Fig. 1. Two examples of simultaneous recording of arterial blood pressure (AP) in the radial artery, blood flow velocity in the middle cerebral artery (VMCA), and intracranial pressure (ICP). Determination of the critical closing pressure (CCP) by extrapolation of the regression curve of the pressure–flow relation of a single heartbeat (beat 3 in both examples) to the x-axis (pressure). Patient A with generalized edema of the brain: ICP = 14 mmHg; CCP was calculated as 27 mmHg. Patient B after severe head trauma with multiple contusions of the brain: CCP was calculated as 67 mmHg. Simultaneous recorded ICP was 65 mmHg.