A cascade model of dynamic cerebral autoregulation.

Area of Science:

• Physiology
• Neuroscience
• Biomedical Engineering

Background:

• Cerebral blood flow regulation involves macro- and microvascular adjustments.
• Dynamic cerebral autoregulation (dCA) models upstream pressure-flow coupling.
• Downstream microvascular responses are less understood but functionally linked.

Purpose of the Study:

• To test a two-component cascade model for integrated cerebrovascular regulation.
• To assess if dCA and microvascular function (MF) sequentially explain cortical oxygenation dynamics.
• To model the interaction between macro- and microvascular regulation of brain oxygenation.

Main Methods:

• Analysis of data from 41 healthy adults (20-45 years).
• Recording of beat-to-beat mean arterial pressure (MAP), middle cerebral artery flow velocity (CBFV), and cortical oxyhaemoglobin (O2Hb).
• Utilizing transfer function analysis during spontaneous and forced oscillations (sit-stand manoeuvres) to quantify frequency-domain coupling.

Main Results:

• The cascade model's indices strongly correlated with total pathway measures (gain, phase, coherence).
• Linear coupling between MAP and O2Hb dynamics improved under forced oscillations.
• The model successfully represented serial interactions between macro- and microvascular regulation.

Conclusions:

• A two-component cascade model is applicable for integrated cerebrovascular regulation.
• Serial interactions between macro- and microvascular mechanisms shape pressure-oxygenation dynamics.
• The model offers a framework to quantify large- and small-vessel contributions to cerebral blood flow regulation.