Which of the following will shift the oxyhemoglobin dissociation curve to the Right EXCEPT?

Which of the following will shift the oxyhemoglobin dissociation curve to the Right EXCEPT?

• A. Volatile anesthetics
• B. Decreased PaO2
• C. Decreased pH
• D. Increased temperature

Answer: (B)

The key idea is how certain factors alter hemoglobin’s affinity for oxygen, shifting the oxyhemoglobin dissociation curve to the left or right. A rightward shift means hemoglobin holds onto oxygen less tightly and releases it more readily to tissues; a leftward shift means it holds onto oxygen more tightly. Rightward shifts occur with things that increase oxygen unloading: volatile anesthetics, acidosis (decreased pH), increased temperature, higher CO2 levels (Bohr effect), and increased 2,3-DPG. These factors make it easier for tissues to extract O2 from blood. Decreased PaO2, however, does not shift the curve itself. It changes the amount of oxygen dissolved and the saturation you observe at a given point on the curve, but it does not reposition the curve’s curve along the axis. So it’s the one that does not cause a shift to the right. Therefore, the factor that does not shift the curve to the right is the decrease in PaO2.

The key idea is how certain factors alter hemoglobin’s affinity for oxygen, shifting the oxyhemoglobin dissociation curve to the left or right. A rightward shift means hemoglobin holds onto oxygen less tightly and releases it more readily to tissues; a leftward shift means it holds onto oxygen more tightly.

Rightward shifts occur with things that increase oxygen unloading: volatile anesthetics, acidosis (decreased pH), increased temperature, higher CO2 levels (Bohr effect), and increased 2,3-DPG. These factors make it easier for tissues to extract O2 from blood.

Decreased PaO2, however, does not shift the curve itself. It changes the amount of oxygen dissolved and the saturation you observe at a given point on the curve, but it does not reposition the curve’s curve along the axis. So it’s the one that does not cause a shift to the right.

Therefore, the factor that does not shift the curve to the right is the decrease in PaO2.