title: Evaluation of carbon dioxide rebreathing during exercise assisted by noninvasive ventilation with plateau exhalation valve.
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 CO2rebreathing 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 FiCO2significantly increased at peak exercise (0.48%±0.19% vs 1.8%±0.6%) in patients with stable severe COPD. The inflection point of obvious CO2rebreathing 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 CO2rebreathing to COPD patients during exercise. Patients with mean expiratory flow >0.60-0.73 L/s may be predisposed to a higher risk of CO2rebreathing.
authors.affiliation: 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.
authors.forename: Yong-Er
authors.initials: YE
authors.lastname: Ou
authors.affiliation: 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.
authors.forename: Zhi-Min
authors.initials: ZM
authors.lastname: Lin
authors.affiliation: 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.
authors.forename: Dong-Ming
authors.initials: DM
authors.lastname: Hua
authors.affiliation: 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.
authors.forename: Ying
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: 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.
authors.forename: Ya-Ting
authors.initials: YT
authors.lastname: Huo
authors.affiliation: 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.
authors.forename: Qun
authors.initials: Q
authors.lastname: Luo
authors.affiliation: 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.
authors.forename: Rong-Chang
authors.initials: RC
authors.lastname: Chen
mesh_terms: D000368:Aged; D001944:Breath Tests; D002245:Carbon Dioxide / Q000378:metabolism*; D015444:Exercise; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D063087:Noninvasive Ventilation; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy*; D015203:Reproducibility of Results; D012119:Respiration
chemical_list: D002245:Carbon Dioxide
keywords: carbon dioxide rebreathing; chronic obstructive pulmonary disease; exercise; noninvasive ventilation; pulmonary rehabilitation; single-limb circuit