BackgroundForced 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.MethodsA 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.ResultsAll 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% (32/82) and increased to 50% (41/82) in the supine position. EFL (measured by ΔXrs5Hz) and resistance at 5 Hz (Rrs5Hz) negatively correlated with FEV1; those with EFL had lower FEV1 (0.74±0.30 versus 0.94±0.36 L, p=0.01) and FVC (1.7 ±0.55 versus 2.1 ±0.63 L, p= 0.009) and higher BMI [27 (21–36) versus 23 (19–26) kg/m2, p=0.03] compared to those without EFL. During recovery from AECOPD, changes in EFL was observed in association with improvement in breathlessness.ConclusionFOT 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 non-invasive, objective, and effort-independent technique to measure lung function parameters during AECOPD requiring hospital admission.
The Clinical Utility of Forced Oscillation Technique (FOT) during Hospitalisation in patients with exacerbation of COPD
