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 (CBV) 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 unclear.

RESEARCH QUESTION

Does ICP pulse waveform become similar to non-invasively estimated CBV pulse during ICP plateau waves.

MATERIAL AND METHODS

A total of 15 plateau waves recorded in 15 traumatic brain injured patients were analyzed. CBV 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 CBV waveforms. DI was calculated as the sum of absolute sample-by-sample differences between ICP and CBV waveforms, representing the area between the pulses.

RESULTS

ICP increased (19.4 mm Hg [Q1-Q3: 18.2-23.4 mm Hg] vs. 42.7 mm Hg [Q1-Q3: 36.5-45.1 mm Hg], p < 0.001) while CBFV decreased (44.2 cm/s [Q1-Q3: 34.8-69.5 cm/s] vs. 32.9 cm/s [Q1-Q3: 24.7-68.2 cm/s], p = 0.002) during plateau waves. DI was smaller during the plateau waves (20.4 [Q1-Q3: 15.74-23.0]) compared to the baselines (26.3 [Q1-Q3: 24.2-34.7], p < 0.001).

DISCUSSION AND CONCLUSION

The area between corresponding ICP and CBV pulse waveforms decreased during the plateau waves which suggests they became similar in shape. CBV 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.