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25 Cards in this Set
- Front
- Back
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Name some clinical signs of hypoxia
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cyanosis
tachypnea tachycardia/brady arrythmias "dark blood" these are all unreliable tho.. |
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What is the basic principle of pulse ox?
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the absorption of radiation (light) is proportional to the concentration of the substance
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Oxyhemaglobin looks red b/c of the _______ absorption of red light
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decreased
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Deoxyhemoglobin looks dark b/c of the _______ absorption of red light
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increased
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What is "passing radiation thru a sample and measuring how much radiation is absorbed?"
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spectrophotometric techniques
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This is a functional saturation defined as the HbO2 relative to the total of oxyhemoglobin and deoxyhemoglobin
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SPO2
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at 660 nm, the absorbance of oxyhemoglobin (Hb O2) is ____ than deoxyhemoglobin (Hb) by how much?
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less than
10 times |
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at 940 nm (infrared) the absorbance of deoyhemoglobin (Hb) is ____ than oxyhemoglobin (HbO2)by how much?
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less than
2 times |
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what is it called when the points of both Hg and HgO2 absorbances are identical?
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isobestic point
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pulse ox determines ratio b/w Hb and HbO2 -- what is O2 sat if ratio = 1?
660nm/940nm |
85%
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When is sat not very accurate?
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<70%
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When is their additional light absorption due to the influx of this kind of blood?
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arterial - this is what pulse ox is reading, change in light absorption during pulsatile blood flow
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how long is lag time in pulse ox reading?
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60 sec
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Limitations to pulse ox?
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1. lag time
2. early v/q mismatch not detected 3. sensitivity diminished with high FiO2 |
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How do you measure functional sat?
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HbO2/(HbO2 + Hb) x 100
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How do you measure fractional sat?
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HbO2/(HbO2 + Hb + COHb + MetHB) x 100
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what 2 Hb's have the same absorption at 660nm?
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COHb and O2Hb (lab must measure true value - co-oximetry)
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What has equal absorption at 660nm and 940nm and pulls SpO2 reading to 85%?
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MetHb
(benzocaine spray, prilocaine, sulfonamides) |
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What percent of a smoker's hemoglobin may be in COHb?
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15% (add 5% COHb for q ppd)
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What can lead to CO production that we deliver?
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alkali breakdown of flurocarbon anesthetics
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If your pt has high COHg level and sat reads 97% -- is real sat lower/higher?
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Lower, with 40% COHb sat reads 97%, real sat 60%
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Fetal O2Hb curve shifted to ____
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Left
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HbS O2Hb curve shifted to _____
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Right
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Methylene blue has high absorption at 660nm so...
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sat will appear low
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Name some things that effect SpO2
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anemia (less than 8)
Nail polish signal-to-noise ratio |
