Physiology · Respiratory Physiology (Mechanics, Gas Exchange, PFTs, Regulation)

A 28-year-old woman with severe iron deficiency anemia has hemoglobin 7 g/dL, SaO2 of 98 percent, and PaO2 of 100 mmHg. Her approximate arterial oxygen content (mL O2/dL) is:

  • A 5.2
  • B 9.5
  • C 14.2
  • D 19.8
Correct answer: B. 9.5

Explanation

Content equals 1.34 x hemoglobin x SaO2 plus 0.003 x PaO2 = 1.34 x 7 x 0.98 plus 0.3 = about 9.5 mL/dL. Dissolved oxygen contributes only 0.3 mL/dL even at a normal PaO2, which is why content tracks hemoglobin rather than PO2. Option C would fit moderate anemia near 10 to 11 g/dL, and option D approximates normal content at 15 g/dL hemoglobin.

Reference: West's Respiratory Physiology: The Essentials, 11th ed.

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