Which of the following will have the highest magnitude of the increased Alveolar aeriolar gradient at rest?
Interstitial lung disease
Massive Pulmonary embolism
Acute severe asthma
FB leading to upper airway obstruction
Normal alveolar aeriolar gradient is 5-15 mm Hg. In interstitial lung disease, diffusion effect is present but PO2 can be normal and decreases in exercise. Hence in ILD A-a gradient is normal at rest and increases in exercise Massive pulmonary embolism, the increased dead space leads to very low PO2 and an increase of A-a gradient. Choice C and D are easily ruled out as both leads to hypoventilation leading to normal A-a gradient.
COPD and Asthma