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Alveolar and exhaled NO in relation to asthma characteristics – effects of correction for axial diffusion
Author(s) -
HeijkenskjöldRentzhog C.,
Nordvall L.,
Janson C.,
Borres M. P.,
Alving K.,
Malinovschi A.
Publication year - 2014
Publication title -
allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.363
H-Index - 173
eISSN - 1398-9995
pISSN - 0105-4538
DOI - 10.1111/all.12430
Subject(s) - medicine , wheeze , asthma , atopy , exhaled nitric oxide , gastroenterology , pulmonary function testing , exhalation , spirometry , cohort , anesthesia
Background Inflammation in the small airways might contribute to incomplete asthma disease control despite intensive treatment in some subgroups of patients. Exhaled NO (Fe NO ) is a marker of inflammation in asthma and the estimated NO contribution from small airways (Calv NO ) is believed to reflect distal inflammation. Recent studies recommend adjustments of Calv NO for trumpet model and axial diffusion ( TMAD ‐adj). This study aimed to investigate the clinical correlates of Calv NO , both TMAD ‐adjusted and unadjusted. Methods Asthma symptoms, asthma control, lung function, bronchial responsiveness, blood eosinophils, atopy and treatment level were assessed in 410 subjects, aged 10–35 years. Exhaled NO was measured at different flow‐rates and Calv NO calculated, with TMAD ‐adjustment according to C ondorelli. Results Trumpet model and axial diffusion‐adjusted Calv NO was not related to daytime wheeze ( P = 0.27), FEF 50 ( P = 0.23) or bronchial responsiveness ( P = 0.52). On the other hand, unadjusted Calv NO was increased in subjects with daytime wheeze ( P < 0.001), decreased FEF 50 ( P = 0.02) and with moderate‐to‐severe compared to normal bronchial responsiveness ( P < 0.001). All these characteristics correlated with increased Fe NO (all P < 0.05). Unadjusted Calv NO was positively related to bronchial NO flux (J'aw NO ) ( r = 0.22, P < 0.001) while TMAD ‐adjCalv NO was negatively related to J'aw NO ( r = −0.38, P < 0.001). Conclusions Adjusted Calv NO was not associated with any asthma characteristics studied in this large asthma cohort. However, both Fe NO and unadjusted Calv NO related to asthma symptoms, lung function and bronchial responsiveness. We suggest a potential overadjustment by current TMAD ‐corrections, validated in healthy or unobstructed asthmatics. Further studies assessing axial diffusion in asthmatics with different degrees of airway obstruction and the validity of proposed TMAD ‐corrections are warranted.