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.

Sex differences in fitness and cardiac function during exercise in adolescents with chronic fatigue

Females demonstrate less robust Frank-Starling mechanism with respect to cardiac preload than males at rest. We asked whether this phenomenon would also affect cardiac performance during exercise. We hypothesized that stroke volume (SV) response to exercise would be more limited in deconditioned females such that cardiac output would be mainly rate dependent, compared with males. We conducted a chart audit of clinical exercise tests performed by adolescents with chronic fatigue. Oxygen uptake (V˙O2) was measured breath-by-breath at rest and during cycle ergometry, while cardiac output was measured by acetylene rebreathing at rest plus 2-3 subthreshold workloads. SV response was analyzed in two ways: after normalization for body surface area (SV index, SVI) and as percentage change from resting values. Among 304 adolescents (78% females) with chronic fatigue, 189 (80%) of 236 females and 52 (76%) of 68 males were deconditioned (peakV˙O₂ <90% predicted). Heart rate trajectory during exercise was steeper for unfit than fit females, 70 vs 61 beat·min^-1 per L·min^-1 V˙O2, (P=.003); but not for males, 47 vs 42 beat·min^-1 per L·min^-1 V˙O2 (P=.23). The highest measured SVI did not differ between unfit vs fit females (42.8 vs 41.5 mL·m^-2 , P=.39) while fit males showed larger SV during exercise than their unfit peers (highest SVI 55.9 vs 48.0 mL·m^-2 , P=.014). Both qualitative and quantitative sex differences exist in SV responses to exercise among chronically fatigued adolescents, suggesting volume loading may be more efficacious in girls.

Cardiorespiratory function after operation for pectus excavatum

OBJECTIVE

We performed a review of current data to determine the effect that operation has on pulmonary function, aerobic capacity, and stroke volume in patients with pectus excavatum.

STUDY DESIGN

Two reviewers independently assessed clinical trials and collected data on interventions and outcomes. To qualify for inclusion, a study had to include preoperative and postoperative assessment, provide outcomes in either a published percentile or qualified matched control form to control for interval growth, and include only original patient groups.

RESULTS

Postoperative total lung capacity for patients who had Ravitch repair was significantly lower (SMD, 0.71 [CI -1.06, -0.36]; I(2) = 19.6%) than preoperative. Based on 2 studies after removal of the Nuss bar, FEV(1) was significantly increased from preoperative values (SMD, 0.39 [CI, 0.03, 0.74]; I(2) = 0%). Stroke volume increased after surgery (SMD, 0.40 [CI, 0.10, 0.70]; I(2) = 0%) after Ravitch repair. There was a trend toward improved exercise tolerance, but it was not statistically significant.

CONCLUSIONS

Total lung capacity was decreased after Ravitch repair, and FEV(1) was increased after Nuss bar removal. Stroke volume may be increased after Ravitch repair. Exercise tolerance was not improved after either type of surgical repair.

Airway resistance variability and response to bronchodilator in children with asthma

Variability of airway function is a feature of asthma, spanning timescales from months to seconds. Short-term variation in airway resistance (R(rs)) is elevated in asthma and is thought to be due to increased variation in the contractile activation of airway smooth muscle. If true, then variation in R(rs) should decrease in response to bronchodilators, but this has not been investigated. Using the forced oscillation technique, R(rs) and the variation in R(rs) from 4-34 Hz were measured in 39 children with well-controlled mild-to-moderate asthma and 31 healthy controls (7-13 yrs) before and after an inhaled bronchodilator (200 microg salbutamol) or placebo. In agreement with other findings, baseline R(rs) at all frequencies and the sd of R(rs) (R(rs) sd) below 14 Hz were found to be elevated in asthma while neither forced expiratory volume in one second nor the mean forced expiratory flow between 25 and 75% of forced vital capacity were different compared with controls. The present authors found that R(rs) sd changed the most of any measurement in asthma, and this was the only measurement that changed significantly more in children with asthma following bronchodilator administration. The present results show that like airway narrowing, short-term airway variability of resistance may be a characteristic feature of asthma that may be useful for monitoring response to therapy.

Dalhousie dyspnea scales: construct and content validity of pictorial scales for measuring dyspnea

BACKGROUND

Because there are no child-friendly, validated, self-report measures of dyspnea or breathlessness, we developed, and provided initial validation, of three, 7-item, pictorial scales depicting three sub-constructs of dyspnea: throat closing, chest tightness, and effort.

METHODS

We developed the three scales (Throat closing, Chest tightness, and Effort) using focus groups with 25 children. Subsequently, seventy-nine children (29 children with asthma, 30 children with cystic fibrosis. and 20 children who were healthy) aged 6 to 18 years rated each picture in each series, using a 0-10 scale. In addition, each child placed each picture in each series on a 100-cm long Visual Analogue Scale, with the anchors "not at all" and "a lot".

RESULTS

Children aged eight years or older rated the scales in the correct order 75% to 98% correctly, but children less than 8 years of age performed unreliably. The mean distance between each consecutive item in each pictorial scale was equal.

CONCLUSION

Preliminary results revealed that children aged 8 to 18 years understood and used these three scales measuring throat closing, chest tightness, and effort appropriately. The scales appear to accurately measure the construct of breathlessness, at least at an interval level. Additional research applying these scales to clinical situations is warranted.

Measurement of exercise cardiac output by thoracic impedance in healthy children

The purpose of this study was to track changes in stroke volume during exercise by impedance cardiography in order to validate the method, and to obtain such data in a large number of healthy children for reference purposes. One hundred and fifteen healthy children (aged 7-19 years) performed progressive exercise to voluntary exhaustion with work increments every minute on a cycle ergometer. Oxygen uptake (VO(2)) was measured on a breath-by-breath system. Cardiac output was measured with an ICG-M501 impedance cardiograph. Stroke volume was normalized for body surface area and expressed as stroke volume index. Cardiac output was regressed against VO(2), and differences between stroke volume index at rest and exercise were assessed by repeated measures analysis of variance. Cardiac output increased linearly with VO(2) in all subjects: individual slopes and intercepts averaged 5.16 (1.56) l.min(-1) per l.min(-1) VO(2), and 4.25 (1.92) l.min(-1), respectively [mean (SD)]. Stroke volume index rose by an average of 29% from rest to exercise, reaching a maximum of 52 ml.m(-2) in boys and girls. Most subjects demonstrated a continuous, gentle rise in stroke volume index with increasing work rate, though a minority demonstrated a falling index as work increased above the anaerobic threshold, despite rising cardiac output. Impedance cardiography accurately tracks cardiac output and can be a useful clinical and research tool in pediatric cardiology and exercise physiology.

Determinants of physical fitness in children with asthma

RATIONALE

This study was designed to examine the relationships among weight, asthma severity, physical activity, and aerobic fitness in children with asthma.

SUBJECTS AND METHODS

Sixty-four asthmatic children 8 to 12 years old (53% female) were assessed while attending a summer asthma camp. Measures included height and weight, spirometry, histamine bronchial provocation challenge, maximal aerobic power, and questionnaires to quantify habitual activity, perceived activity limitations due to asthma, perceived competence in physical activity, and attitudes toward physical activity. Asthma severity was determined from spirometric indices (forced expiratory volume during the first second), degree of airway hyperresponsiveness, and amount of medication prescribed.

RESULTS

There was no correlation between asthma severity and aerobic fitness. Only perceived competence at physical activity was found to have a significant correlation with aerobic fitness. Appropriate-weight, overweight, or obese (defined by body mass index) children all had similar results for maximum aerobic power and level of habitual activity. However, overweight or obese children reported greater limitation of physical activity. Their asthma-impairment scores were higher than the scores of appropriate-weight peers, although standard measures of pulmonary function were no different among groups. The higher asthma-severity scores were related to greater medication needs in the overweight or obese children with asthma.

CONCLUSIONS

Lower maximum aerobic power in asthmatic children is related more to how capable they perceive themselves than to asthma severity. Overweight asthmatic children experience greater limitation of physical activity and thus are prescribed more medication, although by standard measures of asthma severity, they are very similar to normal-weight peers with asthma. Efforts should be directed at understanding the reasons responsible for reduced exercise tolerance before escalating pharmacologic treatment.

Cardiopulmonary exercise performance in prematurely born children

Prematurely born children have reduced peak VO2 compared with their peers, inferentially attributed to ventilatory limitation. The primary purpose of this study was to compare exercise ventilation and cardiac output in a sample of childhood survivors of lung disease of prematurity with those of a control group to elucidate reasons for lower peak VO2. A secondary aim was to describe and compare the ventilatory response to incremental exercise. Thirty-two children, aged 8-9 y, were recalled for lung function and progressive exercise tests. Fifteen of them also performed submaximal exercise with measurement of cardiac output (indirect [CO2] Fick) and physiologic dead space. Results were compared with those of term-born, age- and sex-matched, control children. Pulmonary function tests showed mild airflow limitation. Peak VO2 was lower in prematurely born children compared with control children, and was correlated with lean body mass. Their heart rate-VO2 relationship and stroke volume were similar to that of term-born control children. Children with a history of bronchopulmonary dysplasia and hyaline membrane disease as infants exhibited greater exercise hyperpnea than did healthy control children, because of higher breathing frequency, and maintained lower end-tidal PCO2 during submaximal exercise. Physiologic dead space normalized for body weight was similar in preterm and term-born children. Lower peak VO2 in this population is not caused by cardiopulmonary factors, but is best predicted by lean body mass. Ventilation did not limit exercise performance, although it appears that breathing during exercise is regulated differently in prematurely born children than in term-born children.

High frequency ventilation trial. Nine year follow up of lung function

The high frequency ventilation (HIFI) trial for hyaline membrane disease (HMD) showed no advantage of high frequency over conventional ventilation in pulmonary outcomes after 24 months. The present study tested the hypothesis that there would be no significant difference in childhood lung function between patients who had been ventilated by either method. Thirty-two children aged 8-9 years who completed the HIFI trial were asked to return for pulmonary function tests. For purposes of analysis, the patient population was divided according to mode of ventilation, and by diagnosis of bronchopulmonary dysplasia (BPD) or HMD. Results were compared to those of 15 term-born, matched, controls. Lung function tests showed a mildly obstructive pattern in prematurely born children. More severe obstruction was seen in those children who had physician-diagnosed asthma or who had used bronchodilators in the past. The prevalence of mild obstructive pattern on pulmonary function testing in preterm infants with HMD or BPD was similar in those who received high frequency vs. conventional ventilation. Factors other than the mode of ventilation exert greater influence on pulmonary outcome in survivors of lung disease of prematurity.

Impedance cardiography accurately measures cardiac output during exercise in children with cystic fibrosis

OBJECTIVES

After validation of impedance cardiography (ICG) in healthy children, this same device was tested in children with cystic fibrosis (CF) to validate its capability of measuring cardiac output (Q) in this population.

DESIGN

Comparative study of ICG vs the indirect Fick (CO2) method.

SETTING

Tertiary care children's teaching hospital.

PATIENTS

Twenty-one CF children with mean FEV1 of 77 +/- 21% predicted.

MEASUREMENTS

ICG results were compared with CO2 rebreathing (RB) measurements of Q with sampling of capillary blood gases at two levels of exercise (0.5 and 1.5 W/kg). ICG measurements were made each minute, and duplicate RB measurements from 6 to 8 min at each workload. Q was regressed against oxygen uptake and results by each method were compared.

RESULTS

Mean bias (QRB-QICG) was -0.09 +/- 0.94 L/min. The largest deviation of QICG from QRB was +33%, and 83% of corresponding QICG values were within +/-20% of QRB result.

CONCLUSIONS

This device gives rapid, accurate, noninvasive Q measurements in children with CF.