QuestionSBA
QuestionChoice
In anaemia, haemoglobin affinity is unchanged i.e. the percentage of haemoglobin binding sites that are occupied with oxygen remains the same. Therefore, despite there being less haemoglobin overall, the oxygen saturation of haemoglobin remains unchanged. In carbon monoxide poisoning, the number of haemoglobin is unchanged but carbon monoxide displaces oxygen that would normally bind to haemoglobin and causes a low haemoglobin oxygen saturation.
10024345
a
Haemoglobin saturation (Hb SaO2) is normal in anaemia and reduced in carbon monoxide poisoning
QuestionChoice
CaO2 is reduced in **both** carbon monoxide poisoning and anaemia. The total arterial oxygen concentration includes the oxygen bound to haemoglobin as well as the oxygen concentration in the plasma. As both anaemia and carbon monoxide affect haemoglobin, the oxygen-carrying capacity is reduced (the plasma oxygen concentration is unaffected however). This reduces the overall arterial oxygen concentration.
10024346
b
CaO2 (total arterial oxygen concentration) is reduced in carbon monoxide poisoning and normal in anaemia
QuestionChoice
Haemoglobin concentration is reduced in anaemia and **normal** in carbon monoxide poisoning. This is because, in carbon monoxide poisoning, carbon monoxide displaces oxygen at haemoglobin binding sites as it has a higher affinity than oxygen. This reduces the oxygen-carrying capacity, however the number of haemoglobin molecules remains unaffected.
10024349
e
Haemoglobin concentration is reduced in both anaemia and carbon monoxide poisoning
QuestionChoice
Haemoglobin-oxygen concentration is reduced in **both** anaemia and carbon monoxide poisoning. Carbon monoxide displaces oxygen at haemoglobin binding sites as it has a higher affinity than oxygen. This reduces the oxygen-carrying capacity and hence the haemoglobin-oxygen concentration.
10024348
d
Haemoglobin-oxygen concentration is reduced in anaemia and normal in carbon monoxide poisoning
QuestionChoice
PaO2 is normal in both anaemia and carbon monoxide poisoning. The partial pressure of oxygen refers to the pressure of oxygen in the plasma, not the overall concentration of oxygen in the blood i.e. it does not include oxygen bound to haemoglobin. As it is only the oxygen bound to haemoglobin (the oxygen-carrying capacity) that is affected in anaemia and carbon monoxide poisoning, the PaO2 is unaffected.
10024347
c
PaO2 is reduced in anaemia and normal in carbon monoxide poisoning
Concept
Chapter
2693
5769
Gaseous exchange and transportation
Topic
150
Respiratory physiology
17267
What impact do anaemia and carbon monoxide poisoning have on blood oxygen transportation?
a