Ch.9 Carbon Dioxide Equilibrium & Transport

**what are ways CO2 is transported to the lungs?

• plasma (transported through plasma) →dissolved CO2 in plasma

• in RBCs (most ___ is formed here)

• HCO3 bicarbonate (carried by this) plasma HCO3

• protein compound

**how is CO2 transported to lungs via bicarbonate?

• most (90%) CO2 in blood enters RBCs

• HCO3 generated through hydrolysis → diffuses into plasma → H+ produces is buffered by Hb and generates HCO3

**for CO2, does the RBC or plasma transport move faster?

RBC due to carbonic anhydrase (not present in plasma)

**how much CO2 is produced @ body tissue?

200 mL of CO2 each min

what is CO2 a byproduct of?

oxidative (aerobic) metabolism

what is the average CO2 diffusion gradient between tissues & arterial blood entering capillaries? Capillary blood & alveoli?

6mmHg → causes CO2 to diffuse into systemic capilllaries

**CO2 PCO2 mmhg?

• at rest= produces 200 mL

• tissue PCO2= 46 mmHg

• capillary PCO2= 40 mmHg

• PvO2= 46 mmHg

• alveolar PCO2= 40 mmHg

**what are the percentages of CO2 transported to the lungs through the plasma?

carbamino compound → 1

bicarbonate → 5

dissolved CO2 → 5

**what are the percentages of CO2 transported to the lungs through the RBCs?

carbamino-Hb→ 21%

bicarbonate → 63

dissolved CO2 → 5

**how is CO2 converted to HCO3?

• hydrolysis reaction

H2O + CO2 ↔ H2CO3 ↔ HCO3- + H+

• carbonic anhydrase speeds up the reaction (catalyst)

how does ventilation affect CO2?

• ventilation eliminates CO2 @ same rate body tissue generates CO2 → produces A & a CO2 of 40mmHg

why do we treat CO2 as an acid?

• conc of dissolved CO2 in plasma ≠ conc plasma H2CO3

• dissolved CO2 is directly proportional to H2CO3 conc

**how is CO2 regulated by the lungs?

• hyperventilation

• hypoventilation

•reversed reactions, hydration reactions shifts to left

**what is the role of hyperventilation in CO2 regulation by the lungs?

• ↓ CO2 = ↓ PaCO2 = L hydrolysis reaction

• CO2 elimination momentarily exceeds CO2 production

• HCO3 then ↓

• more ventilatory work to eliminate CO2

• ↓ blood acid levels

• ↓ H+ → pH normalizes

**what is the role of hypoventilation in CO2 regulation by the lungs?

• ↑ CO2 = ↑ PaCO2 = R hydrolysis reaction shift

• CO2 production momentarily exceeds CO2 elimination

• A gas & blood eventually equilibrate, CO2 elimination matches CO2 production by $ higher PACO2

• ↓ ventilatory reserve , less ventilatory work to eliminate CO2

• ↑ blood acid levels

• ↑ H+ —> pH normalizes

what is the haldane effect?

affinity of Hb for CO2 is greater when not combined with O2