The P50 for normal adult hemoglobin is approximately?

The P50 for normal adult hemoglobin is approximately?

• A. 15 mm Hg
• B. 25 mm Hg
• C. 35 mm Hg
• D. 45 mm Hg

Answer: (B)

P50 is the partial pressure of oxygen at which hemoglobin is 50% saturated, reflecting the oxygen affinity of Hb. For normal adult hemoglobin under typical physiological conditions (body temperature, normal pH), the dissociation curve crosses 50% saturation around 25–27 mmHg, so 25 mmHg is the closest approximate value. Values much lower would indicate unusually high affinity (left shift), while values much higher would indicate unusually low affinity (right shift).

P50 is the partial pressure of oxygen at which hemoglobin is 50% saturated, reflecting the oxygen affinity of Hb. For normal adult hemoglobin under typical physiological conditions (body temperature, normal pH), the dissociation curve crosses 50% saturation around 25–27 mmHg, so 25 mmHg is the closest approximate value. Values much lower would indicate unusually high affinity (left shift), while values much higher would indicate unusually low affinity (right shift).