Chapter 5: Doppler Segmental Pressures (LE) Flashcards
Doppler segmental pressure capabilities
asses presence/ severity of arterial disease
combine with doppler velocity or volume pulse waveform
segmental pressure results: stenosis vs occlusion
cannot differentiate between stenosis vs occlusion
segmental pressure results: ? area of obstruction
cannot precisely localize area of obstruction
segmental pressure results: CFA vs iliac disease
cannot distinguish between CFA or iliac disease
segmental pressure results: calcified vessels
give falsely elevated doppler pressures
ex: diabetics, end stage renal disease
segmental pressure results: uncompensated CHF
gives decreased ankle and brachial indices
segmental pressure results: cuffs are too small/too tight
elevated pressures
patient positioning for segmental perssures
pt should rest 20 minutes prior to exam
supine
legs same level as heart
if the cuff is too large for a limb segment
BP is falsely lower
if the cuff is too narrow for a limb segment
BP is falsely higher
technique
cuff placed straight on extremity, not on bony prominence
cuff bladder placed over artery
width of cuff should be about 20% greater than diameter of limb
the cuff bladder placement is important because
appropriate technique ensures the bladder inflation transmits pressure quickly into the tissue to compress the artery
The four cuff method (bilateral)
brachial high thigh above knee below knee ankle
the four cuff method size
12 x 40 cm
cuff bladders longer for thighs
three cuff method (bilateral)
brachial
one thigh cuff (19 x 40cm)
below knee
ankle
three cuff method size
thigh cuff 19 x 40cm but all else
12 x 40 cm
difference between 4 cuff and 3 cuff method
two thigh cuffs provide prx and dst pressure measurements but falsely elevate BPs
3 cuff is more accurate due to one cuff on thigh
optimizing doppler signal for segmental pressures
8-10 MHz probe
angle probe 45-60 degrees to skin
angle probe so blood flow moves antegrade (towards the probe)
due to vessel angulation, probe angle behind the knee may be closer to
90 degrees to skin
order of segmental pressures
Brachial (upper arm, brachial artery)
Ankle (PTA or DPA, peroneal only if necessary)
Calf (PTA or DPA whichever has highest pressure)
Above the knee (same as calf, can use pop artery if difficult to obtain)
High thigh
what is the reason you start at the ankle and move proximally
to eliminate possibility of underestimating the systolic pressure measurement
what is required of the BP cuff to make this accurate
complete cessation of blood flow is required
cuff inflated to 20-30mmHg beyond last audible Doppler arterial signal
OR
inflate cuff 20-30mmHg higher than the highest brachial pressure
if pressure measurements must be repeated:
the cuff should be fully deflated for about a minute prior to repeat inflation
systolic pressure is recorded as
the pressure at which the first audible doppler arterial signal returns
ABI (ankle/ brachail index) is calculated by
dividing the ankle pressure by the higher of the two brachial pressures
another term for ABI is
ankle/arm pressure index (API)
ABI > 1.0
Normal
ABI >.9 - 1.0
may be wnl
ABI .8-.9
mild arterial disease
ABI .5 - .8
claudication (moderate disease)
ABI < .5
rest pain (severe disease)
in compressible vessels:
falsely elevated and inaccurate pressures
At what point is an ABI considered incompressible/unreliable?
> 1.3 - 1.5
some authors feel that
ankle pressure <50mmHg is better at predicting symptoms at rest than an ABI of .5
Strandness work suggests
ABI of > or = to .5 represents single segment disease and < .5 represents multiple lesions
Segmental pressure drops of what between levels indicates significant obstruction
30 mmHg
A horizontal difference of what suggest obstructive disease
20-30 mmHg suggests diesaes at or above level in the leg with the lower pressure
four cuff technique high thigh pressure
usually > or = to 30 mmHg than highest brachial pressure
Four cuff technique and at knee and below knee pressures
should be at least the same as the highest brachial
Three cuff technique thigh pressure
similar to highest brachial pressure
Toe pressures for foot and toe ulcers that failed to heal
<30mmHg
when ankle pressures cannot be relied upon (diabetics) what is more reliable
toe pressures
benefits of exercise and segmental pressures
helps differentiate between true and pseudo-claudication
determine presences / absence of collaterals
contraindications of exercising for this exam
SOB severe hypertension cardiac problems stroke walking problems
technique for exercise during segmental pressures
pt walks on tredmill at <12% elevation
1.5 MPH for minutes or until symptoms increase to severity where pt must stop
what should you document during exercise
duration of walking
MPH
onset
location and progression of symptoms
post exercise dopplers obtained:
both ankles (abnormal first) then higher brachial
Normal post exercise ABI
increases
Abnormal post exercise ABI
decreases minimally or to a severe amount
with drop after exercise pressures should be obtained
every two minutes until pre exercise pressures are attained
Segmental pressure ABI interpretation includes
Duration of exercise
length of time to recover
pressure changes from pre to post exercise
single level disease recovery
takes 2 to 6 minutes for the ABIs to increase back to resting levels after exercise
Multi level disease recovery
takes 6-12 minutes for the ABIs to increase back to resting levels after exercise
If patient cannot walk on the treadmill what technique should be used
reactive hyperemia
reactive hyperemia is an
alternate method for stressing the peripheral circulation
reactive hyperemia technique
bilat thigh cuffs (19 x 40) inflated to 20-30mmHg above brachial BP
maintain pressure for 3-5 min
ABIs are obtained upon release
how does the reactive hyperemia technique work
produces ischemia and vasodilation distal to the occluding cuffs
normal limb ABI in reactive hyperemia
may show drop of 17-34%
reactive hyperemia single level disease
less than or equal to 50% drop in ankle pressure
reactive hyperemia multi level disease
> 50% ankle pressure drop
why is treadmill testing preferred?
produces physiologic stress that reprodruces patients ischemic symptoms
