Award Date

5-1-2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Interdisciplinary Programs

First Committee Member

Dharini Bhammar

Second Committee Member

Graham McGinnis

Third Committee Member

Keoni Kins

Fourth Committee Member

Lung-Chang Chien

Number of Pages

107

Abstract

Purpose: The troubling link between obesity and asthma in children, along with greater associated detrimental health effects, warrants investigation to better understand the mechanisms driving this relationship as well as its consequences, especially during exercise. Bronchodilators and interval warm-up exercises are recommended by the American Thoracic Society to prevent exercise-induced bronchoconstriction (EIB). Whether interval warm-up exercise can prevent EIB to the same extent as bronchodilators in asthmatic children is unknown but clinically important. Therefore, the first purpose of this study is to investigate the effects of obesity on pulmonary function, exercise tolerance, and exercise-induced bronchoconstriction in asthmatic children. The second purpose of this study is to compare the effects of interval warm-up exercise, bronchodilator, and control on EIB severity in asthmatic children. Methodology: Eleven nonobese (10.6 ± 1.0 yr., BMI: 17.9 ± 1.9 kg/m2) boys (n=8) and girls (n=3) and five overweight/obese (10.5 ± 0.8 yr., BMI: 27.0 ± 4.0 kg/m2) boys (n=3) and girls (n=2) participated in this study. All participants completed a pulmonary function test before and after bronchodilator administration, a cardiopulmonary exercise test, a verification test to confirm maximal oxygen uptake, and Dual-energy X-ray Absorptiometry to determine percent body fat and regional fat distributions. Participants also completed three conditions on separate visits: control, bronchodilator, and interval warm-up exercise. Fifteen minutes after each condition, participants completed an exercise challenge test. Participants completed spirometry and impulse oscillometry (IOS) before each condition, ten minutes after each condition, and at 2, 5, 10, 15, 20, 25, and 30min after completing the exercise challenge test. During exercise testing, gas exchange, ventilation, heart rate, pulse oxygen saturation, breathing pattern, and perceived breathlessness and exertion ratings were measured. Operating lung volumes (i.e., end-expiratory and end-inspiratory lung volumes) were calculated using inspiratory capacity and expressed relative to total lung capacity. After completion of the interval warm-up exercise and exercise challenge tests, participants recorded their top three descriptors of breathlessness using a questionnaire as well as any negative feelings (i.e., anxiety, fear, anger, depression, and frustration) associated with breathlessness using a visual analog scale they experienced during the test. Expiratory flow limitation was indicated when exercise tidal flow volume loops intersected with maximal flow-volume loops. Results: Higher regional (chest and abdomen) and total fat mass and percent fat were associated with higher airway resistance as measured by R5 and R5-R20. No significant linear relationships were found between measures of body composition and exercise tolerance (i.e., % predicted V̇O2max) or EIB. No significant differences were found between interval warm-up exercise and control condition on EIB (i.e., ΔForced expiratory volume in one second [FEV1]). Bronchodilator pre-treatment led to significantly higher FEV1 after administration and at every time point after exercise challenge testing when compared with interval warm-up exercise and control conditions. Conclusion: Overweight/obese children with mild asthma have a similar pulmonary function when compared with nonobese children with asthma based on indices of spirometry, lung volumes, and IOS. Overweight/obesity does not compromise cardiorespiratory fitness or increase EIB in children with mild asthma. Interval warm-up exercise does not produce bronchodilation and does not prevent bronchoconstriction when compared with albuterol in children with mild asthma. Therefore, interval warm-up exercise may not be an effective intervention for EIB.

Keywords

albuterol; asthma; children; exercise-induced bronchoconstriction; high-intensity interval warm-up; obesity

Disciplines

Medicine and Health Sciences

File Format

pdf

File Size

2400 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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