Dynamic Windkessel autoregulation for optical hemodynamic imaging: quantifying microcirculation, oxygen diffusion,...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Physiology

Background:

• Hemodynamic-based neuroimaging is crucial for functional brain studies.
• Coherent hemodynamics spectroscopy (CHS) quantifies cerebral microcirculation and vascular autoregulation using light-based hemodynamic oscillations.
• Existing methods require further refinement for comprehensive autoregulation assessment.

Purpose of the Study:

• Introduce a dynamic Windkessel autoregulation model for noninvasive quantification of microcirculation, oxygen diffusion, and vascular autoregulation.
• Incorporate arteriole vasomotor responses to blood pressure variations.
• Quantify autoregulatory capacity using a dimensionless autoregulation gain index (n).

Main Methods:

• Developed the dynamic Windkessel autoregulation model analyzing low-frequency oscillations (LFOs).
• Integrated the model into WK-PIPE CHS for optical hemodynamic imaging.
• Validated the model on five healthy human subjects using visible structured light under paced breathing.

Main Results:

• The model accurately reproduced microcirculation and arterial blood flow/volume LFO responses.
• Successfully quantified local tissue oxygen diffusion rate (α=0.179 ± 0.049 s⁻¹).
• Quantified vascular autoregulation (n = 4.68 ± 0.59), with lower 'n' indicating impaired autoregulation.

Conclusions:

• Dynamic Windkessel autoregulation provides a mechanistic framework for assessing vascular autoregulation.
• Offers potential for monitoring cerebrovascular and cardiovascular health.
• Enables early detection of cerebrovascular and cardiovascular dysfunction via optical hemodynamic imaging.