During-exercise Physiological Effects of Nasal High-flow in Patients With Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease is a major cause of disability and mortality worldwide. This disease progressively leads to dyspnea and exercise capacity impairment. Pulmonary rehabilitation teaches chronic obstructive pulmonary disease patients to cope effectively with the systemic effects of the disease and improves exercise capacity, dyspnea and quality of life in patients with chronic obstructive pulmonary disease. However, the best training modality remains unknown. Physiological studies highlight the benefit of high intensity endurance training. However, many patients do not tolerate such a training due to ventilatory limitation and dyspnea. Therefore, a strategy to reduce dyspnea would allow a greater physiological muscle solicitation and improvement. Thus, many studies focus on means to increase exercise tolerance in patients with chronic obstructive pulmonary disease.

Nasal high flow delivers heated and humidified high flow air (up to 60 L/min) through nasal cannula providing physiological benefits such as positive airway pressure and carbon dioxide washout. It can be used in association with oxygen and offers the advantage to overtake the patient's inspiratory flow, providing a stable inspired fraction of oxygen. Nasal high flow has widely been studied in pediatric and adult intensive care units and seems better than conventional oxygen therapy and as effective as noninvasive ventilation with regards to mortality to treat hypoxemic acute respiratory failure.

More recently, nasal-high flow has been shown to improve endurance exercise capacity in patients with chronic obstructive pulmonary disease. However, the underlying physiological mechanisms have not been yet elucidated but may help to optimise the utilization of the device.

Therefore, the primary objective of this study is to assess the respiratory physiological effects nasal high-flow during-exercise in stable patients with chronic obstructive pulmonary disease.

Secondary objectives are to assess the effects nasal high-flow during-exercise on endurance capacity, respiratory drive, dynamic hyperinflation, cardiorespiratory pattern and muscular metabolism.

Experimental design:

Patients referred for pulmonary rehabilitation will be approached to participate in this study. Eligible patients who agree to participate in the study and sign informed consent will perform two constant workload exercise testing the same day with either nasal high-flow or sham nasal high-flow (separated by a 1 hour rest-period) in a randomized order.

Eligibility Criteria:
Inclusion Criteria:

* Age \> 18years and \< 80years;
* Chronic obstructive pulmonary disease Gold III-IV;
* Stable (no exacerbation) in the past 4 weeks;
* Referred for pulmonary rehabilitation (no cardiac, neurological, orthopedic, neuromuscular, psychological or psychiatric contra indication).

Non-inclusion Criteria:

* Acute exacerbation of chronic obstructive pulmonary disease between the incremental cardiopulmonary exercise testing and inclusion;
* Tracheostomy;
* Nasal high flow intolerance;
* Pregnancy or likely to be;
* Unable to consent;
* Patients under guardianship.