Influence of Intermittent Hypoxia on Loop Gain in Healthy Subjects

To evaluate the effect of intermittent hypoxia for 6 hours on the evolution of Loop Gain

Loop gain is the product of 'controller gain' (ventilatory responsiveness to CO₂ above eupnoea) and 'plant gain' (the ventilatory increase required for a given reduction in PaCO₂). Loop gain will be measured before (30 minutes of rest following the participant's arrival) and after (20 minutes before the end of the hypoxia chamber session) the test or control condition (intermittent hypoxia or ambient air). The following ventilatory parameters will be measured using a gas exchange measuring device to calculate loop gain, plant gain and controller gain: * PETCO₂ in mmHg * PETO₂ in mmHg * Minute ventilation (VE), measured in mL/min (tidal volume x respiratory rate). The focus will be on the average loop gain value measured over spontaneous breathing cycles of five to ten minutes. The evaluation criterion will be the difference in the average loop gain value before and after the experimental conditioning (i.e. observation of the change).

To compare the evolution of controller gain and plant gain between experimental conditions in hypoxia and ambient air

We will assess the change in controller and plant gains by measuring the difference before and after the experimental conditioning of these gains. Our focus will be on the average values of the controller and plant gains, which were measured over spontaneous breathing cycles of 5 to 10 minutes, and assessed before and after the experiment.

To compare the change in the quantity of extracellular vesicles between experimental conditions in hypoxia and ambient air.

The quantity of extracellular vesicles was assessed from blood samples using flow cytometry with specific antibodies. This change is expressed as the difference in the following extracellular vesicle concentrations before and after experimental conditioning: * EVs from platelets expressing CD41 * EVs from erythrocytes expressing CD235a * EVs from leukocytes expressing CD45 * EVs from endothelial cells expressing CD146 * EVs from granulocytes expressing CD66b and CD11b * EVs from activated leukocytes expressing CD62L * EVs from activated endothelial cells expressing CD62E * EVs from activated platelets expressing CD62P * CD62P/platelet ratio * EVs carrying the PSGL-1 ligand expressing CD162 * EVs carrying phosphatidylserine expressing annexin V

To assess whether changes in the quantity of extracellular vesicles (and microvesicles) correlate with changes in loop gain, both under experimental conditions in hypoxia and under experimental conditions in ambient air.

We are interested in changes in the quantity of extracellular vesicles, as assessed by the difference in extracellular vesicle concentration before and after the experimental condition. This is measured from blood samples taken. We are interested in the following extracellular vesicles: CD41, CD235a, CD45, CD146, CD66b, CD11b, CD62L, CD62E, CD62P and CD62/platelet annexin V. The change in loop gain will be calculated as for the primary endpoint (the difference in concentration before and after the experimental condition).

To compare changes in loop gain between experimental conditions in hypoxia and ambient air, on the one hand in the subgroup of patients with hyperventilation syndrome and on the other hand in the subgroup of patients without hyperventilation syndrome.

The change in loop gain will be defined in the same way as the primary endpoint, i.e. as the difference between the measurements taken before and after the experimental conditioning. Hyperventilation syndrome will be defined as a Nijmegen score of 23 or above at the inclusion visit.