RT Journal Article SR Electronic T1 The clinical utility of forced oscillation technique during hospitalisation in patients with exacerbation of COPD JF ERJ Open Research JO erjor FD European Respiratory Society SP 00448-2021 DO 10.1183/23120541.00448-2021 VO 7 IS 4 A1 Jaber S. Alqahtani A1 Ahmad M. Al Rajeh A1 Abdulelah M. Aldhahir A1 Yousef S. Aldabayan A1 John R. Hurst A1 Swapna Mandal YR 2021 UL http://openres.ersjournals.com/content/7/4/00448-2021.abstract AB Background Forced Oscillation Technique (FOT) is an innovative tool to measure within-breath reactance at 5 Hz (ΔXrs5Hz) but its feasibility and utility in acute exacerbations of COPD (AECOPD) is understudied.Methods A prospective observational study was conducted in 82 COPD patients admitted due to AECOPD. FOT indices were measured and the association between these indices and spirometry, peak inspiratory flow rate, blood inflammatory biomarkers and patient-reported outcomes including assessment of dyspnoea, quality of life, anxiety and depression and frailty at admission and discharge were explored.Results All patients were able to perform FOT in both sitting and supine position. The prevalence of expiratory flow limitation (EFL) in the upright position was 39% (32 out of 82) and increased to 50% (41 out of 82) in the supine position. EFL (measured by ΔXrs5Hz) and resistance at 5 Hz (Rrs5Hz) negatively correlated with forced expiratory volume in 1 s (FEV1); those with EFL had lower FEV1 (0.74±0.30 versus 0.94±0.36 L, p = 0.01) and forced vital capacity (1.7±0.55 versus 2.1±0.63 L, p = 0.009) and higher body mass index (27 (21–36) versus 23 (19–26) kg·m−2, p = 0.03) compared to those without EFL. During recovery from AECOPD, changes in EFL were observed in association with improvement in breathlessness.Conclusion FOT was easily used to detect EFL during hospitalisation due to AECOPD. The prevalence of EFL increased when patients moved from a seated to a supine position and EFL was negatively correlated with airflow limitation. Improvements in EFL were associated with a reduction in breathlessness. FOT is of potential clinical value by providing a noninvasive, objective and effort-independent technique to measure lung function parameters during AECOPD requiring hospital admission.FOT is easily used to detect EFL during hospitalisation due to AECOPD. FOT is of potential clinical value by providing a noninvasive, objective and effort-independent technique to measure lung function parameters during AECOPD requiring hospital admission. https://bit.ly/3vTJpCI