The aim of this study is to study the combined impact of mechanical ventilation and sepsis on the human diaphragm in order to establish the neutral, protective or destructive character of mechanical ventilation by studying the diameter of the fibers, activation of proteolytic systems, inhibition of protein synthesis, tissue inflammation as well as contractile function.

Inclusion Criteria:

• Patient at least 18 years of age, male or female requiring abdominal or thoracic surgery or multi-organ sampling;
• Affiliated to a social security or similar system;
• Not subject to legal protection;
• Having given consent to participate in the study (or consent from the trusted person)
• Control group (C): non-septic mesocolic programmed abdominal or thoracic surgery: gastrectomy, esophagectomy, pancreatectomy, hepatectomy
• Sepsis group (S): Abdominal or thoracic surgery in a septic context (peritonitis, mediastinitis, pleural abscess)
• Group Mechanical Ventilation (MV): Patient in brain death for which a multi organ sample is planned
• Mechanical Ventilation + Sepsis (S-MV) group: Patient under controlled mechanical ventilation to undergo abdominal or thoracic surgery in a septic context (peritonitis, mediastinitis, pleural abscess)

Exclusion Criteria:

• Pregnant woman (diagnosis of interrogation)
• severe and / or unbalanced chronic respiratory disease; severe malnutrition
• Long-term corticosteroids> 5mg / day for more than 1 month
• Myopathy
• surgery by laparoscopic

By group:

• Control group: Sepsis, preoperative controlled mechanical ventilation and preoperative hemodynamic instability
• Mechanical Ventilation Group: Sepsis, duration of controlled mechanical ventilation <24 hours or> 7 days
• Sepsis Group: Preoperatively controlled mechanical ventilation
• Mechanical Ventilation - Sepsis Group: duration of controlled mechanical ventilation <24 hours or> 7 days