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10 Cards in this Set
- Front
- Back
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What is the importance of the alveolar gas equation (AGE)?
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The alveolar gas equation for calculating PAO2 is essential to understanding any PaO2 value and in assessing if the lungs are properly transferring oxygen into the blood.
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What is the "undiluted" form of the AGE?
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PAO2 = 1-FIO2
FIO2(PB-PH20)-PACO2[FIO2+____] R |
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What is the abbreviated form of the AGE?
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PAO2 = FIO2(PB-47)-1.2(PaCO2)
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What is the respiratory quotient, "R"?
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The respiratory quotient is (CO2 excretion over O2 uptake in the lungs).
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What are the determinants of PaO2?
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Determinants of Pa02 include: PAO2, V/Q matching, diffusion capacity, and mixed venous saturation.
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What is the 'A-a gradient'?
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The difference between PAO2 and PaO2 is commonly referred to as the 'A-a gradient.'
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What is the normal 'A-a gradient'?
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Up to middle age, breathing ambient air, normal P(A-a)O2 ranges between 5 and 20 mm Hg. Breathing an FIO2 of 1.0 the normal P(A-a)O2 ranges up to about 110 mm Hg23.
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What is the significance of an elevated 'A-a gradient'?
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If P(A-a)O2 is increased above normal there is a defect of gas transfer within the lungs; this defect is almost always due to V-Q imbalance.
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What are the causes of a negative 'A-a gradient'?
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The patient was in fact breathing supplemental oxygen during or just prior to the sample drawing; an air bubble in the arterial sample syringe; a quality control or reporting error from the lab; a transcription error - someone wrote down the wrong number; etc.
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What is another abbreviated form of the alveolar gas equation?
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PAO2 = FiO2(PB-PH2O)–PaCO2 / R
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