1. OXYGEN(O2) & CARBONDIOXIDE(CO2)
GAS TRANSPORT
OXYGEN(O2)
&
CARBONDIOXIDE(CO2)

2. Gas Transport
O2 which is taken up by the blood at the lungs is transported to the tissues for use by the cells.
CO2 produced at the cell level is transported to the lungs for elimination.

3. Oxygen (O2) Transport
Most of the O2 in the blood is transported bound to hemoglobin.
Method of O2 Transport
Chemically bound to Hemoglobin – 98.5%
Physically Dissolved in plasma – 1.5%

4. Oxygen Transport
Most O2 in the blood is transported bound to hemoglobin.
Method of O2 Transport
Chemically bound to Hemoglobin – 98.5%
Physically Dissolved in plasma – 1.5%

6. Oxygen Transport Hb is present inside red blood cells [RBC].
Hb is iron bearing protein molecule.
It makes reversible combination with oxygen.
When Hb combines with O2, we call Oxyhemoglobin [HbO2].
Hb + O2  HbO2
When O2 not combined with Hb, we call it reduced Hemoglobin or Deoxyhemoglobin.

7. Gas Transport
Hemoglobin promotes the net transfer of oxygen at both the alveolar and tissue levels.
There is a net diffusion of oxygen from the alveoli to the blood. This occurs continuously until hemoglobin is as much saturated as possible (97.5% at PO2 of100 mm of Hg).
At the tissue cells hemoglobin rapidly delivers oxygen into the blood plasma and on to the tissue cells. Various factors promote this unloading.

8. Factors producing unloading of O2:
An increase in carbon dioxide from the tissue cells into the systemic capillaries increased hemoglobin dissociation from oxygen (shifts the dissociation curve to the right).
Increased acidity has the same effect.
This shift of the curve to the right (more dissociation)
is called the Bohr effect.
Higher temperatures also produces this shift, as does the production of BPG.
Hemoglobin has more affinity for carbon monoxide
as compared to oxygen.

9. CO POISONING
Hemoglobin has more affinity for carbon monoxide(240 times) as compared to oxygen.
CO a poisonous gas, liberated by burning of carbon products, eg. automobile gasoline, coal, wood & tobacco.
Not detected, because it is colorless,
odorless & non irritating and may be
lethal.

12. Oxygen-Hemoglobin (O2-Hb) dissociation(or saturation) curve

16. Factors at the tissue level promoting the unloading of O2 from Hb (Summary)
Shifting of O2 dissociation curve to right or more dissociation [giving] of O2 to tissues or less affinity of O2 for Hb.
The factors are
1- Increase PCO2
2- Increase Acidity [increase H+ ion]
3- Increase Temperature
4- Increase 2,3-BPG [bisphosphoglycerate] or
2,3-DPG [diphosphoglycerate]

17. CO2 Transport CO2 is transported in the blood by three ways:
1. Physically dissolved in Plasma- 10%
2. Bound to Hb- 30% Carbamino-Hb(Hb-CO2)
3. As Bicarbonate- 60%

18. CO2 Transport
Most carbon dioxide (about 60%) is transported as the Bicarbonate Ion.
Carbon dioxide combines with water to form carbonic acid.
The enzyme carbonic anhydrase facilitates this in the erythrocyte.
Carbonic acid dissociates into hydrogen ions and the bicarbonate ion.
2-step, reversible process is favored at the tissue cells.
The reverse of this process (bicarbonate ions forming free molecules of carbon dioxide) occurs in the lungs.
30% of the carbon dioxide is bound to hemoglobin in the blood. This is another means of transport.
About 10% of the transported carbon dioxide is dissolved in the plasma.

19. Gas Transport
Most carbon dioxide (about 60%) is transported as the Bicarbonate Ion.
By the chloride shift, the plasma membrane of the erythrocyte passively facilitates the diffusion of bicarbonate ions (out of the red cell) and chloride ions (inside of the red cell).
By the Haldane effect the removal of oxygen from hemoglobin at the tissue cells increases the ability of hemoglobin to bind with carbon dioxide.

21. Abnormalities in Arterial PO2
Hypoxia
Condition of having insufficient O2 at the cell level
Categories
Hypoxic hypoxia (low arterial blood PO2) eg. high altitude, inadequate gas exchange
Anemic hypoxia (reduced O2 carrying capacity of blood) eg. Less RBC /Hb, CO poisoning
Circulatory hypoxia(too little oxygenated blood is delivered to tissue); Stagnant hypoxia eg. congestive heart failure or circulatory shock
Histotoxic hypoxia (inability of cells to use O2) eg. cyanide poisoning
Hyperoxia
condition of having an above-normal arterial PO2
Can only occur when breathing supplemental O2
Can be dangerous

22. Abnormalities in Arterial PCO2
Hypercapnia
Condition of having excess CO2 in arterial blood
Caused by hypoventilation
Hypocapnia
Below-normal arterial PCO2 levels
Brought about by hyperventilation which can be triggered by
Anxiety states
Fever
Aspirin poisoning

25. Things to be learn from this lecture
Gas transport
Methods of O2 transport
Role of hemoglobin (Hb)in O2 transport
O2-Hb dissociation curve
Factors affecting Hb-O2 dissociation curve
Methods of CO2 transport
Abnormalities of PO2 & PCO2