The Neurovascular Coupling Response Remains Intact During Incremental Ascent to High Altitude (4370m) in Acclimatized Healthy Volunteers
Bibliographic record
Abstract
Neurovascular coupling (NVC) is the link between neuronal metabolic activity and regional cerebral blood flow. NVC is responsible for ensuring adequate delivery of nutrients (O 2 and glucose) during periods of increased neuronal metabolic demand. Exposure to high‐altitude (HA) elicits ventilatory and acid‐base adjustments for maintaining blood pH. Acute exposure to HA causes hypoxic vasodilation. Hypoxia also drives a ventilatory response, inducing hypocapnia, a potent vasoconstrictor. Whether these dynamic and conflicting responses affect NVC during incremental ascent to HA is unclear. The aim of this project was to assess whether changes in arterial blood gases (ABGs) associated with ascent to HA influences the NVC response. Given that CBF is particularly sensitive to changes in PaCO 2 , we hypothesized that hypocapnic vasoconstriction during ascent would decrease the NVC response with ascent. 10 healthy study participants (21.7±1.3 yrs, 70.46±13.65kg, mean±SD) were recruited as part of a research expedition to Everest base camp, Nepal. Resting posterior cerebral artery velocity (PCAv), ABGs (PaO 2 , PaCO 2 ), SaO 2 , arterial blood pH and bicarbonate [HCO 3 − ] were measured at four locations: Calgary (1045m; baseline; BL), Namche (3440m), Deboche (3820m) and Pheriche (4370m). Resting PCAv was measured using transcranial Doppler ultrasound. Arterial blood draws were taken from the radial artery and analysed using a portable blood gas/electrolyte analyser used to monitor changes in ABGs (PaCO 2 , PaO 2 , SaO 2 ), pH and [HCO 3 − ] during ascent. NVC was tested via visual stimulation (VS; Strobe light; 6Hz; 30sec on/off ×3). The NVC response was averaged across three VS trials at each location. NVC was quantified as the change (delta) in mean and peak PCAv from baseline, during VS. A one‐factor‐repeated measures analysis of variance (ANOVA) was used to assess for differences in baseline PCAv, NVC, ABGs, blood pH and [HCO 3 − ] between locations. PaO 2 , PaCO 2 and SaO 2 were significantly decreased from BL at each altitude (P<0.001, P<0.016 and P<0.013, respectively). No significant differences were found for pH at any location compared to BL (P>0.05) due to reductions in arterial [HCO 3 − ] (P<0.043). No significant differences were found in baseline PCAv between locations (P>0.05) or for mean or peak NVC responses (P>0.085 and P>0.08 respectively). As expected, incremental ascent to HA induced a state of hypoxic hypocapnia, as demonstrated by significant reductions in PaO 2 , SaO 2 and PaCO 2 , whereas arterial pH was maintained via reductions in [HCO 3 − ]. Our data suggests that NVC remains remarkably intact during incremental ascent to HA in healthy acclimatized individuals. Despite the array of superimposed stressors associated with ascent to HA, CBF and NVC regulation may be a unique function of arterial pH maintenance. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".