Feasibility and challenges of using multiple breath washout in COPD

Alan Bell, Philip J. Lawrence, Dave Singh, Alexander Horsley

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Lung clearance index (LCI), derived from multiple-breath washout (MBW), is a well-established assessment of ventilation inhomogeneity in cystic fibrosis (CF) but has not been widely applied in other conditions characterised by heterogeneous airways disease, such as COPD. The aim of this study was to evaluate the sensitivity, repeatability and practicality of LCI in patients with COPD. Methods: Fifty-four COPD patients completed MBWN2 (using an ExhalyzerTM device), spirometry and plethysmography. Twenty patients repeated MBWN2, MBWSF6 (using a separate InnocorTM gas analyser) and spirometry at a second visit ≥24 hrs later. Results: Mean (standard deviation) COPD LCIN2 was 12.1 (2.2); mean (SD) LCI Z-score 5.8 (2.0). LCIN2 increased across GOLD stages 1 to 3 and was abnormal (Z score >1.65) in all COPD patients, including those with FEV1 ≥80% predicted. LCI was repeatable (median intra-test coefficient of variation 4.1%) and reproducible (limits of agreement -1.8 to 1.6) after mean of 16 days. Functional residual capacity (FRC) measurements were significantly greater using nitrogen than SF6 or plethysmography (mean FRCN2 139% predicted vs. FRCpleth 125% predicted, p<0.0001). Conclusions: LCI is most suitable as a measure of early airways disease in COPD in those with well-preserved FEV1, with similar repeatability and limitations to that observed in CF. Using the Exhalyzer system to perform MBWN2 however appeared to substantially over-read FRC. This needs correcting before FRCN2 measurements using this system can be reliably deployed.
Original languageEnglish
JournalThe International Journal of Chronic Obstructive Pulmonary Disease
Early online date10 Jul 2018
DOIs
Publication statusPublished - 2018

Keywords

  • COPD Multiple breath washout Lung volumes Lung physiology Functional Residual Capacity Lung Clearance Index

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