Brain tissue oxygen (P_btO₂) monitoring is used to measure oxygen delivery to the cerebral tissue and to identify cerebral ischemia and hypoxia in patients with traumatic brain injury, stroke, or aneurysm or traumatic subarachnoid hemorrhage. It’s also used to monitor other patients at risk for secondary
brain injury. Secondary brain injury typically results when complications, such as elevated intracranial pressure (ICP), shivering, agitation, seizures, fever, hypotension, hypovolemia, anemia, and hypoxia, cause cerebral hypoxia. Cerebral hypoxia, in turn, can lead to cerebral ischemia.

P_btO₂ monitoring is achieved using a P_btO₂ probe that’s inserted through an intracranial bolt or tunneled under the scalp using a probe guide and trocar. When used with an intracranial bolt, the system measures ICP, brain tissue temperature, and P_btO₂ saturation. It can detect early changes in ICP and P_btO₂ so that treatment interventions can be performed before secondary brain injury occurs. Contraindications of P_btO₂ monitoring include anticoagulation therapy, insertion site infection, and coagulopathy.

The normal value for P_btO₂ ranges between 20 and 35 mm Hg. Decreased levels occur when there’s an increased oxygen demand or a decrease in oxygen delivery. Increased levels occur when there’s increased oxygen delivery or decreased oxygen demand.