Expiratory flow limitation in a cohort of highly symptomatic COPD patients

Abstract

The question addressed by the studySmall 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.Materials/patients and methodsSeventy 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).ResultsEFLHigh 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.Answer to the questionOverall, 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.

Oscillometry-Defined Small Airway Dysfunction in Patients with Chronic Obstructive Pulmonary Disease

“…Dean et al [ 22 ] found that 37.4% of COPD patients (n=147) had EFL T . The pre-BD EFL T of our cohort was 41.3%, which is comparable to both studies [ 21 , 22 ]. Mikamo et al [ 19 ] examined the effects of EFL T among 74 patients with COPD using a lower cutoff of ∆X5 (0.55 cm H2O/L/sec).…”

“…Dean et al [ 22 ] reported no significant changes in ∆X5 values in patients with COPD between baseline and after 2 years of treatment, irrespective of baseline EFL T . Beech et al [ 21 ] also observed that despite 6 months of treatment, EFL T persisted in the majority of patients. Crim et al [ 17 ] found little variability in impedance parameters over 3 months.…”

“…Paredi et al [ 20 ] observed that ∆X5 in COPD patients was higher than that in asthma patients, and ∆X5 can differentiate between these two diseases. Beech et al [ 21 ] observed that 47.8% of COPD patients (n=70) had EFL T . Dean et al [ 22 ] found that 37.4% of COPD patients (n=147) had EFL T .…”

Investigation of the Methodology of Specific Airway Resistance Measurements in COPD

“…The abnormality seen in the SR aw loop of a COPD patient may result from expiratory flow limitation (EFL), which is a phenomenon where choke points form in the intrathoracic airways during tidal exhalation. 1,[19][20][21] Diminished elastic recoil and airway remodelling in these patients contribute to airway narrowing that occurs earlier during exhalation, and results in gas trapping and ventilation inhomogeneity. This can be seen as an asymmetry between the inspiratory and expiratory parts of the SR aw loop.…”