FIGURE 2.

Computed tomography scans illustrate typical appearance of the different catheter positions. The arrow identifies the brain tissue PO₂ (PbtO₂) probe in each case. Top left, the PbtO₂ probe in normal-appearing right frontal lobe in a patient with a diffuse brain injury. Top right, the PbtO₂ probe in brain after evacuation of a subdural hematoma. The probe was placed at the time of surgery in brain tissue. The brain appears normal but has been compressed by the subdural hematoma. Bottom left, a PbtO₂ probe in the left frontal lobe near a contusion. If the contusion expands, this tissue is likely to become involved or to be compressed. Bottom right, a PbtO₂ within a contusion in the right frontal lobe.