Transport of Respiratory Gases Seminar.pptx

how are the respiratory gases ie oxygen and carbon dioxide transported in the body

1. Transport of Respiratory Gases Smrithi Rajeev M.Sc. Respiratory Therapy Moderated by – Thankamani V Department of Respiratory Therapy

2. Contents Introduction Transport of oxygen in various forms Oxygen-hemoglobin dissociation curve Transport of carbon dioxide in various forms Carbon dioxide dissociation curve

3. Blood serves to transport the respiratory gases Oxygen is transported from the alveoli of the lungs to the cells Carbon dioxide is transported from the cells to the alveoli of the lungs.

4. Transport of Oxygen As simple physical solution(3%) In combination with hemoglobin(97%)

5. As simple solution Oxygen which dissolves in water of plasma is transported in physical form 0.3ml/100ml of plasma, 3 percent of the total oxygen Poor solubility of oxygen in the water content of plasma

6. In combination with Hemoglobin Oxygen combines with hemoglobin and forms oxyhemoglobin 97 percent of oxygen is transported by this method. Hemoglobin accepts oxygen readily whenever the pao2 in the blood is more And gives out oxygen whenever the pao2 in the blood is less .

7. Hemoglobin is a metalloprotein with four subunits, each composed of an iron-containing heme and a polypeptide chain. Iron is present in the ferrous state. One molecule of oxygen can bind to the iron atom of a heme group, giving each hemoglobin the ability to transport four oxygen molecules.

8. Oxygen carrying capacity of Hb Amount of oxygen transported by blood Normal Hb content blood is 15g% 15g% of Hb should carry 20.1ml% of oxygen i.e., 20.1 ml of oxygen in 100 ml of blood. Oxygen carrying capacity of blood Oxygen carrying capacity of hemoglobin is the amount of oxygen transported by 1 gram of hemoglobin. 1.34ml/g

9. Oxy-hemoglobin dissociation curve It is the curve that determines the relationship between partial pressure of oxygen and its percentage saturation of hemoglobin with oxygen. Hemoglobin’s affinity for oxygen Under normal conditions the oxyhemoglobin dissociation curve is ‘S’ shaped or sigmoid shaped. Lower part of the curve - dissociation of oxygen from the Hb Upper part of the curve – uptake of oxygen by the Hb depending on the pao2

10. P 50 It is the oxygen tension at which hemoglobin saturation with oxygen is 50% Normal value - 25-27 mm Hg. At 40mm Hg of pao2 the saturation is 75% It becomes 95% when the pao2 is 100mm Hg Increased p50 indicates decreased affinity for oxygen and ODC curve shifts to the right and vice versa.

11. Factors affecting the ODC curve Shift to left indicates acceptance of oxygen by Hb (association) Shift to the right indicated dissociation of oxygen from the hemoglobin.

12. Shift to Right Decreased pao2 Increased paco2 (Bohr effect) Increase in the hydrogen ion concentration and decrease in the ph (acidity) Increase in the body temperature Excess of 2,3 diphosphoglycerate in RBC. (muscular exercise and in high altitude) Bohr effect. It is the effect by which the presence of carbon dioxide decreases the affinity of Hb for oxygen In tissues due to continuous metabolic activities the paco2 is high and pao2 is less. Pressure gradient is created and CO2 enters the blood and O2 is released from the blood to the tissues. ODC curve shifts to the right

13. Shift to Left In fetal blood because the fetal hemoglobin has more affinity towards oxygen than adult hemoglobin Decrease in the hydrogen ion concentration and increase in the ph (alkalinity)

14. Transport of Carbon Dioxide Carbon dioxide is transported from the cells to the alveoli of lungs in 4 forms As dissolved form (7%) As carbonic acid (negligible) As bicarbonate (63%) As carbamino compounds (30%)

15. 1. As dissolved form Diffuses into the blood dissolves in plasma forming simple solution. 3ml/100ml of plasma. 7% 2. As carbonic acid Part of the dissolved carbon dioxide in plasma combines with the water to form carbonic acid.

16. 3. As bicarbonate About 63% of the carbon dioxide is transported as bicarbonate. From plasma carbon dioxide enters the RBS’s and combines with water to form carbonic acid. Carbonic anhydrase enzyme accelerates this reaction Carbonic acid dissociates into hydrogen ions and bicarbonate ions. Due to high concentration of bicarbonate ions it diffuses through the cell membrane to the plasma.

17. Hamburger Phenomena Chloride shift Exchange of chloride ion for a bicarbonate ion between RBC’s and plasma. Negatively charged HCO3 move out into the RBC’s into the plasma to combine with Na+ and forms sodium bicarbonate and the negatively charged chloride ions move into the RBC’s to maintain the electrolyte equilibrium

18. Significance of Chloride Shift Responsible for regulating and controlling the affinity of hemoglobin for oxygen through the chloride ion interaction . The exchange of bicarbonate for chloride in RBC flushes the bicarbonate from the blood and increases the rate of gas exchange

19. Reverse chloride shift Chloride ions move back into the plasma from RBC’s when blood reaches the alveoli. It occurs in lungs For the elimination of caron dioxide

20. 4. As carbamino compounds 30% Carbon dioxide combines with hemoglobin to form carbamino hemoglobin Combines with plasma proteins to form carbamino proteins. Together called as carbamino compounds.

21. Carbon dioxide dissociation curve Demonstrates the relationship between partial pressure of carbon dioxide and the quantity of carbon dioxide that combines with the blood. Normal carbon dioxide dissociation curve shows that the carbon dioxide content in the blood is 48ml% when the partial pressure of carbon dioxide is 40 mm Hg. 52ml% when the partial pressure of carbon dioxide is 48mm Hg. It becomes 70ml% when the partial pressure of Co2 is 100mg.

22. Haldane effect Combination of oxygen with hemoglobin displaces carbon dioxide from hemoglobin. Excess of oxygen content in the blood cause the curve to shift towards the right. Causes for the Haldane effect Highly acidic hemoglobin has low tendency to combine with carbon dioxide causing it to get displaced from the blood. Hydrogen ions are released in excess and bind with bicarbonate ions to form carbonic acid that dissociates into water and carbon dioxide Carbon dioxide is then released into the alveoli from the blood

23. Significance of Haldane effect Release of co2 from the blood to the alveoli of lungs Uptake of oxygen by the blood

24. References K Sembulingam and Prema Sembulingam; Essentials of Medical Physiology, Chapter no: Page no:

25. Does carbon monoxide poisoning affect Spo2 reading?