PMID- 34800158 OWN - NLM STAT- MEDLINE DCOM- 20220314 LR - 20220314 IS - 1439-6327 (Electronic) IS - 1439-6319 (Linking) VI - 122 IP - 2 DP - 2022 Feb TI - Duration at high altitude influences the onset of arrhythmogenesis during apnea. PG - 475-487 LID - 10.1007/s00421-021-04842-x [doi] AB - 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 < 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). 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. CI - (c) 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature. FAU - Berthelsen, Lindsey F AU - Berthelsen LF AD - Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 1-059A Li Ka Shing Centre for Health Research Innovation, 8602-112 St, Edmonton, AB, T6G 2E1, Canada. FAU - van Diepen, Sean AU - van Diepen S AD - Faculty of Medicine and Dentistry, Department of Critical Care and Division of Cardiology, Department of Medicine, University of Alberta, Edmonton, AB, Canada. FAU - Steele, Andrew R AU - Steele AR AD - Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 1-059A Li Ka Shing Centre for Health Research Innovation, 8602-112 St, Edmonton, AB, T6G 2E1, Canada. FAU - Vanden Berg, Emily R AU - Vanden Berg ER AD - Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 1-059A Li Ka Shing Centre for Health Research Innovation, 8602-112 St, Edmonton, AB, T6G 2E1, Canada. FAU - Bird, Jordan AU - Bird J AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada. FAU - Thrall, Scott AU - Thrall S AD - Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 1-059A Li Ka Shing Centre for Health Research Innovation, 8602-112 St, Edmonton, AB, T6G 2E1, Canada. AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada. FAU - Skalk, Alexandra AU - Skalk A AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada. FAU - Byman, Britta AU - Byman B AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada. FAU - Pentz, Brandon AU - Pentz B AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada. FAU - Wilson, Richard J A AU - Wilson RJA AD - Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada. FAU - Jendzjowsky, Nicholas G AU - Jendzjowsky NG AD - The Lundquist Institute for Biomedical Innovation at Harbor, UCLA Medical Center, Torrance, CA, USA. FAU - Day, Trevor A AU - Day TA AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada. FAU - Steinback, Craig D AU - Steinback CD AUID- ORCID: 0000-0001-7190-7046 AD - Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 1-059A Li Ka Shing Centre for Health Research Innovation, 8602-112 St, Edmonton, AB, T6G 2E1, Canada. craig.steinback@ualberta.ca. LA - eng GR - 06637/Natural Sciences and Engineering Research Council of Canada/ GR - 04915/Natural Sciences and Engineering Research Council of Canada/ GR - 03941/Natural Sciences and Engineering Research Council of Canada/ PT - Journal Article DEP - 20211120 PL - Germany TA - Eur J Appl Physiol JT - European journal of applied physiology JID - 100954790 SB - IM MH - Adult MH - *Altitude MH - Apnea/*physiopathology MH - Arrhythmias, Cardiac/*physiopathology MH - Autonomic Nervous System/*physiopathology MH - Electrocardiography MH - Female MH - Humans MH - Hypoxia/physiopathology MH - Male MH - Oximetry OTO - NOTNLM OT - Altitude OT - Apnea OT - Arrhythmia OT - Hypoxia EDAT- 2021/11/21 06:00 MHDA- 2022/03/15 06:00 CRDT- 2021/11/20 12:05 PHST- 2021/08/27 00:00 [received] PHST- 2021/11/04 00:00 [accepted] PHST- 2021/11/21 06:00 [pubmed] PHST- 2022/03/15 06:00 [medline] PHST- 2021/11/20 12:05 [entrez] AID - 10.1007/s00421-021-04842-x [pii] AID - 10.1007/s00421-021-04842-x [doi] PST - ppublish SO - Eur J Appl Physiol. 2022 Feb;122(2):475-487. doi: 10.1007/s00421-021-04842-x. Epub 2021 Nov 20.