PURPOSE To conduct a validation study of a Doppler guide wire for potential neuroendovascular applications. METHODS A 12-MHz, 0.018-inch Doppler guide wire was evaluated in eight swine under various blood flow conditions using two types of in vivo cerebrovascular models (physiologic and arteriovenous shunting). Flow conditions were mechanically and pharmacologically altered. Doppler average p...

PURPOSE Several different anti-hypertensive regimens have been introduced for the prevention of systemic hyperdynamic responses after electrically induced seizures. In the present study, the effects of anti-hypertensive medications on cerebral circulation were studied. METHODS Systemic blood pressure was controlled by several anti-hypertensive medications, nicardipine, prostaglandin EI, alpre...

BACKGROUND This study was designed to determine the minimal mean flow velocity and pressure-flow relation necessary to preserve human consciousness. METHODS Passive upright tilt provocation was used in conjunction with transcranial Doppler in 80 patients with a history of syncope of unknown etiology. Cerebral blood flow velocity, blood pressure, and heart rate were monitored noninvasively. ...

Intracranial pressure (ICP) and continuous transcranial Doppler ultrasound signals were monitored in 20 head-injured patients and simultaneous synchronous fluctuations of middle cerebral artery (MCA) velocity and B waves of the ICP were observed. Continuous simultaneous monitoring of MCA velocity, ICP, arterial blood pressure, and expired CO2 revealed that both velocity waves and B waves occurr...

The effects of loud sound on the microvasculature of the cochlea are not well characterized or understood. Morphological changes in the stria vascularis and changes in blood flow are known to occur during or following sound stimulation, however, the effects on cochlear blood flow appear to be complex. Studies have shown that noise exposure may produce increases in blood flow, decreases in blood...

A consecutive cohort of 73 very low birthweight infants was studied to determine the presence or absence of beat to beat variability in the velocity of blood flow in the cerebral circulation and its relation with respiration. One minute epochs of information included recordings of cerebral blood flow velocity estimated with Doppler ultrasound, blood pressure, spontaneous respiratory activity, a...

Conventional ultrasound scanners can only display the blood velocity component parallel to the ultrasound beam. Introducing a laterally oscillating field gives signals from which the transverse velocity component can be estimated using 2:1 parallel receive beamformers. To yield the performance of the approach, this paper presents simulated and experimental results, obtained at a blood velocity ...

Ankle exercises are commonly used to facilitate venous return in the lower extremity and to prevent deep vein thrombosis. Moreover, the respiratory cycle affects venous return. This study examined the effects of ankle exercise combined with deep breathing on the blood flow velocity in the femoral vein. Twenty healthy males (mean age 21.3 years), who had no medical history of lower extremity dis...