Transcranial Doppler Systolic Flow Index and ICP-Derived Cerebrovascular Reactivity Indices in Traumatic Brain Injury
Bibliographic record
Abstract
The purpose of our study was to explore relationships between transcranial Doppler (TCD) indices of cerebrovascular reactivity and those derived from intracranial pressure (ICP). Goals included: A) confirming previously described co-variance patterns of TCD/ICP indices, and B) describing thresholds for systolic flow index (Sx; correlation between systolic flow velocity [FVs] and cerebral perfusion pressure [CPP]) associated with outcome. In a retrospective cohort of traumatic brain injury (TBI) patients: with TCD and ICP monitoring, we calculated various continuous indices of cerebrovascular reactivity: A) ICP (pressure reactivity index [PRx]: correlation between ICP and mean arterial pressure [MAP]; PAx: correlation between pulse amplitude of ICP [AMP] and MAP; RAC: correlation between AMP and CPP) and B) TCD (mean flow index [Mx]: correlation between mean flow velocity [FVm] and CPP; Mx_a: correlation between FVm and MAP; Sx: correlation between FVs and CPP; Sx_a: correlation between FVs and MAP; Dx: correlation between diastolic flow velocity [FVd] and CPP; Dx_a: correlation between FVd and MAP). We assessed the relationships via various statistical techniques, including: principal component analysis, agglomerative hierarchal clustering, and k-means cluster analysis (KMCA). We performed sequential χ2 testing to define thresholds associated with outcome for Sx/Sx_a. Outcome was assessed at 6 months via dichotomized Glasgow Outcome Score (GOS): A) Favorable (GOS 4 or 5) versus Unfavorable (GOS 3 or less), B) Alive versus Dead. We analyzed 410 recordings in 347 patients. All analyses confirmed our previously described co-variance of Sx/Sx_a with ICP-derived indices. Sx displayed thresholds of −0.15 for unfavorable outcome (p < 0.0001) and −0.20 for mortality (p < 0.0001). Sx_a displayed thresholds of +0.05 (p = 0.019) and −0.10 (p = 0.0001) for alive/dead and favorable/unfavorable outcomes. TCD systolic indices are most closely associated with ICP indices. Sx and Sx_a likely provide better approximation of ICP indices, compared with Mx/Mx_a/Dx/Dx_a. Sx provides superior outcome prediction, versus Mx, with defined thresholds.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".