The aim of this study is to better discriminate respiratory muscle dysfunction by comparing the measurements of thoracoabdominal motion obtained by an optoelectronic recording and the conventional tests of respiratory muscle strength. The final objective is to better select in the future the patients who need more specific assessment of diaphragmatic function like "maximal transdiaphragmatic pressure" measurement and "phrenic nerve stimulation".

All patients which had suspected respiratory muscle dysfunction will have usual exploration of the respiratory muscles according to the clinician prescription. These explorations can include :

• Lung volumes in seating and supine position
• Maximal inspiratory and expiratory pressures
• Maximal sniff pressures

And when diaphragmatic dysfunction is suspected :

• Maximal transdiaphragmatic pressure
• Phrenic nerve conduction

These patients will also beneficiate to the determination of volume variations of the upper rib cage, the lower rib cage and the abdominal compartments by using Opto-electronic plethysmography.

Inclusion Criteria:

• suspicion of respiratory muscle dysfunction
• indication of diaphragm exploration

Exclusion Criteria:

• acute respiratory failure

Neuromuscular patients