Chapter 9 - Plethysmography UE and LE

Question 1

Limitations of plethysmography

Answer 1

1) cannot be specific to single vessel
2) cannot discriminate between major arteries and collateral branches
3) obesity makes it hard to perform

Question 2

Steps for pneumo- (true) plethysmography

Answer 2

1) Inflate cuffs to 40-65 mmHg

2) Measure systolic and diastolic wave forms

Question 3

Photoplethysmography (PPG) principle

Answer 3

1) transducer, amplifier and strip chart recorder
2) detects cutaneous blood flow recording pulsation (not volume changes)
3) Increase flow, increase light attenuation, decrease reflection, displays as positive excursion on waveform
4) cannot quantify flow but can give qualitative information

Question 4

AC/DC mode for arterial or venous studies for photoplethysmography

Answer 4

Arterial study = AC mode

venous study = DC mode

Question 5

Volume plethysmography interpretation

Answer 5

Normal: sharp systolic peak, dicrotic wave
Mild abnormal: absent dicrotic wave
Moderate abnormal: flattened peak, upslope and downslope nearly equal
Severely abnormal: absent or low amplitude wave

Question 6

Third type of plethysmography

Answer 6

Water displacement plethysmography

no longer used