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Updated: Jul 31, 2026
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Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Published on: March 21, 2013
Cerebrovascular responses during lower body negative pressure-induced presyncope
K Kuriyama1, T Ueno, R E Ballard
1Department of Health Administration, School of Health Sciences and Nursing, Faculty of Medicine, The University of Tokyo, Japan.
Aviation, Space, and Environmental Medicine
|October 29, 2000
Summary
Cerebral blood flow (CBF) is maintained during lower body negative pressure (LBNP)-induced presyncope, despite falling blood pressure. This suggests cerebrovascular hemodynamics remain stable before fainting.
Area of Science:
- Physiology
- Space Medicine
- Cardiovascular Research
Background:
- Orthostatic intolerance is common post-spaceflight, potentially linked to reduced cerebral blood flow (CBF).
- CBF may decrease early during orthostatic stress, impacting tolerance.
- Investigating cerebrovascular responses during presyncope is crucial for understanding these effects.
Purpose of the Study:
- To investigate cerebrovascular responses during presyncope induced by lower body negative pressure (LBNP).
- To determine the role of CBF, blood pressure (BP), and heart rate (HR) in presyncope.
Main Methods:
- Eight healthy males underwent stepwise LBNP until presyncope.
- Continuous ECG, arterial tonometry for BP, transcranial Doppler (TCD) for middle cerebral artery CBF velocity, and near-infrared spectroscopy (NIRS) for cerebral oxygenation were used.
- Data focused on the final 2 minutes before presyncope.
Main Results:
- Blood pressure (BP) decreased gradually and then rapidly before presyncope.
- Heart rate (HR) showed no significant change.
- Middle cerebral artery CBF velocity remained stable, while cerebral oxygenation decreased with BP.
- CBF appears maintained in the middle cerebral artery during presyncope.
Conclusions:
- Cerebrovascular hemodynamics are relatively well-maintained during the rapid arterial hypotension preceding syncope.
- This suggests the brain compensates to maintain flow despite significant drops in systemic blood pressure.
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