Elevated carotid body tonic activity contributes to ventilatory acclimatization and de‐acclimatization to high altitude at rest and during exercise
Notice bibliographique
Résumé
Abstract Exposure to hypoxia is associated with increased ventilation, which escalates with continued exposure. Carotid chemoreceptors play a critical role in ventilatory acclimatization to prolonged hypoxia in animals. However, the contribution of carotid chemoreceptor tonic activity to ventilatory acclimatization in humans has not been directly demonstrated. We assessed carotid chemoreceptor tonic activity in lowlanders following acclimatization to high altitude and during de‐acclimatization. Fourteen healthy participants (7 male, 27 ± 4 years) were assessed at 340 m, following 13 days at high altitude (3800 m), and 3 days post‐descent to 1200 m. Carotid chemoreceptor tonic activity was indexed by the two‐breath nadir in minute ventilation () during 1 min of hyperoxia (100% inspired O2), at rest and during cycling exercise, matched for relative intensity [∼50% maximal oxygen consumption ()] and absolute intensity (∼90 W). Resting increased from sea level (12.9 ± 2.3 l/min) to 3800 m (16.8 ± 3.6 l/min, P < 0.001) and 3‐days post‐descent (18.2 ± 3.5 l/min, P < 0.001), with no difference between high altitude and post‐descent (P = 0.366). The hyperoxic nadir in ventilation was greater than sea level at 3800 m (+153%; P = 0.070, Cohen's d = 1.3) and 3‐days post‐descent (+74%; P = 0.048), with no significant difference between 3800 m and post‐descent (P = 0.326). During 50% exercise, the hyperoxic ventilation nadir was also greater than sea level at 3800 m (+225%; P = 0.007) and 3 days post‐descent (+183%; P = 0.004). The degree of ventilatory acclimatization was associated with the change in the hyperoxic nadir in ventilation (as an index of carotid chemoreceptor tonic activity; r2 = 0.60, P = 0.014). In conclusion, carotid chemoreceptor tonic activity is elevated and associated with acclimatization to high altitude, and this persists 3 days post‐descent. image Key points Ascent to high altitude is associated with adjustments in ventilation (i.e. ventilatory acclimatization). Heightened carotid chemoreceptor activity plays a critical role in ventilatory acclimatization to prolonged hypoxia in animals; However, there have been no studies in humans directly assessing the contribution of carotid body tonic activity in ventilatory acclimatization during rest and exercise. We aimed to elucidate the changes in carotid chemoreceptor tonic activity in the process of ventilatory acclimatization and de‐acclimatization during rest and exercise conditions. Ventilation at rest and during exercise increased at high altitude during acclimatization, and this corresponded with increased inhibition of ventilation with hyperoxia. Increased ventilation persisted at 3 days following descent from high altitude, along with the persistence of elevated carotid body tonic activity. We conclude that elevated carotid body tonic activity plays a major role in ventilatory acclimatization to, and de‐acclimatization from, high altitude, and this persists during exercise.
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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 | 0,000 |
| 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 ».