Abstract
Background: It is well known that ozone (O3) exposure induces lung function decrease and airways neutrophilia, but a great variability in airways response has been observed among patients with asthma.
Aim: To find predictors of functional and biological airway response to O3 exposure in mild to moderate asthmatic patients.
Methods: We studied 120 patients with mild-to-moderate asthma (FEV1% 89.4±14.3), randomly exposed to air or O3 (0.3 ppm for 2 hrs) in a challenge chamber. Symptoms and Pulmonary Function Test were measured before and immediately after exposure. Six hours after exposure, induced sputum was collected. Patients were evaluated according to their functional (ΔFEV1air-O3) and neutrophilic (Δneutro%air-O3) response to O3. Age, baseline FEV1%pred, inhaled corticosteroids (ICS) therapy, baseline sputum neutrophils/ml and eosinophils/ml counts, methacholine responsiveness, atopy and smoking habit were considered as possible predictors of functional and neutrophilic response.
Results: FEV1 responders had a lower percentage of ICS-treated patients and lower baseline FEV1 values in comparison with non-responders. Neutrophil responders were younger, more responsive to methacholine challenge and had lower baseline sputum inflammatory cell counts in comparison with non-responders.
Conclusions: Patients without ICS therapy and lower FEV1 are more susceptible to functional response to O3. Bronchial hyperresponsiveness and baseline sputum inflammation may predict a neutrophilic airway response to O3; high sputum neutrophil percentages are protective against a further neutrophilic response to O3. Therefore, determinants of functional and inflammatory responses to O3 are different.
- © 2012 ERS