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Leaks during multiple-breath washout: characterisation and influence on outcomes


Lenherr, Nina; Ramsey, Kathryn A; Jost, Kerstin; Hornwall, Linn; Singer, Florian; Yammine, Sophie; Latzin, Philipp (2018). Leaks during multiple-breath washout: characterisation and influence on outcomes. ERJ Open Research, 4(1):00012-2017.

Abstract

Nitrogen multiple-breath washout (NMBW) 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 NMBW data from 10 children by modifying breath tables. In addition, leaks were applied to the equipment during NMBW 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", signs that enable easy identification of leaks during measurements. Air leaks during measurement significantly influence NMBW 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

Nitrogen multiple-breath washout (NMBW) 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 NMBW data from 10 children by modifying breath tables. In addition, leaks were applied to the equipment during NMBW 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", signs that enable easy identification of leaks during measurements. Air leaks during measurement significantly influence NMBW 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.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Children's Hospital Zurich > Medical Clinic
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:January 2018
Deposited On:07 Dec 2018 09:41
Last Modified:11 May 2020 18:14
Publisher:European Respiratory Society
ISSN:2312-0541
OA Status:Gold
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:https://doi.org/10.1183/23120541.00012-2017
PubMed ID:29497618

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