Simultaneous assessment of central and peripheral chemoreflex regulation of muscle sympathetic nerve activity and ventilation in healthy young men
Notice bibliographique
Résumé
Key points Central chemoreceptor stimulation, by hypercapnia (acidosis), and peripheral, by hypoxia plus hypercapnia, evoke reflex increases in ventilation and sympathetic outflow. The assumption that central or peripheral chemoreceptor‐mediated sympathetic activation elicited when increases parallels concurrent ventilatory responses is unproven. Applying a modified rebreathing protocol that equilibrates central and peripheral chemoreceptor whilst clamping O2 tension at either hypoxic or hyperoxic concentrations, the independent ventilatory and muscle sympathetic stimulus–response properties of the central and peripheral chemoreflexes were quantified and compared in young men. The novel findings were that ventilatory and sympathetic responses to central and peripheral chemoreflex stimulation are initiated at similar recruitment thresholds but individual specific sympathetic responsiveness cannot be predicted from the ventilatory sensitivities of either chemoreceptor reflex. Such findings in young men, if replicated in heart failure or hypertension, should temper present enthusiasm for trials targeting the peripheral chemoreflex based solely on ventilatory responsiveness to non‐specific chemoreceptor stimulation. Abstract In humans, stimulation of peripheral or central chemoreceptor reflexes is assumed to evoke equivalent ventilatory and sympathetic responses. We evaluated whether central or peripheral chemoreceptor‐mediated sympathetic activation elicited by increases in CO2 tension ( ) parallels concurrent ventilatory responses. Twelve healthy young men performed a modified rebreathing protocol designed to equilibrate central and peripheral chemoreceptor tensions with end‐tidal ( ) at two isoxic end‐tidal ( ) such that central responses can be segregated, by hyperoxia, from the net response (hypoxia minus hyperoxia). Ventilation and muscle sympathetic nerve activity (MSNA) were recorded continuously during rebreathing at isoxic of 150 and 50 mmHg. During rebreathing, the values at which ventilation (L min−1) and total MSNA (units) began to rise were identified ( recruitment thresholds) and their slopes above the recruitment threshold were determined (sensitivity). The central chemoreflex recruitment threshold for ventilation (46 ± 3 mmHg) and MSNA (45 ± 4 mmHg) did not differ (P = 0.55) and slopes were 2.3 ± 0.9 L min−1 mmHg−1 and 2.1 ± 1.5 units mmHg−1, respectively. The peripheral chemoreflex recruitment thresholds, at 41 ± 3 mmHg for both ventilation and MSNA were lower (P < 0.05) compared to the central chemoreflex recruitment thresholds. Peripheral chemoreflex sensitivity was 1.7 ± 0.1 L min−1 mmHg−1 for ventilation and 2.9 ± 2.6 units mmHg−1 for MSNA. There was no relationship between the ventilatory and MSNA sensitivity for either the central (r2 = 0.01, P = 0.76) or peripheral (r2 = 0.01, P = 0.73) chemoreflex. In healthy young men, ventilatory and sympathetic responses to central and peripheral chemoreceptor reflex stimulation are initiated at similar recruitment thresholds but individual ventilatory responsiveness does not predict sympathetic sensitivities of either chemoreflex.
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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) | 0,002 | 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 ».