Respiratory muscle dysfunction in critically ill patients is associated with elevated morbidity, including prolonged weaning from mechanical ventilation. The causes for respiratory muscle dysfunction in these patients is poorly understood and no effective treatment is available.

The general hypothesis of the present study is that in critically ill mechanically ventilated subjects respiratory muscle dysfunctions results from loss of myosin induced by activation of proteolytic cascades.

Inclusion Criteria:

• Severe sepsis / septic shock
• Clinical reason for laparotomy
• > 18 years

Exclusion Criteria:

• No informed consent
• Medical history of myopathy
• Unintended weight loss before ICU admission
• Pregnancy
• Chronic use of corticosteroids