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

Abstract

IntroductionImpulse 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 FEV1. 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.MethodsTwenty‐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 FEV1, plethysmographic airway resistance (Raw) and specific Raw (sRaw), and iOS parameters associated with airway resistance. These parameters include resistance at 5 Hz, 10 Hz (R5 and R10: total airway resistance), 20 Hz (R20: large airway resistance), and the difference between R5 and R20 (R5–20: peripheral airway resistance). Reactance at 5 Hz (X5: total airway elastic recoil) and the area under the reactance‐frequency curve (AX: index of small airway patency) were also measured using iOS.ResultsThere was no difference in FEV1 (% pred) or FEV1/FVC between groups and none of our participants showed a positive BD response based on the conventional method of a ≥12% increase in FEV1. Compared with children without obesity, children with obesity presented a greater baseline R5 (7.28 ± 1.20 vs. 5.42 ± 1.44 cmH2O·L−1·s−1; p=0.001), R10 (6.04 ± 1.12 vs. 4.58 ± 1.07 cmH2O·L−1·s−1; p=0.002), R20 (4.76 ± 0.95 vs. 3.94 ± 0.79 cmH2O·L−1·s−1; p=0.025), R5–20 (2.52 ± 0.64 vs. 1.49 ± 0.75 cmH2O·L−1·s−1; p<0.001), and AX (7.65 ± 5.59 vs. 3.75 ± 1.97 cmH2O·L−1; p=0.008), with no difference in X5 (−1.19 ± 0.77 vs. −1.19 ± 0.33 cmH2O·L−1; p=0.667). A group by pre‐to‐post‐BD interaction was found for R5 (p=0.033) and R10 (p=0.024). Both R5 and R10 decreased to a greater extent with BD in children with obesity versus children without obesity (R5: −20.8 ± 9.5% vs. −12.8 ± 15.2%; R10: −21.6 ± 8.6% vs. −14.5 ± 13.1%). In all children (n=35), Raw, sRaw, and all iOS parameters, except for X5, decreased with the BD (p<0.05).ConclusionIn 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 R5 and a 15–30% decrease in R10. Based on these criteria, our finding that R5 and R10 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 InformationNIH 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.