Relationship between airway inflammation and remodeling in patients with asthma and chronic obstructive pulmonary disease

Abstract

Despite a number of important differences in the pathogenesis, course and prognosis of asthma and chronic obstructive pulmonary disease (COPD), these two entities also have common features with airway inflammation being one of them. Airway remodeling is a characteristic feature of asthma, but data on the bronchial wall thickening in COPD patients are still scarce.

Aim: To assess the relation between the inflammatory cell count in the bronchoalveolar lavage fluid (BALF) and thickness of bronchial walls assessed by high resolution computed tomography (HRCT) in asthma and COPD patients.

Material and methods: The study was conducted in 9 patients with mild-to-moderate asthma (M/F 4/5, mean age 35 +/- 10 years) and 11 patients with mild-to-moderate COPD (M/F 7/4, mean age 57 +/- 9 years). In all subjects lung function tests and HRCT scanning of the chest were performed. External (D) and internal (L) diameters of the airways were assessed at five selected lung levels. The lumen area (A(L)), wall area (WA), wall thickness (WT) and bronchial wall thickness (WT/D ratio) were calculated. Eight patients with asthma and 8 patients with COPD underwent fiberoptic bronchoscopy and bronchoalveolar lavage (BAL). Total and differential cell counts were assessed in the BAL fluid.

Results: Mean FEV(1)% pred was 80 +/- 19%, and 73 +/- 20% in asthma and COPD patients, respectively (NS). No significant differences in the total and differential cell counts in BALF were found in patients with asthma and COPD. There were no significant differences in the airway diameter or airway wall thickness. The mean inner airway diameter was 1.4 +/- 0.3 and 1.2 +/- 0.3 mm and the mean lumen area was 1.8 +/- 0.7 and 1.6 +/- 0.7 mm(2) in asthma and COPD, respectively (NS). Negative correlations between the eosinophil count in BALF and inner airway diameter (r=-0.7, P<0.05) and lumen area (r=-0.7, P<0.05) were found in asthmatics. There was no significant relationship between the BALF cell count and airway wall thickness in COPD patients. -

Conclusions: In mild-to-moderate asthma and COPD the airway diameter and thickness are similar. In asthmatics, the airway diameter might be associated with eosinophil count in BAL fluid.

Figure 1

Scheme of the bronchus and the parameters measured in HRCT: D - external diameter, L - internal (luminal) diameter, WT - wall thickness, A_O - total airway area, AL - luminal area, WA - wall area.