A stage of mechanisms of pathological cerebral blood flow reduction due to severe central hypovolemia: a study using maximal lower body negative pressure

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 2026

View at publisher
Authors: Ai Hirasawa, Takuro Washio, Tomoya Suda, Kazukuni Hirabuki, Marina Fukuie, Shotaro Saito, Noritaka Hata, Takeaki Matsuda, Jun Sugawara, Shigehiko Ogoh, Shigeki Shibata
DOI: 10.1152/ajpregu.00181.2025
Cited by: 0
References: 32

Abstract

This study examined cerebral blood flow (CBF) responses to reduced cardiac output (CO) during severe central hypovolemia. The CBF/CO ratio increased but plateaued at 75% lower body negative pressure (LBNP). Decreases in internal carotid and vertebral artery blood flow were smaller than the CO reduction. CBF was maintained at high LBNP levels, likely via peripheral vasoconstriction. However, this compensatory mechanism failed at 75% LBNP, immediately before presyncope, indicating a breakdown in cerebral circulatory regulation.

Fields of Study & Subjects

Cardiovascular Syncope and Autonomic Disorders Heart Rate Variability and Autonomic Control Cardiovascular and exercise physiology

Publication details

Journal / source
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
Volume
330
Issue
4
Pages
R301–R309
Publication date
30 January 2026
Language
EN