Mechanical effects of obesity on central and peripheral airway resistance in nonasthmatic early pubescent children

Background: In children, obesity typically reduces functional residual capacity (FRC), which reduces airway caliber and increases airway resistance. Whether these obesity-related changes in respiratory function can alter bronchodilator responsiveness is unknown. Objective: To investigate bronchodilator responsiveness in nonasthmatic children with and without obesity. Methods: Seventy nonasthmatic children, 8−12 years old, without (n = 19) and with (n = 51) obesity, completed spirometry, impulse oscillometry, and airway resistance measurements through plethysmography pre/post 360 µg of inhaled albuterol. FRC was assessed pre albuterol. A two-way analysis of variance determined the effects of obesity (group) and inhaled albuterol (pre−post) on outcome measures. Results: FRC (%total lung capacity) was 16% lower in children with obesity compared with those without obesity. There was no significant group by pre−post albuterol interaction on any outcome variables. Albuterol inhalation reduced total, central and peripheral airway resistance and increased airway reactance (i.e., less negative) to a similar degree in children with and without obesity. In children with obesity, airway resistance was increased whether measured by impulse oscillometry or plethysmography. However, once airway resistance was adjusted for lung volumes (i.e., specific airway resistance or sR_aw), there were no differences between children with and without obesity. In addition, significant but moderate associations were detected between chest mass and FRC (r = −0.566; p < 0.001), FRC and total airway resistance (i.e., R_aw; r = −0.445; p < 0.001). Conclusions: In nonasthmatic early pubescent children, obesity increases total, central, and peripheral respiratory system resistance. However, the added respiratory system resistance and low lung volume breathing with obesity are not sufficient to reduce bronchodilator responsiveness.