Alveolar and exhaled NO in relation to asthma characteristics – effects of correction for axial diffusion. Issue 8 (4th June 2014)

• Record Type: Journal Article
• Authors: Heijkenskjöld‐Rentzhog, C.; Nordvall, L.; Janson, C.; Borres, M. P.; Alving, K.; Malinovschi, A.
• Is Part Of: Allergy. Volume 69:Issue 8(2014:Aug.)
• Page Start: 1102
• Page End: 1111
• Publication Date: 2014-06-04
• Subjects: Allergy -- Periodicals; 616.97
• DOI: 10.1111/all.12430
• Languages: English
• ISSNs: 0105-4538

Abstract

<abstract abstract-type="main" id="all12430-abs-0001"> <title>Abstract</title> <sec id="all12430-sec-0001" sec-type="section"> <title>Background</title> <p>Inflammation in the small airways might contribute to incomplete asthma disease control despite intensive treatment in some subgroups of patients. Exhaled NO (FeNO) is a marker of inflammation in asthma and the estimated NO contribution from small airways (Calv<sub>NO</sub>) is believed to reflect distal inflammation. Recent studies recommend adjustments of Calv<sub>NO</sub> for trumpet model and axial diffusion (TMAD‐adj). This study aimed to investigate the clinical correlates of Calv<sub>NO</sub>, both TMAD‐adjusted and unadjusted.</p> </sec> <sec id="all12430-sec-0002" sec-type="section"> <title>Methods</title> <p>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<sub>NO</sub> calculated, with TMAD‐adjustment according to Condorelli.</p> </sec> <sec id="all12430-sec-0003" sec-type="section"> <title>Results</title> <p>Trumpet model and axial diffusion‐adjusted Calv<sub>NO</sub> was not related to daytime wheeze (<italic>P </italic>=<italic> </italic>0.27), FEF50 (<italic>P </italic>=<italic> </italic>0.23) or bronchial responsiveness (<italic>P </italic>=<italic> </italic>0.52). On the other hand, unadjusted Calv<sub>NO</sub> was increased in subjects with daytime wheeze (<italic>P </italic><<italic> </italic>0.001), decreased FEF<sub>50</sub> (<italic>P </italic>=<italic> </italic>0.02) and with moderate‐to‐severe compared to normal bronchial responsiveness (<italic>P </italic><<italic> </italic>0.001). All these characteristics correlated with increased FeNO (all <italic>P</italic> < 0.05). Unadjusted Calv<sub>NO</sub> was positively related to bronchial NO flux (J'aw<sub>NO</sub>) (<italic>r</italic> = 0.22, <italic>P </italic><<italic> </italic>0.001) while TMAD‐adjCalv<sub>NO</sub> was negatively related to J'aw<sub>NO</sub> (<italic>r</italic> = −0.38, <italic>P </italic><<italic> </italic>0.001).</p> </sec> <sec id="all12430-sec-0004" sec-type="section"> <title>Conclusions</title> <p>Adjusted Calv<sub>NO</sub> was not associated with any asthma characteristics studied in this large asthma cohort. However, both FeNO and unadjusted Calv<sub>NO</sub> 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.</p> </sec> </abstract>