Prevalence of small airway dysfunction among GOLD stages in COPD patients

Abstract

Background and Aim: In COPD patients, the exact role of Small Airway Dysfunction (SAD) in the clinical features and progression of the disease has not clearly been established. Aim of our study was to evaluate the prevalence of SAD among patients with different level of severity (GOLD stages). Methods: We prospectively enrolled COPD outpatients from University Hospital of Parma. By an Impulse Oscillometry System (IOS) we recorded data about SAD; in particular, we have assessed the fall in resistance from 5 Hz to 20 Hz (R5-R20, kPa sL-1) used as value of peripheral airway resistance. Reactance at 5 Hz (X5, kPasL-1) as value of conductance was also measured. We also categorized the patients according to the old GOLD classification, related to airflow obstruction (I, II, III, IV) and the new GOLD classification, related to classes of risk (A, B, C, D). Results: 180 patients (75% males; mean age 67 y; mean FEV 1 53% of predicted) were studied. According to the old and the new GOLD classifications, the percentage of patients were 13%, 43%, 32%, 12% (for the stage I, II, III and IV), and 35%, 21%, 11%, 33% (for the stage A, B, C, D), respectively. Among the first to the last GOLD stages, we found a progressive and significant increase and decrease distribution of R5-R20 and X5, respectively (see Figure). Conclusions: In COPD patients, the prevalence of SAD progressively increases with the airflow obstruction degree and classes of risk.