Respiratory System Model Parameters Track Changes in Lung Function after Bronchodilation

Impulse Oscillometry (IOS) provides respiratory resistance, Rrs, and reactance, Xrs, between 3 - 35 (Hz). We measured IOS parameters in 26 randomly selected Anglo children 6-19 years in El Paso TX. An expert pulmonologist classified Rrs and Xrs as: Normal (n = 5 ); Possible Small Airway Impairment, Possible SAI, (n = 4); Definite SAI (n = 6); or Asthma (n = 11). We used the extended RIC (eRIC) and augmented RIC (aRIC) models of the human respiratory system to derive Large (R) and Peripheral (Rp) airway resistance, and small airway compliance, Cp. IOS Rrs and Xrs at selected frequencies reflecting large and peripheral airway function. Model-derived parameters were compared between pre- and post-bronchodilator tests. IOS Xrs at low frequencies (AX) and model-derived Cp were the most sensitive parameters for detecting bronchodilator responses, which were significant in children with SAI and asthma. Model-derived Cp correlated closely with AX. We conclude that response to bronchodilator in children with SAI is sensitively measured by IOS. Electrical equivalent model parameters are as sensitive as primary IOS data in detecting bronchodilator response.