1. Gas Transport
Prof. K. Sivapalan

2. Transport of gases in Blood
2013
Gas Transport

3. Reaction of Oxygen with Haemoglobin
Iron atoms in Hb bind reversibly with O2- Oxygination.
4Hb + 4O2 ↔ Hb4O8
Oxygen dissociation curve illustrates the relation of PO2 to saturation.
The sigmoid curve is the result of changing affinity of Hb to oxygen.
When fully saturated, 1 g Hb carries ml oxygen
2013
Gas Transport

4. Factors Affecting the Affinity of Haemoglobin to Oxygen
Factors that reduce the affinity [shift the curve to right, increase P50]
Rise in temperature
Fall in pH
Rise in 2,3-biphosphoglycerate
P50- partial pressure at which 50 % haemoglogin is saturated.
2013
Gas Transport

5. Reaction with CO
Carbon monoxide reacts with haemoglobin in the same way as oxygen but the affinity is 250 times more.
2013
Gas Transport

6. 2,3- Biphosphoglycerate It binds to β chain of deoxy haemoglobin
Alkalinity, thyroid hormone, androgens and growth hormone increase it.
Exercise causes increase in 60 minutes but it may not occur in trained athlets.
2013
Gas Transport

7. Color Changes of Haemoglobin
Haemoglobin is blue
Oxyhaemoglobin is pink
Cyanisis- blue discolorization dueto deoxigination.
It becomes apperant if deoxy haemoglobin is more than 5g/dl
Carboxy haemoglobin is cherry red
2013
Gas Transport

8. Transport of Carbon Dioxide
Considerable amount of CO2 remains dissolved in plasma.
CO2 enters red cells and carbonic anhydrase catalyses formation of Hydrogen and bicarbonate.
CO2 reacts with NH2 in proteins [haemoglobin and plasma proteins] to form carbamino compound.
2013
Gas Transport

9. Bicarbonate Formation and Chloride Shift
The dissociation of carbonic acid formed in red cells as H+ and HCO3- will not proceed unless at least one is removed.
The Hb is a good buffer and takes up H+ and the reaction continues.
The resulted HCO3- concentration rises and difuses into plasma.
The electrical in-equilibrium drags Cl- into red cell.
This increases osmolality and the red cell volume increases.
70 % of the CO2 is transported as HCO3-
2013
Gas Transport

10. Summary of CO2 in DL blood
Arterial Blood [PCO2- 40 mm Hg]
Added in tissues/ removed in lungs
Venous blood [PCO2- 46 mm Hg]
Dissolved
2.6 mL
0.4 mL
3.0 mL
Carbimino compound
0.8 mL
3.4 mL
Bicarbonate
43.8 mL
2.5 mL
46.3 mL
Total
49.0 mL
3.7 mL
52.7 mL pH
7.4
7.36
2013
Gas Transport

11. Carbon Dioxide Dissociation Curve
2013
Gas Transport

12. Interaction of Oxygen and Carbon Dioxide with Haemoglobin
Increase of CO2 promotes dissociation of O2- Bohr Effect.
Oxygination tends to displace CO2 from blood- Haldane effect.
Oxy haemoglobin is more acidic
Less tendancy to form carbamino compounds.
Less tendancy to accept hydrogen ion.
2013
Gas Transport

13. Summary of Changes in Lungs
Oxygen up take- 250 ml/min.
Carbon dioxide output- 200 ml/min.
Respiratory exchange ratio-
CO2/O2 = 200/250 =0.8
Oxygen uptake is facilitated by carbon dioxide dissociation and carbon dioxide dissociation is facilitated by oxygenation.
2013
Gas Transport

14. Physiologic Shunt of Venous Blood
Drainage of small amounts of bronchial blood into pulmonary vein
Left ventricular blood draining into the chamber directly.
The result is blood in aorta with 95 % saturation of oxygen.
2013
Gas Transport

15. Exchange in Tissues
The cells are using oxygen and the partial pressure is very low.
The cells are producing carbon dioxide and the partial pressure is high.
The gases diffuse according to the Partial pressure difference through the tissue fluid.
Higher temperature, higher PCO2, more acidity facilitate de-oxigenation and deoxigenation facilitates CO2 reaction with haemoglobin
2013
Gas Transport

16. Supply of Oxygen
When tissue metabolism increases, the tissue partial pressure falls.
Slight fall in partial pressure results in dissociation of more oxygen from haemoglobin.
Myoglobin in muscles releases oxygen when the partial pressure is very low.
2013
Gas Transport