A decrease in temperature would shift the oxygen dissociation curve to the left or right?

• A. Decrease temperature
• B. Increase temperature
• C. Increase PaCO2
• D. Increase pH

Answer: (A)

Lower temperature increases hemoglobin’s affinity for oxygen, moving the oxygen-hemoglobin dissociation curve to the left. That means at a given partial pressure of oxygen, hemoglobin binds more O2 and delivers it less readily to tissues. In the lungs, this higher affinity helps loading of O2 when O2 is abundant. Conversely, higher temperature decreases affinity and shifts the curve to the right, promoting easier oxygen release in tissues. Other factors like higher PaCO2 or lower pH also shift the curve to the right, while lower PaCO2 or higher pH would shift it to the left.