Clinical Research Directory

Inclusion Criteria: * Patient is on invasive mechanical ventilation more 48 hours * Age \> 18 years * Patients are ventilated using Maquet Servo-I, Draeger Infinity V500 or Draeger Evita XL mechanical ventilators in "pressure support", "volume controlled", or "pressure controlled" ventilation modes. * Haemodynamically stable (mean blood pressure ≥ 65 mmHg) * Patients or, in the case that the patient is unable, next of kin understand and accept oral and written information describing the study or patient consent retrospectively in case of emergency inclusion. Exclusion Criteria: * The absence of an arterial catheter for blood sampling. * Medical history of home mechanical ventilation * Severe ARDS (PaO2/FiO2 ≤ 100 mmHg) * Head trauma or other conditions where intra-cranial pressure may be elevated and tight regulation of arterial CO2 level is paramount. * Severe neurological patients (Glasgow coma score \<10, neurologic damage with limited prognosis, stroke hemiplegia). * Known or suspected severe myopathy or neuropathy (including ICU neuromyopathy) * Quadriplegia * Severe heart failure * Broncho alveolar fistula with more than 100ml leakage * History of home mechanical ventilation * Pregnancy.