Blood gas analyzers critical thinking.txt
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What does the sanz electrode measure, describe the components, and explain its prrinciple of operation.
Measures pH by measuring the H+ ion potential across pH sensitive glass. Has two chemical half-cells, reference and measuring electrode, connected by a KCL bridge
What does the severinghaus electrode measure, describe the components, and explain its priciple opertation
Measure PCO2. Modified sanz electrode, double electrode, inner reference and out measuring. Two membranes: nylon and silastic. Aqueous bicarbonate solution, hydrolysis occurs as CO2 diffuses across outer membrane, measures difference in H+ ion between outer and inner reference.
What does the Clark electrode measure, describe the components, and explain its principle operartion.
Measures PO2. Polarographic electrochemical principal. O2 diffuses through teflon or polypropylene membrane slowly, constant 0.6V applied, Oxidation reduction reaction consumes electrons, measures current needed to maintain constant voltage as electrons are consumed.
What does the co-oximeter measre, describe the components, and explain its principle of operation.
Measures hemoglobin and saturation of oxyhemoglobin, carboxyhemoglobin, reduced hemoglobin, metHb. Spectrophotometry; blood hemolyzed in cuvette measuring chamber. Light at many wavelengths pass through, measures how much absorbed vs. refelcted, read assaturation for various type of hemoglobin
What will a water bath temperature of less than 37oC have on the measured pH, PaCO2, and PaO2?
Increase in pH, decrease PaO2 and PaCO2
What will a water bath with temperature of more than 37oC have on pH, PaO2 and PaCO2?
Decrease in pH, increase in PaO2 and PaCO2
Why is it important to eject a small amount of blood from the syringe sample onto gauze before injecting the sample machine?
to prvent air bubbles or clots from entering the machine and creating data arrors or machine malfunction.
Under what circunstances and how often should a 2 point calibration be performed on a blood gas analyzer?
After maintance/repairs, quality control/or other reagent is changed, or 4 hours/50 samples.
Under what circumstance and how often should a 1 point calibration be performed on a blood gas analyzer?
Idealy before evey sample, or at least every 2 mins before another sample is ran
Given a PB of 750 mmHg, calc 10% CO2 and 12% calibration points.
(750mmHg - 47) X 0.10 = 70.3 mmHg and (750 mmHg - 47mmHg) X .12 = 84.4mmHg
List at least five common causes fopr error.
Air bubble in sample, clot in sample chamber, excess heparin in sample, controls not in range, and machine not calibrated before reading sample.
A PT is being treated for smoke inhalation and 3o burns. Silver sulfadiazine has been applied to large portions of the PT's body surface. How might the PT's conditions affect the analysis of blood for co-oximetry?
Silver sulfidiazine produced nitrates which can increase the blood level of metHb and render the results inaccurate if metHb level > 10%
Indentify 3 factors that would make the reading of a co-oximeter unreliable.
Dirty cuvette chamber, intravascular dyes, incompletely hemolyzed blood.
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