TRANSPORT OF CARBON DIOXIDE

1. DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
TRANSPORT OF
CARBON DI-OXIDE.

2. OBJECTIVES.
 Diffusion of CO2 in blood.
 Transport of CO2 in blood.
 Release of Co2 in lungs.
 Other facts about CO2 transport.
Thursday, December 8, 2016

3. INTRODUCTION.
 Transport occurs along conc
gradient
 Intracellular PCo2 – 46 mm
Hg
 Interstitial fluid PCO2 – 45
mm Hg
 Arterial blood – 40 mm Hg
 venous blood Pco2 – 45 mm
Hg
 Alveolar air Pco2 – 40 mm
Hg.
Thursday, December 8, 2016

4. CO2 transport
 From cell into
interstitial fluid against
difference of 1 mm Hg.
 From interstitial fluid to
tissue capillaries
against 5 mm Hg.
 From venous blood to
alveolar air against conc
difference of 5 mm Hg.
Thursday, December 8, 2016

5. DIFFUSION OF CO2 IN BLOOD.
 Intracellular PCO2 46
mm Hg.
 Interstitial fluid PCO2
45 mm Hg.
 So CO2 transfer in conc
difference of 1 mm Hg.
Thursday, December 8, 2016

6. TRANSPORT OF CO2 IN
BLOOD.
 In Dissolved form
 In Bicarbonate form.
 In Carbamino compound form.
Thursday, December 8, 2016

7. IN DISSOLVED FORM
 Venous blood with PCO2 45
mm Hg contains 2.7ml/100ml
CO2 in dissolved form.
 Arterial blood with PCO2 40
mm Hg contains 2.4ml/100ml
CO2 in dissolved form.
 0.3 ml/100 ml transferred
 7 % of total transport.
Thursday, December 8, 2016

8. IN BICARBONATE FORM (70%)
 Chloride shift or
Hamburger
phenomenon.
Thursday, December 8, 2016

9. Thursday, December 8, 2016

10. IN CARBAMINO COMPOUND FORM
(23%)
 In plasma – CO2 combines with amino group of
plasma proteins – forms Carbamino proteins.
 Co2 +PrNH2 Pr.NH.COOH
 In RBC – combines with amino group of Hb – forms
Carbamino Haemoglobin
 CO2 + HbNH2 Hb.NH.COOH
Thursday, December 8, 2016

11. IN CARBAMINO COMPOUND
FORM (23%)
 This combination of CO2 with Hb – Reversible
 Slower than reaction of CO2 with water bcoz more
CO2 transported as Bicarbonates (70%) than
carbamino compounds (23%)
Thursday, December 8, 2016

12. CARBON DIOXIDE
DISSOCIATION CURVE
 Relationship between
PCO2 & total CO2
content.
 Relationship is nearly
linear over wide range
of PCO2
Thursday, December 8, 2016

13. FACTORS AFFECTING CO2
DISSOCIATION CURVE
 OXYGEN
 DPG
 BODY
TEMPERATURE.
Thursday, December 8, 2016

14. OXYGEN
 Deoxyhaemoglobin is
capable of loading more
Co2 than
oxyhaemoglobin.
 Also oxygenation of Hb
in lungs increases Co2
unloading – Haldane
Effect.
Thursday, December 8, 2016

15. OXYGEN
 Blood with PCO2 40 mmHg
reaching the tissue is capable of
drawing CO2 more at PO2 40
mm Hg than at PO2 100 mmHg.
So dissociation curve shift to left
in tissue.
 Blood with PCO2 45 mmHg
reaching the lung is capable of
leaving CO2 more at PO2 100
mm Hg than at PO2 40 mmHg. So
dissociation curve shift to right
in lungs.
Thursday, December 8, 2016

16. DPG
 2,3- DPG competes
with CO2 for same site
on Hb in reduced
blood so decreases
formation of
carbamino-Hb.
 So shifts curve to
Right decreasing CO2
carrying capacity.
Thursday, December 8, 2016

17. BODY TEMPERATURE.
 Causes curve to shift to left.
 Increasing carrying capacity.
Thursday, December 8, 2016

18. RELEASE OF CO2 IN LUNGS.
 Venous blood with PCO2
45 mm Hg & PO2 40 mm
Hg contains CO2 52ml/100
ml.
 Alveolar air with Pco2 40
mmHg, PO2 100 mmHg
contains CO2 48ml/100ml.
 So total diffusion of 4
ml/100 ml.
Thursday, December 8, 2016

19. RELEASE OF CO2 FROM
CARBAMINOHAEMOGLOBIN INTO PLASMA
 O2 enters the RBC &
convert Deoxy Hb – to
Oxy Hb which has low
affinity for CO2 &
releases co2 from
Carbamino-
haemoglobin into
plasma.
HALDANE EFFECT
Thursday, December 8, 2016

20. RELEASE OF CO2 FROM
CARBONATE INTO PLASMA
 Oxyhemoglobin is
strong acid – increases
H+ ion conc – to
neutralize HCO3- ions
enters RBC & Cl-
ions
leaves RBC
 Reversal of chloride
shift.
Thursday, December 8, 2016

21. DIFFUSION OF CO2 FROM
PLASMA TO ALVEOLI
 PCO2 of plasma of Pul
arterial blood 45 mm
Hg & PCO2 of alveolar
air is 40 mm Hg.
 So pressure gradient of
5 mm Hg Co2
transported from
plasma to alveoli.
Thursday, December 8, 2016

22. OTHER FACTS ABOUT CO2
TRANSPORT.
 Comparison of different vehicles for CO2
transport.
 Rate of total CO2 transport.
 Changes in blood pH during transport of CO2
 Respiratory Quotient.
 Definition
 Normal value
 Respiratory quotient depends upon the type of uel
consumed.
Thursday, December 8, 2016

23. COMPARISON OF DIFFERENT
VEHICLES FOR CO2 TRANSPORT.
 Plasma – not good transporter (0.2ml/100 ml)
 Bicarbonate also not a good transporter – beyond
PO2 40 mmHg no further transport of CO2
 Whole Blood ideal vehicle
Thursday, December 8, 2016

24. RATE OF TOTAL CO2
TRANSPORT.
 At Rest – 4ml/100 ml from tissue to lungs so
200ml/min (with CO 5L)
 Depending on severity up to 4L/min.
 Change in pH is prevented by conversion of CO2 to
Bicaronate ions.
Thursday, December 8, 2016

25. CHANGES IN BLOOD PH
DURING TRANSPORT OF CO2
 Arterial pH – 7.4
 Venous blood – 7
 Fall due to formation
of carbonic acid.
 During exercise excess
change in pH is
prevented by blood
buffers.
Thursday, December 8, 2016

26. RESPIRATORY QUOTIENT.
 Definition – it is defined as the ratio of the rate of
CO2 excretion & rate of O2 consumption/min
 RESPIRATORY EXCHANGE RATIO
 Can be easily estimated by knowing amount of O2
removed from inspired air to amount of CO2 added
to the expired air per min.
Thursday, December 8, 2016

27. RESPIRATORY QUOTIENT.
 Normal value –
4ml/5ml = 0.8
 Respiratory quotient
depends upon the type
of fuel consumed.
 Carbohydrate as entire
source – ratio is 1
 Proteins & fats as
source <1, only fats 0.7
Thursday, December 8, 2016

28. Thank
You