (TGA) and 16 for tetralogy of Fallot (TF)] and was compared with 16 age-matched controls (nl). The results show that the reproducibility of this new assessment method was excellent (coefficient of variation for S3: 8.6%). S3 was significantly steeper (P<0.05) in the patients (1.31 +/- 0.22 for TGA and 1.28 +/- 0.16 for TF) compared with the nl (1.10 +/- 0.22). Also, the difference between S3 and the slope of VCO2 vs. VO2 below the VAT was significantly higher in the patients (0.37 +/- 0.22 for TGA and 0.31 +/- 0.10 for TF) than in controls (0.22 +/- 0.06). The steeper slopes were associated with lower than normal values for VAT and O2 during exercise. It is concluded that the analysis of the steepness of the slope of CO2 is a sensitive, reproducible, and objective approach to evaluate the integrative cardiopulmonary response to exercise. It complements the assessment of a subnormal VAT by reflecting the extent of anaerobic metabolism.

Aerobiosis↗
PubMed1995

Serial cardiorespiratory exercise testing in patients with congenital heart disease.

Aerobic capacity of patients with different forms of congenital heart disease was serially evaluated in 79 patients and the evolution was correlated with the lesion and the level of daily activity. The patients were divided into six groups: patients with a small ventricular septal defect (VSD) with mini shunt (n = 14), mild pulmonary valve stenosis with gradient < 40 mm Hg (PS) (n = 12), mild to moderate aortic valve stenosis (gradient 36 +/- 17 mmHg) (AS) (n = 12), patients 4.7 +/- 2.1 years after repair of tetralogy of Fallot (PO-TF) (n = 16), patients 2.2 +/- 2.9 years after closure of a high flow/high gradient VSD (PO-VSD) (n = 13), and patients 2.6 +/- 1.7 years after Fontan repair (Fontan-PO) (n = 12). Aerobic capacity was assessed by determination of the ventilatory anaerobic threshold (VAT). VAT reflects the highest aerobic exercise level prior to a disproportionate increase of CO2 and ventilation relative to O2 uptake; it is independent of patient motivation. Data are expressed as percentage of normal O2 uptake at VAT, determined in 234 age/gender matched controls. The habitual level of physical activity was assessed by a standardised questionnaire. Aerobic capacity in all subgroups of patients, even with very mild defects, was at or below the lower limit of normal. Children left unrestricted from physical exercise (VSD, PS, PO-VSD) had no change over the study period. However, aerobic capacity of patients with medically imposed physical restrictions (AS) and significant residual haemodynamic lesions (PO-TF, Fontan) decreased with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Reliability of subjective estimates of exercise capacity after total repair of tetralogy of Fallot.

Sixty-nine patients (age 10 +/- 3.5 years, median 9.7 years) operated on for tetralogy of Fallot, underwent exercise testing 5.1 +/- 2.5 years after total correction. Aerobic capacity was assessed by the ventilatory threshold method. After the exercise test, parents completed a validated standardized questionnaire to evaluate the habitual level of physical activity of their child. They were then asked to place their child into one of three groups, describing their child's activity level, compared to normals (below average, average and above average). In the average and above-average groups, 73% and 65% of the patients were misclassified when compared to objective exercise testing. However, in the below-average group, no misclassifications were found. Subjective estimates of activity level, and consequently exercise tolerance, were poorly associated with objective measurements of exercise performance in these patient groups. Our results question the reliability of self-reported estimates of physical activity level and consequently exercise capacity in children after surgical correction of tetralogy of Fallot.

Activities of Daily Living↗
PubMed1993

Cardiorespiratory exercise performance after Senning operation for transposition of the great arteries.

OBJECTIVE: To assess the cardiorespiratory response to graded exercise in patients after the Senning operation for transposition of the great arteries. DESIGN: Cross sectional study. Exercise performance was assessed by determination of the ventilatory anaerobic threshold. This was defined as the exercise intensity at which the ventilatory equivalent for oxygen (VE/VO2) started to increase systematically without a concomitant increase in the ventilatory equivalent for carbon dioxide (VE/VCO2). SETTING: Outpatient department. PATIENTS: Sequential sample of 20 patients studied 5-10 years (mean 7.3 years) after the Senning operation. Age at exercise testing varied from 5 to 11 (mean 7.8) years. RESULTS: The ventilatory threshold in the patients was significantly lower than normal (p < 0.005) and averaged 79.3% (SD 13%) and 80% (12%) of the predicted normal value for age and weight, respectively. Also, the ventilatory threshold was surpassed sooner (mean 3.2 (range 2-5) minutes) in the patients than in normal controls (3.9 (2.6-4.6) minutes). The lower ventilatory threshold was associated with a subnormal oxygen uptake (ml/min/kg) during submaximal exercise, a higher than normal ventilatory equivalent for oxygen ratio, and a lower end tidal carbon dioxide tension in the patients compared with normal controls. In half of the patients heart rate was lower during graded exercise. This relative bradycardia was not associated with a normal ventilatory threshold, as often seen in fit young people. No major disturbances in rhythm were observed during exercise. CONCLUSION: Exercise performance, assessed by respiratory gas exchange, was slightly but significantly lower than normal in patients after the Senning operation. A subnormal ventilatory threshold, associated with a higher than normal ventilatory response during submaximal exercise, supports the hypothesis that oxygen delivery to tissues is slightly impaired in these patients.

Anaerobic Threshold↗
PubMed1992

Evaluation of breath-by-breath measurement of respiratory gas exchange in pediatric exercise testing.

In adults, breath-by-breath analysis has been used for measuring respiratory gas exchange during exercise. The present study evaluates the validity and reproducibility of this method in children. In 21 patients with various types of congenital heart disease, steady state exercise testing was performed on a motor-driven treadmill. Based on simultaneous measurements of VO2, VCO2, VE and R, comparisons were made between the breath-by-breath and Douglas bag methods. No significant differences were found between both methods for any of the variables. In seven other patients the reproducibility of cardiorespiratory variables during exercise was assessed. No significant difference was found for the cardiorespiratory variables during any of the tests and the coefficients of variation were comparable to data obtained in adults. It is concluded that the breath-by-breath method for measuring respiratory values can be applied in children with an acceptable degree of validity and reproducibility.

Adolescent↗
PubMed1991

Cardiorespiratory exercise capacity after surgical closure of atrial septal defect is influenced by the age at surgery.

To study the influence of age at the time of the operation on long-term functional performance in children undergoing surgery for atrial septal defect (ASD) of the secundum type, exercise tolerance was assessed in 24 patients and values were compared with those of normal subjects. Patients were divided into two groups: 11 patients had surgery before the age of 5 years (group 1) and 13 patients had surgery at a later age (group 2). There were no significant differences between groups 1 and 2 with regard to the pulmonary-to-systemic flow ratio, pulmonary artery pressure, and the interval between surgery and exercise testing. Performance capacity was assessed by determination of the ventilatory threshold during submaximal exercise. The mean value for the ventilatory threshold in group 1 was normal (99.4 +/- 15.1% of the age-predicted normal value). In the children who were more than 5 years of age at the time of the operation, the ventilatory threshold was below normal (84.5 +/- 10.9% of the age-predicted normal value). Furthermore, in group 2 more patients (77%) had values that were below normal (below the 95% confidence limit of the age-predicted normal value) compared with group 1 (27%). It is concluded that functional performance capacity is better when surgical closure of ASD is performed in early childhood and before the age of 5 years rather than at a later age.

Adolescent↗
PubMed1990

Exercise therapy and hypocaloric diet in the treatment of obese children and adolescents.

Fourteen obese children and adolescents were treated with a combined therapy of low calorie diet and exercise and their progress compared to that of 11 obese children treated with diet only. Children treated with combination therapy were encouraged to perform aerobic exercises daily, for a period of time which was calculated to consume approximately 250 kcal per exercise session. After 4 months of therapy, a significantly (P less than 0.05) larger decrease of % overweight was observed in the group of children treated with diet and exercise (-25 +/- 13.5%) than in those treated with diet only (-15.8 +/- 10.5%). Treatment compliance was better in the group treated with diet and exercise than in the group which followed a low calorie diet only. We think that unsupervised exercise therapy can be successfully combined with a low calorie diet in the treatment of childhood obesity.

Adolescent↗
PubMed1989

Cardiorespiratory response to exercise in congenital complete atrioventricular block.

In 8 patients aged 8 to 17 years with congenital complete atrioventricular (AV) block, exercise testing was performed on a treadmill. Cardiorespiratory endurance performance was assessed by determination of the ventilatory threshold. The mean value for ventilatory threshold was significantly lower (p less than 0.005) than the normal mean value and averaged 76 +/- 16%, 75 +/- 17% and 75 +/- 16% of the predicted normal value in children of the same sex and comparable age, weight and height, respectively. The ventricular rate at rest varied from 36 to 56 beats/min and increased to a mean value of 106 +/- 25 on exercise. When expressed as a percentage of the normal value, the heart rate was subnormal (below the 95% confidence limit) in all patients, throughout different exercise levels. For the same exercise intensity the oxygen uptake, expressed as ml/min/kg, was significantly lower (p less than 0.02) in patients than in normal individuals. This suggests an inadequate hemodynamic adjustment to the relative exercise bradycardia and a higher than normal anaerobic/aerobic energy supply. Exercise testing was found to be useful in the assessment of congenital AV block, because the resting heart rate did not permit prediction of the relative exercise bradycardia or the degree of exercise intolerance.

Adolescent↗
PubMed1989

Habitual level of physical activity and cardiorespiratory endurance capacity in children.

A total of 257 healthy children (140 boys, 117 girls) varying in age from 5.7 to 18.5 years underwent graded exercise tests on a treadmill. Cardiorespiratory endurance capacity was assessed by determination of the ventilatory threshold, which was defined as the highest exercise intensity before a disproportionate increase occurred in pulmonary ventilation (VE) relative to oxygen uptake (VO2). The purpose of the present study was to investigate the relationship between the habitual level of physical activity (HLPA) and the cardiorespiratory endurance capacity in children. The HLPA was assessed by a standardized questionnaire. In boys and girls HLPA increased gradually with advancing age. For the group as a whole, the boys reached the highest values for HLPA. The most active boys reached the highest value for ventilatory threshold and the lowest value was found in the less active ones, except for the age span of 12-16 years. It is concluded that more active boys showed a higher cardiorespiratory endurance capacity, as assessed by the ventilatory threshold, compared to less active ones, except during puberty. It can be postulated that during puberty this effect may be overruled by the influence of other more dominant growth-related factors. In girls, because HLPA was rather low, there was no discriminative effect of HLPA on exercise performance, as would be expected.

Adolescent↗
PubMed1988

Cardiorespiratory exercise testing after venous switch operation in children with complete transposition of the great arteries.

In 14 children who underwent a venous switch operation for complete transposition of the great arteries, exercise testing was performed 3 to 15 years (mean 8) after the operation. Exercise performance capacity was assessed by the determination of the ventilatory threshold during exercise and by the oxygen uptake (VO2) reached at a heart rate of 170 beats/min (VO2,170). The ventilatory threshold was defined as the highest oxygen uptake (VO2) at which the pulmonary ventilation (VE) stops to increase linearly when related to VO2. During exercise above this threshold a disproportionate increase in VE relative to VO2 is observed. The mean ventilatory threshold was significantly lower (p less than 0.01) than the normal mean value and averaged 72 +/- 15%, 67 +/- 15% and 70 +/- 13% of the predicted normal value for children of comparable age, weight and height, respectively. The mean value for VO2,170 also was significantly lower (p less than 0.05) than the normal mean value for children of comparable age, weight and height, and averaged 81 +/- 20%, 81 +/- 18% and 80 +/- 18%, respectively. Compared with normal control subjects of the same sex and age, the ventilatory threshold was surpassed sooner (p less than 0.001) and reached after 2 +/- 1 min instead of the 4 +/- 1 min required by the controls. In nearly half of the patients, a lower than normal (i.e. below the 95% confidence limit) heart rate response to exercise was observed. Theoretically, this could be interpreted as indicating a normal or high physical performance capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1987

Cardiorespiratory function during exercise in obese children.

Fifteen obese children, aged 4 to 16 years and ranging in body weight from 27.3 to 95 kg (median 67.5) and percentage overweight from 22 to 127% (median 40), underwent graded exercise testing on a treadmill and were compared with healthy peers of comparable age. Cardiorespiratory performance capacity was assessed by determination of the ventilatory threshold. This was defined as the highest oxygen uptake at which the pulmonary ventilation stops to increase linearly with increasing exercise intensity. The ventilatory threshold, expressed as ml O2/min/kg, was significantly (p less than 0.05) lower than in normal children and averaged 70.6 +/- 13.5% of the normal mean value, matched for age. The habitual level of physical activity, assessed by a questionnaire, was 27% lower (p less than 0.01) in the obese children compared to healthy controls. As the ventilatory threshold was strikingly lower and also exceeded sooner in the majority of the obese children, compared with normal controls, it may be assumed that obese children avoid moderate or strenuous exercise, because of the higher degree of effort needed. This may contribute to the maintenance of overweight.

Adolescent↗
PubMed1986

Ventilatory anaerobic threshold for evaluating exercise performance in children with congenital left-to-right intracardiac shunt.

The ventilatory response to graded treadmill exercise was studied in 50 children with congenital heart disease (CHD), a left-to-right intracardiac shunt, and compared to that of age and sex-matched healthy children. In all these children, a breakpoint in the minute ventilation (VE) in relation to increasing oxygen uptake (VO2) was detected. Because of the reported coincidence of the nonlinear increase in VE and lactate with increasing VO2, this threshold has been named "ventilatory anaerobic threshold" (VAT), expressed in ml O2 X min-1 X kg-1. VAT correlated well with VO2 (ml X min-1 X kg-1), reached at a heart rate of 170/min (VO2,170). Compared to normal children, however, a significantly (p less than 0.05) larger percentage (56%) of the patients showed a subnormal value (below the 95% confidence limit) for VAT than for VO2,170 (28%). Furthermore, when expressed as a percentage of the mean normal value, the mean VAT (89 +/- 14.4% SD) was significantly (p less than 0.05) lower than the mean VO2,170 (103 +/- 17.2%). VAT (ml O2 X min-1) correlated significantly with body weight and height, even after adjusting for age, and with the percentiles of body weight and height. VAT constitutes a useful noninvasive criterion for evaluating exercise performance in children with CHD, at least those forms with a left-to-right intracardiac shunt, and it is significantly more sensitive than the VO2,170 in detecting decreased cardiorespiratory endurance capacity.

Adolescent↗