Plethysmography (UE, LE) Flashcards
What does Plethysmography do?
Checks changes in volume PVR
What are the capabilities of plethysmography?
-In combination with Doppler segmental pressures helps differentiate true claudication from non-vascular sources.
- Detect presence/absence of arterial disease while defining tis functional aspects
- Helps localize the level of obstruction
What is PPG mainly used for?
Evaluation of digits and penile vessels
What are the limitations of Plethysmography (UE, LE)?
- Cannot be specific to one vessel
- Cannot discriminate between major arteries and collateral branches
- Difficult to perform on obese patients
How should the patient be positioned?
- Most exams can be done with the limbs in a resting position (supine)
*Patient can be sitting for evaluation of upper limb digits
What are the physical principles of plethysmography?
Volume (air) Plethysmography
** measurement of volume changes
A measured amount of air is sequentially inflated into a cuf to pressure ranging from _____________.
10 - 65, depending on cuff size
A pressure transducer converts the pressure changes into _____.
Analog waveforms that display on strip-charts
Chart paper speed = __________
25 mm/sec
What the amount of cuff pressure in diastole and systole?
Diastole: fixed
Systole: increases as arteries expand
What does a photo-plethysmography consist of?
Transducer, Amplifier, Strip-chart recorder
What does photo-plethysmography detect?
Cutaneous blood flow
What does photocell consist of?
light emitting diode and photo-sensor
What transmits infrared light into subcutaneous tissue with backscattered light reflected back to the adjacent photo sensor?
Diode
What determines the amount of reflection with photo-plethysmography?
cutaneous blood flow
Blood attenuates light in what?
proportion to its content in tissue
Increased blood flow results in:
increased attenuation
Increased blood flow results in increased attenuation which decreases what?
reflection
How is increased blood flow displayed?
positive upstroke of the waveform
How is decreased reflection displayed?
positive upstroke of the waveform
What is the positioning for Volume Plethysmography?
Supine, with heels slightly elevated on cushion
What method is used for Volume Plethysmography?
3 to 4 cuff method
What does the machine do when activated?
Perform a self-calibration
What bilateral pressures are obtained?
Brachial
Begin with the upper part of extremity, moving distally. Record at lest _________ cycles.
3
Artifact is common due to what?
Improper cuff placement
Volume plethysmography and _______ are complementary.
Pressures
Both “volume” and “photo” plethysmography are evaluated using:
qualitative criteria
Normal interpretation of Photo-plethysmography PPG?
fairly rapid upslope, sharp systolic peak with reflected wave
Mildly abnormal interpretation of Photo-plethysmography PPG?
Sharp peak, absent reflected wave, downslope is bowed away from baseline
Moderately abnormal interpretation of Photo-plethysmography PPG?
Flattened systolic peak, upslope and downslope more delayed; reflective wave (notch) absent
Severely abnormal interpretation of Photo-plethysmography PPG?
Low amplitude, or may be absent
Abnormal waveforms always reflect:
hemodynamically significant disease proximal to level of tracing
Reduced amplitude with no changes in the contour is likely to reflect what?
insignificant disease, unless it is unilateral
Why might a fair waveform quality be accompanied by abnormal segmental pressures?
because collaterals can underestimate significant of obstruction based upon plethysmography
How is displacement measured with displaced plethysmography?
by the height of the water in the chimney
How is volume measured with displaced plethysmography?
spirometer
What does pule plethysmography refer to?
transient changes in (limb) volume related to the “pulse by pules” activity of the left ventricle; the body part expands when arterial inflow exceeds venous outflow
