In sickle cell, O2 consumption

• A. Decreases
• B. Unchanged
• C. Increases
• D. Variable

Answer: (C)

The main idea is how oxygen delivery, extraction, and consumption behave in sickle cell disease. Anemia lowers the amount of oxygen carried in the blood (arterial O2 content), so delivering O2 to tissues is more challenging. To compensate, tissues increase their extraction of O2 from the blood, raising the difference between arterial and venous O2 (the arteriovenous O2 difference). This higher extraction, along with any rise in metabolic demand during crises or stress, pushes the overall oxygen consumption upward. So, despite reduced oxygen content, the body's response is to take more O2 from what arrives, leading to increased O2 consumption. Decreases or unchanged consumption would not fit the compensatory increase in extraction and metabolic demand, and saying it’s variable misses the consistent tendency toward higher consumption in this context.