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Assessing Cerebral Autoregulation via Oscillatory Lower Body Negative Pressure and Projection Pursuit Regression
Published on: December 10, 2014
Waveform-Derived Metrics of Intracranial Compliance: Validation and Pulsatile Dynamics
Ihsane Olakorede1, Stefan Yu Bögli2,3, Marek Czosnyka2,4
1Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK. imo25@cam.ac.uk.
Neurocritical Care
|August 3, 2026
Summary
The pulse shape index (PSI) accurately assesses intracranial compliance, reflecting the P2/P1 ratio. However, a multiparametric approach including amplitude and reserve indices is crucial for comprehensive intracranial monitoring.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Critical Care Medicine
Background:
- Intracranial pressure (ICP) waveform interpretation is vital for assessing intracranial compliance but lacks robust validation.
- Current methods rely on visual interpretation, introducing subjectivity and variability.
- Objective, validated methods are needed for accurate intracranial compliance assessment.
Purpose of the Study:
- To evaluate the Pulse Shape Index (PSI) as a validated measure of intracranial compliance.
- To compare PSI against the established P2/P1 ratio and other physiological indices.
- To determine the added value of pulse amplitude and compensatory reserve in compliance assessment.
Main Methods:
- Analysis of 4388 ICP and transcranial Doppler (TCD) segments from 96 recordings.
- Calculation of PSI, P2/P1 ratio, ICP pulse amplitude (AMP), pressure-volume compensatory reserve index (RAP), and TCD-derived compliance indices (CA, CI).
- Statistical analysis using correlation, mixed-effects models, ROC, and precision-recall analyses.
Main Results:
- PSI strongly correlated with P2/P1 (r ≈ 0.74-0.76) and showed high discrimination for impaired compliance (AUC ≈ 0.93).
- RAP and intracranial compliance (CI) exhibited weak, variable associations with P2/P1.
- ICP pulse amplitude (AMP) provided significant complementary information, improving model fit and classification performance.
Conclusions:
- PSI is a reliable, automated method for assessing intracranial compliance based on waveform morphology.
- Waveform morphology alone is insufficient; incorporating AMP and RAP is essential for a comprehensive multiparametric approach.
- This study supports the use of a combined approach for enhanced intracranial monitoring.
