Exercise testing in pediatrics

Physical exercise and cardiovascular response: design and implementation of a pediatric CMR cohort study

To examine feasibility and reproducibility and to evaluate the cardiovascular response to an isometric handgrip exercise in low-risk pediatric population using Cardiovascular Magnetic Resonance measurements. In a subgroup of 207 children with a mean age of 16 years participating in a population-based prospective cohort study, children performed an isometric handgrip exercise. During rest and exercise, continuous heart rate and blood pressure were measured. Cardiovascular magnetic resonance (CMR) measurements included left ventricular mass, aortic distensibility and pulse wave velocity at rest and left ventricular end-diastolic and end-systolic volumes, ejection fraction, stroke volume and cardiac output during rest and exercise. 207 children had successful CMR measurements in rest and 184 during exercise. We observed good reproducibility for all cardiac measurements. Heart rate increased with a mean ± standard deviation of 42.6% ± 20.0 and blood pressure with 6.4% ± 7.0, 5.4% ± 6.1 and 11.0% ± 8.3 for systolic, diastolic and mean arterial blood pressure respectively (p-values < 0.05). During exercise, left ventricular end-diastolic and end-systolic volumes and cardiac output increased, whereas left ventricular ejection fraction slightly decreased (p-values < 0.05). Stroke volume did not change significantly. A sustained handgrip exercise of 7 min at 30-40% maximal voluntary contraction is a feasible exercise-test during CMR in a healthy pediatric population, which leads to significant changes in heart rate, blood pressure and functional measurements of the left ventricle in response to exercise. This approach offers great novel opportunities to detect subtle differences in cardiovascular health.

Reference Values of Cardiopulmonary Exercise Test Parameters in the Contemporary Paediatric Population

BACKGROUND

The evaluation of health status by cardiopulmonary exercise test (CPET) has shown increasing interest in the paediatric population. Our group recently established reference Z-score values for paediatric cycle ergometer VO_2max, applicable to normal and extreme weights, from a cohort of 1141 healthy children. There are currently no validated reference values for the other CPET parameters in the paediatric population. This study aimed to establish, from the same cohort, reference Z-score values for the main paediatric cycle ergometer CPET parameters, apart from VO_2max.

RESULTS

In this cross-sectional study, 909 healthy children aged 5-18 years old underwent a CPET. Linear, quadratic, and polynomial mathematical regression equations were applied to identify the best CPET parameters Z-scores, according to anthropometric parameters (sex, age, height, weight, and BMI). This study provided Z-scores for maximal CPET parameters (heart rate, respiratory exchange ratio, workload, and oxygen pulse), submaximal CPET parameters (ventilatory anaerobic threshold, VE/VCO₂ slope, and oxygen uptake efficiency slope), and maximum ventilatory CPET parameters (tidal volume, respiratory rate, breathing reserve, and ventilatory equivalent for CO₂ and O₂).

CONCLUSIONS

This study defined paediatric reference Z-score values for the main cycle ergometer CPET parameters, in addition to the existing reference values for VO_2max, applicable to children of normal and extreme weights. Providing Z-scores for CPET parameters in the paediatric population should be useful in the follow-up of children with various chronic diseases. Thus, new paediatric research fields are opening up, such as prognostic studies and clinical trials using cardiopulmonary fitness outcomes. Trial registration NCT04876209-Registered 6 May 2021-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04876209 .

Cardiopulmonary fitness in children with asthma versus healthy children

OBJECTIVES

To evaluate, with a cardiopulmonary exercise test (CPET), the cardiopulmonary fitness of children with asthma, in comparison to healthy controls, and to identify the clinical and CPET parameters associated with the maximum oxygen uptake (VO_2max) in childhood asthma.

DESIGN

This cross-sectional controlled study was carried out in CPET laboratories from two tertiary care paediatric centres. The predictors of VO_2max were determined using a multivariable analysis.

RESULTS

A total of 446 children (144 in the asthma group and 302 healthy subjects) underwent a complete CPET. Mean VO_2max was significantly lower in children with asthma than in controls (38.6±8.6 vs 43.5±7.5 mL/kg/min; absolute difference (abs. diff.) of -4.9 mL/kg/min; 95% CI of (-6.5 to -3.3) mL/kg/min; p<0.01) and represented 94%±9% and 107%±17% of predicted values, respectively (abs. diff. -13%; 95% CI (-17 to -9)%; p<0.01). The proportion of children with an impaired VO_2max was four times higher in the asthma group (24% vs 6%, p<0.01). Impaired ventilatory efficiency with increased VE/VCO₂ slope and low breathing reserve (BR) were more marked in the asthma group. The proportion of children with a decreased ventilatory anaerobic threshold (VAT), indicative of physical deconditioning, was three times higher in the asthma group (31% vs 11%, p<0.01). Impaired VO_2max was associated with female gender, high body mass index (BMI), FEV1, low VAT and high BR.

CONCLUSION

Cardiopulmonary fitness in children with asthma was moderately but significantly altered compared with healthy children. A decreased VO_2max was associated with female gender, high BMI and the pulmonary function.

TRIAL REGISTRATION NUMBER

NCT04650464.

Impaired aerobic capacity in adolescents and young adults after treatment for cancer or non-malignant haematological disease

PURPOSE

Childhood cancer survivors are at increased risk for cardiovascular disease. Maximal oxygen uptake (VO_2max) is a major determinant of cardiovascular morbidity. The aim of this study was to compare aerobic capacity, measured by cardiopulmonary exercise test (CPET), of adolescents and young adults in remission with that of healthy controls and to identify the predictors of aerobic capacity in this population.

METHOD

This is a controlled cross-sectional study.

RESULTS

A total of 477 subjects (77 in remission and 400 controls), aged from 6 to 25 years, were included, with a mean delay between end of treatment and CPET of 2.9 ± 2.3 years in the remission group. In this group, the mean VO_2max was significantly lower than in controls (37.3 ± 7.6 vs. 43.3 ± 13.1 mL/kg/min, P < 0.01, respectively), without any clinical or echocardiographic evidence of heart failure. The VAT was significantly lower in the remission group (26.9 ± 6.0 mL/kg/min vs. 31.0 ± 9.9 mL/kg/min, P < 0.01, respectively). A lower VO_2max was associated with female sex, older age, higher BMI, radiotherapy, and hematopoietic stem cell transplantation.

CONCLUSION

Impaired aerobic capacity had a higher prevalence in adolescents and young adults in cancer remission. This impairment was primarily related to physical deconditioning and not to heart failure.

TRIAL REGISTRY

NCT04815447.

IMPACT

In childhood cancer survivors, aerobic capacity is five times more impaired than in healthy subjects. This impairment mostly reflects early onset of physical deconditioning. No evidence of heart failure was observed in this population.

Normative Values for Cardiopulmonary Exercise Stress Testing Using Ramp Cycle Ergometry in Children and Adolescents

OBJECTIVES

To provide sex, age, and race specific reference values for ramp cycle ergometer cardiopulmonary exercise test (CPET) in children in the US.

STUDY DESIGN

Retrospective review was conducted of all cardiopulmonary CPET data from our Exercise Physiology Laboratory on healthy children and adolescents (6-18 years) with body mass index between the 5th and 95th percentiles and structurally normal hearts who performed a ramp cycle ergometry stress test between 1999 and 2015. Twenty-eight exercise variables were included: peak oxygen consumption, oxygen consumption at ventilatory anaerobic threshold, peak work rate, resting and peak heart rate and blood pressure, resting pulmonary function testing, and ventilatory responses to progressive exercise using breath-by-breath gas exchange. Owing to the nonlinear association between CPET results and age, fractional polynomials were used in the mixed-effects regression models to describe the sex- and age-specific normative values with 95% CIs, after adjusting for race and body mass index.

RESULTS

We analyzed data on 1829 children (average age, 13.6 ± 2.6 years; 52% male). After 12 years of age, males generally had higher peak values for aerobic capacity and work rate. There were progressive increases with age for both sexes in resting pulmonary function and ventilatory response to exercise, peak aerobic and work rate, and oxygen pulse. Notably, there was an age-related decrease in ventilatory equivalents of oxygen and carbon dioxide at the ventilatory anaerobic threshold.

CONCLUSIONS

Future research using prospective, inclusive, and statistically planned cohorts with standardized laboratory approaches and confirmed interoperability should be considered as a focus for validating normative pediatric CPET values in the future.

The Cardiovascular Stress Response as Early Life Marker of Cardiovascular Health: Applications in Population-Based Pediatric Studies-A Narrative Review

Stress inducement by physical exercise requires major cardiovascular adaptations in both adults and children to maintain an adequate perfusion of the body. As physical exercise causes a stress situation for the cardiovascular system, cardiovascular exercise stress tests are widely used in clinical practice to reveal subtle cardiovascular pathology in adult and childhood populations with cardiac and cardiovascular diseases. Recently, evidence from small studies suggests that the cardiovascular stress response can also be used within research settings to provide novel insights on subtle differences in cardiovascular health in non-diseased adults and children, as even among healthy populations an abnormal response to physical exercise is associated with an increased risk of cardiovascular diseases. This narrative review is specifically focused on the possibilities of using the cardiovascular stress response to exercise combined with advanced imaging techniques in pediatric population-based studies focused on the early origins of cardiovascular diseases. We discuss the physiology of the cardiovascular stress response to exercise, the type of physical exercise used to induce the cardiovascular stress response in combination with advanced imaging techniques, the obtained measurements with advanced imaging techniques during the cardiovascular exercise stress test and their associations with cardiovascular health outcomes. Finally, we discuss the potential for cardiovascular exercise stress tests to use in pediatric population-based studies focused on the early origins of cardiovascular diseases.

Heart rate agreement between the 20-meter shuttle run test and virtual system in healthy children: a cross-sectional study

Background

Earlier studies evaluated the physiological responses to video games in children with different clinical conditions; however, no study has compared active video games with an incremental field test in healthy children. The purpose of this study was to verify the agreement between the 20-m shuttle run test (20 m-SRT) and virtual system (VS).

Methods

This is a cross-sectional study of 235 children (9.0 ± 0.8 years, 109 boys). The two tests were performed one week apart and the children were instructed not to engage in any physical exercise or sports in the 24 h preceding each test. Their resting heart rate was monitored for one minute and then throughout the tests. To evaluate the influence of motivation on the 20 m SRT and (VS), at the end of the tests the children were asked to rate their motivation on a scale of zero to 10, zero being “not cool” and 10 “awesome”. Perceived exertion at the end of the tests was assessed using the modified Borg scale.

Results

Maximum heart rate (HRmax) did not differ between the 20 m-SRT and VS (194.4 ± 10.2 bpm vs. 193.2 ± 13.8 bpm, respectively). Both tests were similar for intensity > and < 96% HRmax. The children showed greater exertion on the Borg scale and motivation during the VS. The multiple logistic regression model showed that motivation (p = 0.98), sex (p = 0.53), age (p = 0.61), nutritional status (p = 0.65), and speed (p = 0.18) were not predictive factors of the child’s reaching HRmax.

Conclusion

VS can be used as a tool to evaluate the intensity of maximal exercise tests, given that the percentage of children who achieved HRmax did not differ between the VS and 20 m SRT. The perceived exertion scales were correlated, but only the modified Borg scale correlated with HRmax in the 20 m SRT. The tests are motivational, and most children obtained the maximum VS score.

A novel treadmill protocol for exercise testing in children: the British Columbia Children's Hospital protocol

BACKGROUND

Exercise testing in children is widely recommended for a number of clinical and prescriptive reasons. Many institutions continue to use the Bruce protocol for treadmill testing; however, with its incremental changes in speed and grade, it has challenges for practical application in children. We have developed a novel institutional protocol (British Columbia Children's Hospital (BCCH)), which may have better utility in paediatric populations.

AIM

To determine if our institutional protocol yields similar peak responses in minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (RER), metabolic equivalents (METS) and heart rate (HR) when compared with the traditional Bruce protocol.

METHODS

On two different occasions, 70 children (boys=33; girls=37) aged 10-18 years completed an exercise test on a treadmill using each of the protocols. During each test, metabolic gas exchange parameters were measured. HR was monitored continuously during exercise using an HR monitor.

RESULTS

Physiological variables were similar between the two protocols (median (IQR); rs): VE (L/min) (BCCH=96.7 (72.0-110.2); Bruce=99.2 (75.6-120.0); rs=0.95), peak VO2 (mL/min) (BCCH=2897 (2342-3807); Bruce=2901 (2427-3654); rs=0.94) and METS (BCCH=16.2 (14.8-17.7); Bruce=16.4 (14.7-17.9); rs=0.89). RERs were similar (BCCH=1.00 (0.96-1.02); Bruce=1.03 (0.99-1.07); rs=0.48). Total exercise time (in seconds) was longer for the BCCH protocol: BCCH=915 (829-1005); Bruce=810 (750-919); rs=0.67.

CONCLUSION

The BCCH protocol produces similar peak exercise responses to the Bruce protocol and provides an alternative for clinical exercise testing in children.

Pulmonary function and fitness years after treatment for hypersensitivity pneumonitis during childhood

BACKGROUND

Hypersensitivity pneumonitis (HP) is an immune-mediated diffuse lung disease. Significant improvement in lung function and diffusing capacity after treatment was previously demonstrated, while long-term data focusing specifically on peripheral airway impairment and peak oxygen uptake (fitness) are lacking. Hence, the aim of this study was to conduct a comprehensive study to determine the stability of pulmonary function and fitness in patients previously diagnosed with HP.

METHODS

We performed a cross-sectional follow-up study with inclusion of longitudinal data if available in patients previously diagnosed with biopsy and high-resolution computed tomography-verified HP during childhood. We performed multiple breath wash-out (LCI2.5 ), spirometry (FEV1 ), bronchiodilator responsiveness test, diffusing capacity (DLCO and DLCO /VA ), body-plethysmography (TLC), and peak oxygen uptake (VO2peak ). St. George Respiratory Questionnaire was used as a measure of respiratory quality of life.

RESULTS

Twenty two patients were assessed. LCI2.5 was abnormal in 47.4% compared to abnormal FEV1 in only 9.1% and without significant bronchiodilator responsiveness. DLCO and TLC were abnormal in 40.9 and 13.6%, respectively, while DLCO /VA was within normal range. Only 11.1% demonstrated abnormal VO2peak . All longitudinally assessed outcomes remained unchanged between end of treatment and time of follow up.

CONCLUSIONS

A large proportion of patients previously diagnosed with HP had abnormal LCI2.5 in contrast to normal spirometry. Spirometric outcomes, TLC, and diffusing capacity were persistently slightly reduced, but stable, and VO2peak was excellent at time of follow-up. Long-term prognosis in children with HP appears favorable although persistent peripheral airway involvement of unknown clinical significance was demonstrated in almost half of the patients. Pediatr Pulmonol. 2016;51:830-837. © 2015 Wiley Periodicals, Inc.

[Assessment of exercise capacity in congenital heart disease]

For many years, the treatment of congenital heart diseases has been a field in which, based on the seriousness of these conditions, treatment options were viewed with the greatest deference. This has conditioned, in many cases, the interventions to be undertaken in each. In this sense, exercise was thought to have a negative impact and thus the practise of almost any physical activity was limited. Although there has recently been a change in the paradigm with respect to exercise, this idea continues to hold sway. For many cardiopathies, the information obtained through a stress test is essential in order to implement and supervise an exercise program. The aim of this study is to analyze the parameters within the stress test which allow for an adequate stratification of the risk to subjects with congenital heart diseases who undertake exercise, as well as their values in accordance with the type of pathology, the gravity of such, and the age of the patients. Furthermore, these parameters will be analyzed for both their survival markers and the protocols that can best be adjusted for patients with these characteristic.

Effectiveness of the modified progressive aerobic capacity endurance run test for assessing aerobic fitness in Hispanic children who are obese

The purpose of this study was to evaluate the effectiveness of the progressive aerobic capacity endurance run (PACER) and a newly designed modified PACER (MPACER) for assessing aerobic fitness in Hispanic children who are obese. Thirty-nine (aged 7-12 years) children who were considered obese (≥ 95 th body mass index [BMI] percentile) and 16 children who were considered normal weight (<85th BMI percentile) participated in this study. Performance outcomes included test duration (in minutes) and exercise heart rate (HR) (first-stage and peak HR) for each test. Ninety-five percent confidence intervals and independent t-tests were used to assess differences in primary outcomes. Mean PACER test duration was 1.6 ± 0.6 and 3.1 ± 1.3 minutes for children who were obese and normal weight, respectively. Modified PACER duration was higher than 3 minutes for the obese (3.6 ± 0.6 minutes) and normal weight (5.3 ± 1.2 minutes) groups. Children first-stage HR, expressed as a percent of peak HR, was above the predicted anaerobic threshold during the PACER, but below the anaerobic threshold during the MPACER. Relative first-stage HR was not significantly different between groups for the PACER, but they were significantly different between groups for the MPACER. In conclusion, the MPACER was a better alternative than the PACER for assessing aerobic fitness in Hispanic children who were normal weight and obese. When validated, this modified field test could be used to assess aerobic fitness in Hispanic children, particularly those who are overweight or obese. Additionally, the study provides evidence in which physical educators, personal trainers, and others most apt to assess aerobic fitness in children who are obese, should modify tests originally designed for the population who are normal weight.

Pulmonary function and exercise capacity in children following lung resection surgery

PURPOSE

To study lung function and exercise capacity in children following lung resection surgery.

METHODS

Children aged 6-18 years who had lung resection surgery were studied and compared to normal children (age and sex matched). All had spirometry/body plethysmography and exercise stress test (performed by treadmill and modified Balke protocol).

RESULTS

13 Patients and 13 controls were studied (age 13.2 ± 3.3 years; 46.2 % male). The age at the time of lung resection surgery was 6.5 ± 4.7 years. The time interval between post-surgery and the tests was 6.8 ± 4.4 years. The most common indication for lung resection surgery was congenital lung malformations (61.5 %). 76.9 % of the patients had abnormal lung function. Exercise intolerance due to pulmonary limitations was found in 23.1 % of the patients. At the anaerobic threshold, the V(O2) was not different between the patients and the controls. However, at the end of the exercise, the patients demonstrated lower peak V(O2) than the controls (33.6 ± 6.0 vs. 39.3 ± 8.7 ml/min/kg; p < 0.01).

CONCLUSIONS

Abnormal lung functions and exercise intolerance were found in children following lung resection surgery. Children who had lung resection surgery had lower exercise capacity than normal children if the exercise was beyond the anaerobic threshold.

Functional improvement and social participation through sports activity for children with mental retardation: a field study from a developing nation

BACKGROUND

While the positive effect of sports and exercise on physical and psychological well being is well documented within the general population, the effects of sports on the functional ability of a child with mental retardation are limited.

OBJECTIVES

To determine if sports activities have been detrimental in improving functional ability in sample of children with mental retardation based in Kolkata, a metropolis in India.

STUDY DESIGN

Field level study.

METHODS

Six sports associations registered under the Sports Authority of India for training children with mental retardation were shortlisted on the basis of four criteria. From the register, every third name (gender irrespective) belonging to the second (12-15 years) and third (15-21 years) subclasses (out of the four categories laid down in the Special Olympics participation rules) against a constraint of at least two years active attendance in the sports facility for the child was selected. A sample of 31 children was drawn and the WHO Disability Assessment Schedule 2.0 (WHODAS 2.0) 12-item version was administered to the caregiver-teacher-coach team of the sample. Relative changes in scores between the point when the survey was conducted and the point when the child joined the sports facility was used as the dependent variable for regression analysis. The number of years in active sports, in school age of the respondent and base score of the children when they joined school were the independent variables.

RESULTS

For seven of the WHODAS 2.0 12-item attributes, the number of years in sports activities was found to have a statistically significant effect (p < 0.01) on the functional well being of children with mild to moderate mental retardation. The number of years in school was also another statistically significant factor (p < 0.01) responsible for this improvement. The children, however, perceived of being not welcome in community activities, but participated in activities meant exclusively for them.

CONCLUSIONS

This small study showed that the proposition that number of years in sports activities was a significant factor responsible for improving the functioning of children with mild to moderate mental retardation.

Cardiopulmonary exercise testing in congenital heart disease: equipment and test protocols

Cardiopulmonary exercise testing (CPET) in paediatric cardiology differs in many aspects from the tests as performed in adult cardiology. Children's cardiovascular responses during exercise testing present different characteristics, particularly oxygen uptake, heart rate and blood pressure response, which are essential in interpreting haemodynamic data. Diseases that are associated with myocardial ischaemia are very rare in children. The main indications for CPET in children are evaluation of exercise capacity and the identification of exercise-induced arrhythmias. In this article we will review exercise equipment and test protocols for CPET in children with congenital heart disease. (Neth Heart J 2009;17:339-44.).

Cardiopulmonary exercise testing in congenital heart disease: (contra)indications and interpretation

Cardiopulmonary exercise testing (CPET) in paediatric cardiology differs in many aspects from the tests performed in adult cardiology. Children's cardiovascular responses during exercise testing present different characteristics, particularly oxygen uptake, heart rate and blood pressure response, which are essential in interpreting haemodynamic data. Diseases that are associated with myocardial ischaemia are rare in children. The main indications for CPET in children are evaluation of exercise capacity and the identification of exercise-induced arrhythmias. In this article we will review the main indications for CPET in children with congenital heart disease, the contraindications for exercise testing and the indications for terminating an exercise test. Moreover, we will address the interpretation of gas exchange data from CPET in children with congenital heart disease. (Neth Heart J 2009;17:385-92.).

Results of exercise stress testing in patients with diffuse pulmonary arteriovenous malformations

Patients with diffuse pulmonary arteriovenous malformations (PAVMs) are subject to frequent complications and need to be followed closely. As part of this follow-up, we have employed exercise stress testing (EST) as an aid to assess their status. Twenty patients from a cohort of 35 with diffuse PAVMs have undergone EST using a standard cycle ergometer test. All patients had previously undergone pulmonary angiography, noncontrast chest computed tomography (CT), and repair of large focal PAVMs, prior to EST. Mean room air oxygen saturation at baseline and at maximum exercise (85% of maximum heart rate) were tabulated. Serial studies in six children and young adults were plotted by year and compared using the patient as their own control. Fourteen females and six males ranging in age from 4 to 50 years (mean 22 years) were studied. Baseline mean oxygen saturation was 84% and fell to 73% at maximum exercise. There was no significant difference between those with unilateral and bilateral involvement (P = 0.09). In four of the six patients with serial EST, the baseline and exercise oxygen saturations were quite stable. In the two patients who became symptomatic, with age, growth, and more activity, complete embolization of one or more segments of the lung improved their EST and functionality. Based on our previous work in patients with diffuse PAVMs, EST appears to offer a relatively safe and noninvasive method for assessing these patients. Our limited experience with serial EST suggests a good correlation with decreased functionality in these patients.

Decreased maximal aerobic capacity in pediatric chronic kidney disease

Adult and pediatric patients with ESRD have impaired maximum oxygen consumption (VO(2) max), a reflection of the cardiopulmonary system's ability to meet increased metabolic demands. We sought to determine factors associated with decreased VO(2) max in pediatric patients with different stages of CKD. VO(2) max was measured using a standardized exercise testing protocol in patients with stage 2 to 4 chronic kidney disease (CKD) (n = 46), in renal transplant recipients (n = 22), in patients treated with maintenance hemodialysis (n = 12), and in age-matched healthy controls (n = 33). VO(2) max was similar between children with stage 2 CKD and controls, whereas lower VO(2) max was observed among children with stage 3 to 4 CKD, those treated with hemodialysis, and transplant recipients. In univariate analysis, VO(2) max was significantly associated with body mass index, resting heart rate, C-reactive protein, serum triglycerides, serum creatinine, and measures of diastolic function; no significant associations with left ventricular structure or systolic function were identified. In multivariate regression analysis, patient category versus control and the presence of diastolic dysfunction were independent predictors of lower VO(2) max. These results suggest that aerobic capacity is decreased in the early stages of CKD in children and that lower VO(2) max can be predicted by the presence of diastolic dysfunction, even if systolic function is normal.

Continuous ratings of breathlessness during exercise by children and young adults with asthma and healthy controls

Although it is recommended and common practise for adults with respiratory disease to rate symptoms (e.g., dyspnea and/or leg discomfort) during exercise testing, there are no reports on whether children can rate their perception of breathlessness during exercise. Our aims were to evaluate the ability of children and young adults with asthma to continuously rate breathlessness on the 0-10 category-ratio (CR-10) scale with a computerized system during cycle ergometry, and to compare their results with those of healthy subjects. At an initial visit, subjects were familiarized with equipment and exercise protocol, and practised rating breathlessness while cycling. At a follow-up visit (2-4 days later), subjects performed incremental exercise and rated breathlessness using a computer system, mouse, and monitor. Changing the position of the mouse caused movement of a vertical bar located adjacent to the CR-10 scale to indicate the severity of breathlessness. Baseline characteristics of the 14 subjects with asthma (age, 15 +/- 3 years) and 33 healthy subjects (age, 16 +/- 2 years) were similar. The two groups had comparable levels of fitness as measured by peak oxygen consumption (VO(2)). Correlations between exercise physiologic variables (power production, VO(2), and minute ventilation) and breathlessness ratings were >0.90. Subjects reported progressively more ratings of breathlessness with increasing exercise intensities. There were no differences between groups for slopes, x-intercepts, and absolute thresholds relating physiologic variables and breathlessness. In conclusion, children and young adults with asthma as well as healthy individuals of comparable age successfully used the computerized system to rate breathlessness continuously during cycle ergometry. Both groups reported more ratings of breathlessness with this technique as exercise progressed.