Small airway collapse during expiration, known as expiratory flow limitation (EFL), can be detected using oscillometry and is associated with worse clinical outcomes in chronic obstructive pulmonary disease (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.
Seventy patients were recruited. Clinical characteristics and lung function metrics were collected at baseline and 6 months. Impulse oscillometry (IOS) was used to detect presence of EFL. Patients were defined as EFLHigh (ΔX5 ≥0.28 kPa L s−2); EFLIntermediate (ΔX5 0.1–0.27 kPa L s−2) and EFLNone (ΔX5 <0.1 kPa L s−2).
EFLHigh was present in 47.8% of patients at baseline. ΔX5 showed excellent repeatability over 6 months (rho=0.78, p<0.0001, ICC=0.88), with the best repeatability observed in EFLNone and EFLHigh patients (ICC=0.77 and 0.65 respectively). Compared to EFLNone patients, EFLHigh had a higher BMI, worse health-related quality of life and increased peripheral airway resistance. EFLIntermediate was more variable over time with less severe physiological impairment.
Overall, these data indicate that EFLHigh is a common, and relatively stable, component of disease pathophysiology in highly symptomatic COPD patients. EFLHigh was also associated with worse quality of life and obesity.