Alveolar-arterial Partial Pressure Oxygen Gradient (A-a O2 gradient)

Alveolar-arterial gradient (A-a gradient) is a measurement of the difference between the alveolar concentration of oxygen and the arterial concentration of oxygen.It can be used in diagnosing the source of hypoxemia.For example, in conditions of high altitude or hypoventilation in which the lung parenchyma is normal, the A-a gradient should be within normal limits.In contrast, in persons with