Duration at High Altitude Influences the Onset of Arrhythmogenesis During Apnea
Notice bibliographique
Résumé
Excitation of both sympathetic and parasympathetic systems occur concurrently at high‐altitude (chronic hypoxia), via the carotid chemoreflex. We have demonstrated this autonomic conflict manifests as cardiac arrhythmias during voluntary apnea. We sought to determine the duration of hypoxic exposure at high‐altitude necessary to unmask cardiac arrhythmias during instances of voluntary apnea. We hypothesized that the occurrence of cardiac arrhythmias during apnea would be increased following 24 hours of high‐altitude exposure. Measurements of oxygen saturation (SpO 2 ; pulse oximetry) and continuous electrocardiogram (ECG; lead II) were collected in 22 participants (8 females) at low altitude (1045m) and over 8 consecutive days at high‐altitude (3800m). Following a 2 minute baseline participants performed an end‐expiratory apnea to volitional breakpoint. ECG rate and rhythm were evaluated at baseline and during apnea. The nadir heart rate was used to quantify bradycardia and abnormal ECG rhythm was classified based on origin (e.g., sinus node) and type (e.g., sinus arrest). Differences in resting ventilation, SpO 2 , and the heart rate response to apnea on each day at high‐altitude (Day 1‐8) were compared to that at low altitude (Day 0) using a repeated‐measures ANOVA design, with a Holm‐Sidak post‐hoc analysis where main effect of time was significant. Baseline SpO 2 was lower for all days at high‐altitude (average of all days, 89±3) compared to low altitude (98 ± 2) (p<0.01). At high‐altitude (all days), baseline heart rate was higher compared to low altitude (p<0.01). A main effect of time (p<0.01) was identified for the delta change in heart rate during apnea. At low altitude, the average apnea induced decrease in heart rate was ‐9±15bpm, whereas the average decrease in heart rate at high altitude (all days) was ‐24±16bpm. Bradycardia became more pronounced with acclimatization, with the greatest drop in heart rate (‐31±16bpm) occurring on Day 5. At low altitude 14% (3/22) of participants developed arrhythmias during apnea. At high‐altitude, cardiac arrhythmias during apnea became most prevalent (>50%) following Day 5. Changes in saturation during apnea and apnea duration were not associated with the magnitude of bradycardia during apnea (saturation, r= ‐0.007 p=0.92; apnea duration, r=0.005 p=0.94). Interestingly, the magnitude of bradycardia was correlated with the incidence (percentage) of arrhythmia per day (r=0.8; p=0.004), suggesting a similar underlying mechanism. Our data indicate chronic hypoxia is associated with a progressive increase in vagal tone, as indicated by augmented bradycardia during apnea and progressively increased incidence of arrhythmia at high‐altitude. Additionally, the increased incidence of arrhythmia with acclimatization suggests that chemoreflex sensitization may play a role in this phenomenon. This study provides insight into cardiac electrophysiology at high‐altitude and has implications as a future functional model for exploring the effects of heightened chemoreflex stress on autonomic control of heart.
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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 ».