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Alveolar–arterial gradient - Wikipedia

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The Alveolar–arterial gradient (A-aO 2,[1] or A–a gradient), is a measure of the difference between the alveolar concentration (A) of oxygen and the arterial (a) concentration of oxygen. It is a useful parameter for narrowing the differential diagnosis of hypoxemia.[2] The A–a gradient helps to assess the integrity of the alveolar capillary unit. For example, in high altitude, the arterial oxygen PaO 2 is low but only because the alveolar oxygen (PAO 2) is also low. However, in states of ventilation perfusion mismatch, such as pulmonary embolism or right-to-left shunt, oxygen is not effectively transferred from the alveoli to the blood which results in an elevated A-a gradient. In a perfect system, no A-a gradient would exist: oxygen would diffuse and equalize across the capillary membrane, and the pressures in the arterial system and alveoli would be effectively equal (resulting in an A-a gradient of zero).[2] However even though the partial pressure of oxygen is about equilibrated be

Alveolar–arterial gradient - Wikipedia Jump to content From Wikipedia, the free encyclopedia Respiratory parameter for differential diagnosis of hypoxemia Pathophysiology sample values BMP / ELECTROLYTES : Na + = 140 Cl − = 100 BUN = 20 / Glu = 150 \ K + = 4 CO 2 = 22 PCr = 1.0 ARTERIAL BLOOD GAS : HCO 3 − = 24 p a CO 2 = 40 p a O 2 = 95 pH = 7.40 ALVEOLAR GAS : p A CO 2 = 36 p A O 2 = 105 A-a g = 10 OTHER: Ca = 9.5 Mg 2+ = 2.0 PO 4 = 1 CK = 55 BE = −0.36 AG = 16 SERUM OSMOLARITY / RENAL : PMO = 300 PCO = 295 POG = 5 BUN:Cr = 20 URINALYSIS : UNa + = 80 UCl − = 100 UAG = 5 FENa = 0.95 UK + = 25

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