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D.E. Hokanson,
Inc. Appl. Note:85315
Protocol for PPG Venous Reflux Test :
Set-up
The subject should sit with the legs in a
non - weight bearing position. Place the
photo transducer on the inside of the
patient’s leg about 12cm. above the
malleolus (ankle bone) using clear, double
sided adhesive tape. Use another piece of
tape to secure the wire from the transducer
to the skin about 5 to 10 cm. from the
transducer head. This is so that the
transducer is not disturbed by motion.
Technique
Several techniques are used to cause the
calf muscle pump to empty the veins in the
calf. One is to have the patient dorsiflex
and plantarflex the foot sequentially five
times vigorously. Another is to squeeze the
subject’s calf five times in quick
succession. Following the emptying manoeuvre
the subject should relax. The photo
plethysmograph (PPG) is used in Venous or DC
mode with the baseline set slightly below
the top of the chart before starting the
test. As the emptying manoeuvre is performed
the output of the PPG will drop in a
stepwise fashion. Afterward, during recovery
stage, the tracing will return to the
baseline, more or less as blood refills the
calf veins.
Theory
The theory behind the test is that refilling
will occur relatively slowly due only to
arterial inflow through the muscle in the
normal case, but if the venous valves are
not competent refilling will occur quickly
as blood runs back down the leg through the
veins.
Normal Response
The time for refilling is measured from the
end of the emptying manoeuvre to the point
where the tracing either levels off or peaks
out. In normal subjects this refilling time
will be greater than 23 seconds. Abnormals
have refilling times of less than 20
seconds.
Further Tests
When the test shows an abnormal response,
further tests should be performed with an
SC10 tourniquet cuff above and below the
knee. Inflate the cuff to 50 mm Hg to
occlude the superficial veins and repeat the
test. If the test goes from abnormal to
normal with a cuff above the knee this
indicates a problem in the greater saphenous
vein. If the testis still abnormal with an
above-knee cuff, but becomes normal when the
cuff is placed below the knee, then the
problem is indicated to be in the lesser
saphenous vein. When subsequent tests do not
show a marked improvement from the original
test which was conducted with no cuff to
occlude the superficial veins, then there is
an indication of multiple problems.
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