Respiratory Physiology & Anatomy

Question 1

Right-shift of Hgb-O2 dissociation curve

Answer 1

Occurs when the affinity of Hgb for O2 is decreased. Results in an increased P50 (increased P02 required to acheive 50% saturation of Hgb). Faciliates unloading of 02 from arterial blood to the tissues.

Causes:

• Bohr effect (increase in PCO2 or decrease in pH)
• Increase in T (e.g. exercise)
• Increase in 2,3-DPG concentration (bind to beta chains of deoxyhemoglobin to decrease binding affinity; adapatation to chronic hypoxemia)

Question 2

Left-shift of Hgb-O2 dissociation curve

Answer 2

Occurs when the affinity of Hgb for O2 is increased. Results in a decreased P50 (decreased P02 required to acheive 50% saturation of Hgb). Impedes unloading of 02 from arterial blood to the tissues.

Causes:

• Decreased PCO2, increased pH, decreased T
• Decreased 2,3-DPG concentration
• HbF(does not bind 2,3-DPG as avidly as adult Hgb)
• CO poisoning (replaces O2 on Hgb and increases affinity of remaining sites for O2)