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Evaluation of carbon dioxide rebreathing during exercise assisted by noninvasive ventilation with plateau exhalation valve

Authors Ou YE, Lin ZM, Hua DM, Jiang Y, Huo YT, Luo Q, Chen RC

Received 6 September 2016

Accepted for publication 21 December 2016

Published 16 January 2017 Volume 2017:12 Pages 291—298

DOI https://doi.org/10.2147/COPD.S121637

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Professor Hsiao-Chi Chuang

Peer reviewer comments 4

Editor who approved publication: Dr Richard Russell

Yong-er Ou,* Zhi-min Lin,* Dong-ming Hua, Ying Jiang, Ya-ting Huo, Qun Luo, Rong-Chang Chen

State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, People’s Republic of China

*These authors contributed equally to this work

Abstract: Noninvasive ventilation with a plateau exhalation valve (PEV) is often used as an adjunct to exercise to achieve a physiologic training effect in severe chronic obstructive pulmonary disease (COPD) patients. However, during exercise, with the increase of exhalation flow and respiratory rate and limited capability of PEV to exhale gases out of the circuit, it is still unknown whether CO2 rebreathing occurs in COPD patients ventilated during exercise assisted by single-limb circuit with a PEV. A maximal symptom-limited cycle exercise test was performed while ventilated on pressure support (inspiratory:expiratory pressure 14:4 cmH2O) in 18 male patients with stable severe COPD (mean ± standard deviation, forced expiratory volume in 1 s: 29.5%±6.9% predicted). At rest and during exercise, breathing pattern, mean expiratory flow, mean expiratory flow of PEV, and the mean inspiratory fraction of CO2 (tidal fractional concentration of inspired CO2 [FiCO2]) reinsufflated from the circuit was measured for each breath. In comparison with rest, with the significant increase of mean expiratory flow (0.39±0.15 vs 0.82±0.27 L/s), fractional concentration of end-tidal CO2 (2.6%±0.7% vs 5.5%±0.6%), and the significant decrease of mean expiratory flow of PEV (0.41±0.02 vs 0.39±0.03 L/s), tidal FiCO2 significantly increased at peak exercise (0.48%±0.19% vs 1.8%±0.6%) in patients with stable severe COPD. The inflection point of obvious CO2 rebreathing was 0.67±0.09 L/s (95% confidence interval 0.60–0.73 L/s). Ventilated by a single-limb tubing with PEV caused CO2 rebreathing to COPD patients during exercise. Patients with mean expiratory flow >0.60–0.73 L/s may be predisposed to a higher risk of CO2 rebreathing.

Keywords: carbon dioxide rebreathing, noninvasive ventilation, exercise, chronic obstructive pulmonary disease, single-limb circuit, pulmonary rehabilitation

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