Inclusion Criteria:  Severe isolated TBI (GCS<8, AIS =<3), CT-verified TBI (tSDH,tEDH, tSAH, contusion bleedings) caused by blunt or penetrating trauma. Established intracranial monitoring (ICP, MD, LiCox pBtO2) at NICU. Age >= 18 Time from trauma from 0 to 4 days. Informed consent from Close relative. Systemic hyperoxygenation can be used in patients with pBtO2 <20 mmHg, based on clinical decision.  Exclusion Criteria:  Major extracranial injury, AIS >3 Brain dead or expected survival <24 hours Pregnancy Respiratory insufficiency FiO2> 40%  6. No consent from relative.