Cerebrovascular and ventilatory responses to acute isocapnic hypoxia in healthy aging and lung disease: effect of vitamin C
Bibliographic record
Abstract
Acute hypoxia increases cerebral blood flow (CBF) and ventilation (V̇e). It is unknown if these responses are impacted with normal aging, or in patients with enhanced oxidative stress, such as (COPD). The purpose of the study was to 1) investigate the effects of aging and COPD on the cerebrovascular and ventilatory responses to acute hypoxia, and 2) to assess the effect of vitamin C on these responses during hypoxia. In 12 Younger, 14 Older, and 12 COPD, we measured peak cerebral blood flow velocity (V̄p; index of CBF), and V̇e during two 5-min periods of acute isocapnic hypoxia, under conditions of 1) saline-sham; and 2) intravenous vitamin C. Antioxidants [vitamin C, superoxide dismutase (SOD), glutathione peroxidase, and catalase], oxidative stress [malondialdehyde (MDA) and advanced protein oxidation product], and nitric oxide metabolism end products (NOx) were measured in plasma. Following the administration of vitamin C, vitamin C, SOD, catalase, and MDA increased, while NOx decreased. V̄p and V̇e sensitivity to hypoxia was reduced in Older by ∼60% (P < 0.02). COPD patients exhibited similar V̄p and V̇e responses to Older (P > 0.05). Vitamin C did not have an effect on the hypoxic V̇e response but selectively decreased the V̄p sensitivity in Younger only. These findings suggest a reduced integrative reflex (i.e., cerebrovascular and ventilatory) during acute hypoxemia in healthy older adults. Vitamin C does not appear to have a large influence on the cerebrovascular or ventilatory responses during acute hypoxia.
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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 | 0.000 |
| 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 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".