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Relationship between volume flow and velocity in the cerebral circulation
Journal of Neurology, Neurosurgery, and Psychiatry
|December 1, 1970
Summary
Cerebral blood flow velocity is not a reliable indicator of cerebral blood flow, especially at higher flow rates. Mean circulation time is an unreliable measure for assessing cerebral blood flow.
Area of Science:
- Neurology
- Physiology
- Medical Imaging
Background:
- Cerebral blood flow (CBF) is critical for brain function.
- Understanding the relationship between CBF and its measurable parameters is essential for diagnosing and managing neurological conditions.
Purpose of the Study:
- To investigate the relationship between cerebral circulation velocity and cerebral blood flow.
- To determine the reliability of velocity as an indicator of flow under various physiological conditions.
Main Methods:
- Radioisotope techniques were employed in baboon models.
- Cerebral circulation was studied under controlled variations in partial pressure of carbon dioxide (PaCO2), systemic arterial pressure, intracranial pressure, and perfusion pressure.
Main Results:
- Cerebral blood flow velocity increased non-linearly with flow only at low flow rates.
- At higher flow rates, velocity increases became progressively smaller, indicating a decoupling from flow.
- Mean circulation time was found to be an unreliable indicator of cerebral blood flow.
Conclusions:
- Cerebral blood flow velocity is not consistently proportional to cerebral blood flow across all physiological ranges.
- The findings suggest limitations in using velocity measurements for accurately assessing cerebral blood flow, particularly in dynamic conditions.