Abstract
The applicability and interpretation of inert tracer gas washout tests is hampered by the lack of feasible protocols and reproducibility data. We assessed feasibility, variability and reproducibility of a new easy to perform double tracer gas (DTG) single-breath washout (SBW) test and compared this with conventional nitrogen washouts.
In 40 healthy nonsmokers and 20 patients with stable chronic obstructive pulmonary disease (COPD), we performed three N2 vital capacity SBWs, three N2 multiple-breath washouts and three tidal DTG-SBW tests. Follow-up was after 1 week, 1 month and 6 months. Main outcomes were the lung clearance index (LCI) (N2 multiple-breath washout), slope of phase III (dN2) (N2 vital capacity SBW) and slope of phase III (SIIIDTG) (DTG-SBW).
In healthy subjects, mean±sd LCI at baseline was 6.94±0.61, dN2 0.99±0.42% N2 per litre and SIIIDTG −0.206±0.108 g·mol−1·L−1. In COPD, LCI and dN2 were significantly higher (LCI 12.23±2.67, dN2 7.43±5.38% N2 per litre; p<0.001) and SIIIDTG significantly steeper (−0.653±0.428 g·mol−1·L−1, p<0.001). Reproducibility was high for main outcome parameters: the intraclass correlation coefficient over 6 months was 0.77 (0.86 in COPD) for LCI, 0.82 (0.89) for dN2 and 0.83 (0.93) for SIIIDTG.
The tidal DTG-SBW is a reproducible test in healthy and COPD subjects that seems attractive for use in routine clinical settings.
Abstract
DTG-SBW may play a role in detection and monitoring of small airway diseases or as an outcome in drug trials http://ow.ly/x15bw
Footnotes
For editorial comments see page 1113.
This article has supplementary material available from www.erj.ersjournals.com
Clinical trial: This study is registered in the German Clinical Trials Register with identifier number DRKS00003541.
Support statement: This study is part of an investigator-initiated trial supported in equal parts by grants from Chiesi GmbH (Hamburg, Germany) and the Robert Bosch Foundation (grant number KKF-12-8; Robert-Bosch Stiftung GmbH, Stuttgart, Germany).
Conflict of interest: Disclosures can be found alongside the online version of this article at www.erj.ersjournals.com
- Received May 19, 2013.
- Accepted May 14, 2014.
- ©ERS 2014