This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 3, Subject name: Physiology
Least (A-V )O2 difference is seen in 
Select and explain. 
A. Hypoxic hypoxia, B. Anemic hypoxia, C. Stagnant hypoxia, D. Histotoxic hypoxia
D: Histotoxic hypoxia
Answer: D: Histotoxic hypoxia 
Explanation: Histotoxic hypoxia Cause Decreased ability of cell to use O2 Examples Cyanide poisoning PaO2 Normal Hb content Normal Aerial O2 content or %O2 saturation Normal A-V PO2 difference Decreased Peripheral chemoreceptor stimulation Present (toxin prevents chemoreceptor to use oxygen) Cyanosis Present