The half-life of carboxyhemoglobin in a patient breathing 100% O2 is approximately:

The half-life of carboxyhemoglobin in a patient breathing 100% O2 is approximately:

• A. 5 minutes
• B. 1 hour
• C. 2 hours
• D. 4 hours

Answer: (B)

Carboxyhemoglobin formation blocks oxygen transport, and its removal depends on how quickly CO dissociates from hemoglobin. Exposing the lungs to high oxygen tensions drives CO off Hb more rapidly, so its half-life shortens when a patient breathes 100% O2. The established value is about one hour for the half-life of carboxyhemoglobin on 100% oxygen, meaning COHb concentration falls by half roughly every hour. On room air the half-life is much longer (around 4–5 hours), and hyperbaric oxygen can shorten it further (roughly 20–30 minutes). So the best answer is that the half-life is about one hour.

Carboxyhemoglobin formation blocks oxygen transport, and its removal depends on how quickly CO dissociates from hemoglobin. Exposing the lungs to high oxygen tensions drives CO off Hb more rapidly, so its half-life shortens when a patient breathes 100% O2. The established value is about one hour for the half-life of carboxyhemoglobin on 100% oxygen, meaning COHb concentration falls by half roughly every hour. On room air the half-life is much longer (around 4–5 hours), and hyperbaric oxygen can shorten it further (roughly 20–30 minutes). So the best answer is that the half-life is about one hour.