Validation of Pressure Reactivity and Pulse Amplitude Indices against the Lower Limit of Autoregulation, Part I: Experimental Intracranial Hypertension
Bibliographic record
Abstract
The purpose of this study was to provide validation of intracranial pressure (ICP) derived continuous indices of cerebrovascular reactivity against the lower limit of autoregulation (LLA). Utilizing an intracranial hypertension model within white New Zealand rabbits, ICP, transcranial Doppler (TCD), laser Doppler flowmetry (LDF), and arterial blood pressure were recorded. Data were retrospectively analyzed in a cohort of 12 rabbits with adequate signals for interrogating the LLA. We derived continuous indices of cerebrovascular reactivity: PRx (correlation between ICP and mean arterial pressure [MAP]), PAx (correlation between pulse amplitude of ICP [AMP] and MAP), and Lx (correlation between LDF-based cerebral blood flow [CBF] and cerebral perfusion pressure [CPP]). LLA was derived via piecewise linear regression of CPP versus LDF or CPP versus systolic flow velocity (FVs) plots. We then produced error bar plots for PRx, PAx, and Lx against 2.5 mm Hg bins of CPP, to display the relationship between these indices and the LLA. We compared the CPP values at clinically relevant thresholds of PRx and PAx, to the CPP defined at the LLA. Receiver operating curve (ROC) analysis was performed for each index across the LLA using 2.5 mm Hg bins for CPP. The mean LLA was 51.5 ± 8.2 mm Hg. PRx and PAx error bar plots demonstrate that each index correlates with the LLA, becoming progressively more positive below the LLA. Similarly, CPP values at clinically relevant thresholds of PRx and PAx were not statistically different from the CPP derived at the LLA. Finally, ROC analysis indicated that PRx and PAx predicted the LAA, with areas under the curve (AUCs) of 0.795 (95% confidence interval [CI]: 0.731-0.857, p < 0.0001) and 0.703 (95% CI: 0.631-0.775, p < 0.0001), respectively. Both PRx and PAx generally agree with LLA within this experimental model of intracranial hypertension. Further analysis of clinically used indices of autoregulation across the LLA within pure arterial hypotension models is required.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".