Abstract
Nitrogen multiple-breath washout (N2MBW) is increasingly used in patients with cystic fibrosis. The current European Respiratory Society/American Thoracic Society consensus statement for MBW recommends the rejection of measurements with leaks. However, it is unclear whether this is necessary for all types of leaks. Here, our aim was to 1) model and 2) apply air leaks, and 3) to assess their influence on the primary MBW outcomes of lung clearance index and functional residual capacity.
We investigated the influence of air leaks at various locations (pre-, intra- and post-capillary), sizes, durations and stages of the washout. Modelled leaks were applied to existing N2MBW data from 10 children by modifying breath tables. In addition, leaks were applied to the equipment during N2MBW measurements performed by one healthy adolescent.
All modelled and applied leaks resulted in statistically significant but heterogeneous effects on lung clearance index and functional residual capacity. In all types of continuous inspiratory leaks exceeding a certain size, the end of the washout was not reached. For practical application, we illustrated six different “red flags”, i.e. signs that enable easy identification of leaks during measurements.
Air leaks during measurement significantly influence N2MBW outcomes. The influence of leaks on MBW outcomes is dependent on the location, relation to breath cycle, duration, stage of washout and size of the leak. We identified a range of signs to help distinguish leaks from physiological noise.
Abstract
The influence of leaks on nitrogen MBW outcomes is complex, dynamic and dependent on the size, duration, location and position of leaks during the washout and breathing cycle http://ow.ly/PbHV30hB91H
Footnotes
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Support statement: This research was funded by the Swiss Society of Cystic Fibrosis (CFCH), Foundation Botnar, and University of Basel and UKBB. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. Funding information for this article has been deposited with the Crossref Funder Registry.
Conflict of interest: None declared.
- Received January 29, 2017.
- Accepted December 13, 2017.
- Copyright ©ERS 2018
This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial Licence 4.0.