Chapter 25 Flashcards
what are capabilities of PPG of venous studies?
to document venous insufficiency/ quantitate venous reflux in patinets with chronic swelling, venous ulcers and/or varicose veins
what are limitations of Venous PPG?
contraindicated in acute deep vein thrombosis
improper placement of PPG senor results in inaccurate info e.g over a varicose vein
thickening of skin may prevent adequate penetration of infrared light
intact skin required for senor placement
what is patient positioning for PPG for venous?
seated with legs dangling ie. non weight bearing
what does PPG measure?
volume changes
not rue plethys but determines blood in content of skin (microciculation, which reflects intravenous volume
what do photocells consists of?
light emitting diode and photo sensor
what does the diode transmits
infrared light into sub tissues, which is reflected back to photosensor light is not absorbed
what does the cutaneous blood flow determines?
the reflection
what is the relationship between reflection and blood flow?
inverse
what is electrical coupling?
method to increase gain and display signal
only two types available: DC and AC
allows one type of current to pass and blocks the other type
what is DC coupling?
direct current electric voltage that is either positive or negative current flows in only one direction batteries are DC detects slower changes in blood content used for venous studies
what is AC coupling?
alternating current electric voltage that reverses polarity (+ -) 60 times a second current flow in both directions wall plugs deliver 120 volts of AC detects fast changes in blood content used for arterial studies
T/F PPG cannot be calibrated volumetrically like with APG
true
T/F important to maintain the same size or gain setting throughout study
true
T/F little difference in tracing should mean a significant difference in blood volume
false
significant difference
how is the display on a venous PPG?
tiny arterial pulsations usually evident superimposed on tracing of venous flow
