Exertional Dyspnea in Childhood: Is There an Iceberg Beneath the Apex?

Effects of Obesity and Sex on Ventilatory Constraints during a Cardiopulmonary Exercise Test in Children

PURPOSE

Ventilatory constraints are common during exercise in children, but the effects of obesity and sex are unclear. The purpose of this study was to investigate the effects of obesity and sex on ventilatory constraints (i.e., expiratory flow limitation (EFL) and dynamic hyperinflation) during a maximal exercise test in children.

METHODS

Thirty-four 8- to 12-yr-old children without obesity (18 females) and 54 with obesity (23 females) completed pulmonary function testing and maximal cardiopulmonary exercise tests. EFL was calculated as the overlap between tidal flow-volume loops during exercise and maximal expiratory flow-volume loops. Dynamic hyperinflation was calculated as the change in inspiratory capacity from rest to exercise.

RESULTS

Maximal minute ventilation was not different between children with and without obesity. Average end-inspiratory lung volumes (EILV) and end-expiratory lung volumes (EELV) were significantly lower during exercise in children with obesity (EILV: 68.8% ± 0.7% TLC; EELV: 41.2% ± 0.5% TLC) compared with children without obesity (EILV: 73.7% ± 0.8% TLC; EELV: 44.8% ± 0.6% TLC; P < 0.001). Throughout exercise, children with obesity experienced more EFL and dynamic hyperinflation compared with those without obesity ( P < 0.001). Also, males experienced more EFL and dynamic hyperinflation throughout exercise compared with females ( P < 0.001). At maximal exercise, the prevalence of EFL was similar in males with and without obesity; however, the prevalence of EFL in females was significantly different, with 57% of females with obesity experiencing EFL compared with 17% of females without obesity ( P < 0.05). At maximal exercise, 44% of children with obesity experienced dynamic hyperinflation compared with 12% of children without obesity ( P = 0.002).

CONCLUSIONS

Obesity in children increases the risk of developing mechanical ventilatory constraints such as dynamic hyperinflation and EFL. Sex differences were apparent with males experiencing more ventilatory constraints compared with females.

Creating a data dictionary for pediatric autonomic disorders

PURPOSE

Whether evaluating patients clinically, documenting care in the electronic health record, performing research, or communicating with administrative agencies, the use of a common set of terms and definitions is vital to ensure appropriate use of language. At a 2017 meeting of the Pediatric Section of the American Autonomic Society, it was determined that an autonomic data dictionary comprising aspects of evaluation and management of pediatric patients with autonomic disorders would be an important resource for multiple stakeholders.

METHODS

Our group created the list of terms for the dictionary. Definitions were prioritized to be obtained from established sources with which to harmonize. Some definitions needed mild modification from original sources. The next tier of sources included published consensus statements, followed by Internet sources. In the absence of appropriate sources, we created a definition.

RESULTS

A total of 589 terms were listed and defined in the dictionary. Terms were organized by Signs/Symptoms, Triggers, Co-morbid Disorders, Family History, Medications, Medical Devices, Physical Examination Findings, Testing, and Diagnoses.

CONCLUSION

Creation of this data dictionary becomes the foundation of future clinical care and investigative research in pediatric autonomic disorders, and can be used as a building block for a subsequent adult autonomic data dictionary.

The role of cardiopulmonary exercise testing in evaluating children with exercise induced dyspnoea

Exercise induced dyspnoea (EID) is a common manifestation in children and adolescents. Although EID is commonly attributed to exercise induced bronchoconstriction, several conditions other than asthma can cause EID in otherwise healthy children and adolescents. Cardiopulmonary exercise testing (CPET) offers a non-invasive comprehensive assessment of the cardiovascular, ventilatory and metabolic responses to exercise and is a powerful diagnostic and prognostic tool. CPET is a reproducible, non-invasive form of testing that allows for comparison against age- and gender-specific norms. CPET can assess the child's exercise capacity, determine the limiting factors associated with this, and be used to prescribe individualised interventions. EID can occur due to asthma, exercise induced laryngeal obstruction, breathing pattern disorders, chest wall restriction and cardiovascular pathology among other causes. Differentiating between these varied causes is important if effective therapy is to be initiated and quality of life improved in subjects with EID.

Ventilatory Limitation of Exercise in Pediatric Subjects Evaluated for Exertional Dyspnea

Purpose: Attribution of ventilatory limitation to exercise when the ratio of ventilation (V˙E) at peak work to maximum voluntary ventilation (MVV) exceeds 0.80 is problematic in pediatrics. Instead, expiratory flow limitation (EFL) measured by tidal flow-volume loop (FVL) analysis – the method of choice – was compared with directly measured MVV or proxies to determine ventilatory limitation.

Methods: Subjects undergoing clinical evaluation for exertional dyspnea performed maximal exercise testing with measurement of tidal FVL. EFL was defined when exercise tidal FVL overlapped at least 5% of the maximal expiratory flow-volume envelope for > 5 breaths in any stage of exercise. We compared this method of ventilatory limitation to traditional methods based on MVV or multiples (30, 35, or 40) of FEV₁. Receiver operating characteristic curves were constructed and area under curve (AUC) computed for peak V˙E/MVV and peak V˙E/x⋅FEV₁.

Results: Among 148 subjects aged 7–18 years (60% female), EFL was found in 87 (59%). Using EFL shown by FVL analysis as a true positive to determine ventilatory limitation, AUC for peak V˙E/30⋅FEV₁ was 0.84 (95% CI 0.78–0.90), significantly better than AUC 0.70 (95% CI 0.61–0.79) when 12-s sprint MVV was used for peak V˙E/MVV. Sensitivity and specificity were 0.82 and 0.70 respectively when using a cutoff of 0.85 for peak V˙E/30⋅FEV₁ to predict ventilatory limitation to exercise.

Conclusion: Peak V˙E/30⋅FEV₁ is superior to peak V˙E/MVV, as a means to identify potential ventilatory limitation in pediatric subjects when FVL analysis is not available.