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
what is the technique for venous PPG?
sensor applied to lower leg approx 5-10cms above medial malleolus (must not be over a varicosity)
strip chart recorder
patients performs exaggerated dorsiflexions to empty calf veins
manual compressions of calf can be performed. must be done bilaterally to ensure consistency
tracing records VRT
if <20seconds apply tourniquet applied to elminate influence of superficial system
what is strip chart recorder?
running at slow speed (usually 5mm/s)
stylus records on heat sensitive paper
what is normal refill time?
> 20 seconds without tourniquet
what is VRT time with superficial system incompetence
VRT of <20 second without tourniquet but normalizes >20 seconds with an tourniquet
what is VRT time with deep system incompetence?
VRT of <20 seconds with and without tourniquet application
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Chapter 148
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Chapter 295
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Chapter 392
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Chapter 443
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Chapter 561
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Chapter 617
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Chapter 725
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Chapter 827
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Chapter 923
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Chapter 1011
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Chapter 1130
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Chapter 1246
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Chapter 1372
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Chapter 1453
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Chapter 1540
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Chapter 1631
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Chapter 1759
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Chapter 188
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Chapter 1946
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Chapter 2041
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Chapter 2120
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Chapter 2256
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Chapter 2324
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Chapter 2446
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Chapter 2520
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Chapter 2611
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Chapter 2710
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Chapter 2865
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Chapter 2929
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Chapter 3030
