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Dynamics of cerebral blood flow regulation explained using a lumped parameter model
Mette S Olufsen1, Ali Nadim, Lewis A Lipsitz
1Department of Mathematics, North Carolina State University, Raleigh, North Carolina 27695, USA. msolufse@unity.ncsu.edu
Summary
Sudden drops in blood pressure during posture changes trigger a biphasic cerebrovascular resistance response. This involves initial vasoconstriction followed by vasodilation, aiding cerebral blood flow regulation.
Area of Science:
- Physiology
- Cardiovascular Research
- Cerebrovascular Dynamics
Background:
- The dynamic cerebral blood flow response to hypotension during posture changes remains unclear.
- Understanding the cardiovascular system's adaptation to arterial pressure changes is crucial.
Purpose of the Study:
- To investigate the beat-to-beat changes in middle cerebral artery blood flow velocity during hypotension.
- To model the cerebrovascular resistance response to posture-induced arterial pressure changes.
Main Methods:
- Utilized a two-resistor, one-capacitor windkessel model.
- Measured beat-to-beat middle cerebral artery blood flow velocity (transcranial Doppler) and finger arterial pressure (Finapres).
- Analyzed dynamic variations in systemic and peripheral cerebrovascular resistances.
Main Results:
- The model demonstrated a biphasic cerebrovascular resistance response: an initial increase followed by a decline.
- This initial increase in resistance correlated with a widened cerebral blood flow pulse.
- The biphasic pattern suggests an initial vasoconstriction followed by autoregulatory vasodilation.
Conclusions:
- The study elucidates the dynamic cerebrovascular resistance changes during hypotension.
- A windkessel model effectively reproduces observed cerebral blood flow dynamics.
- Findings support a biphasic autoregulatory mechanism involving vasoconstriction and vasodilation.