Flashcards in Plethysmography UE and LE Deck (27)
Limitations of plethysmography?
a) cannot be specific to one vessel. Tracing reflects all arterial flow beneath the cuff.
b) cannot discriminate between major arteries and collateral branches
c) difficult to preform on obese patients
What does PVR stand for?
pulse volume recording
What is the process of volume plethysmography?
a) measured amount of air is sequentially inflated into a cuff to pressure ranging from 10 to 65 mmHg depending on cuff size
b) as arterial flow moves under the cuff, momentary volume changes in the limb segment occur.
c) these changes beneath cuff are converted to pulsatile pressure changes within the air filled cuff bladder
d) A pressure transducer converts the pressure changes into analog waveforms for display on strip-chart recorder
What occurs during diastole and systole?
diastole: fixed amount of air pressure in cuff
systole: air pressure in cuff increases as arteries expand
What does PPG stand for?
What does PPG detect?
cutaneous blood flow rather than truly measuring volume change.
What do the PPG photocells consist of?
light emitting diode and photo-sensor
How does the PPG work?
the diode transmits infrared light into subcutaneous tissue with backscattered light reflected back to the adjacent photo-sensor
Blood attenuates light in proportion to its content in tissue. _____ blood flow results in _______ reflection.
Normal and mildly abnormal PPG waveforms?
normal: fairly rapid upslope, sharp systolic peak with reflective wave
mildly abnormal: sharp peak, absent reflected wave, downslope is bowed away from baseline
moderately abnormal and severely abnormal PPG waveforms?
moderately: flattened systolic peak, upslope and downslope more delayed, reflected wave (notch) absent
severely: low amplitude or may be absent
Abnormal waveforms always reflect hemodynamically significant disease proximal or distal to level of tracing?
A fair waveform quality may accompany abnormal segmental pressures because _____ can underestimate significance of obstruction based upon plethysmography.
How is displacement plethysmography demonstrated?
Any change in volume of the enclosed part will displace an equal amount of water. Displacement is measured by the height of water in the chimney.
Pulse plethysmongraphy refers to transient changes in limb volume related to the pulse by pulse activity of the left ventricle. The body part expands when _____ inflow exceeds ________ outflow.
What is is the pulse recorded speed for toes?
The increase in toe volume is secondary to obstruction of venous out flow. Plethysmography measures what volume changes?
All volume changes
Technique for fingers with cold stress?
a) after resting study is preformed, hands are immersed in ice cold water for 3 minutes if possible
b) following cold stress, waveforms and pressures are obtained immediately and five minutes later
c) document patient symptoms, skin color observations and other pertinent findings on the report form
Waveform amplitudes are usually greater in toes or fingers?
What is the difference between normal and abnormal waveforms in digits?
Normal has a prolonged down stroke with a notch halfway down. Abnormal has a sharp anacrotic notch present higher on the downslope
What describes the peaked pulse characteristically seen in the digit pulse contours of patients with raynauds phenomena?
sumner and strandness
Following cold immersion, abnormal cold sensitivity is likely if the amplitude fails to return to baseline levels within how many minutes?
digit pressure measurements
normal toe P's vary 60-80% of brachial P's
Capabilities of transcutaneous oximetry TcPO2?
Wound healing and amputation level determination.
Reflects tissue oxygen tension and relies on a balance between oxygen supply and consumption.
What are the principles of transcutaneous oximetry TcPo2?
Electrode heats skin to 45 degrees C
Blood flow increase, lipid layer in fatty tissue melts, more oxygen escapes through skin and measured by sensor in electrode.
After manual calibration of transcutaneous oximetry, it take approximately how long to obtain pO2 reading?