Regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young men
Abstract Hyperthermia is known to induce hypocapnia‐driven reductions in cerebral blood flow; however, it is unknown if it causes changes in hemodynamic pulsatility that negatively influence cerebrovascular function. This retrospective analysis aimed to assess cerebrovascular hemodynamic pulsatile b...
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Wiley
2025-02-01
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| Online Access: | https://doi.org/10.14814/phy2.70258 |
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| author | Spencer J. Skaper Brooke R. Shepley Ibrahim Amr Wafai Philip N. Ainslie Anthony R. Bain Kurt J. Smith |
| author_facet | Spencer J. Skaper Brooke R. Shepley Ibrahim Amr Wafai Philip N. Ainslie Anthony R. Bain Kurt J. Smith |
| author_sort | Spencer J. Skaper |
| collection | DOAJ |
| description | Abstract Hyperthermia is known to induce hypocapnia‐driven reductions in cerebral blood flow; however, it is unknown if it causes changes in hemodynamic pulsatility that negatively influence cerebrovascular function. This retrospective analysis aimed to assess cerebrovascular hemodynamic pulsatile buffering (damping factor; DFi) during poikilocapnic (HT) and isocapnic (HT‐C) hyperthermia. We hypothesized that HT would reduce cerebral DFi, while HT‐C would attenuate the reduction in DFi by limiting increases in resistance. Ten healthy males were passively heated +2°C from normothermia (BL). Blood flow through the internal carotid artery (ICA) and vertebral artery (VA) was measured using vascular ultrasound. Blood velocity through the middle cerebral artery (MCA) and the posterior cerebral artery (PCA) was measured using transcranial ultrasound. DFi was calculated as the ratio of proximal to distal pulsatility index (PI): Anterior cerebral DFi = PIICA/PIMCA; Posterior cerebral DFi = PIVA/PIPCA. Anterior DFi decreased in both HT (1.08 ± 0.19 a.u; p = 0.007) and HT‐C (1.12 ± 0.231 a.u; p = 0.021) conditions from BL values (1.27 ± 0.14 a.u). No changes were observed in posterior DFi, p = 0.116. Irrespective of PaCO2 clamping, both hyperthermic conditions reduced anterior DFi, suggesting other mechanisms are responsible for cerebrovascular hemodynamic buffering. Posterior DFi responses were not observed, suggesting preferential buffering of the hyperthermic posterior circulation (VA–PCA). |
| format | Article |
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| issn | 2051-817X |
| language | English |
| publishDate | 2025-02-01 |
| publisher | Wiley |
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| series | Physiological Reports |
| spelling | doaj-art-c9e24002f85b407d8348f617df7a94aa2025-08-20T02:45:02ZengWileyPhysiological Reports2051-817X2025-02-01134n/an/a10.14814/phy2.70258Regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young menSpencer J. Skaper0Brooke R. Shepley1Ibrahim Amr Wafai2Philip N. Ainslie3Anthony R. Bain4Kurt J. Smith5Cerebrovascular Health Exercise and Environmental Research Sciences (CHEERS) Laboratory, Department of Exercise Science, Physical & Health Education University of Victoria Victoria British Columbia CanadaFaculty of Human Kinetics University of Windsor Windsor Ontario CanadaFaculty of Human Kinetics University of Windsor Windsor Ontario CanadaCentre for Heart, Lung and Vascular Health, School of Health and Exercise Science University of British Columbia – Okanagan Kelowna British Columbia CanadaFaculty of Human Kinetics University of Windsor Windsor Ontario CanadaCerebrovascular Health Exercise and Environmental Research Sciences (CHEERS) Laboratory, Department of Exercise Science, Physical & Health Education University of Victoria Victoria British Columbia CanadaAbstract Hyperthermia is known to induce hypocapnia‐driven reductions in cerebral blood flow; however, it is unknown if it causes changes in hemodynamic pulsatility that negatively influence cerebrovascular function. This retrospective analysis aimed to assess cerebrovascular hemodynamic pulsatile buffering (damping factor; DFi) during poikilocapnic (HT) and isocapnic (HT‐C) hyperthermia. We hypothesized that HT would reduce cerebral DFi, while HT‐C would attenuate the reduction in DFi by limiting increases in resistance. Ten healthy males were passively heated +2°C from normothermia (BL). Blood flow through the internal carotid artery (ICA) and vertebral artery (VA) was measured using vascular ultrasound. Blood velocity through the middle cerebral artery (MCA) and the posterior cerebral artery (PCA) was measured using transcranial ultrasound. DFi was calculated as the ratio of proximal to distal pulsatility index (PI): Anterior cerebral DFi = PIICA/PIMCA; Posterior cerebral DFi = PIVA/PIPCA. Anterior DFi decreased in both HT (1.08 ± 0.19 a.u; p = 0.007) and HT‐C (1.12 ± 0.231 a.u; p = 0.021) conditions from BL values (1.27 ± 0.14 a.u). No changes were observed in posterior DFi, p = 0.116. Irrespective of PaCO2 clamping, both hyperthermic conditions reduced anterior DFi, suggesting other mechanisms are responsible for cerebrovascular hemodynamic buffering. Posterior DFi responses were not observed, suggesting preferential buffering of the hyperthermic posterior circulation (VA–PCA).https://doi.org/10.14814/phy2.70258carbon dioxidecerebral blood flowcerebral hemodynamicshyperthermiapulsatility |
| spellingShingle | Spencer J. Skaper Brooke R. Shepley Ibrahim Amr Wafai Philip N. Ainslie Anthony R. Bain Kurt J. Smith Regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young men Physiological Reports carbon dioxide cerebral blood flow cerebral hemodynamics hyperthermia pulsatility |
| title | Regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young men |
| title_full | Regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young men |
| title_fullStr | Regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young men |
| title_full_unstemmed | Regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young men |
| title_short | Regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young men |
| title_sort | regional cerebral pulsatile hemodynamics during isocapnic and poikilocapnic hyperthermia in young men |
| topic | carbon dioxide cerebral blood flow cerebral hemodynamics hyperthermia pulsatility |
| url | https://doi.org/10.14814/phy2.70258 |
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