Time-Dependent Changes in Cerebral Blood Flow and Arterial Pressure During Mild +G_z Hypergravity

Area of Science:

• Space Physiology
• Aerospace Medicine
• Human Physiology

Background:

• Artificial hypergravity is explored as a countermeasure for spaceflight deconditioning.
• Previous studies indicated decreased cerebral blood flow during +1.5-Gz centrifugation without changes in heart-level arterial pressure.
• This study reanalyzed data to detail time-dependent cerebral blood flow and arterial pressure changes.

Purpose of the Study:

• To clarify time-dependent changes in cerebral blood flow and arterial pressure during mild +1.5-Gz hypergravity.
• To investigate the physiological responses to artificial hypergravity relevant to spaceflight.

Main Methods:

• Reanalysis of physiological data from 13 male subjects during 20 minutes of +1.5-Gz centrifugation.
• Measurement of mean cerebral blood flow velocity in the middle cerebral artery (MCBFVMCA) and mean arterial pressure at heart (MAPheart) and middle cerebral artery (MAPMCA) levels.
• Data averaged every 5 minutes and compared to pre-hypergravity baseline.

Main Results:

• Mean arterial pressure at the middle cerebral artery level (MAPMCA) significantly decreased (-16.7% to -24.7%) throughout centrifugation.
• Mean cerebral blood flow velocity in the middle cerebral artery (MCBFVMCA) showed a non-significant decrease initially, followed by significant reductions (-5.5% to -6.9%) from 5 to 20 minutes.
• Heart-level arterial pressure (MAPheart) did not change significantly.

Conclusions:

• Mild +1.5-Gz hypergravity caused a significant and sustained decrease in MAPMCA, while MCBFVMCA gradually decreased and stabilized.
• Understanding these distinct time-dependent cardiovascular responses is vital for optimizing artificial hypergravity as a spaceflight countermeasure.
• The findings highlight the importance of considering regional arterial pressure changes in cerebral blood flow regulation during hypergravity exposure.