Which factor is NOT associated with a rightward shift of the oxyhemoglobin dissociation curve?

The oxyhemoglobin dissociation curve illustrates how readily hemoglobin binds to oxygen and how readily it releases oxygen. A rightward shift in this curve indicates that hemoglobin has a reduced affinity for oxygen, meaning it releases oxygen more readily to tissues, which is often a response to physiological conditions requiring increased oxygen delivery.

Decreased blood acidity, also known as an increase in pH, does not contribute to a rightward shift. Instead, higher pH levels encourage hemoglobin to retain its affinity for oxygen, making it less likely to release oxygen to the tissues. Consequently, this is why decreased blood acidity is associated with a leftward shift of the curve, where hemoglobin holds onto oxygen more tightly.

Increased temperature, increased carbon dioxide levels, and increased blood acidity (lower pH) all promote a rightward shift in the curve. Elevating temperature enhances metabolic activity and encourages oxygen unloading. Similarly, higher carbon dioxide levels lead to greater production of carbonic acid, which lowers blood pH (increasing acidity), thereby promoting a rightward shift. These physiological adaptations are vital in situations such as exercise or increased metabolic demand, where more oxygen delivery to tissues is crucial.