The Effects of Acute High Altitude Exposure and Arterial Blood Gas Manipulation on Neurovascular Coupling in Healthy Humans
Bibliographic record
Abstract
Neurovascular coupling (NVC) is the temporal and spatial link between local neuronal activity and regional cerebral blood flow. High altitude elicits several vasoactive stimuli, which alter cerebrovascular tone through changes in arterial blood gases (ABGs). Previous work from our group has found NVC to remain intact during ascent to high altitude. However, given the incremental nature of the ascent profile, NVC was determined in individuals that were fully acclimatized. This study aimed to assess the effects of 1) rapid ascent to and residence at high altitude (pre vs. post acclimatisation) and 2) the isolated and combined effects of ABG manipulation on NVC response magnitude. We hypothesized that acute exposure to high altitude would impair NVC. 12 healthy participants (5 female) were recruited for this expedition. Arterial blood draws from the radial artery and NVC were measured at baseline (1045m) and on days 2 and 9 at altitude (3800m). End‐tidal gas challenges were used to elicit the isolated and combined effects of blood gas manipulation, specifically isocapnic‐hypoxia and hyperoxia gas challenges. Cerebral blood velocity was measured through the posterior cerebral artery (PCAv) using transcranial Doppler ultrasound. NVC was measured as the peak (Δpeak) and mean (Δmean) changes in PCAv during intermittent visual stimulation (VS). In addition, NVC was quantified as the change in total area under the curve (ΔtAUC) during VS. Lastly, the NVC waveform was compartmentalised into three distinct temporal regions (0‐10, 11‐20‐ and 20‐30‐seconds post‐stimulus onset) to assess mechanistic involvement during the NVC response. Immediate and chronic exposure to high altitude elicited hypoxic‐hypocapnia, evidenced by reductions in both PaO 2 and PaCO 2 (P<0.001). However, arterial pH was unchanged following acute exposure to high‐altitude (P=0.72) due to reductions in arterial bicarbonate (P< 0.001), indicative of a compensatory renal metabolic acidosis. No significant differences were observed for Δpeak, Δmean, ΔtAUC NVC response between baseline and days 2 and/or 9 at altitude (P>0.05). Moreover, neither the independent effects of hypoxia and hypocapnia, nor combined hypoxic‐hypocapnia affected Δpeak, Δmean or ΔtAUC NVC response (P >0.05). Finally, no significant differences in the magnitude of the haemodynamic response across temporal regions of the NVC response were observed during acute and sustained exposure to high altitude (P>0.05) and/or isolated and combined manipulation of ABGs (P>0.05). Our results reveal remarkable stability of the NVC response magnitude during pronounced physiological stressor associated with rapid ascent and residence at high altitude.
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 | 0.000 | 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) | 0.001 | 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".