Conditions that cause a shift of the oxygen dissociation curve to the right will result in which of the following?

• A. Higher Oxygen Saturation for a Given PaO2
• B. Lower Oxygen Saturation for a Given PaO2
• C. Stable Oxygen Saturation for a Given PaO2
• D. No Change in Oxygen Saturation

Answer: (B)

Shifting the hemoglobin-oxygen dissociation curve to the right means lower affinity of hemoglobin for oxygen. This Bohr-like effect is seen with higher temperature, higher CO2, lower pH (acidosis), and increased 2,3-BPG. Because hemoglobin holds onto oxygen less tightly, it releases more O2 to tissues. As a result, at the same arterial PO2 (PaO2), the hemoglobin is less saturated with oxygen, so the oxygen saturation (SaO2) is lower. That’s why the correct outcome is a lower saturation for a given PaO2. In contrast, a leftward shift (higher affinity) would raise SaO2 at the same PaO2, while no change or stability would not reflect the physiology of increased oxygen unloading.