Quantitative Analysis of Similarity Between Cerebral Arterial Blood Volume and Intracranial Pressure Pulse Waveforms during Intracranial Pressure Plateau Waves

Introduction Both intracranial pressure (ICP) and cerebral arterial blood volume (CaBV) have a pulsatile character related to the cardiac cycle. The evolution of the shape of ICP pulses under increasing ICP or decreasing intracranial compliance is well documented. Nevertheless, the exact origin of the alterations in the ICP morphology remains unsclear. Research question Does ICP pulse waveform become similar to non-invasively estimated CaBV pulse during ICP plateau waves. Material and Methods A total of 15 plateau waves recorded in 15 traumatic brain injured patients were analyzed. CaBV pulse waveforms were calculated using global cerebral blood flow model from transcranial Doppler cerebral blood flow velocity (CBFV) signals. The difference index (DI) was used to quantify the similarity between ICP and CaBV waveforms. DI was calculated as the sum of absolute sample-by-sample differences between ICP and CaBV waveforms, representing the area between the pulses. Results ICP increased (19.4 mm Hg (IQR: 18.2–23.4 mm Hg) vs. 42.7 mm Hg (IQR: 36.5–45.1 mm Hg) , p<0.001) while CBFV decreased (44.2 cm/s (IQR: 34.8–69.5 cm/s) vs. 32.9 cm/s (IQR: 24.7–68.2 cm/s), p=0.002) during plateau waves. DI was smaller during the plateau waves 20.4 (IQR: 15.74–23.0) compared to the baselines: 26.3 (IQR: 24.2–34.7), p<0.001. Discussion and Conclusion The area between corresponding ICP and CaBV pulse waveforms decreased during the plateau waves which suggests they became similar in shape. CaBV may play a significant role in determining the shape of ICP pulses during the plateau waves and might be a driving force in formulating ICP elevation.