Brain tissue oxygen tension and its response to physiological manipulations: influence of distance from injury site in a swine model of traumatic brain injury
Bibliographic record
Abstract
OBJECTIVE The optimal site for placement of tissue oxygen probes following traumatic brain injury (TBI) remains unresolved. The authors used a previously described swine model of focal TBI and studied brain tissue oxygen tension (P bt O 2 ) at the sites of contusion, proximal and distal to contusion, and in the contralateral hemisphere to determine the effect of probe location on P bt O 2 and to assess the effects of physiological interventions on P bt O 2 at these different sites. METHODS A controlled cortical impact device was used to generate a focal lesion in the right frontal lobe in 12 anesthetized swine. P bt O 2 was measured using Licox brain tissue oxygen probes placed at the site of contusion, in pericontusional tissue (proximal probe), in the right parietal region (distal probe), and in the contralateral hemisphere. P bt O 2 was measured during normoxia, hyperoxia, hypoventilation, and hyperventilation. RESULTS Physiological interventions led to expected changes, including a large increase in partial pressure of oxygen in arterial blood with hyperoxia, increased intracranial pressure (ICP) with hypoventilation, and decreased ICP with hyperventilation. Importantly, P bt O 2 decreased substantially with proximity to the focal injury (contusion and proximal probes), and this difference was maintained at different levels of fraction of inspired oxygen and partial pressure of carbon dioxide in arterial blood. In the distal and contralateral probes, hypoventilation and hyperventilation were associated with expected increased and decreased P bt O 2 values, respectively. However, in the contusion and proximal probes, these effects were diminished, consistent with loss of cerebrovascular CO 2 reactivity at and near the injury site. Similarly, hyperoxia led to the expected rise in P bt O 2 only in the distal and contralateral probes, with little or no effect in the proximal and contusion probes, respectively. CONCLUSIONS P bt O 2 measurements are strongly influenced by the distance from the site of focal injury. Physiological alterations, including hyperoxia, hyperventilation, and hypoventilation substantially affect P bt O 2 values distal to the site of injury but have little effect in and around the site of contusion. Clinical interpretations of brain tissue oxygen measurements should take into account the spatial relation of probe position to the site of injury. The decision of where to place a brain tissue oxygen probe in TBI patients should also take these factors into consideration.
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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 | 0.001 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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".