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

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  • Additional Information
    • Source:
      Publisher: published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society Country of Publication: United States NLM ID: 101607800 Publication Model: Print Cited Medium: Internet ISSN: 2051-817X (Electronic) Linking ISSN: 2051817X NLM ISO Abbreviation: Physiol Rep Subsets: MEDLINE
    • Publication Information:
      Original Publication: [Malden MA] : published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society, 2013-
    • Subject Terms:
      Hypercapnia*/physiopathology ; Heart Rate*/physiology ; Hypoxia*/physiopathology ; Apnea*/physiopathology ; Bradycardia*/physiopathology; Humans ; Female ; Male ; Adult ; Young Adult ; Blood Pressure/physiology ; Carbon Dioxide/metabolism
    • Abstract:
      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/m 2 ) underwent three gas challenges: hypercapnia (+5 torr end tidal partial pressure of CO 2 [P ET CO 2 ]), hypoxia (50 torr end tidal partial pressure of O 2 [P ET O 2 ]), and hypercapnic hypoxia (combined hypercapnia and hypoxia), with each condition interspersed with normocapnic normoxia. Heart rate and rhythm, blood pressure, P ET CO 2 , P ET O 2 , 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.
      (© 2024 The Author(s). Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)
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    • Grant Information:
      RGPIN-2020-05385 Government of Canada|Natural Sciences and Engineering Research Council of Canada (NSERC)
    • Contributed Indexing:
      Keywords: arrhythmia; bradycardia; breath‐hold; chemoreflex; diving response
    • Accession Number:
      142M471B3J (Carbon Dioxide)
    • Publication Date:
      Date Created: 20240614 Date Completed: 20240614 Latest Revision: 20240618
    • Publication Date:
      20240618
    • Accession Number:
      PMC11176737
    • Accession Number:
      10.14814/phy2.16054
    • Accession Number:
      38872580