Last updated on October 2018

Reducing Exercise-induced Bronchoconstriction in Children With Asthma and Obesity


Brief description of study

In obese children, excess fat exerts an increased mechanical burden on the respiratory system, particularly during exercise. It is unclear whether this burden reduces respiratory function and exercise tolerance and increases severity of exercise-induced bronchoconstriction in obese asthmatic children. The investigators propose that most of the respiratory effects in obese asthmatic children are the result of low lung volume breathing (i.e., reduced functional residual capacity). The first objective of this study is to investigate respiratory function, exercise tolerance, and exercise-induced bronchoconstriction in obese vs. nonobese asthmatic children. Guidelines from the American Thoracic Society strongly recommend interval warm-up exercise before planned exercise to reduce exercise-induced bronchoconstriction severity. However, no empirical data on the effects of interval warm-up exercise on exercise-induced bronchoconstriction severity are available in obese asthmatic children, where excess fat exerts such an unfavorable burden on the respiratory system, particularly during exercise. Thus, the second objective of this study is to investigate the effects of interval warm-up exercise on exercise-induced bronchoconstriction severity in obese and nonobese asthmatic children. Our approach will be to investigate exercise tolerance, respiratory function, and exercise-induced bronchoconstriction severity and the effects of (1) 8x30sec interval warm-up & (2) pretreatment with a bronchodilator compared with a no-treatment control on exercise-induced bronchoconstriction severity in 8-12 yr, prepubescent, obese and nonobese asthmatic children.

[Aim 1]: To investigate respiratory function and exercise tolerance [Hypothesis]: Obesity in children with asthma will reduce respiratory function and exercise tolerance [Aim 2]: To investigate exercise-induced bronchoconstriction. [Hypothesis]: Obesity in children with asthma will increase exercise-induced bronchoconstriction severity as evidenced by a greater maximum % fall in forced expiratory volume in the first second after an exercise challenge test.

[Aim 3]: To investigate the effects of interval warm-up exercise on exercise-induced bronchoconstriction severity. [Hypothesis]: Interval warm-up exercise will reduce exercise-induced bronchoconstriction severity after an exercise challenge test to a similar extent as bronchodilator and better than control, although to a greater extent in nonobese asthmatic children.

Detailed Study Description

The investigators will enroll prepubescent, 8 - 12 yr old, obese (body mass index > 95th percentile; N=25) and nonobese (body mass between 16th and 84th percentile; N=25) children with mild asthma. The investigators will investigate the severity of exercise-induced bronchoconstriction during planned exercise performed 15 minutes after the following three conditions performed on separate days in a random order: (1) 8x30sec interval warm-up, (2) short-acting beta agonist or albuterol, & (3) control, in prepubescent, 8 - 12 yr old, obese and nonobese children with mild asthma. The investigators will also investigate differences in pulmonary function, exercise tolerance, and severity of exercise-induced bronchoconstriction between obese and nonobese children.

The investigators will measure the following in all participants:

  1. Pulmonary function: spirometry, lung volumes, diffusing capacity of lung for carbon monoxide, maximum voluntary ventilation, maximal inspiratory and expiratory pressures, airway resistance, and expired nitric oxide
  2. Exercise tolerance during graded cycle ergometry: Gas exchange, ventilation, heart rate, blood pressure, pulse oximetry, electrocardiogram
  3. Ratings of perceived breathlessness and exercise induced bronchoconstriction in response to a 6 minute high-intensity exercise challenge after three conditions performed on three separate days:

Three conditions that will precede the exercise challenge include:

  1. 8x30sec of interval warm-up 15min prior to exercise challenge: This includes eight 30sec bouts of high-intensity interval exercise at 85-95% of HRmax, with 45sec of recovery between.
  2. Two puffs of albuterol 15 min prior to exercise challenge
  3. Control: seated rest for 15min prior to exercise challenge

Clinical Study Identifier: NCT03586544

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