Self-mixing in a diode laser as a method for cardiovascular diagnostics

Area of Science:

• Biomedical Optics
• Laser Physics
• Cardiovascular Physiology

Background:

• Accurate measurement of cardiovascular parameters like pulse wave velocity is crucial for diagnosing vascular diseases.
• Conventional interferometric methods for blood flow and pulse wave analysis are often complex, bulky, and require precise alignment.

Purpose of the Study:

• To develop a simple, compact, and robust optical method for measuring pulse wave profile, pulse wave delay time, and blood flow.
• To utilize the self-mixing effect in diode lasers for non-invasive physiological measurements.

Main Methods:

• Recording Doppler frequency shifts from moving blood vessel walls or particles using a self-mixing diode laser.
• Simultaneous signal extraction via a photodiode and laser pump current resistor.
• Measurement of pulse wave delay time relative to electrocardiogram (ECG) signals.
• Flow velocity measurement of erythrocyte-sized particles in liquid suspension.

Main Results:

• Successful detection of arterial pulsations, yielding pulse wave profiles and delay times.
• Measurement of pulse wave delay times in different body regions relative to ECG.
• Accurate measurement of liquid suspension flow velocity.
• Demonstration of the device's simplicity, compactness, robustness, and self-aligning capabilities.

Conclusions:

• The developed self-mixing diode laser method offers a simple and effective approach for cardiovascular monitoring.
• This technique provides valuable information on pulse wave characteristics and blood flow.
• The system's advantages over conventional interferometric methods make it suitable for practical applications.