Evaluating microcirculation by pulsatile laser Doppler signal

Area of Science:

• Physiology
• Biomedical Engineering
• Cardiovascular Research

Background:

• Laser Doppler flowmetry (LDF) is widely used for microcirculation monitoring but lacks absolute measurement capabilities.
• Current LDF analysis often relies on relative changes in flux or frequency domain analysis.
• There is a need for novel methods to better discriminate microcirculatory states.

Purpose of the Study:

• To investigate the relationship between pressure and flux using heartbeat as a trigger to differentiate microcirculatory conditions.
• To propose and validate new pulsatile indices for microcirculation assessment.
• To determine if these new indices can distinguish between hypertensive and normotensive models.

Main Methods:

• Developed a synchronized-averaging method using heartbeat as a trigger to analyze normalized pressure and flux signals.
• Proposed three pulsatile indices: peak delay time (PDT), pressure rise time, and flux rise time (FRT).
• Measured abdominal aortic blood pressure and renal cortex flux (RCF) in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY).

Main Results:

• The mean renal cortex flux (RCF) did not significantly differ between SHR and WKY rats.
• Peak delay time (PDT) was significantly longer in SHR (87.14 ms) compared to WKY (76.92 ms).
• Flux rise time (FRT) was also significantly longer in SHR (66.56 ms) than in WKY (58.02 ms).

Conclusions:

• Pulsatile indices, specifically PDT and FRT, derived from synchronized pressure and flux signals, can effectively discriminate microcirculatory conditions.
• These novel indices provide an additional dimension for analyzing LDF signals, surpassing limitations of traditional methods.
• The findings suggest a potential for improved diagnosis and monitoring of microcirculatory dysfunction.