PT  - JOURNAL ARTICLE
AU  - Amaryllis Haccuria
AU  - Sébastien Michiels
AU  - Alain Michils
AU  - Alain Van Muylem
TI  - Interaction between airway calibre and exhaled NO: The allergen challenge model
DP  - 2013 Sep 01
TA  - European Respiratory Journal
PG  - P3550
VI  - 42
IP  - Suppl 57
4099  - http://erj.ersjournals.com/content/42/Suppl_57/P3550.short
4100  - http://erj.ersjournals.com/content/42/Suppl_57/P3550.full
SO  - Eur Respir J2013 Sep 01; 42
AB  - Background : High fractionated exhaled nitric oxide (FENO) detected in asthma patients reflects increased airway inflammation. However, FENO may be affected by airway calibre reduction, thus introducing a bias in FENO use for asthma control.Aim: to assess the impact on FENO of changes in both airway calibre and inflammation using the allergen challenge model.Methods: FEV1 (forced expired volume in one second) and FENO were measured during early (EAR) and late (LAR) responses to a house dust mite challenge in 15 mild allergic asthmatics. Ventilation distribution using single breath washout test with inert gases (He and SF6) was also performed to identify the sites of airway constriction, since different constriction sites result in different FENO reductions.Results: In EAR, mean FEV1 fall was 36.8%, FENO decreased by 22% (p=0.002) and SHe was greater than ΔSSF6 (+189.4% and +82.2%, p=0.001).In LAR, for a FEV1 fall of 31.7%, FENO decreased by 28.7% (p=0.002) with the same ΔSHe, ΔSSF6 pattern (+155.8% vs +76%, p=0.001).8 hours after EAR, whereas FEV1 was still lowered (p<0.001) FENO returned to baseline (p=0.085).At 24 hours, when FEV1 returned to baseline, FENO increased by 38.7% (p=0.04).Conclusion: In mild allergic asthma, changes in airway calibre significantly modulate changes in FENO levels resulting from concomitant changes in airway inflammation. Therefore, correct interpretation of FENO changes in asthma patients may require integration of changes in airway calibre occurring concomitantly. Airway constriction and inflammatory processes after allergen exposure seem to involve similar regions of the bronchial tree, mainly the conductive airways.