Shear-mediated dilation of the internal carotid artery occurs independent of hypercapnia
Bibliographic record
Abstract
Evidence for shear stress as a regulator of carotid artery dilation in response to increased arterial CO2was recently demonstrated in humans during sustained elevations in CO2(hypercapnia); however, the relative contributions of CO2and shear stress to this response remains unclear. We examined the hypothesis that, after a 30-s transient increase in arterial CO2tension and consequent increase in internal carotid artery shear stress, internal carotid artery diameter would increase, indicating shear-mediated dilation, in the absence of concurrent hypercapnia. In 27 healthy participants, partial pressures of end-tidal O2and CO2, ventilation (pneumotachography), blood pressure (finger photoplethysmography), heart rate (electrocardiogram), internal carotid artery flow, diameter, and shear stress (high-resolution duplex ultrasound), and middle cerebral artery blood velocity (transcranial Doppler) were measured during 4-min steady-state and transient 30-s hypercapnic tests (both +9 mmHg CO2). Internal carotid artery dilation was lower in the transient compared with steady-state hypercapnia (3.3 ± 1.9 vs. 5.3 ± 2.9%, respectively, P < 0.03). Increases in internal carotid artery shear stress preceded increases in diameter in both transient (time: 16.8 ± 13.2 vs. 59.4 ± 60.3 s, P < 0.01) and steady-state (time: 18.2 ± 14.2 vs. 110.3 ± 79.6 s, P < 0.01) tests. Internal carotid artery dilation was positively correlated with shear rate area under the curve in the transient ( r2= 0.44, P < 0.01) but not steady-state ( r2= 0.02, P = 0.53) trial. Collectively, these results suggest that hypercapnia induces shear-mediated dilation of the internal carotid artery in humans. This study further promotes the application and development of hypercapnia as a clinical strategy for the assessment of cerebrovascular vasodilatory function and health in humans. NEW & NOTEWORTHY Shear stress dilates the internal carotid artery in humans. This vasodilatory response occurs independent of other physiological factors, as demonstrated by our transient CO2test, and is strongly correlated to shear area under the curve. Assessing carotid shear-mediated dilation may provide a future avenue for assessing cerebrovascular health and the risk of cerebrovascular events.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".