Exhaled nitric oxide fraction in asthmatic children: relationship with spirometric patterns and spirometric response to exercise

Abstract

Introduction: Respiratory epithelium normally produces nitric oxide and its synthesis and release increase in eosinophilic inflammation. Exhaled nitric oxide levels (FeNO) correlate with other signs of eosinophilic inflammation in bronchial biopsies, BAL, and induced sputum. Forced spirometry reflects the functional status of the respiratory system; it is an important tool for diagnosing asthma and monitoring its progression. Changes induced in it by bronchodilators or exercise are indicators of the status of the bronchi.

Objective: To estimate the relationship between FeNO levels and: 1) basal and post bronchodilator spirometry patterns; 2) the response to exercise challenge test.

Materials and methods: Population: 1) children diagnosed with moderate asthma (MA), treated with inhaled corticosteroids (ICS), and 2) a subgroup of children with MA, treated with ICS, who reported exercise-related respiratory symptoms.

Methods: 1) Measurement of FeNO (Bedfont NO breath, UK) according to recommended methodology and of basal and post-bronchodilator spirometry (according to ATS/ERS standards; Micro Lab-Micro Medical Ltd.-UK spirometer); 2) measurement of FeNO followed by exercise challenge test in treadmill (ATS/ERS standards).

Results: 1) 229 children (56% M), mean age 11 years (6-19). FeNO ≥ 30 ppb was associated with a positive response to bronchodilator in FEF, P (0.01) 2) 45 children (51% M), age 11 to (8-18). 16 EIB + High FeNO (> 30 ppb) was associated with positive test (sensitivity 93.3%, specificity 58%).

Duscussion/Conclusion: Elevated FeNO was associated with a positive response to bronchodilator in distal flows and bronquial reactivity to exercise.