The Impact of Acute High Altitude Exposure (3800m) And Isocapnic Hypoxia/Hyperoxia on Neurovascular Coupling in Healthy Volunteers
Notice bibliographique
Résumé
Neurovascular coupling (NVC) is the co‐ordination of regional cerebral blood flow relative to local neuronal activity. Manipulation of arterial blood gases has a direct impact on cerebrovascular tone. Hypoxia has a vasodilatory effect whereas hypocapnia incurs vasoconstriction of cerebral vessels. The aims of this study were to determine whether acute exposure to high altitude and acute isocapnic hypoxia/hyperoxia affect the NVC response. We hypothesized that acute exposure to high‐altitude would impair NVC due to the ventilatory induced acid‐base disturbance associated with hypoxic exposure. 14 healthy volunteers were assessed at baseline (1045m) and on days 2 and 9 residing at altitude (3800m). Cerebral blood velocity through the posterior cerebral artery (PCAv) was measured using transcranial Doppler ultrasound. NVC was measured as the peak and mean changes in PCAv during visual stimulation, represented as a percentage change from resting PCAv. Arterial blood was sampled from the radial artery. Ventilatory gas control was achieved via an end‐tidal forcing system. At baseline, participants were exposed to separate ventilatory challenges: room air and isocapnic hypoxia designed to mimic the O 2 availability at 3800m and 5360m, respectively. On days 2 and 9 at 3800m, participants were exposed to three separate gas challenges: room air and isocapnic hyperoxia/hypoxia. The hyperoxia and hypoxia challenges were designed to mimic the O 2 availability at 1045m and 5360m, respectively. NVC was assessed during each gas challenge using a 30‐sec standardized strobe light stimulus (6Hz). Exposure to high altitude elicited hypoxic‐hypocapnia, demonstrated by significant reductions in PaO 2 and PaCO 2 (both P<0.001). No significant changes in arterial pH were observed following acute exposure to 3800m (P=0.72) due to a compensatory renal metabolic acidosis, evidenced by significant reductions in arterial bicarbonate (P<0.001). No significant differences in peak or mean NVC response were found between baseline and days 2/9 at altitude (P=0.41, P=0.55 respectively). No significant differences were found for mean NVC response during isocapnic hypoxia or hyperoxia challenges relative to room air (P>0.16). Significant reductions were found during isocapnic hypoxia for peak NVC response at baseline and day 2 at altitude (P<0.04). However, no significant differences for peak NVC response were observed on day 9 (P=0.53). Our data illustrates that NVC remains intact following acute exposure to high altitude and during acute isocapnic manipulation of O 2 availability. Future studies should examine the independent effects of CO 2 manipulation and acid‐base disturbance on cerebrovascular function. Support or Funding Information Expedition was funded by National Sciences and Engineering Research Council of Canada. In addition, Jack Leacy is a PhD trainee funded by the Department of Physiology, University College Cork
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».