title: Changes in internal carotid artery flow velocities with cerebral vasodilation and constriction.
abstract: Non-invasive Doppler-shift ultrasound, together with spectral analysis, have been used to study the changes in internal carotid artery flow velocity patterns that occur with cerebral vasoconstriction and vasodilation provoked by over-breathing and breath-holding. Significantly different waveform shapes, characteristic for each vessel, were demonstrated from the internal and external carotid arteries, making identification of the internal carotid certain. In 5 healthy subjects over-breathing for 3 minutes significantly lowered the mean height of the internal carotid waveform by an average of 32% (p less than 0.001). Breath-holding for 40-60 seconds raised the mean height by an average of 31% (p less than 0.001). The pulsatility index of the waveforms varied inversely to mean height. These results show that the effects of cerebral dilation or constriction are easily detected by flow-velocity changes in the internal carotid artery.
mesh_terms: D001783:Blood Flow Velocity; D002245:Carbon Dioxide / Q000097:blood; D002343:Carotid Artery, Internal / Q000502:physiology*; D002560:Cerebrovascular Circulation; D006801:Humans; D012119:Respiration; D014463:Ultrasonography; D014661:Vasoconstriction; D014664:Vasodilation
chemical_list: D002245:Carbon Dioxide