Oxygen Dissociation Curve

Question 1

Oxygen dissociation curve?

Answer 1

• The oxygen dissociation curve describes the relationship between the percentage of saturated haemoglobin and partial pressure of oxygen in the blood.
• It is not affected by haemoglobin concentration

Question 2

Basics?

Answer 2

• shifts to left = for given oxygen tension there is increased saturation of Hb with oxygen i.e. decreased oxygen delivery to tissues
• shifts to right = for given oxygen tension there is reduced saturation of Hb with oxygen i.e. enhanced oxygen delivery to tissues

Question 3

Shifts to Left = Lower oxygen delivery?

Answer 3

• HbF, methaemoglobin, carboxyhaemoglobin
• Low [H+] (alkali)
• Low pCO2
• Low 2,3-DPG
• Low temperature

Question 4

Shifts to Right = Raised oxygen delivery?

Answer 4

• Raised [H+] (acidic)
• Raised pCO2
• Raised 2,3-DPG*
• Raised temperature

Question 5

The L rule?

Answer 5

Shifts to L → Lower oxygen delivery, caused by:

• Low [H+] (alkali)
• Low pCO2
• Low 2,3-DPG
• Low temperature

Another mnemonic is ‘CADET, face Right!’ for CO2, Acid, 2,3-DPG, Exercise and Temperature