Question 11: CO poisoning causes which type of hypoxia?
- A. Anemic hypoxia (Correct Answer)
- B. Hypoxic hypoxia
- C. Stagnant hypoxia
- D. Histotoxic hypoxia
Explanation: ***Anemic hypoxia***
- **Carbon monoxide (CO)** binds to **hemoglobin** with an affinity much higher than oxygen, forming **carboxyhemoglobin**.
- This effectively reduces the **oxygen-carrying capacity of the blood**, mimicking a severe anemia, despite normal arterial PO2.
*Hypoxic hypoxia*
- Occurs when there is **insufficient oxygen delivery to the blood** due to low arterial PO2, as seen in high altitudes or respiratory diseases.
- In CO poisoning, **arterial PO2 is typically normal**, distinguishing it from hypoxic hypoxia.
*Stagnant hypoxia*
- Results from **inadequate blood flow** to tissues, leading to reduced oxygen delivery, as observed in heart failure or shock.
- CO poisoning primarily affects oxygen transport by hemoglobin, not the **rate of blood flow**.
*Histotoxic hypoxia*
- Characterized by the **inability of tissues to utilize oxygen** effectively, even when oxygen delivery is adequate, as seen in cyanide poisoning inhibiting cytochrome oxidase.
- In CO poisoning, tissues can utilize oxygen; the problem is the **reduced availability of oxygen** from hemoglobin.