URR Segmental Pressures and Plethysmography Flashcards
how is the probe?
-8-10 MHz pencil probe
-zero crossing detector - counts each time the reflected signal crosses through the baseline over time
-does NOT display a range of frequency shifts, displays average shift as single line
waveforms?
normal are triphasic with rapid upslope, sharp peak, rapid downstroke, a small peak below baseline representing diastolic flow reversal, followed by small peak of flow above baseline
-change in waveform to biphasic or monophasic flow between two segments indicates disease between the 2 sites
what happens to waveforms during exercise?
normal = no change
abnormal= change in arterial phasicity, delayed uplope, delayed downslope, lower amplitude
limitations?
-bandages, casts, wounds
-room temp affects resistance
-cant precisly localize area of obstruction
-improper angels can degrade waveforms
-underestimates high velocities and overestimates low velocities
-cant detect flow velocities less than 6 cm/s
for LE segmental pressures patient should do what before?
should rest on back for 10-15 mins to produce accurate pressures
the cuff width should be how?
20% greater than diameter of the part
-if too wide, pressure underestimates
-if too small, pressure overestimates
Most common cuff method?
4 cuff method
-2 cuffs below knee and 2 above
-allows eval of prox and distal thigh pressures
-causes overestimation of thigh pressures due to using smaller cuffs for 2 thigh pressures
size of cuffs?
-brachial, ankle, and calf normally can use the same blood pressure cuff. usually 10-12cm
-12 cm of larger cuffs usually used for thighs or other areas in larger patients
-7 cm cuff used for wrist and 2.5 used for digits
what offers more accurate measurement of mid thigh?
3 cuff method by using larger cuff, but cannot differentiate distal femoral from pop disease
the below the knee or upper calf cuff should be placed where?
just distal to the tibial tubercle or pressure readings will be falsely elevatedq
the lower calf cuff should be placed where?
distal edge 2-3 cm above the medial malleolus
what arteries area examined in the calf by CW?
ATA and PTA
sometimes people use the branch of the ATA otherwise known as?
dorsalis pedis (DPA)
brachial blood pressures are prohibited on the ipsilateral arm of a what patient?
mastectomy
-if bilateral, neither brachial pressure should be taken
normal pressures for 4 cuff method?
-12 cm cuff for upper thigh, lower thigh, calf, 10 or 12 cm cuff for ankle or arm
-high thigh pressure > brachial pressure by 30-40 mmHg which indicates a thigh brachial index of >1.2
-distal thigh and calf pressures should be the same as brachial
-<30 mmHg difference between 2 adjacent levels in same leg
-< 20 mmHg difference between same level in both legs
normal pressures for 3 cuff method?
-18-20 cm for the thigh, 12 cm cuff for calf, 10 or 12 cm cuff for ankle or arm
-thigh pressure very similar to brachial
-most accurate method of thigh pressure assessment
-<30 mmHg difference between 2 adjacent levels in same leg
-< 20 mmHg difference between same level in both legs
if both thigh pressures are below the highest brachial what should be suspected
aortoiliac disease
rest pain is seen in patients with an ankle pressure of:
< 50 mmHg
falsely elevated ankle pressures means what?
medial calcification, cuff too loose, cuff too small, patient not supine
ABI over 1.3, ankle pressures that are > 200mmHG or 30% higher than the brachial pressure indicates
noncompressibility of the lower extrem vessel under the cuff, usually due to medial calcification
falsely reduced ankle pressures means what?
cuff too large, congestive heart failure, coarctation
reduction in cardiac output with CHF and reduced cardiac EF% will cause what
decrease in ABI bilat
coarctation of the aorta can cause what
decreased ankle pressures and ABIs bilat
Pressures usually obtained in the following order
-brachial
-ankle (use PTA and DPA, use vessel with highest pressure to calculate ABI and to obtain the remaining thigh/calf
-calf (PTA or DPA)
-thigh (PTA or DPA)
-high thigh (4 cuff method only, use to locate suspected disease in thigh)
ABI diagnostic criteria?
-normal = > 1,0
-asymptomatic/ minimal disease = .9-1.0
-claudication/ mild to moderate disease = .5-.9
-rest pain/severe disease = < ,5
-medial calcification causes abnormal increase in ankle pressure and ABI value = >1.30
Strandness criteria
-ABI > 0.5 = single vessel disease
-ABI < 0.5 = multiple vessel disease
ankle pressures < 80 mmHg associated with non-healing wounds
to calculate the ABI, always use the highest of the two?
brachial pressures
which two arteries do you always use one of the higher pressures to calculate ABI?
PTA and DPA
what would you use to calculate ABI in this instance?
RT arm 140 mm/Hg
LT arm 145 mm/Hg
RT PTA 70 mm/Hg
RT DPA 55 mm/Hg
LT PTA 145 mm/Hg
LT DPA 165 mm/Hg
RT 70/145 = .48
LT 165/145 = 1.13
digit pressures?
-use 2-2.5 cm cuff
-patient supine with mild elevation of the head or toes
-finger pressures should be obtained with the patient sitting upright with the hand placed on a positioning wedge or pillow for stability
-cuffs wrapped around digits and inflated 20-30 mmHg above the ankle pressures
-used in diabetic patients due to medial calcification of calf/leg arteries
-medial calcification can result in a normal or elevated ABI with monophasic flow in the calf arteries
-digital arteries are not typically affected by medial calcifications
-most accurate way to obtain pressures in diabetic patient
digit ratios?
-finger/brachial index = normal > .8
-toe/brachial index = normal -6-.8 ; .2-.5 claudication; ,.2 rest pain
-limitations include poor cuff placement, patient anxiety, room temp
contraindicaitons?
-suspected or known acute DVT - use waveform analysis only or use of a toe/brachial index
-recent surgery, trauma site or ulcers that should not be compressed by cuffs
-hx of lower limb stent replacement, or recent saphenous vein artrerial bypass grafting
-morbidly obese patients - high thigh pressure may be unobtainable or inaccurate
-patients with significant tremors or involuntary movements that may cause waveforms to be suboptimal or unreliable
limitations?
-cannot differentiate stenosis from occlusion
-cannot precisely localize an area of obstruction
-cannot discriminate between iliac and CFA disease
-cannot discriminate between pop and prox calf disease
-limited value in the presence of multi level disease or collaterals
-decreased cardiac output can cause reduced ABI values
-increased ankle pressures with medial calcification
-improper angles of insonation can reduce signal used to asssess pressure
-improper cuff size
why treadmill exercise testing
-performed to compare the results to the resting segmental pressure exam
-helps to differentiate true claudication from psuedoclaudication
-can assess the presence or absence of collateral formation
-exercise induces peripheral vasodilation and can be used to eval autoregulation
-antegrade diastolic flow increases with exercise
how to do treadmill exercise?
-patient should walk up to 5 mins or until intolerable symptoms occur
-immediatly obtain ankle pressures post exercise then every 2 mins until pre exercise baseline pressures have returned
what should happen after exercise?
-diminished pulsatility in the flow pattern is normal
-ankle and arm pressures will normally rise mildly with a normal response to exercise
-the ABI will remain relatively constatn in the normal patient because the arm pressures will increase together, a small increase in the ABI is also normal
-pressures decrease to normal levels within 5 mins of cessation of exercise
what happens after exercise with obstruction?
-single level: pressures and ABI drop and return to normal 2-6 mins after
-multilevel: pressures and ABI drop and return to normal 6-12 mins after
increased or no change in ABI after exercise indicates the leg is
psuedoclaudication; true claudication will be associated with a drop in ankle pressure
contraindications for exercise?
-known disease in one extrem that is untreated
-inability to walk without assistance
-hx of stroke with residual paralysis
-shortness of breath
-systemic HTN with systolic pressure > 200 mmHg
-noncompressible calf arteries
-unstable angina and/or use of nitroglycerin for chest pain
-hx of cardiac procedure or myocardial infarction
reactive hyperemia
-the transient increase in blood flow that occurs after a brief period of ischemia
-commonly occurs following the removal of a tourniquet, unclamping an artery during surgery, or after vessel recanalization caused by a device or medication
post occlusive reactive hyperemia testing
uses occlusive cuffs to simulate exercise in patients unable to perform treadmill testing
-needed for patients with poor cardiac output, hx of angina, difficulty walking or breathing, short walking tolerance, pulmonary problems, amputation of the leg
-patients with untreated disease in one leg will undergo reactive hyperemia when evaling symptoms in the opposite leg; the untreated disease can limit treadmill tolerance when trying to demonstrate new disease in the opposite leg
reactive hyperemic testing abnorm results?
-ankle pressure drops 35-50% = single level disease
-ankle pressure drops > 50% = multiple level disease
-< 100% increase in flow velocity when cuff released
cuff method for reactive hyperemic testing?
-elevate legs to 45 degrees to drain venous blood
-inflate wide thigh cuff to 30-50 mmHg above brachial pressure
-lower legs back to table and maintain pressure in thigh cuff for up to 5 min
-pressures obtained upon release of cuff
-obtain pressures for every 30 sec until pressures return to baseline pressures
what is the purpose of PVR?
pulse volume recording
-measures volume changes from ALL vessels under the cuff
-alternating current used for arterial evaluation
-direct current used for venous evaluation
-differentiates true claudication/vascular disease from nonvascular causes for symptoms
-determines level of obstruction but cannot depict the specific vessel involved
-can be used to assess suspected popliteal entrapment syndrome
other names for PVR?
-arterial plethysmography
-volume plethysmography
limitations for PVR?
-obesity
-cold room/warm room
-smoking prior to exam
-patient motion
-cuffs too tight or too loose
-parkinsons disease/tremors
-cannot precisely locate the vessel with the obstruction
-false results when collateral flow present
how to do PVR?
-toe evaluation should be performed
-finger pressures should be obtained with the patient upright
-place 2-4 pressure cuff on extrems
-12 cm cuffs placed on thighs, calves, and ankles; 7 cm cuff wrist
-12 cm cuff on upper arm, 10 cm cuff upper forearm, 7 cm cuff wrist
-PVR tracings performed thigh to ankle both legs at the same time (segmental pressures performed one leg at a time)
-cuffs inflated to 50-60 mmHg and held constant
-start with the cuff on the prox extrem and move distally to obatain tracings
normal PVR?
-demonstrates rapid upstroke, sharp systolic peak, prolonged downstroke and prominent reflection (dicrotic notch)
-NO FLOW REVERSAL
-calf tracings normally demonstrate a waveform with good amplitude and dicrotic notch
-
abnormal PVR?
-increased peripheral resistance will lead to increased amplitude and dicrotic notch
-hemodynamic changes will be displayed as a loss of the notch adn decreased amplitude of the wave
-mild disease causes loss of reflection, but the waveform maintains the sharp peak
-severe disease causes a damped wave with low amplitude, slow upstroke and minimal difference between systolic and diastolic volumes
PVR is commonly used for what two appendages?
digital and penile flow
what is photoplethysmography?
-infrared light released into tissues
-red blood cells reflect the light to photocells where it is measured
-detects cutaneous blood flow/volume changes
-hemoglobin absorbs the light, the lower the blood volume in the leg, the more reflection of the light demonstrated
-used in diabetic patients due to medial calcification of calf/leg arteries
-waveforms are similar to PVR tracings, both are volume assessments by different methods; air vs light
-no affected by calcified vessels
how to do photoplethysmography?
-sensor attached to plantar surface of toes
-several waveforms recorded with the size control set to 10 for consistency of eval of different vessels and on different exams
normal photoplethysmography tracing?
demonstrates rapid upstroke, sharp systolic peak and prominent reflection (dicrotic notch)
abnormal photoplethysmography?
-mild disease causes loss of the reflection but maintains the sharp peak
-severe disease causes a damped wave with slow upslope, low amplitude peak and slow downslope with minimal difference between systolic and diastolic volumes
limitations of photoplethysmography??
-strap around digit is too tight
-poor sensor contact
-patient movement
-cold room, warm room
-patient anxiety
-smoking before exam
