The O2 Capacity of Blood (PK6)

Question 1

What factors affect normal Hb concentration?

Answer 1

• Dietary
• Reduced RBC count (anaemia)
• CO poisoning

Question 2

Which curve (saturation or content) changes with reduced O2 capacity?

Answer 2

Content

Question 3

How is the O2 content graph different with reduced O2 capacity?

Answer 3

• Same shape
• All values lower (shorter graph)

Question 4

Why is carbon monoxide bad?

Answer 4

• Undetectable - no colour, taste, odour, etc.
• Binds to Hb at same site as O2 with 210x affinity
  > At equilibrium 0.1% CO will occupy same amount of Hb as 21% O2

Question 5

Why is CO poisoning fatal but anaemia not?

Answer 5

• Due to shapes of graph, O2 is only released at a much lower PO2 in CO poisoning when compared with anaemia
• This level is fatally low for tissues