Compromised Cerebrovascular Regulation and Cerebral Oxygenation in Pulmonary Arterial Hypertension
Bibliographic record
Abstract
Background Functional cerebrovascular regulatory mechanisms are important for maintaining constant cerebral blood flow and oxygen supply in heathy individuals and are altered in heart failure. We aim to examine whether pulmonary arterial hypertension ( PAH ) is associated with abnormal cerebrovascular regulation and lower cerebral oxygenation and their physiological and clinical consequences. Methods and Results Resting mean flow velocity in the middle cerebral artery mean flow velocity in the middle cerebral artery ( MCA v mean ); transcranial Doppler), cerebral pressure‐flow relationship (assessed at rest and during squat‐stand maneuvers; analyzed using transfer function analysis), cerebrovascular reactivity to CO 2 , and central chemoreflex were assessed in 11 patients with PAH and 11 matched healthy controls. Both groups also completed an incremental ramp exercise protocol until exhaustion, during which MCA v mean , mean arterial pressure, cardiac output (photoplethysmography), end‐tidal partial pressure of CO 2 , and cerebral oxygenation (near‐infrared spectroscopy) were measured. Patients were characterized by a significant decrease in resting MCA v mean ( P <0.01) and higher transfer function gain at rest and during squat‐stand maneuvers (both P <0.05). Cerebrovascular reactivity to CO 2 was reduced ( P =0.03), whereas central chemoreceptor sensitivity was increased in PAH ( P <0.01), the latter correlating with increased resting ventilation ( R 2 =0.47; P <0.05) and the exercise ventilation/CO 2 production slope ( V ˙ E / V ˙ CO 2 slope; R 2 =0.62; P <0.05) during exercise for patients. Exercise‐induced increases in MCA v mean were limited in PAH ( P <0.05). Reduced MCA v mean contributed to impaired cerebral oxygen delivery and oxygenation (both P <0.05), the latter correlating with exercise capacity in patients with PAH ( R 2 =0.52; P =0.01). Conclusions These findings provide comprehensive evidence for physiologically and clinically relevant impairments in cerebral hemodynamic regulation and oxygenation in PAH .
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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 | 0.000 | 0.001 |
| 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) | 0.001 | 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".