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Cerebral blood flow velocity and cranial fluid volume decrease during +Gz acceleration
Y Kawai1, S C Puma, A R Hargens
1NASA Ames Research Center, Gravitational Research Branch, Moffett Field, CA 94035-1000, USA.
Journal of Gravitational Physiology : a Journal of the International Society for Gravitational Physiology
|September 7, 2001
Summary
High +Gz acceleration significantly reduces cerebral blood flow (CBF) velocity and cranial fluid volume. This study monitored CBF velocity and fluid shifts during simulated high-G exposure.
Area of Science:
- Aerospace Medicine
- Human Physiology
- Cardiovascular Research
Background:
- Understanding the physiological effects of +Gz acceleration is crucial for aviation safety.
- Cerebral blood flow (CBF) and cranial fluid dynamics are key factors during high-G exposure.
Purpose of the Study:
- To investigate the impact of graded +Gz acceleration on cerebral blood flow velocity and cranial fluid volume in humans.
- To determine the relationship between +Gz exposure and physiological changes in the brain.
Main Methods:
- Transcranial Doppler ultrasonography was used to measure CBF velocity.
- Rheoencephalography was employed to assess cranial fluid volume changes.
- Subjects were exposed to graded +Gz acceleration until vision loss (physiological end point).
Main Results:
- Mean CBF velocity decreased by 48% at the point of peripheral vision loss (5.7 Gz).
- Cranial impedance, indicating fluid loss, increased significantly (p<0.05).
- Both CBF velocity reduction and cranial impedance increase correlated with Gz levels.
Conclusions:
- +Gz acceleration without straining maneuvers significantly reduces mean CBF velocity.
- A caudal fluid shift from intra- and extracranial tissues likely occurs during +Gz exposure.
- These findings highlight the cerebrovascular challenges associated with high-G environments.
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