Expiratory flow limitation in a cohort of highly symptomatic COPD patients

THE QUESTION ADDRESSED BY THE STUDY: Small airway collapse during expiration, known as expiratory flow limitation (EFL), can be detected using oscillometry and is associated with worse clinical outcomes in COPD. This study investigated the prevalence of EFL in a cohort of highly symptomatic patients, evaluated clinical and lung function characteristics of patients with EFL and studied the repeatability of EFL over 6 months. MATERIALS/PATIENTS AND METHODS: 70 patients were recruited. Clinical characteristics and lung function metrics were collected at baseline and 6 months. Impulse oscillometry was used to detect the presence of EFL. Patients were defined as EFL(High) (change in reactance measured at 5 Hz (ΔX(5)) ≥0.28 kPa·L(−1)·s(−1)); EFL(Intermediate) (ΔX(5) 0.1–0.27 kPa·L(−1)·s(−1)) and EFL(None) (ΔX(5) <0.1 kPa·L(−1)·s(−1)). RESULTS: EFL(High) was present in 47.8% of patients at baseline. ΔX(5) showed excellent repeatability over 6 months (ρ=0.78, p<0.0001, intraclass correlation coefficient (ICC) 0.88), with the best repeatability observed in EFL(None) and EFL(High) patients (ICC 0.77 and 0.65, respectively). Compared to EFL(None) patients, EFL(High) had a higher body mass index, worse health-related quality of life and increased peripheral airway resistance. EFL(Intermediate) was more variable over time with less severe physiological impairment. ANSWER TO THE QUESTION: Overall, these data indicate that EFL(High) is a common, and relatively stable, component of disease pathophysiology in highly symptomatic COPD patients. EFL(High) was also associated with worse quality of life and obesity.