Closed circuit rebreathing to achieve inert gas wash-in for multiple breath wash-out

Horsley, Alex R.; O'Neill, Katherine; Downey, Damian G.; Elborn, J. Stuart; Bell, Nicholas J.; Smith, Jaclyn; Owers-Bradley, John

Abstract

Multiple breath wash-out (MBW) testing requires prior wash-in of inert tracer gas. Wash-in efficiency can be enhanced by a rebreathing tracer in a closed circuit. Previous attempts to deploy this did not account for the impact of CO2 accumulation on patients and were unsuccessful. We hypothesised that an effective rebreathe wash-in could be delivered and it would not alter wash-out parameters.

Computer modelling was used to assess the impact of the rebreathe method on wash-in efficiency. Clinical testing of open and closed circuit wash-in–wash-out was performed in healthy controls and adult patients with cystic fibrosis (CF) using a circuit with an effective CO2 scrubber and a refined wash-in protocol.

Wash-in efficiency was enhanced by rebreathing. There was no difference in mean lung clearance index between the two wash-in methods for controls (6.5 versus 6.4; p=0.2, n=12) or patients with CF (10.9 versus 10.8; p=0.2, n=19). Test time was reduced by rebreathe wash-in (156 versus230 s for CF patients, p<0.001) and both methods were well tolerated. End wash-in CO2 was maintained below 2% in most cases.

Rebreathe–wash-in is a promising development that, when correctly deployed, reduces wash-in time and facilitates portable MBW testing. For mild CF, wash-out outcomes are equivalent to an open circuit.

Citation

Horsley, A. R., O'Neill, K., Downey, D. G., Elborn, J. S., Bell, N. J., Smith, J., & Owers-Bradley, J. (2016). Closed circuit rebreathing to achieve inert gas wash-in for multiple breath wash-out. ERJ Open Research, 2(1), https://doi.org/10.1183/23120541.00042-2015

• Journal Article Type: Article
• Acceptance Date: Nov 19, 2015
• Publication Date: Jan 22, 2016
• Deposit Date: Dec 21, 2016
• Publicly Available Date: Dec 21, 2016
• Journal: ERJ Open Research
• Electronic ISSN: 2312-0541
• Publisher: European Respiratory Society
• Peer Reviewed: Peer Reviewed
• Volume: 2
• Issue: 1
• DOI: https://doi.org/10.1183/23120541.00042-2015
• Public URL: https://nottingham-repository.worktribe.com/output/771886
• Publisher URL: http://openres.ersjournals.com/content/2/1/00042-2015
• Contract Date: Dec 21, 2016