International guidelines recommend simple spirometry for bronchiectasis patients. However, pulmonary pathophysiology of bronchiectasis is very complex and still poorly understood. Our objective was to characterize lung function in bronchiectasis and identify specific functional sub-groups.

This was a multicenter, prospective, observational study enrolling consecutive adults with bronchiectasis during stable sate. Patients underwent body-plethysmography before and after acute bronchodilation testing, diffusing lung capacity (DLCO) with a 3-year follow up. Air trapping and hyperinflation were a residual volume (RV) > 120%predicted and a total lung capacity>120%predicted. Acute reversibility was: ΔFEV1 ≥12% and 200 mL from baseline (FEV1rev) and ΔRV ≥10% reduction from baseline (RVrev). Sensitivity analyses included different reversibility cutoffs and excluded patients with concomitant asthma or chronic obstructive pulmonary disease.

187 patients were enrolled (median age: 68 years; 29.4% males). Pathophysiological abnormalities often overlapped and were distributed as follows: air trapping (70.2%), impaired DLCO (55.7%), airflow obstruction (41.1%), hyperinflation (15.7%) and restriction (8.0%). 9.7% of patients had normal lung function. RVrev (17.6%) was more frequent than FEV1rev (4.3%). Similar proportions were found after multiple sensitivity analyses. Compared with non-reversible patients, patients with RVrev had more severe obstruction (mean(SD) FEV1%pred: 83.0% (24.4) vs 68.9% (26.2); P = 0.02) and air trapping (RV%pred, 151.9% (26.6) vs 166.2% (39.9); P = 0.028).

Spirometry alone does not encompass the variety of pathophysiological characteristics in bronchiectasis. Air trapping and diffusion impairment, not airflow obstruction, represent the most common functional abnormalities. RVrev is related to worse lung function and might be considered in bronchiectasis' workup and for patients’ functional stratification.