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Airway reactance predicts static lung hyperinflation in severe asthma
Yen-Jung L1, Hsin-Kuo K2,3, Sheng-Wei P2,4, Jia-Yih F2,4, Kang-Cheng S2,5, Yang L1, Sheau-Ning Y6, Yi-Han H2,7#, Diahn-Warng P2,7#
1Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
2School of Medicine, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
3Division of Respiratory Therapy, Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
4Division of Pulmonary Immunology & Infectious Diseases, Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
5Division of Clinical Respiratory Physiology, Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
6Department of Pharmacy, Taipei Veterans General Hospital, Taipei, Taiwan
7Division of General Chest Medicine, Department of Chest Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
#These authors contributed equally to this work.
J Investig Allergol Clin Immunol 2024; Vol. 34(2)
Background: Static lung hyperinflation (SLH) measured by body plethysmography (Pleth) in asthma is associated with poor outcomes. The severity of SLH may be associated with small airway dysfunction (SAD), which can be measured by impulse oscillometry (IOS).
Objective: This study aims to determine the correlation between SLH and SAD in patients with severe asthma and the improvement of SLH and SAD in response to treatment.
Methods: We analyzed data from patients who were enrolled in the Taiwan Severe Asthma Registry, which was a prospective observational cohort. Pleth and IOS were regularly performed. The relationship between spirometric and IOS parameters was determined. Changes in the clinical outcomes in response to treatment were analyzed.
Results: In 107 patients with severe asthma, 83 (77.6%) had SLH by increased residual volume to total lung capacity (RV/TLC) ratio. Most patients were older female with worse pulmonary function and SAD compared with those without SLH. The SAD by increased airway resistance/reactance was significantly correlated with SLH. Airway reactance at 5 Hz (X5) ≤ −0.21 [kPa/(L/s)] detected SLH with the area under the receiver operating characteristic curve of 0.84 (p < 0.0001, sensitivity = 85.2%, and specificity = 83.3%). After 12 months, patients who received add-on biologics treatment had significantly reduced exacerbation, fractional exhaled nitric oxide level, blood eosinophil counts, improved forced expiratory volume in the first second, X5, and a trend of reduced RV/TLC ratio compared with those without biologics treatment.
Conclusion: In severe asthma, airway reactance X5 could be a novel parameter to assess SLH.
Key words: Body plethysmography, Impulse oscillometry, Static lung hyperinflation, Severe asthma