Segmental Plethysmography Flashcards
What is “plethysmography”?
It is an instrument that measures changes in volume.
What are the two different names for segmental plethysmography?
- “pulse volume recording” or PVR
- “Volume pulse recording” or VPR
Where and why is the segmental plethysmography used?
It is used in the LE to measure blood volume changes with each pulse in a part of the limb.
When is there more blood?
There is more blood during systole.
When is there less blood?
There is less blood during diastole.
What does a segmental plethysmography create after analyzing those volume changes?
It creates a waveform.
When doing a VPR,PVR, how should you inflate the cuffs?
You should inflate the cuffs bilaterally at the same time. to 60 mmHg and hold. For the toe, inflate to 40 mmHg.
How many cycles should you obtain from a VPR, PVR?
Obtain a minimum of 3 cycles.
When is there a measurable change in volume of the limb?
During the systolic pulse of blood flow under the cuff.
What do the waveforms taken from a VPR, PVR reflect?
It reflects the volume of blood coming into the arteries in the limb under the cuff.
What is a VPR, PVR interpretation based upon?
- Waveform contour.
- Amplitude changes within the levels.
- Amplitudes depend on cardiac stroke volume, blood pressure, vasomotor tone, and blood.
- Amplitudes vary from patient to patient.
What are the the two very influential factors in technique that effect PVR amplitude?
- Size of limb
2. Unequal snugness of cuff side to side.
What does a normal waveform contour look like?
- Sharp narrow peak.
- Dicrotic notch on the downslope.
- OR downslope bowed toward the baseline.
What are some of the typical normal amplitudes?
- Thigh: >15 mm
- Calf: >20 mm (the calf is normally higher than the thigh)
- Ankle: >15 mm
What does a mildly abdnormal waveform look like?
They have a sharp systolic peak with the loss of the dicrotic notch. The down-slope is straight or starting to bow away from the baseline.
What does a moderately abnormal waveform look like?
It has a blunt peak, absent dicrotic notch, and a down-slope that may be equal to the up-slope.
What does a severely abnormal waveform look like?
It is flat or very low amplitude waveform with equal up-slope and down-slope.
Describe an aortic-iliac obstruction (AI)?
Low thigh wave with no dicrotic notch and straight or bowed out down-slope. Distal waves have same contour and calf will be higher than the thigh.
Describe an femoro-popliteal obstruction (FP)?
Normal thigh wave. The calf amplitude is lower than thigh with abnormal shape. The ankle wave will continue same calf contour but lower amplitude.
Describe an AI+SFA obstruction?
Low thigh, abnormal contour. Calf lower than thigh, abnormal contour.
Describe a SFA and IP obstruction?
Thigh normal height and shape. The calf is lower than thigh and ankle has worsening of contour.
In VPR,PVR where is disease located?
Proximal to the cuff.
What are the advantages of a VPR, PVR?
- Ease of use
- Patient tolerance
- Indicator of global perfusion to the limb
- Not affected by calcium
What are the disadvantages of a VPR, PVR?
Qualitative analysis.
What are the limitations to a VPR, PVR?
- Cannot discern stenosis from occlusion.
- Low amplitudes in obese patients and vert large upper thighs.
