15- PPT O2 and CO2 Transport in Blood

Question 1

how is oxygen transported

Answer 1

dissolved and bound to hemoglobin

• dissolved O2 = solubility coefficient x PaO2
• hemoglobin bound = hemoglobin x 1.34 x SaO2

Total arterial O2 = dissolved + hemoglobin bound

Question 2

P50

Answer 2

PO2 at which hemoglobin is 50% saturated with O2

Question 3

O2 pressure reflects

Answer 3

kinetic energy

Question 4

Bohr effect

Answer 4

effect of pH and CO2 on Hb affinity for O2

the following DECREASES affinity of Hb for O2

• increased CO2
• increased H+ (lower pH)
• increased temperature
• increased 2,3-DPG levels

Question 5

O2 dissociation curve

Answer 5

a shift to the right of the curve indicates less affinity of Hb for O2

-which increases the gradient for diffusion of O2 into the tissues

Question 6

Anemia and CO affect on O2 transport

Answer 6

• both decrease content of O2 in blood without affecting arterial O2 but venous is affected
• you need to increase venous flow (decrease resistance) to get more blood flowing cause there is less O2 in the blood
• during anemia and CO poisoning the PO2 must decrease more to deliver the same O2
• note that CO shifts the dissociation curve to the left

Question 7

how is CO2 transported?

Answer 7

dissolved (5%)

bound to Hb (25%)

as HCO3 (70%)

normal physiological range is from 40-60mmHg

Question 8

Haldane effect

Answer 8

• hypoxia increases CO2 content

- deoxygenated blood can hold more CO2 (and H+) than oxygenated blood

Question 9

CO2 and O2 transport in tissues (not lungs)

Answer 9

1. CO2 goes from tissue to plasma (some dissolves out) then into erythrocyte
2. CO2 either binds to Hb to form carbamino compounds

OR

2. gets converted to HCO3 and H+ using carbonic anyhydrase and goes out into the plasma again (Cl- goes into the RBC when HCO3 leaves)
3. O2 bound to Hb gets dissociated and O2 leaves to go into the tissues (some of that Hb is what CO2 attaches to to form a carbamino compound)

Question 10

CO2 and O2 transport in the lungs

Answer 10

1. O2 leaves the alveolus and goes into the erythrocyte through the plasma briefly
2. Hb detaches CO2 and attaches to the O2
   - HCO3 is also going into the erythrocyte from the plasma while Cl- goes into the plasma and the HCO3 gets turned back into the CO2 to be breathed out as well
3. CO2 is formed from that and it gets dissolved out into the plasma then into the alveolus to get breathed out

Question 11

explain how erythrocyte and carbonic anhydrase and the chloride shift are both important to CO2 transport

Answer 11

• carbonic anhydrase increases the rate of conversion of CO2 to H2CO3
• CO2 + H2O -> H2CO3 -> H+ + HCO3
• the chloride shift minimizes HCO3- in the erythrocytes

Question 12

Normal physiological levels:

PaO2 =
PvO2 =

total arterial O2 =

hb levels =

PCO2 (arterial) =
PCO2 (venous) =

Answer 12

PaO2 = 95-100mmHg
PvO2 = 40mmHg

total O2 = 20ml/100ml

hb levels = 15 g/dl

PCO2 (arterial) = 40mmHg
PCO2 (venous) = 45mmHg

Question 13

key marker for lung disease

Answer 13

PaO2 level thats not 100 mmHg

arterial O2 content

Question 14

how to determine whether the pt is hypo or hyperventilating

Answer 14

look at the PCO2

• if its below normal then hyperventilation
• if its above normal then hypoventilation