Flow-independent nitric oxide parameters in asthma: a systematic review and meta-analysis

摘要

Introduction. Fractional exhaled nitric oxide (F_ENO) has been proposed as a non-invasivemarker of inflammation in the lungs.Measuring F_ENO at severalflowrates enables the calculation of flowindependent NO-parameters that describe the NO-exchange dynamics of the lungsmore precisely.The purpose of this studywas to compare the NO-parameters between asthmatics and healthy subjects in a systematic review andmeta-analysis. Methods.Asystematic search was performed in Ovid Medline,Web of Science, Scopus and Cochrane Library databases. All studies with asthmatic and healthy control groups with at least one NO-parameter calculated were included. Results. From 1137 identified studies, 33 were included in the meta-analysis. All NO-parameters (alveolar NO concentration (C_ANO), bronchial flux of NO(J_(aw)NO), bronchialmucosal NO concentration (C_(aw)NO) and bronchial wall NO diffusion capacity (D_(aw)NO)) were found increased in glucocorticoid-treated and glucocorticoid-na?ve asthma. J_(aw) NO and C_ANO were most notably increased in both study groups. Elevation of Daw NO and Caw NO seemed less prominent in both asthma groups. Discussion.We found that all theNO-parameters are elevated in asthma as compared to healthy subjects. However, results were highly heterogenous and the evidence on C_(aw) NO and D_(aw) NO is still quite feeble due to only few studies reporting them.To gainmore knowledge on the NO-parameters in asthma, nonlinear methods and standardized study protocols should be used in future studies.