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- Title
Duration at high altitude influences the onset of arrhythmogenesis during apnea.
- Authors
Berthelsen, Lindsey F.; van Diepen, Sean; Steele, Andrew R.; Vanden Berg, Emily R.; Bird, Jordan; Thrall, Scott; Skalk, Alexandra; Byman, Britta; Pentz, Brandon; Wilson, Richard J. A.; Jendzjowsky, Nicholas G.; Day, Trevor A.; Steinback, Craig D.
- Abstract
<bold>Purpose: </bold>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.<bold>Methods: </bold>Measurements of steady-state chemoreflex drive (SS-CD), continuous electrocardiogram (ECG) and SpO2 (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 (PETCO2/SpO2).<bold>Results: </bold>Bradycardia during apnea was greater at high altitude compared to low altitude for all days (p < 0.001). Cardiac arrhythmias occurred during apnea each day but became most prevalent (> 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).<bold>Conclusion: </bold>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.
- Subjects
INFLUENCE of altitude; MOUNTAIN sickness; APNEA; ARRHYTHMIA; VAGAL tone; PULSE oximetry; BRADYCARDIA
- Publication
European Journal of Applied Physiology, 2022, Vol 122, Issue 2, p475
- ISSN
1439-6319
- Publication type
journal article
- DOI
10.1007/s00421-021-04842-x