Airway Hyperresponsiveness Measured By Impulse Oscillometry Following EVH

Abstract

1562 The efficacy of impulse oscillometry (IOS) to measure change in airway resistance is yet to be established. PURPOSE: To evaluate lung function change after eucapnic voluntary hyperventilation and compare IOS and maximal expiratory flow measurements. METHODS: Seventeen subjects (8 AHR+, 9 AHR−) performed a 6-min eucapnic voluntary hyperventilation challenge (EVH) at 85% MVV. Pre- and 5-, 10-, and 15-min post-IOS and spirometry were performed to determine change in airway resistance (Raw) and FEV1. Lung function evaluation required the subject to breathe at resting tidal volumes for 30 s for IOS measurements; a maximal expiratory flow volume maneuver immediately followed the IOS maneuver. RESULTS: AHR+ subjects had significantly greater peak falls in FEV1 than AHR- subjects following EVH (31.7 ± 15.7 vs 8.1 ± 1.67, p<0.05). Likewise, airway resistance (Raw) was significantly greater for AHR+ than for AHR- subjects (8.3 ± 3.73 vs 3.10 ± 0.97, p<0.05). Raw at 5Hz was strongly correlated to FEV1 in AHR+ subjects and AHR- subjects (r = −0.77 and −0.59; p<0.05). Resonant frequency (Fres) and the area of reactance integrated from 5Hz to Fres were also significantly correlated to FEV1 (r = −0.77 and – 0.73; p<0.05). CONCLUSION: IOS can be used to determine AHR and supplement spirometry in lung function evaluation. Supported in part by VIASYS Health Care.