Baseline airway inflammation may be a determinant of the response to ozone exposure in asthmatic patients

Context: It is well known that ozone exposure decreases lung function and increases airway neutrophilia, but large variability has been observed among asthmatic patients. Objective: To find possible predictors of functional and inflammatory airway response to ozone in asthmatic patients. Materials and methods: We studied 120 patients with mild-to-moderate asthma, randomly exposed to either air or ozone (0.3 ppm for 2 h) in a challenge chamber. Symptoms and pulmonary function test (PFT) were measured before and immediately after exposure. Six hours after exposure, induced sputum was collected. Patients were evaluated according to their functional (FEV1 responders) or neutrophilic (neutrophil responders) response to ozone. We considered, as possible predictors of response: age, baseline FEV1, previous treatment with inhaled corticosteroids (ICS), baseline sputum neutrophils, baseline sputum eosinophils, methacholine responsiveness, atopy and smoking habit. Results: FEV1 responders had lower baseline FEV1, and a lower percentage of these had received ICS treatment. Neutrophil responders were younger, with lower baseline sputum inflammation and greater methacholine responsiveness. These results were confirmed by multivariate logistic analysis. Discussion and conclusion: Patients not previously treated with ICS and patients with lower FEV1 are more prone to functional response to ozone. Lower baseline airway inflammation and greater bronchial hyperresponsiveness may predict neutrophilic airway response to ozone in asthmatic patients. Thus, determinants of functional and inflammatory responses to ozone are different.