Photoplethysmography quantitative

Phlebological method for the determination of volume fluctuations of the cutaneous-subcutaneous venous plexus under the conditions of a standardized exercise program (e.g. muscle pump test).

Based on numerous study results, the following biophysical relationships can be established:

• There is a connection between the pressure changes in the deep vein system and the photopletysmographically measurable filling fluctuations in the superficial vascular networks
• A change in pressure in the venous system always causes an increase in selective dermal light reflection (increase in the PPG signal)
• Standardized movement programs allow for definite statements about the venous pumping performance of the functional hemodynamic unit over the time axis and amplitude.

A largely standardized muscle pump test has become established and generally accepted as a procedure. The patient performs 8 foot rocking exercises within 16 seconds while sitting down. With the heel supported on the ground, the patient performs 8 defined dorsal extensions of the foot.

The PPG sensors are attached about 10 cm above the inner ankle. The pumping dynamics drive blood from the superficial venous system into the deep venous system and from the deep venous system against gravity proximally, i.e. towards the heart. As unidirectional valve systems, the physiologically existing venous valves prevent the blood from falling back into the periphery. The outflow of blood from the superficial venous system leads to a reduction in the diameter of the vessels and thus to an increase in the light reflection signal. The height of the curve (V0) is given as the percentage change in reflection to the resting reflection and allows conclusions to be drawn about the real pumping capacity of the muscle pump. At rest, after the end of the muscle pump action, the leg veins fill up again due to the physiological, constant arterial inflow. The PPG curve slowly approaches its initial value again (T0= refilling time).

In venous diseases, a pathological valve function leads to a rapid regression of the blood column. The replenishment time (T0: given in seconds) is drastically reduced.

The following parameters were found:

Normal hemodynamics: T0==/< 25 s (seconds)

Grade I (mild haemodynamic disorder): T0= 20-25 s

Grade II (moderate hemodynamic disorder): T0= < 20 s

Grade III (severe haemodynamic disorder): T0= < 10 s

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