Impulse Oscillometry Discerns the Peripheral Airway Response to an Inhaled Bronchodilator between Obese and Nonobese Children

Impulse oscillometry (iOS) is a useful tool to distinguish between central and peripheral airway resistance. For example, iOS has shown that peripheral airway resistance is greater in children with versus those without obesity, despite no difference in FEV 1 . Considering the added peripheral airway resistance in children with obesity, we sought to determine if iOS can detect potential differences in the peripheral airway response to an inhaled bronchodilator (BD) between children with and those without obesity. Methods Twenty‐four children with and eleven without obesity, ages 8–12yrs, completed iOS and spirometry testing before and 15mins after the administration of four puffs of an inhaled BD (Ventolin ® , 90μg). A mixed models ANOVA (group by pre‐to‐post‐BD) was used to determine differences in FEV 1 , plethysmographic airway resistance (Raw) and specific Raw (sRaw), and iOS parameters associated with airway resistance. These parameters include resistance at 5 Hz, 10 Hz (R 5 and R 10 : total airway resistance), 20 Hz (R 20 : large airway resistance), and the difference between R 5 and R 20 (R 5–20 : peripheral airway resistance). Reactance at 5 Hz (X 5 : total airway elastic recoil) and the area under the reactance‐frequency curve (AX: index of small airway patency) were also measured using iOS. Results There was no difference in FEV 1 (% pred) or FEV 1 /FVC between groups and none of our participants showed a positive BD response based on the conventional method of a ≥12% increase in FEV 1 . Compared with children without obesity, children with obesity presented a greater baseline R 5 (7.28 ± 1.20 vs. 5.42 ± 1.44 cmH 2 O·L −1 ·s −1 ; p =0.001), R 10 (6.04 ± 1.12 vs. 4.58 ± 1.07 cmH 2 O·L −1 ·s −1 ; p =0.002), R 20 (4.76 ± 0.95 vs. 3.94 ± 0.79 cmH 2 O·L −1 ·s −1 ; p =0.025), R 5–20 (2.52 ± 0.64 vs. 1.49 ± 0.75 cmH 2 O·L −1 ·s −1 ; p <0.001), and AX (7.65 ± 5.59 vs. 3.75 ± 1.97 cmH 2 O·L −1 ; p =0.008), with no difference in X 5 (−1.19 ± 0.77 vs. −1.19 ± 0.33 cmH 2 O·L −1 ; p =0.667). A group by pre‐to‐post‐BD interaction was found for R 5 (p=0.033) and R 10 (p=0.024). Both R 5 and R 10 decreased to a greater extent with BD in children with obesity versus children without obesity (R 5 : −20.8 ± 9.5% vs. −12.8 ± 15.2%; R 10 : −21.6 ± 8.6% vs. −14.5 ± 13.1%). In all children (n=35), Raw, sRaw, and all iOS parameters, except for X 5 , decreased with the BD ( p <0.05). Conclusion In addition to greater central and peripheral airway resistance in children with obesity, iOS also detected a greater peripheral airway response to a BD in children with obesity. Although no established criteria exist for children ages 8–12yrs, the American Thoracic Society defines an airway response in preschool children as a 20–40% decrease in R 5 and a 15–30% decrease in R 10 . Based on these criteria, our finding that R 5 and R 10 dropped by 20.8% and 21.6% in children with obesity indicates potential peripheral airway hyperresponsiveness in children with obesity. However, further research is warranted to establish the meaning of, or normal criteria for, peripheral airway responsiveness in prepubescent children. Support or Funding Information NIH R01 HL136643, Texas Health Presbyterian Hospital Dallas, King Charitable Foundation Trust, and Dr. Pepper Snapple. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .