Expiratory flow limitation in a cohort of highly symptomatic COPD patients

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.

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).

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.

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.