This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': 'Alveolar-arterial 02 tension gradient increases in A/E- \nSelect and explain. \nA. Hypoventilation, B. Right to left shunt, C. Diffusion defect, D. Ventilation perfusion abnormality', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e. Hypoventilation Alveolar arterial 02 gradient is decreased in hypoventilation. Alveolar arterial 02 gradient (or A - a gradient) is a useful measure of oxygenation of blood. Its normal value in a healthy adult is less than 15 mm Hg. It increases in the following condition Diffusion defect across the respiratory membrane. Right to left shunting of blood. Ventilation perfusion abnormality Decreases in the surface area of the membrane e.g. Emphysema. In hypoventilation (A-a) gradient decreases.", 'role': 'assistant'}]