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Hoiland, RL, Smith, KJ, Carter, HH, Lewis, NCS, Tymko, MM, Wildfong, KW, Bain, AR, Green, DJ and Ainslie, PN (2017) Shear-Mediated Dilation of the Internal Carotid Artery Occurs Independent of Hypercapnia. American Journal of Physiology Heart and Circulatory Physiology. ISSN 1522-1539
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Abstract
Evidence for shear stress as a regulator of carotid artery dilation in response to increased arterial carbon dioxide was recently demonstrated in humans during sustained elevations in CO2 (hypercapnia); however, the relative contributions of CO2 and shear stress to this response remains unclear. We examined the hypothesis that, following a 30-second transient increase in arterial CO2 tension and consequent increase in internal carotid artery shear stress, internal carotid artery diameter would increase, indicating shear-mediated dilation, in the absence of concurrent hypercapnia. In 27 healthy participants the partial pressures of end-tidal O2 and CO2, ventilation (pneumotachography), blood pressure (finger-photoplethysmography), heart-rate (electrocardiogram), internal carotid artery flow, diameter and shear stress (high resolution duplex ultrasound) and middle cerebral artery blood velocity (transcranial Doppler) were measured during 4-minute steady state and transient 30-second hypercapnic tests (both +9mmHg CO2). Internal carotid artery dilation was lower in the transient, compared to the steady state hypercapnia (3.3±1.9% vs. 5.3±2.9%, respectively; P<0.03). Increases in internal carotid artery shear stress preceded increases in diameter in both the transient (time: 16.8±13.2s vs. 59.4±60.3s; P<0.01) and steady state (time: 18.2±14.2s vs. 110.3±79.6s; P<0.01) tests. Internal carotid artery dilation was positively correlated with shear rate area under the curve in the transient (r(2)=0.44; P<0.01), but not steady state (r(2)=0.02; P=0.53) trial. Collectively, these results suggest that hypercapnia induces shear-mediated dilation of the internal carotid artery in humans. This study further promotes the application and development of hypercapnia as a clinical strategy for the assessment of cerebrovascular vasodilatory function and health in humans.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | 0606 Physiology, 1116 Medical Physiology |
| Subjects: | R Medicine > RC Internal medicine > RC1200 Sports Medicine |
| Divisions: | Sport & Exercise Sciences |
| Publisher: | Amercian Physiological Society |
| Related URLs: | |
| Date Deposited: | 25 May 2017 11:09 |
| Last Modified: | 04 Sep 2021 11:35 |
| DOI or ID number: | 10.1152/ajpheart.00119.2017 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/6418 |
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