Changes in forced oscillation mechanics and symptoms prior to COPD exacerbations during home telemonitoring

Abstract

Introduction: Early detection of acute exacerbations in COPD (AECOPD) may allow early intervention, however practical markers are limited. The forced oscillation technique (FOT) is known to be a sensitive predictor of recovery from AECOPD in hospital. As a home monitoring tool, the feasibility of FOT has been established, but not its utility in detection of AECOPD. Aim: To study changes in resistance (Rrs) and reactance (Xrs) versus symptoms obtained from home telemonitoring prior to AECOPDs. Methods: Severe to very severe COPD patients were monitored over a period of 8-9 months. They performed unsupervised FOT measurements once daily using the Resmon Pro Diary (Restech srl, Milan, Italy). Daily symptoms were assessed by an electronic diary based on the COPD Assessment Test (CAT). AECOPD was assessed by weekly phone interviews, and defined as initiation of oral/systemic steroid or antibiotic treatment, a visit to the emergency department or hospitalisation. Daily Rrs, Xrs and their coefficient of variation (CV, over a 7-day running window) and CAT scores within a week prior to an AECOPD were compared using one-way repeated measures ANOVA. Results: Data from 10 patients are presented (7:3 male:female, mean±SD age 69.7±10.8 years, %predFEV1 38.4±5.2). 27 AECOPDs were identified; 3 excluded due to missing FOT/CAT data. Out of the FOT indices examined, only CV Xrs changed significantly with time (p=0.0018), from 20.9±12.2% at 7 days to 26.6±3.9% at 1 day prior to AECOPD. Daily CAT increased from 21.8±6.2 to 23.7±7.5, but not significantly (p=0.08). Conclusions: FOT is more sensitive than symptoms in detecting changes prior to an AECOPD, and may be useful as an early marker.