Brain Perfusion and Arterial Blood Flow Velocity During Prolonged Body Tilting

作者：Montero David^*; Rauber Sven

来源：Aerospace Medicine and Human Performance, 2016, 87(8): 682-687.

DOI：10.3357/AMHP.4546.2016

• intrathoracic blood volume
• brain blood flow
• cerebral autoregulation
• transcranial Doppler

BACKGROUND: It remains unknown whether brain perfusion is preserved and mirrored by middle cerebral blood flow velocity (MCA BFV) during prolonged changes in body posture. Herein, we examined the impact of sustained (180 min) 30 degrees head-up (HUT) and head-down (HDT) tilt on brain perfusion, as determined by MCA BFV and blood flow in the extracranial arteries.
METHODS: In 10 healthy male subjects, arterial diameters, BFVs, and blood flows were determined in the left internal carotid (ICA) and vertebral (VA) arteries using duplex Doppler ultrasound in supine rest, and 5, 20, 60, 120, and 180 min following 30 degrees HUT and HDT. MCA BFV was recorded throughout with transcranial Doppler ultrasound.
RESULTS: ICA as well as VA diameters and blood flows were unaltered during HUT. Likewise, brain blood flow and MCA BFV were preserved with HUT. In the HDT protocol, ICA and VA diameters were gradually increased, although ICA, VA, and brain blood flows were preserved. MCA BFV was progressively reduced during HDT. In addition, MCA BFV was positively associated with ICA BFV (beta = 0.9) and negatively associated with ICA diameter (beta = -125.5). MCA BFV was positively associated with brain blood flow during HUT (beta = 0.2) but not HDT.
CONCLUSIONS: Brain perfusion is preserved whereas MCA BFV is progressively decreased and associated with extracranial arterial BFV during sustained 30 degrees HDT. Therefore, MCA BFV may not be a surrogate of brain perfusion in conditions including prolonged HDT.

• 出版日期2016-8