D-PPG Muscle Pump Test (Venous Reflux)

Description

The Venous Reflux Test (with D-PPG – Digital Photoplethysmography) is a non-invasive screening method for the functional assessment of the hemodynamics of the leg vein system and to determine the competence of the venous valves. Insufficient competence of the superficial venous valves, for example, may require the patient to wear compression stockings for compensation.

By attaching optical sensors 10cm proximal to the medial malleolus, the amount of venous blood flow in the area can be recorded. The patient is asked to perform dorsal reflections to reduce the venous pressure, which the system detects as an increase in volume V₀. After the movements stop, the refill time (T₀) can be observed.

Due to its rapid and non-invasive application, the D-PPG Muscle Pump Test for venous reflux is a common and widely applied measurement procedure.

Air-VFT (Venous-Function-Test)

A similar test can be conducted with the application of pneumatic measurement cuffs only. It is sometimes considered to be more accurate, as the cuff records all of the limb’s circumference thus covering a larger area of measurement. Except for the cuffs, the test is conducted and interpreted identically to the D-PPG muscle pump measurement regarding the venous filling time T₀.

Measurement Principle

The measurement is made on the seated patient. The sensors are ideally placed 10cm proximal to the medial malleolus. The angle between thigh and lower leg should be about 110°, so the leg should be slightly stretched forward.

At the beginning of this measurement, the blood is pumped out of the veins of the lower leg with the help of dorsal reflections and the associated activation of the calf muscles. This can be seen from the visible rhythmic waves in the measurement.

In the process, venous blood is pumped out of the venous system. This is followed by a resting period until the end of the measurement, during which the venous refilling is recorded.

If the venous reflux test indicates the suspicion of venous insufficiency, a tourniquet cuff can be applied above or below the knee to compress the superficial veins, excluding their influence on the measurement. This allows to discriminate between deep and superficial valve incompetency.

PPG sensors with applied tourniquet cuffs

The possible curve patterns and their respective interpretation generally are as described below:

Main Parameter

Parameter	Unit	Description
Venous Pump Volume V₀	%	The pump volume indicates how well the patient pumps venous blood, through leg movement, in the direction of the heart. The pump volume should be greater than 3%, but this is highly diverging from patient to patient. Additionally, this value may also vary depending on sensor position and skin structure.
Venous Fill Time T₀	Sec.	The fill time is an indicator for the tightness of the venous valves. Defective venous valves lead to a quick backflow of the blood to the leg, which shortens the fill time. Intact venous valves lead to a slow and continuous replenishment of the veins through the arteries. The fill time value is then 25 seconds or higher.
Venous Half-Life T₅₀	Sec.	The venous half-life indicates the time needed to refill half of the venous pump volume. In case the veins refill quicker at the beginning, this indicator decreases.
Skin Temperature	°C	Within the measurement screen, the skin temperature is displayed below the left and right sensor as well as on the results table as an additional informative parameter.

Medical Applications

Suspicion of Venous Insufficiency
Suspicion of Venous Valve Incompetence
Suspicion of Venous Occlusion

Test Examples

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	Normal Sufficient pump volume > 3% Flat, round bodied wave form Long refill time > 25s
	Slightly insufficient veins Sufficient pump volume > 3% Fast falling, sagging wave form Refill time < 25s
	Severe vein insufficiency Pump volume < 3% Immediately falling wave form Refill time < 10s
	Post thrombotic syndrome Pump volume close to 0% No significant rise of the curve Refill time close to 0s
	Improvable insufficiency Improved refill time when measuring with Tourniquet Superficial insufficiency Good therapy prognosis
	Non-improvable insufficiency No improvement in refill time when measuring with Tourniquet Deep insufficiency Bad therapy prognosis
	Worsening insufficiency Worsening refill time when measuring with Tourniquet Deep insufficiency compensated by superficial veins Might get even worse with therapy of superficial veins
Venous Refill Time > 25s …….. Normal venous system 20s – 25s …….. Venous insufficiency Stage 1 10s – 19s …….. Venous insufficiency Stage 2 0s – 9s …….. Venous insufficiency Stage 3	Venous Pump Volume More than 3% …. normal Less than 3% …. reduced