Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disease characterized by progressive obstruction of the airways. In advanced stages, it can progress to chronic respiratory failure with major respiratory repercussions.

Biologically, hyperinflation manifests as alveolar hypoventilation, which causes hypercapnia. Mechanically, it is responsible for an increase in ventilatory work associated with diaphragmatic muscle dysfunction and fatigue, leading to exercise incapacity.

Physical inactivity is a major predictor of mortality in patients with COPD. The recommendations of the European Respiratory Society (ERS) and the American Thoracic Society (ATS) emphasize the importance of exercise in the treatment and management of COPD.

Respiratory rehabilitation has been shown to have an indisputable effect on dyspnea and the quality of life of COPD patients. Current guidelines for respiratory rehabilitation recommend interventions at a frequency of at least 2 to 3 supervised high-intensity training sessions per week. A minimum of 4 weeks of physical training is necessary to achieve a significant improvement in quality of life, dyspnea, and endurance.

A reduction in the duration and intensity of sessions is often necessary, thus limiting the desired benefits of respiratory rehabilitation.

Non-invasive ventilation (NIV) provides mechanical respiratory assistance by helping inspiration and optimizing expiration through a non-invasive interface such as a mask. Its use during exercise in severe COPD is to try to correct hypercapnia, reduce dynamic hyperinflation by helping the respiratory muscles to improve their work, and reduce dyspnea and the feeling of muscle weakness.

However, the modalities in terms of ventilation mode and inspiratory support pressures are not clearly established.

The objective of this study is therefore to compare different levels of ventilatory assistance during exercise to determine whether the level of inspiratory assistance during exercise significantly improves endurance in these patients and, in particular, whether high-intensity ventilatory assistance (inspiratory assistance 21 +/- 3 cmH20) provides a greater benefit in terms of endurance time compared to moderate intensity (inspiratory assistance 13 +/- 3 cmH20) or low intensity (inspiratory assistance < 6 cmH20).

Inclusion Criteria:

• -COPD stage GOLD III or IV
• Baseline hypercapnia PaCO2 > 45 mmHg OR Alveolar hypoventilation during exercise (increase in PaCO2 > 5 mmHg),
• Exhaustion of more than 80% of ventilatory reserve OR max power < 50 Watts
• Affiliation or entitlement to social security coverage
• Signature of informed consent

Exclusion Criteria:

• BMI > 35
• Recent acute respiratory exacerbation < 4 weeks
• Severe unstable cardiac disease
• Pneumothorax or pneumomediastinum
• Pathological hypotension
• Cerebrospinal fluid leak, recent head trauma, or cranial surgery
• Severe bulbar disorder
• Dehydration
• Severe orthopedic or neurological disorder compromising rehabilitation.
• Patient deprived of liberty or patient under guardianship
• Pregnant woman