Weaning Algorithm for Mechanical VEntilation

Inclusion criteria: * Patient remains on mechanical ventilation at 24 hours following intubation. * Age \> 18 years * Patient consent or, in the case that the patient is unable, advice from the next of kin or treating physician following understanding and acceptance of oral and written information describing the study. Exclusion criteria: * The absence of an arterial catheter for blood sampling at study start. * Mechanical ventilation initiated for more than 48 hours. * Medical history of home mechanical ventilation which may lead to prolonged stay in the ICU, including long term oxygen therapy and non-invasive ventilation not associated with sleep apnoea. * Patients mechanically ventilated in a ventilator mode, and by a ventilator not supported by the Beacon Caresystem on screening. * Respiratory failure likely requiring extracorporeal support. * Severe cardiogenic shock likely requiring extracorporeal support. * Severe isolated right heart failure. * Head trauma or other conditions where intra-cranial pressure may be elevated and tight regulation of arterial CO2 level is paramount. * Primary (non-overdose related) neurological patients (Glasgow coma score \<10, neurologic damage with limited prognosis, stroke hemiplegia). * End stage liver disease. * Repeated ICU admission within same hospital admission and/or likely to have prolonged ICU stay with mechanical ventilation (\>21 days) * Pregnancy.