2019B12 Draw the oxygen-haemoglobin and carbon dioxide-haemoglobin dissociation curves
on the same axes (content vs. partial pressure). Compare and contrast these two curves.

 

List:

·         Graph

·         Table of normal values

·         Table of comparison

 

 

Normal values:

 

Oxygen

Carbon dioxide

Pa (mmHg)

100

40

Ca (mL/100mL)

20

48

Pv (mmHg)

40

46

Cv (mL/100mL)

15

52

a-v difference (mL/100mL)

5

4

 

HCO3- 60%

Carbamino 30%

Dissolved 10%

Arterial storage

Hb-bound 98.5%

Dissolved 1.5% (∝ partial pressure)

HCO3- 90%

Carbamino 5%

Dissolved 5% (∝ partial pressure)

 

Curve comparison:

 

Oxygen

Carbon dioxide

Shape

Sigmoid (law of mass action + co-operative binding)

Linear

Slope

Shallower

-Large a-v difference in pO2

-Large ↓PaO2 in shunt

Steeper

-Small a-v difference in pCO2

-Small ↑PaCO2 in shunt

Shift

Right shift -> ↓affinity if:

-↑H+, ↑pCO2 (Bohr effect)

-↑[2,3-DPG]

-↑Temp

Left shift -> ↑affinity if:

-↓SO2 (Haldane effect)

Upper section

 

-Implication for shunt

Flat

 

-↑VA and ↑PiO2 cause minimal improvement in oxygenation

Linear

 

-↑VA easily restores ventilation

 

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