Analysis of Time-Series Changes in Blood Flow and Vascular Resistance across Multiple Sites during Active Orthostatic...

The autonomic nervous system regulates blood flow during postural changes to maintain homeostasis and cerebral perfusion, preventing symptoms such as dizziness and syncope. Previous orthostatic studies have primarily focused on a single region, such as the brain or peripheral blood vessels, limiting insight into systemic regulatory control. This study investigated blood flow regulation during an active orthostatic test by simultaneously measuring blood flow in the brain, left forearm, and right lower extremity using diffuse correlation spectroscopy. Results showed that lower limb blood flow decreased significantly while vascular resistance increased during upright posture, whereas cerebral blood flow remained relatively stable. These findings suggest that increased lower limb resistance compensates for the maintenance of cerebral perfusion, providing information on orthostatic blood flow regulation and its implications for autonomic dysfunction.Clinical Relevance- Understanding the differences in deep blood flow and vascular resistance responses at different sites during the orthostatic test may provide a detailed understanding of the pathogenesis of orthostatic hemodynamic disorders.