Cerebral circulation during mild +Gz hypergravity by short-arm human centrifuge

Area of Science:

• Cardiovascular Physiology
• Neuroscience
• Aerospace Medicine

Background:

• Cerebral circulation is vital for brain function.
• Understanding how the brain adapts to altered gravity is crucial for spaceflight and aviation.
• Dynamic cerebral autoregulation maintains stable brain blood flow.

Purpose of the Study:

• To investigate the effects of mild +Gz hypergravity on cerebral circulation and dynamic cerebral autoregulation.
• To assess changes in cerebral blood flow velocity, arterial pressure, and carbon dioxide levels.
• To evaluate the brain's ability to regulate blood flow under simulated high-G conditions.

Main Methods:

• 15 healthy men were exposed to 1.5 Gz using a short-arm centrifuge.
• Continuous arterial pressure waveform, middle cerebral artery blood flow velocity, and end-tidal carbon dioxide were measured.
• Spectral and transfer function analysis assessed dynamic cerebral autoregulation between mean arterial pressure and mean CBF velocity.

Main Results:

• Mean CBF velocity decreased by 7% and end-tidal carbon dioxide by 12% at 1.5 Gz.
• Arterial pressure variability increased significantly in low and high frequencies.
• Transfer function gain between arterial pressure and CBF velocity decreased, indicating improved dynamic cerebral autoregulation.

Conclusions:

• Mild +Gz hypergravity reduces steady-state cerebral blood flow.
• Dynamic cerebral autoregulation is enhanced in low and high frequencies under mild hypergravity.
• Improved autoregulation may be a compensatory mechanism against reduced global CBF.