• Masanori Yasuo, Yoshiaki Kitaguchi, Fumiya Kinota, Makoto Kosaka, Kazuhisa Urushihata, Atsuhito Ushiki, Hiroshi Yamamoto, Satoshi Kawakami, and Masayuki Hanaoka.
• The First Department of Internal Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan. Electronic address: yasumasa@shinshu-u.ac.jp.
• Respir Investig. 2018 May 1; 56 (3): 222-229.

BackgroundPulmonary function tests (PFTs) comprise the traditional method for detecting central airway obstruction (CAO) and evaluating therapeutic effects, but are effort-dependent. By contrast, the forced oscillation technique (FOT) is performed during tidal breathing in an effort-independent mode and is universally used to assess respiratory function in patients with chronic obstructive pulmonary disease (COPD) and asthma. We used the FOT to measure airway resistance and reactance in patients with CAO before and after interventional bronchoscopy and compared the results to data obtained using PFTs.MethodsTwelve patients with CAO were recruited from December 2013 to July 2016. The FOT, PFTs, chest computed tomography (CT), COPD Assessment Test (CAT), and the modified Medical Research Council (mMRC) dyspnea scale were employed before and after interventional bronchoscopy. The minimum airway cross-sectional area (MACSA) was calculated using a CT image calculator.ResultsOf the 12 patients, 6 had tracheal obstruction and 6 had bronchial obstruction. All FOT measurements, except ΔX5, were significantly improved after interventional bronchoscopy in all cases. The significance of the improvement was greater with the FOT than PFTs. The MACSA, CAT, and mMRC dyspnea scale scores also significantly improved in all cases. Furthermore, only alteration of resistance at 20 Hz (R20) significantly correlated with the alteration of the MACSA after intervention. No significant correlations were found for PFTs.ConclusionsThe FOT is suitable and convenient for assessing therapeutic results in patients with tracheobronchial CAO. The alteration of R20 is useful for estimating the airway dilation of CAO after interventional bronchoscopy.Copyright © 2018 The Japanese Respiratory Society. Published by Elsevier B.V. All rights reserved.

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