Carbon Dioxide Rebreathing During Exercise Assisted by Non-invasive Ventilation

Study Overview
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Brief Summary
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The purpose of this study was to evaluate whether CO2 rebreathing occurs in healthy subjects or patients with COPD ventilated during exercise assisted by the single-limb circuit with a plateau exhalation valve at a given inspiratory positive airway pressure and a minimal level of expiratory positive airway pressure (EPAP) and whether there is a potential threshold for predicting CO2 rebreathing.

Detailed Description
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Non-invasive ventilation circuit consists of single-limb tubing for inspiration and expiration, including a plateau exhalation valve. As exhaled gases was vented out the plateau exhalation valve at a constant rate, during exercise, with the increase of exhalation flow, single-limb circuit with a plateau exhalation valve might cause carbon dioxide(CO2) rebreathing. Therefore, our aim in the present study was to evaluate whether CO2 rebreathing occurs in COPD patients ventilated during exercise assisted by the single-limb circuit with a plateau exhalation valve and estimate a potential threshold for predicting CO2 rebreathing.

Official Title
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Evaluation of Carbon Dioxide Rebreathing During Exercise Assisted by Non-invasive Ventilation

Conditions
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Pulmonary Disease, Chronic Obstructive

Intervention / Treatment
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* Device: BiPAP® Vision® ventilator（Ventilator, Philips Respironics™ BiPAP® Vision® ）


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: presented clinically stable (no exacerbation in the 4 weeks prior to study participation or with no change in medications); physician diagnosed COPD, forced expiratory volume in 1s (FEV1) < 50% predicted; dyspnea as a main symptom that limited daily activities. Exclusion Criteria: subjects with obvious pulmonary bullae demonstrated by chest CT scan or X-ray; examination or facial trauma/malformation, recent facial, upper airway or upper gastrointestinal tract surgery, that would preclude receiving NIV therapy; a history of coronary artery disease or cardiac arrhythmias or potential electrocardiographic alterations; a history of uncontrolled hypertension, or other respiratory diseases; oxygen saturation(SpO2) < 88% at rest with a fraction of inspired oxygen (FiO2) ≥ 0.5; patients with musculoskeletal or neurological disorders; or failure to comply with the research protocol.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: COPD patients<br>Oxygen was delivered to the face mask by a tube at a constant rate (5L/min) to keep the fingertip oxygen saturation at 90% or above. Ventilatory assistance was delivered using a BiPAP® Vision® ventilator (Respironics, Murrysville, Pennsylvania, USA) in BiPAP mode applied via a tightly fitting full face mask (Curative, Suzhou, China). A symptom-limited cycle exercise test was performed while assisted by non-invasive ventilation (NIV). All measurements were recorded at inspiratory pressure of 14 cmH2O, expiratory pressure of 4 cmH2O during rest and exercise. Breathing pattern, mean exhalation flow, mean plateau exhalation valve flow, the mean inspiratory fraction of CO2 (tidal FiCO2) reinsufflated from the circuit between the mask and the exhalation valve was measured for each breath. | Device: BiPAP® Vision® ventilator（Ventilator, Philips Respironics™ BiPAP® Vision® ）<br>* See details from arm descriptions.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| mean exhalation valve flow |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| mean exhalation flow |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 
| mean inspiratory fraction of CO2 for each tidal volume |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 
| fraction of end-tidal carbon dioxide partial pressure |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 
| inspiratory time |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 
| expiratory time |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 
| respiratory rate |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 
| inspiratory tidal volume |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 
| expiratory tidal volume |  | Measurements were collected continuously throughout a symptom-limited cycle exercise test （test lasts for about 8-12 min） while subjects breathed through the full face mask. Analyses were made breath by breath during the whole test process. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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COPD, noninvasive ventilation, exercise, CO2 rebreathing