FiO2 Closed Loop Control Ventilation

Inclusion Criteria: * The subject's legally authorized representative will provide signed and dated informed consent. * Age 18 - 65, inclusive. * Admission to a surgical or neurosurgical intensive care unit following traumatic injury or acute surgical illness * Requirement for endotracheal intubation * Requirement for mechanical ventilation * Patient is currently receiving inspired oxygen concentration (FiO2) \>=40% Exclusion Criteria: * Age under 18 or over 65 * Isolated or severe head injury (Glasgow Coma Scale = 6 or less) with expected survival less than 24 hours * Brain death * Anticipated survival less than 48 hours * Pregnant female * Patient in whom a pulse oximeter cannot detect a reliable signal due to hypotension, hypothermia, or other injury * Known carbon monoxide poisoning * Uncontrolled diabetic * Patient who is unable to maintain SpO2 level of 88% at an FiO2 of 100% due to their medical condition. (NOTE: Being in the trial would impose no additional risk to a patient who presents with this condition however, data from a patient presenting with this pathophysiology would not provide insight into the performance of the controller as it would simply maintain that patient on an FiO2 of 100%.) * Patient with chronic hypercarbia. * Patient where a physician believes that FiO2 PCLC could be detrimental to the management of the patient. * Prisoner * SpO2 to SaO2 difference \>4% * Patient with core temperature \<35 C