{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,27]],"date-time":"2026-10-27T22:39:03Z","timestamp":1793140743781,"version":"4.5.0"},"reference-count":33,"publisher":"Wiley","issue":"11","license":[{"start":{"date-parts":[[2024,6,14]],"date-time":"2024-06-14T00:00:00Z","timestamp":1718323200000},"content-version":"vor","delay-in-days":13,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000038","name":"Natural Sciences and Engineering Research Council of Canada","doi-asserted-by":"publisher","award":["RGPIN\u20102020\u201005385"],"award-info":[{"award-number":["RGPIN\u20102020\u201005385"]}],"id":[{"id":"10.13039\/501100000038","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["physoc.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Physiological Reports"],"published-print":{"date-parts":[[2024,6]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>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\u2010six healthy participants (12 females; 23\u2009\u00b1\u20092\u2009years; BMI 24\u2009\u00b1\u20093\u2009kg\/m<jats:sup>2<\/jats:sup>) underwent three gas challenges: hypercapnia (+5\u2009torr end tidal partial pressure of CO<jats:sub>2<\/jats:sub> [P<jats:sub>ET<\/jats:sub>CO<jats:sub>2<\/jats:sub>]), hypoxia (50\u2009torr end tidal partial pressure of O<jats:sub>2<\/jats:sub> [P<jats:sub>ET<\/jats:sub>O<jats:sub>2<\/jats:sub>]), and hypercapnic hypoxia (combined hypercapnia and hypoxia), with each condition interspersed with normocapnic normoxia. Heart rate and rhythm, blood pressure, P<jats:sub>ET<\/jats:sub>CO<jats:sub>2<\/jats:sub>, P<jats:sub>ET<\/jats:sub>O<jats:sub>2<\/jats:sub>, and oxygen saturation were measured continuously. Hypercapnic hypoxic apneas induced larger bradycardia (\u221219\u2009\u00b1\u200916\u2009bpm) than normocapnic normoxic apneas (\u221211\u2009\u00b1\u200915\u2009bpm; <jats:italic>p<\/jats:italic>\u2009=\u20090.002), but had a comparable response to hypoxic (\u221219\u2009\u00b1\u200915\u2009bpm; <jats:italic>p<\/jats:italic>\u2009=\u20090.999) and hypercapnic apneas (\u221214\u2009\u00b1\u200914\u2009bpm; <jats:italic>p<\/jats:italic>\u2009=\u20090.059). Hypercapnic apneas were not different from normocapnic normoxic apneas (<jats:italic>p<\/jats:italic>\u2009=\u20090.134). After removal of the normocapnic normoxic heart rate response, the change in heart rate during hypercapnic hypoxia (\u221211\u2009\u00b1\u200916\u2009bpm) was similar to the summed change during hypercapnia+hypoxia (\u22129\u2009\u00b1\u200910\u2009bpm; <jats:italic>p<\/jats:italic>\u2009=\u20090.485). Only hypoxia contributed to this bradycardic response. Under apneic conditions, the cardiac response is driven by hypoxia.<\/jats:p>","DOI":"10.14814\/phy2.16054","type":"journal-article","created":{"date-parts":[[2024,6,14]],"date-time":"2024-06-14T07:41:19Z","timestamp":1718350879000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Influence of hypercapnia and hypercapnic hypoxia on the heart rate response to apnea"],"prefix":"10.14814","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-4658-9125","authenticated-orcid":false,"given":"Benjamin R.","family":"O'Croinin","sequence":"first","affiliation":[{"name":"Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation University of Alberta  Edmonton Alberta Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9891-8757","authenticated-orcid":false,"given":"Desmond A.","family":"Young","sequence":"additional","affiliation":[{"name":"Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation University of Alberta  Edmonton Alberta Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lauren E.","family":"Maier","sequence":"additional","affiliation":[{"name":"Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation University of Alberta  Edmonton Alberta Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sean","family":"van Diepen","sequence":"additional","affiliation":[{"name":"Department of Critical Care Medicine, Faculty of Medicine and Dentistry University of Alberta  Edmonton Alberta Canada"},{"name":"Division of Cardiology, Department of Medicine, Faculty of Medicine and Dentistry University of Alberta  Edmonton Alberta Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Trevor A.","family":"Day","sequence":"additional","affiliation":[{"name":"Department of Biology, Faculty of Science and Technology Mount Royal University  Calgary Alberta Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7190-7046","authenticated-orcid":false,"given":"Craig D.","family":"Steinback","sequence":"additional","affiliation":[{"name":"Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation University of Alberta  Edmonton Alberta 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