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A mechanical model of cerebral circulation during sustained acceleration
S Cirovic1, C Walsh, W D Fraser
1Institute for Aerospace Studies, University of Toronto, ON, Canada. cirovics@mie.utoronto.ca
Aviation, Space, and Environmental Medicine
|August 17, 2001
Summary
High Gz forces can impair brain blood flow. A mechanical model simulating cerebral circulation shows that venous collapse significantly impacts flow, but elevated pressures can restore normal circulation.
Area of Science:
- Biomedical Engineering
- Cardiovascular Physiology
- Aerospace Medicine
Background:
- High positive Gz (gravitational force) can compromise cerebral blood supply despite normal central blood pressure.
- Understanding Gz effects on cerebral circulation is crucial for protecting individuals in high-G environments.
Purpose of the Study:
- To simulate the impact of sustained positive Gz on cerebral circulation using a mechanical model.
- To investigate the mechanisms by which Gz affects blood flow in the brain.
Main Methods:
- A mechanical model simulating extracranial arteries and veins within a skull-cerebrospinal fluid analog was developed.
- Water flow driven by pressure difference, with gravitational vector changes simulated by tilting the model.
- Vessel collapse and pressure dynamics within the cranial analog were analyzed.
Main Results:
- Flow reduction occurred with increasing tilt angle, primarily due to descending arm (venous) collapse.
- Elevated end-pressures restored flow by opening the collapsed descending arm.
- Pressure within the cranial analog remained close to the venous tubing pressure, preventing collapse.
Conclusions:
- The primary Gz effect on flow is mediated by changes in collapsed venous resistance.
- Restoring venous capacitance and increasing end-pressures can mitigate Gz-induced flow reduction.
- Cranial pressure dynamics are governed by the constant volume constraint of the container.