TY - JOUR T1 - Novel volumetric capnography indices measure ventilation inhomogeneity in cystic fibrosis JF - ERJ Open Research JO - erjor DO - 10.1183/23120541.00440-2021 SP - 00440-2021 AU - Sotirios Fouzas AU - Anne-Christianne Kentgens AU - Olga Lagiou AU - Bettina Sarah Frauchiger AU - Florian Wyler AU - Ilias Theodorakopoulos AU - Sophie Yammine AU - Philipp Latzin Y1 - 2021/01/01 UR - http://openres.ersjournals.com/content/early/2021/12/16/23120541.00440-2021.abstract N2 - Background Volumetric capnography (VCap) is a simpler alternative of multiple-breath washout (MBW) to detect ventilation inhomogeneity (VI) in patients with cystic fibrosis (CF). However, its diagnostic performance is influenced by breathing dynamics. We introduce two novel VCap indices, the Capnographic Inhomogeneity Indices (CIIs) that may overcome this limitation and explore their diagnostic characteristics in a cohort of CF patients.Methods We analysed 320 N2-MBW trials from 50 CF patients and 65 controls (age 4-18 years) and calculated classical VCap indices, such as slope III (SIII) and the capnographic index (KPIv). We introduced novel CIIs based on a theoretical lung model, and assessed their diagnostic performance compared to classical VCap indices and the lung clearance index (LCI).Results Both CIIs were significantly higher in CF patients compared with controls (mean±SD CII1 5.9±1.4% versus 5.1±1.0%, p=0.002; CII2 7.7±1.8% versus 6.8±1.4%, p=0.002) and presented strong correlation with LCI (CII1 R2=0.47 and CII2 R2=0.44 in CF patients). Classical VCap indices showed inferior discriminative ability (SIII 2.3±1.0%/L versus 1.9±0.7%/L, P=0.013; KPIv 3.9±1.3% versus 3.5±1.2%, P=0.071), while the correlation with LCI was weak (SIII R2=0.03; KPIv R2=0.08 in CF patients). CIIs showed lower intra-subject inter-trial variability, calculated as coefficient of variation for three and relative difference for two trials, than classical VCap indices, but higher than LCI (CII1 11.1±8.2% and CII2 11.0±8.0% versus SIII 16.3±13.5%; KPIv 15.9±12.8%; LCI 5.9%±4.2%).Conclusion CIIs detect VI better than classical VCap indices and correlate well with LCI. However, further studies on their diagnostic performance and clinical utility are required.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.Conflicts of interest: Sotirios Fouzas has nothing to disclose.Conflicts of interest: Anne-Christianne Kentgens repots no other conflicts of interest.Conflicts of interest: Olga Lagiou has nothing to disclose.Conflicts of interest: Bettina Sarah Frauchiger has nothing to disclose.Conflicts of interest: Florian Wyler has nothing to disclose.Conflicts of interest: Ilias Theodorakopoulos has nothing to disclose.Conflicts of interest: Sophie Yammine repots no other conflicts of interest.Conflicts of interest: P. Latzin reports grants from Vertex and Vifor paid to the institution, personal and honoraria paid to the institution from Vertex, Vifor and OM Pharma, and for participation on a Data Safety Monitoring Board or Advisory Board personal from Santhera (DMC) and personal and fees paid to the institution from Polyphor, Vertex, OM pharma and Vifor, all outside the submitted work. ER -