F - Gas Transport - Karius Flashcards
Alveolar oxygen is
The oxygen in lungs minus the oxygen used by tissue
Solubility of O2
Limited solubility in water and therefore plasma
0.3 ml O2/dl blood/100 mmHg
What does the solubility of O2 number mean?
If PaO2 is 100 mmHg, each dl of blood will carry 0.3 ml O2
*In order to meet this demand hearts would have to pump 83 liters of blood/min - solution is hemoglobin
PaO2 refers to the dissolved oxygen
Hb is how saturated with a PO2 > 60 mmHg?
85% saturated
-enough to supply metabolic demands
What are some factors that cause a right shift (decreased) in O2 curve? And where do you normally see this?
Fever, high CO2 or low pH, 2,3-DPG
Normal in the tissues so O2 leaves Hb
Is all oxygen taken up by the tissue?
No, as indicated by the PO2 of 40 mmHg
-
What is the oxygen saturation of venous blood? And what would the O2 content be?
75%
O2 content = 20.1 x 75% = 15.2 ml O2/dl blood
a-v O2 difference
How much oxygen was used by the tissue being perfused
*19.8 - 15.2 = 4.6
Dependent on tissue need
Ex. fat needs little, skeletal m. a lot
Metabolic processes in the cell results in
CO2 + H2O + Heat
Ratio of O2 to CO2 if the fuel is carbohydrates
1:1 ratio
Ratio of O2 to CO2 if the fuel is fats
7:10
7 CO2s produced for every 10 O2 consumed
Ratio of O2 to CO2 if the fuel is mix of fuels
8:10 = .8
200 CO2s produced for every 250 O2s consumed
Respiratory Quotient
The ratio between CO2 produced and the O2 consumed
Equation = RQ = Volume of CO2 produced divided by volume of O2 consumed
Solubility of CO2
Has greater solubility in water (plasma)
6 ml O2/dl blood/100 mmHg (vs. .3 for O2)
PCO2 of venous blood
45 mmHg
Haldane Shift
The presence of O2 on the heme reduces the affinity of the Hb chain for the CO2
Amount of CO@ carried in carbamino compounds
3ml/dl
7%
Most of the cO2 in the blood is carried as
Bicarbonate (HCO3)
86% - 44 ml of CO2
The chloride shift
In venous blood
H2O goes in and carbonic anhydrase(HCO3) is transported out of the cell with an anti porter that takes Cl- into the cell
HCO3 converted back to what in the lungs?
CO2
CO2 is then free to diffuse into the alveoli
Many of the H+ are displaced from the Hb as oxygen starts to bind
PAO2 calculation
Alveolar partial pressure of O2
PlO2 ((760 - 47) x O2%) - PaCO2/0.8
A-a O2 gradient
PAO2 - PaO2
-useful in determining the health of the alveoli
Normal < 20 mmHg
An increase in A-a O2 gradient indicates
A diffusion impairment
