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Updated: May 5, 2026

Employing the Forced Oscillation Technique for the Assessment of Respiratory Mechanics in Adults
Published on: February 9, 2022
Regional differences in bronchial reactivity assessed by respiratory impedance
Egidio Beretta1, Francesco Tana2, Gabriele Simone Grasso1
1Dept. of Health Sciences, University of Milano-Bicocca, 20900 Monza, Italy.
Abstract:
We used the Impulse Oscillometric System (IOS) to gain information concerning the distribution of hyper-reactivity along the bronchial tree during methacholine challenge test (MCT). 37 subjects underwent MCT until reaching the provocative dose (PD20). At each dose, we estimated respiratory resistance at 5 and 20Hz (R5, R20), and reactance at 5Hz (X5). In non-responsive subjects (N=14) no changes in R5, R20, and X5 were observed during MCT. In responsive subjects, a wide spectrum of responses was found concerning frequency dependence and PD20. We describe two phenotypes representing the extremes of response. For PD20>400μg (N=13), MCT caused equal changes of resistance/reactance on varying oscillation frequencies, suggesting a homogeneous bronchoconstriction along the bronchial tree. For PD20<200μg (N=10), a remarkable frequency dependence was observed, with increase in R5, no change in R20, and decrease in X5, suggesting hyper-responsiveness of the distal airways paralleled by a change in visco-elastic properties of lung parenchyma.
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