Metabolic effects ofCO2

Alice Skoumalová

Overview of oxidative fuel metabolism:

Carbon dioxide transport:

CO2 in the blood:

1. as HCO3- (ionization of H2CO3) 75-85 %

2. as carbamino groups (CO2 reacts with amino groups of proteins) 10-15 %

3. dissolved CO2 5-12 %

Partial pressures air-inspiration air-expiration arterial blood venous blood

pO2 (kPa) 21 15,3 12 – 13,3 4,6 - 6pCO2 (kPa) 0,03 4,4 4,6 – 6 5,3 – 6,6

CO2 + H2O H2CO3 H+ + HCO3-

erythrocytes (carbonate dehydratase)

O2 and CO2 transport:

Bohr effect (the increase in acidity of hemoglobin as it binds O2, releases H+)

Isohydric carriage of CO2 (Hb‘s ability to take up H+ with no change in pH through Bohr effect)

Chloride shift (the exchange of Cl- and HCO3- between the plasma and the erythrocyte)

Hypercapnia protects against free radical damage duringhypoxia-ischemia:

• Stabilization of the iron-transferrin complex• Shift of the oxygen-hemoglobin saturation curve to the right• Effects on metabolism (improve aerobic metabolism, reduced lactate

production, ATP generation)• Direct inhibition of the free radicals

Perinatal brain hypoxic-ischemic damageMechanical ventilationChronic respiratory failure

CO2: protective effect or radical damage ?