Non-invasive arterial exam Flashcards
what are the 6 basic non-invasive lab tests for diagnosing PVD in the lower extremity?
- segmental BP
- doppler ultrasound
- toe blood pressures
- ABI
- plethysmography
- transcutaneous oxygen pressure
describe the change in pressure from mid thigh to ankle as you do a segmental BP.
pressure will decrease normally from mid-thigh to ankle
what are some signs of obstruction when taking a segmental BP?
> 20-30mmHg difference btwn adjacent cuffs
30mmHg change along leg from thigh to ankle
20mmHg difference btwn opposite leg, at same level
what does the ABI tell you?
ankle systolic BP/ brachial systolic BP
what does the ABI measure?
measures arterial flow only to the ankle
what are the ABI values needed for successful healing after foot surgeries?
ABI >0.35 in arteriosclerosis
>0.45 in diabetics
what is the normal ABI range?
0.9 to 1.3
an ABI of 0.7 is classified as what?
intermittent claudication
an ABI of 0.5 is classified as what?
rest pain
an ABI of 0.3 is classified as what?
skin loss
why do diabetics have falsely elevated ABI values?
due to severe arterial calcification- so it takes more cuff pressures to constrict the arteries
what is the ABI for intermittent claudication?
0.7
what is the ABI for rest pain?
0.5
what is the ABI for skin loss/ulcers?
0.3
___ is a function of how fast blood cells are moving
Pitch
*the faster the cells move, the higher the pitch
___ is a function of how many blood cells the ultrasound waves hit
Loudness
*the more cells hit, the louder the sound
what relationship does aortic pressure and velocity of blood flow have with each other?
directly proportional
*peak aortic pressure corresponds to peak flow velocity of vessels
what does a normal doppler US waveform look like?
triphasic (3 sounds and 3 peaks)
what does a mild obstruction doppler US waveform look like?
biphasic
if there was loss of arterial rebound due to calcification of artery, what would the doppler US waveform look like?
mild obstruction- biphasic
what would a moderate obstruction doppler US waveform look like?
monophasic
what would a severe obstruction doppler US waveform look like?
no sound
what 3 things should you listen for with Doppler?
- # of sounds
- pitch
- loudness
Describe what you would expect to hear on Doppler if your probe was over the obstruction.
pitch is higher but loudness is lower
of RBC flowing thru is less, but those that are squeezing thru are flowing faster!
Describe what you would expect to hear on Doppler if your probe was on either side of the obstruction?
pitch is lower but loudness is higher
there is a greater # of RBC collecting there, but their velocity is lower
healing potential can be measured by what 2 ways?
- absolute pressures
2. toe-brachial index
what absolute pressure do you need to have good healing potential?
> 45mmHg
what toe-brachial index do you need to have high healing potential?
> 0.6
what toe-brachial index do you need to have moderate healing potential?
> 0.4
what toe-brachial index do you need to have low healing potential?
> 0.2
what toe-brachial index will not heal?
below 0.2
what is plethysmography?how can it be measured?
takes advtg of the fact that as the artery fills with blood, it expands and contracts as it empties
- Photoplethysmography (PPG): infared light and photocells
- pressure cuffs- pneumoplethysmography or pulse volume recording (PVR) or pressure cuff recording (PCR)
what is photoplethysmography (PPG)?
uses a light probe to detect how much blood has entered the artery
what does a normal waveform for photo plethysmography look like?
2 distinct peaks w/ a distinct dichrotic notch
*the greater the volume of blood, the more RBC, and the more color change and the more defined the peaks
what does a normal waveform for a PVR look like?
1 rounded peak
*no dichrotic notch like there is in the arm and on PPG
what is transcutaneous oxygen pressure (TcPO2)?
measures partial oxygen tension on skin surface
the more RBC to the skin, the more O2
how does TcO2 relate to arterial PO2?
TcPO2= arterial PO2
what range for TcO2 is best to indicate good healing potential?
10-50mmgHg
*>40 is best standard to use
