Impact of BPEs on determination of the mean ICP-derived score RAP. From different individuals undergoing ICP monitoring as part of surveillance of SAH, RAP was measured from two nearby Raumedic Neurovent P sensors placed via the same burr hole. Thereby the sensors measure ICP from the same compartment without pressure gradients. Trend plots of RAP [correlation coefficient (R) between the intracranial pressure (ICP) wave amplitude (A) and the mean ICP level (P)] of signals 1 and 2 are presented for three individuals. RAP was determined during 100 consecutive 4-minute periods for signals 1 (blue line) and 2 (red line). The horizontal lines at RAP 0.6 illustrate a commonly used upper normal threshold for RAP. a In this individual, the average of RAPSignal 1 was 0.50 (blue line) and the average of RAPSignal 2 − 0.04 (red line). b In this individual, the average of RAPSignal 1 was 0.64 (blue line) while average of RAPSignal 2 was 0.16 (red line). c In this individual, the average of RAPSignal 1 was 0.17 (blue line), and the average of RAPSignal 2 0.59 (red line).