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Duration at high altitude influences the onset of arrhythmogenesis during apnea
Purpose Autonomic control of the heart is balanced by sympathetic and parasympathetic inputs. Excitation of both sympathetic and parasympathetic systems occurs concurrently during certain perturbations such as hypoxia, which stimulate carotid chemoreflex to drive ventilation. It is well established...
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Published in: | European journal of applied physiology 2022-02, Vol.122 (2), p.475-487 |
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Main Authors: | , , , , , , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Purpose
Autonomic control of the heart is balanced by sympathetic and parasympathetic inputs. Excitation of both sympathetic and parasympathetic systems occurs concurrently during certain perturbations such as hypoxia, which stimulate carotid chemoreflex to drive ventilation. It is well established that the chemoreflex becomes sensitized throughout hypoxic exposure; however, whether progressive sensitization alters cardiac autonomic activity remains unknown. We sought to determine the duration of hypoxic exposure at high altitude necessary to unmask cardiac arrhythmias during instances of voluntary apnea.
Methods
Measurements of steady-state chemoreflex drive (SS-CD), continuous electrocardiogram (ECG) and SpO
2
(pulse oximetry) were collected in 22 participants on 1 day at low altitude (1045 m) and over eight consecutive days at high-altitude (3800 m). SS-CD was quantified as ventilation (L/min) over stimulus index (P
ET
CO
2
/SpO
2
).
Results
Bradycardia during apnea was greater at high altitude compared to low altitude for all days (
p
50%) following Day 5 at high altitude. Changes in saturation during apnea and apnea duration did not affect the magnitude of bradycardia during apnea (ANCOVA; saturation,
p
= 0.15 and apnea duration,
p
= 0.988). Interestingly, the magnitude of bradycardia was correlated with the incidence of arrhythmia per day (
r
= 0.8;
p
= 0.004).
Conclusion
Our findings suggest that persistent hypoxia gradually increases vagal tone with time, indicated by augmented bradycardia during apnea and progressively increased the incidence of arrhythmia at high altitude. |
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ISSN: | 1439-6319 1439-6327 |
DOI: | 10.1007/s00421-021-04842-x |