CH 9/10 Plethysmography - upper and lower extremities/digital pressures

Plethysmography

in combination with doppler segmental pressures, this test helps to differentiate true arterial claudication from nonvascular sources

digits, penile vasculature

photoplethysmography is most often used to evaluate what 2 things

not specific to a single vessel

dificult to discriminate between major arteries and collateral

limitations of Plethysmography

Volume Plethysmography

Patient supine, heels slightly elevated
3-4 cuff method used
40-65mmHg of air is introduced into the cuffs.
Arterial flow move underneath the cuff.
Volume changes occur
Changes converted within the cuff
Transducer converts pressure changes into analog waveforms on strip chart recorder (paper speed = 25mm/sec

PVR (pulse volume recording)

VPR (volume pulse recording)

PCR (pulse contour recording)

other terms to describe volume plethysmographic waveforms

Photoplethysmography (PPG)

this test consists of a transducer, amplifier, and strip chart recorder

Photoplethysmography (PPG)

detects cutaneous blood flow and records pulsatations (instead of recording volume changes)

Photoplethysmography (PPG)

Consists of a transducer, amplifier, and strip chart recorder.
Detects cutaneous blood flow
Diode sends light
Light reflects off of blood

increased, decreases, positive

in Photoplethysmography (PPG), cutaneous blood flow determines the reflection

any increase in blood flow results in ____ attenuation which ___ the reflection and is displayed as a ___ excursion of the waveform

Sharp systolic peak with prominent dicrotic notch

What is considered a normal waveform for volume plethysmography?

sharp peak, absent dicrotic reflective wave; downslope is bowed away from the baseline

What is considered a mildly abnormal waveform for volume plethysmography?

flattened systolic peak, upslope and downslope is bowed away from the baseline

What is considered a moderately abnormal waveform for volume plethysmography?

absent or low amplitude pulse wave with equal upslope and downslope time

What is considered a severly abnormal waveform for volume plethysmography?

proximal

moderately or severely abnormal plethysmographic waveforms always reflect hemodynamically significant disease prx or dst to the level of the tracing

Displacement Plethysmography

Waterfilled in a watertight container
Hand is immersed
Change in volume displaces equal amount of water
Displacement measured by chimney
Volume change measured by spirometer

technique for obtaining digital pressures and plethysmography in the toes

This study is often done with a physiological lower extremity arterial test, if not bilateral brachial and ankle doppler pressures are obtained to rule out any proximal disease
Patient supine
Head elevated 10-20 degrees
The cuff should be at least 1.2 times that of the toe
Typically a 2.0- 2.5 cm cuff is used for the fingers and toes
The great toe cuff should be between 2.5 and 3.0 cm
Plethysmographic waveforms are recorded for the great toe bilaterally
Great toe pressures are obtained using "endpoint detectors"

technique used if using a PPG to obtain toe pressures

The digit cuff is placed at the base of the toe
The photocell is securely attached to the underside of the distal portion of the great toe
The pulse is recorded with slow recording speed (5 mm/sec
The examiner inflates the cuff to suprasystolic pressure (about 20-30 mmHg higher than the ankle pressure) at which point their should be no pulsations
The increase in toe volume (rise from A to B) is secondary to venous outflow obstruction.
Slowly deflate the cuff, watching for return of the first pulsation thats is followed by other pulsations, at which it is recorded as the toe pressure

technique for finding digital pressures and plethysmographic waveforms in the fingers using the cold stress method

This technique is used to document the presence of absence of intermittent digital ischemia in response to cold exposure
After the resting study is performed, the feet or hands (depending on which digits are being tested) are immersed in ice cold water for three minutes or to the patient's tolerance
The skin is towel dried and waveforms and pressures obtained at the following times: Immediately after cold stress, and 5 minutes after cold stress
If the resting study indicates that one side has more significant disease, the post cold stress information is obtained from that side first
Document patient's symptoms, skin color observations, and other pertinent findings

.8-.9

normal finger brachial index in upper extremity digits