Shear-mediated dilation of the internal carotid artery occurs independent of hypercapnia
| Autor: | Philip N. Ainslie, Nia C. S. Lewis, Daniel J. Green, Kevin W. Wildfong, Michael M. Tymko, Kurt J. Smith, Howard H. Carter, Anthony R. Bain, Ryan L. Hoiland |
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| Rok vydání: | 2017 |
| Předmět: |
Male
Physiology Vasodilation 030204 cardiovascular system & hematology Mechanotransduction Cellular Hypercapnia RC1200 Young Adult 03 medical and health sciences 0302 clinical medicine Physiology (medical) medicine.artery Shear stress Humans Medicine business.industry Carbon Dioxide Transcranial Doppler Cerebral blood flow Shear (geology) Anesthesia Dilation (morphology) Female Stress Mechanical medicine.symptom Internal carotid artery Shear Strength Cardiology and Cardiovascular Medicine business Blood Flow Velocity Carotid Artery Internal 030217 neurology & neurosurgery |
| Zdroj: | American Journal of Physiology-Heart and Circulatory Physiology. 313:H24-H31 |
| ISSN: | 1522-1539 0363-6135 |
| DOI: | 10.1152/ajpheart.00119.2017 |
| Popis: | Evidence for shear stress as a regulator of carotid artery dilation in response to increased arterial CO2 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, after a 30-s 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, 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-min steady-state and transient 30-s hypercapnic tests (both +9 mmHg CO2). Internal carotid artery dilation was lower in the transient compared with 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 transient (time: 16.8 ± 13.2 vs. 59.4 ± 60.3 s, P < 0.01) and steady-state (time: 18.2 ± 14.2 vs. 110.3 ± 79.6 s, P < 0.01) tests. Internal carotid artery dilation was positively correlated with shear rate area under the curve in the transient ( r2 = 0.44, P < 0.01) but not steady-state ( r2 = 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. NEW & NOTEWORTHY Shear stress dilates the internal carotid artery in humans. This vasodilatory response occurs independent of other physiological factors, as demonstrated by our transient CO2 test, and is strongly correlated to shear area under the curve. Assessing carotid shear-mediated dilation may provide a future avenue for assessing cerebrovascular health and the risk of cerebrovascular events. |
| Databáze: | OpenAIRE |
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