TY - JOUR T1 - Controlled <em>versus</em> free breathing for multiple breath nitrogen washout in asthma JF - ERJ Open Research JO - erjor DO - 10.1183/23120541.00487-2021 SP - 00487-2021 AU - Blake M. Handley AU - Jack Bozier AU - Edward Jeagal AU - Sandra Rutting AU - Robin E. Schoeffel AU - Paul D. Robinson AU - Gregory G. King AU - Stephen Milne AU - Cindy Thamrin Y1 - 2021/01/01 UR - http://openres.ersjournals.com/content/early/2021/10/08/23120541.00487-2021.abstract N2 - Multiple Breath Nitrogen Washout (MBNW) is an emerging clinical test for assessing ventilation heterogeneity [1], often characteristically increased in asthma. MBNW indices both indicate and predict response to asthma treatment [2–4], and therefore may be an important tool for guiding treatment decisions [2]. Two established breathing protocols are currently in use: 1-litre tidal volume-controlled breathing (CB) [5, 6] and unrestricted free breathing (FB) [7]. The CB protocol requires targeted tidal volume (VT) and respiratory rate (RR), whereas the FB protocol encourages relaxed tidal breathing, making it more suitable for paediatrics [8]. Two recently-published studies in healthy adults showed that indices of conductive and acinar ventilation heterogeneity (Scond and Sacin, respectively), and to a lesser extent, lung clearance index (LCI), were not comparable between breathing protocols [9, 10]. Importantly, differences between the protocols were dependent on the magnitude of ventilation heterogeneity. Thus, the assumption is that these effects would be amplified in disease, where ventilation heterogeneity is greater and clinical utility is most relevant. However, this has not been confirmed to date. We hypothesised that people with asthma, where ventilation heterogeneity is greater, would exhibit greater differences between the two protocols, than the differences seen in healthy adults.FootnotesThis manuscript has recently been accepted for publication in the ERJ Open Research. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJOR online. Please open or download the PDF to view this article.Conflict of interest: Mr. Handley has nothing to disclose.Conflict of interest: Dr. Bozier has nothing to disclose.Conflict of interest: Edward Jeagal has nothing to disclose.Conflict of interest: Dr. Rutting has nothing to disclose.Conflict of interest: Robin Schoeffel has nothing to disclose.Conflict of interest: Dr. Robinson has nothing to disclose.Conflict of interest: Dr. King reports grants, personal fees, non-financial support and other from AstraZeneca, Boehringer Ingelheim, CycloPharm, GlaxoSmithKline, Novartis, Menarini, MundiPharma, grants from National Health &amp;amp; Medical Research Council, Asthma Foundation, outside the submitted work.Conflict of interest: Dr. Milne has nothing to disclose.Conflict of interest: Dr. Thamrin reports non-financial support from Restech SRL, Milan, Italy, grants from AstraZeneca, UK, outside the submitted work. ER -