In the critical patient, lung ultrasound is routinely performed for acute respiratory distress, adult respiratory distress syndrome and for hemodynamic evaluation. Its diagnostic performance is superior to that of chest radiography in the context of pleuropulmonary parenchymal pathologies. The search for lung sliding is performed to diagnose a pneumothorax or to search for the correct placement of the endotracheal intubation tube. However, this analysis is qualitative and is sometimes difficult to interpret. At present, there is no global evaluation technique at the patient's bed allowing to analyze simultaneously the alveolar recruitment, the pulmonary over-distension and the quality of the lung sliding, whereas the pulmonary damage is most often heterogeneous. The justification of our research project is based on the need to develop and validate a means of global and regional quantification of the mechanical and aeration properties of the lung parenchyma by the analysis of the acoustic markers of the pleura (pleural strain) by the ultrasound technique of speckle tracking. The aim is to establish the normal values of the pleural strain in healthy volunteers, in spontaneous ventilation and then in non-invasive mechanical ventilation, in order to vary the lung volume.

Inclusion Criteria:

-Healthy volunteer male or female between 18 and 50 years old

Exclusion Criteria:

• History of traumatic or spontaneous pneumothorax
• History of connective tissue disease
• Any history of chronic respiratory disease
• Presence of an ongoing clinical respiratory Ear-Nose-Throat (ENT) or pulmonary syndrome (rhinitis, sinusitis, bronchitis, lung disease)
• History of gastro-duodenal reflux or stomach surgery