Which condition would most likely cause a rightward shift of the oxyhemoglobin dissociation curve?

Which condition would most likely cause a rightward shift of the oxyhemoglobin dissociation curve?

• A. Fever (increased temperature)
• B. Alkalosis (increased pH)
• C. Hypocapnia (low PaCO2)
• D. Hypothermia (low temperature)

Answer: (A)

The main idea is how factors that affect hemoglobin’s affinity for oxygen shift the oxyhemoglobin curve. A rightward shift means hemoglobin releases O2 more easily to tissues (decreased affinity), which happens when metabolic demand is high or conditions raise temperature, CO2, or acidity. Fever raises body temperature, and higher temperature destabilizes the bond between hemoglobin and oxygen. That makes the curve shift to the right and increases the PO2 needed to saturate hemoglobin (P50 goes up), so more O2 is delivered where it’s needed. In contrast, higher pH (alkalosis), lower CO2 (hypocapnia), and lower temperature (hypothermia) all favor hemoglobin holding onto O2 more tightly, producing a leftward shift. So fever best explains a rightward shift.

The main idea is how factors that affect hemoglobin’s affinity for oxygen shift the oxyhemoglobin curve. A rightward shift means hemoglobin releases O2 more easily to tissues (decreased affinity), which happens when metabolic demand is high or conditions raise temperature, CO2, or acidity. Fever raises body temperature, and higher temperature destabilizes the bond between hemoglobin and oxygen. That makes the curve shift to the right and increases the PO2 needed to saturate hemoglobin (P50 goes up), so more O2 is delivered where it’s needed.

In contrast, higher pH (alkalosis), lower CO2 (hypocapnia), and lower temperature (hypothermia) all favor hemoglobin holding onto O2 more tightly, producing a leftward shift. So fever best explains a rightward shift.