Background: A complex relationship between arachidonic acid metabolites and nitric oxide (NO) synthesis has been reported in asthma. The effects of inhaled aspirin on fractional exhaled NO (FENO) in patients with aspirin-tolerant (ATA) and aspirin-inducible (AIA) asthma compared with normal controls have been investigated.
Methods: The FENO was measured baseline, after saline and lysine-aspirin (L-ASA) bronchial challenge in 10 patients with ATA and in 10 patients with AIA [mean (PD20FEV1 L-ASA): 14.7 ± 12.7 mg], who had comparable age and baseline FEV1. Ten healthy subjects served as controls. Sputum eosinophils were counted after saline and after L-ASA challenge in the two groups of asthmatics.
Results: Asthmatic patients had baseline FENO significantly higher than controls (29.7 ± 6.8 vs 9.8 ± 2.05 p.p.b. respectively, P < 0.0001). No difference was observed in methacholine PD20FEV1 and baseline FENO between ATA and AIA patients. After L-ASA inhalation, FENO increased significantly only in patients with AIA, reaching the peak value 4 h after bronchoconstriction (from 31.1 ± 6 to 43 ± 4.8 p.p.b., P < 0.001), while no change was observed in patients with ATA and in controls. Sputum eosinophils increased significantly after L-ASA inhalation only in patients with AIA (from 8.1 ± 2.7 to 11.1 ± 2.8%, P < 0.005) and there was a significant relationship between the increase in sputum eosinophils and the increase in FENO after ASA challenge.
Conclusion: Exhaled NO may indicate eosinophilic airway inflammation during ASA exposure in patients with ASA inducible asthma.