AEMCA Practice Exam

What causes a right shift in the oxygen dissociation curve?

1. Decrease in temperature, alkalosis, decreased DPG

2. Increase in temperature, acidosis, increase in DPG

3. Decrease in CO2, decrease in temperature, increased pH

4. Increased affinity for hemoglobin, increase in CO2, basic pH

The correct answer is: Increase in temperature, acidosis, increase in DPG

A right shift in the oxygen dissociation curve is primarily caused by factors that reduce hemoglobin's affinity for oxygen, making it easier for oxygen to be released to tissues. An increase in temperature raises the metabolic activity of tissues, which enhances oxygen delivery by promoting offloading from hemoglobin. Additionally, acidosis, which occurs when the pH levels drop, indicates increased carbon dioxide (CO2) levels within the tissues, resulting in a higher concentration of hydrogen ions. This also promotes the release of oxygen as hemoglobin's affinity decreases. Furthermore, an increase in 2,3-bisphosphoglycerate (DPG) produced during glycolysis in red blood cells is essential in this process. Elevated DPG levels signal the body to release more oxygen to tissues, especially in conditions of hypoxia or high metabolic demand. In contrast, a decrease in temperature or an increase in pH would lead to a left shift in the oxygen dissociation curve, indicating an increase in hemoglobin's affinity for oxygen. Thus, B encompasses all the correct physiological responses that cause a right shift in the curve, reflecting a body’s need to enhance oxygen delivery during times of increased demand or lower pH levels due to increased CO2.