Short‐term hypoxia does not promote arrhythmia during voluntary apnea

Busch, Stephen A.; Diepen, Sean van; Roberts, Richard J.; Steele, Andrew R.; Berthelsen, Lindsey F.; Smorschok, Megan P; Bourgoin, Cody; Steinback, Craig D.

doi:10.14814/phy2.14703

Cited by 4 publications

(12 citation statements)

References 60 publications

(106 reference statements)

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“…During previous investigations of this phenomenon, we have demonstrated that the blood pressure peak does not occur until post apnea, with a lower relative change in blood pressure during apnea at high compared to low altitude (Busch et al 2018). Additionally, with relatively short (average < 1 min) apnea duration, it seems unlikely that the baroreflex is the primary mediator of the observed bradycardic response (Busch et al 2021). Finally, our results demonstrate a clear effect of high altitude on both the heart rate (i.e., bradycardia) and rhythm response to apnea, while baroreflex engagement may be similar across conditions, as it has been previously demonstrated that baroreflex gain is similar between low and high altitude (Simpson et al 2019).…”

Section: Considerationssupporting

confidence: 73%

“…Ventilation has been clearly shown to suppress sympathetic activity during hypoxia (Kato et al 1988;Busch et al 2020a), and our previous work has demonstrated a pronounced bradycardia during apnea following prolonged hypoxic exposure, indicating heightened parasympathetic tone that is only unmasked during apnea (Busch et al 2018). Additionally, this bradycardic response to apnea is absent when hypoxia is reversed following administration of supplemental oxygen (100% O 2 ; Busch et al 2018) and during apnea at low altitude (Busch et al 2021). In the current study, augmented bradycardia was evident during apnea following even 1 day (~ 24 h) at high altitude, suggesting that hypoxic exposure results in elevated cardiac parasympathetic tone which becomes apparent in the absence of ventilation.…”

Section: Discussionmentioning

confidence: 99%

“…Although within the current framework we are unable to definitively determine a mechanism for this phenomenon, our results suggest that progressive chemoreflex sensitization throughout acclimatization underlies the development of cardiac arrhythmias during voluntary apnea. The fact that elevated parasympathetic tone is not unmasked with acute hypoxic exposure (Busch et al 2021), despite a marked increase in sympathetic activity that develops rapidly and is maintained throughout hypoxic exposure (Hansen and Sander 2003;Sander 2016;Simpson et al 2020), indicates a differential effect of time course on both autonomic limbs which may be related to concurrent changes in chemosensitivity (Masuyama et al 1990;Khoo et al 1996;Busch et al 2018) and or changes in adrenergic/cholinergic receptor density and sensitivity to autonomic drive (Kacimi et al 1993). The use of apnea at high altitude may provide a future functional model for exploring the effects of heightened chemoreflex stress on autonomic control of heart rate and rhythm.…”

Section: Perspectives and Conclusionmentioning

confidence: 99%

“…We further demonstrated that chemoreflex activation and sensitization is critical for these responses (Busch et al 2018). Interestingly, apnea during normoxia does not promote these cardiac events (Busch et al 2018(Busch et al , 2021, nor are they evident during apnea following acute (i.e., < 5 h) hypoxic exposure (Busch et al 2021). These data suggest that prolonged chemoreflex sensitization (e.g., days) and concurrent changes in autonomic balance at high altitude, as opposed to acute activation (minutes to hours), is critical for the genesis of bradyarrythmias during hypoxic apnea.…”

Section: Introductionmentioning

confidence: 96%

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Duration at high altitude influences the onset of arrhythmogenesis during apnea

et al. 2021

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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.

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Section: Considerationssupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Perspectives and Conclusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Duration at high altitude influences the onset of arrhythmogenesis during apnea

et al. 2021

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“…Varcoe and colleagues described the fetal cardiovascular responses to acute hypoxia in pregnant sheep (92), while another report revealed that the combination of a stressful maternal environment and a Western diet decreased cognitive function in the offspring male mice (93). The relationship between both obstructive sleep apnea and voluntary apnea to urine biomarkers of the renin-angiotensin system and cardiac arrhythmias was recently reported in two articles in Physiological Reports (94,95). The spleen is often overlooked in physiology studies, but spleen volume after food intake was recently reported and was linked to splanchnic circulation (96).…”

Section: Physiological Reportsmentioning

confidence: 99%

An American Physiological Society cross-journal Call for Papers on “Inter-Organ Communication in Homeostasis and Disease”

Bodine

Brooks

Bunnett

et al. 2021

American Journal of Physiology-Lung Cellular and Molecular Phys

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The acquisition of multicellularity has led to the higher-order organization of cells, tissues, and organs over the course of evolution (1-4), which has necessitated the parallel development of communication systems between these anatomical entities. These communication systems include the neurons of the nervous system, and a variety of soluble mediators, including peptides, proteins, and metabolites, which constitute the inter-organ communication network (ICN) (5-7).Although the term "physiology" was first coined in 1542 ( 8) by Jean François Fernel (1497-1558), physician to the court of King Henry II of France, an appreciation of communication between organs reaches back to ancient times. The first published account of an experimental demonstration of the physiological role of inter-organ communication is probably that of Galen of Pergamon (129-216) -who is often regarded as the founder of experimental physiology-while documenting the role of the pharyngeal nerves (9). Since then, disturbances to inter-organ communication have been credited with pivotal roles in a broad spectrum of disease states (10-15). In addition to pathophysiology, the role of interorgan communication in homeostasis was recognized by Walter B. Cannon (1871-1945, who served as 6 th President of our American Physiological Society (APS), when Cannon, building on the pioneering work of French physiologist Claude Bernard (1813-1878) on the milieu intérieur (16), coined the term "homeostasis" [first, "homeostatics" (17)] in his seminal article in Physiological Reviews in 1929 (18).

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Influence of hypercapnia and hypercapnic hypoxia on the heart rate response to apnea

O'Croinin,

Young,

Maier

et al. 2024

Physiological Reports

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We aimed to determine the relative contribution of hypercapnia and hypoxia to the bradycardic response to apneas. We hypothesized that apneas with hypercapnia would cause greater bradycardia than normoxia, similar to the response seen with hypoxia, and that apneas with hypercapnic hypoxia would induce greater bradycardia than hypoxia or hypercapnia alone. Twenty‐six healthy participants (12 females; 23 ± 2 years; BMI 24 ± 3 kg/m2) underwent three gas challenges: hypercapnia (+5 torr end tidal partial pressure of CO2 [PETCO2]), hypoxia (50 torr end tidal partial pressure of O2 [PETO2]), and hypercapnic hypoxia (combined hypercapnia and hypoxia), with each condition interspersed with normocapnic normoxia. Heart rate and rhythm, blood pressure, PETCO2, PETO2, and oxygen saturation were measured continuously. Hypercapnic hypoxic apneas induced larger bradycardia (−19 ± 16 bpm) than normocapnic normoxic apneas (−11 ± 15 bpm; p = 0.002), but had a comparable response to hypoxic (−19 ± 15 bpm; p = 0.999) and hypercapnic apneas (−14 ± 14 bpm; p = 0.059). Hypercapnic apneas were not different from normocapnic normoxic apneas (p = 0.134). After removal of the normocapnic normoxic heart rate response, the change in heart rate during hypercapnic hypoxia (−11 ± 16 bpm) was similar to the summed change during hypercapnia+hypoxia (−9 ± 10 bpm; p = 0.485). Only hypoxia contributed to this bradycardic response. Under apneic conditions, the cardiac response is driven by hypoxia.

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Short‐term hypoxia does not promote arrhythmia during voluntary apnea

Cited by 4 publications

References 60 publications

Duration at high altitude influences the onset of arrhythmogenesis during apnea

Duration at high altitude influences the onset of arrhythmogenesis during apnea

An American Physiological Society cross-journal Call for Papers on “Inter-Organ Communication in Homeostasis and Disease”

Influence of hypercapnia and hypercapnic hypoxia on the heart rate response to apnea

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