Gas Exchange + Transport: CO2 Flashcards
what are most acid-base problems due to
CO2 transport –> remove CO2 to prevent this
transport of CO2 from tissue and loss of CO2 at the resp surface
CO2 not just a gas but source of acid
what occurs when CO2 dissolves in an aqueous solution
CO2 + H2O –> H2CO3 –> HCO3- + H+ –> H+ + CO3^2-
H+ = acid
what is the total content of CO2
sum of [CO2diss] + [H2CO3-] + [HCO3-] + [CO3^2-]
is there a CO2 carrier in the blood
no specific carrier for CO2 in blood so blood doesn’t become saturated with CO2 (unlike O2)
how is CO2 transported
- dissolved
- bound to Hb
- plasma proteins
how is dissolved CO2 transport
carbon dioxide is much more soluble in blood than oxygen
about 5% of carbon dioxide is transported unchanged –> simply dissolved in plasma
about 5% of CO2 transported
how is CO2 transported in Hb
combines reversibly with amino groups on Hb –> not the FE^2+
oxyhemaglobin –> carbaminohemaglobin (blue tinge)
how is CO2 transported in plasma proteins
CO2 binds to amino groups on other proteins
what is the haldane effect
- Hb has higher affinity for CO2 when it is deoxygenated (to take it up at tissues)
- Hb has lower affinity for CO2 when it is oxygenated (to release it at the lungs)
what is the affinity of CO2 at the tissues
deoxygenated blood –> higher affinity for CO2
travels from tissues where it binds with Hb
what is the affinity of O2 and CO2 at the lungs
oxygenated blood
higher affinity for O2
lowers affinity for CO2 causes CO2 release
what is the respiratory exchange ratio
the resp exchange ratio (R) is the ratio of the amount of CO2 produced to the amount of O2 consumed
R = CO2 produced/O2 consumed
how is arterial blood CO2 measured
by blood gas analysis
what is a capnograph
device that measures CO2 concentrations in expired air (alveolar CO2, PaCO2)
mostly used in intubated animals during anaesthesia
what is the resp exchange ratio of glucose, free fatty acid fuel
glucose fuel, R=1
free fatty acid fuel, R=0.7 (more O2 consumed than CO2 produced)
typical mix of free fatty acids and glucose, R=0.8
what are the phases in normal CO2 waveform
phase I: inspiratory baseline which is due to inspired gas with low levels of CO2 (points A-B)
phase II: is the beginning of expiration CO2 begins to travel from the alveoli mixing with gas in anatomic dead space causing rapid rise in CO2 (points B-C)
phase III: alveolar plateau, (points C-D) where the last of the alveolar gas is sampled. Normally at the end tidal CO2 (point D)
phase IV: is the inspiratory downstroke and the beginning of inspiration (point D-E)
