Segmental Plethysmography

Question 1

What is “plethysmography”?

Answer 1

It is an instrument that measures changes in volume.

Question 2

What are the two different names for segmental plethysmography?

Answer 2

• “pulse volume recording” or PVR

- “Volume pulse recording” or VPR

Question 3

Where and why is the segmental plethysmography used?

Answer 3

It is used in the LE to measure blood volume changes with each pulse in a part of the limb.

Question 4

When is there more blood?

Answer 4

There is more blood during systole.

Question 5

When is there less blood?

Answer 5

There is less blood during diastole.

Question 6

What does a segmental plethysmography create after analyzing those volume changes?

Answer 6

It creates a waveform.

Question 7

When doing a VPR,PVR, how should you inflate the cuffs?

Answer 7

You should inflate the cuffs bilaterally at the same time. to 60 mmHg and hold. For the toe, inflate to 40 mmHg.

Question 8

How many cycles should you obtain from a VPR, PVR?

Answer 8

Obtain a minimum of 3 cycles.

Question 9

When is there a measurable change in volume of the limb?

Answer 9

During the systolic pulse of blood flow under the cuff.

Question 10

What do the waveforms taken from a VPR, PVR reflect?

Answer 10

It reflects the volume of blood coming into the arteries in the limb under the cuff.

Question 11

What is a VPR, PVR interpretation based upon?

Answer 11

• 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.

Question 12

What are the the two very influential factors in technique that effect PVR amplitude?

Answer 12

1. Size of limb

2. Unequal snugness of cuff side to side.

Question 13

What does a normal waveform contour look like?

Answer 13

• Sharp narrow peak.
• Dicrotic notch on the downslope.
• OR downslope bowed toward the baseline.

Question 14

What are some of the typical normal amplitudes?

Answer 14

• Thigh: >15 mm
• Calf: >20 mm (the calf is normally higher than the thigh)
• Ankle: >15 mm

Question 15

What does a mildly abdnormal waveform look like?

Answer 15

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.

Question 16

What does a moderately abnormal waveform look like?

Answer 16

It has a blunt peak, absent dicrotic notch, and a down-slope that may be equal to the up-slope.

Question 17

What does a severely abnormal waveform look like?

Answer 17

It is flat or very low amplitude waveform with equal up-slope and down-slope.

Question 18

Describe an aortic-iliac obstruction (AI)?

Answer 18

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.

Question 19

Describe an femoro-popliteal obstruction (FP)?

Answer 19

Normal thigh wave. The calf amplitude is lower than thigh with abnormal shape. The ankle wave will continue same calf contour but lower amplitude.

Question 20

Describe an AI+SFA obstruction?

Answer 20

Low thigh, abnormal contour. Calf lower than thigh, abnormal contour.

Question 21

Describe a SFA and IP obstruction?

Answer 21

Thigh normal height and shape. The calf is lower than thigh and ankle has worsening of contour.

Question 22

In VPR,PVR where is disease located?

Answer 22

Proximal to the cuff.

Question 23

What are the advantages of a VPR, PVR?

Answer 23

• Ease of use
• Patient tolerance
• Indicator of global perfusion to the limb
• Not affected by calcium

Question 24

What are the disadvantages of a VPR, PVR?

Answer 24

Qualitative analysis.

Question 25

What are the limitations to a VPR, PVR?

Answer 25

• Cannot discern stenosis from occlusion.

- Low amplitudes in obese patients and vert large upper thighs.