Resp. 3 - Diffusion and V-Q Relations Flashcards
Dyuring diffusion, what goes into ther alveoli and out of them?
CO2 coming out of blood, into alveoli 9expired through lungs) and O2 diffuses form alveoli into blood.
• CO2 is 20X more soluble then O2. Therfore
diffusion constant for CO2 is greater then O2.
If we have a solution in which Po2 and PCO2 are the same, the conc. Of CO2 would be a lot higher.
Ficks law
How gas gets through BBB. Diffuses through respiratory membrane (thin).
Vgas=A/T D(P1-P2)
- VGAS direct with A, D, and diff in P
Diffusion constant is
Solubility / M.W
Partial pressure in atmosphere
Nitrogen 78.5%
Oxygen 20.93%
H2O 0.5%
Carbon Dioxide 0.04%
Partial pressure in alveoli
Nitrogen 74.9%
Oxygen 13.7%
H2O 5.2%
Carbon Dioxide 6.2%
• The percentages of gases change as we go into the lungs, because the lungs have
metabolic processes, and so CO2 goes form negligible to significant, as as out bodies are warm, H2O increases a lot too. So N2 and O2 decrease.
Because of normal shunts, the amount of O2 in
arterial blood is always < theoretical maximum because of the little bit of CO2 that goes back to the left side of the heart
PO2 and PCO2 (mmHg)
Atmosphere
PO2: 160
PCO2: 0.3
PO2 and PCO2 (mmHg)
Alveolar air
PO2: 100
PCO2: 40
PO2 and PCO2 (mmHg)
Pulmonary veins
PO2: 100
PCO2:40
PO2 and PCO2 (mmHg)
Systemic arteries
PO2: 100
PCO2: 40
PO2 and PCO2 (mmHg)
Cells
PO2: <40
PCO2: >46
PO2 and PCO2 (mmHg)
Systemic veins
PO2: 40
PCO2: 46
PO2 and PCO2 (mmHg)
Pulmonary arteries
PO2: 40
PCO2: 46
What are the pressure gradients found for O2 and CO2
Two gradients,
1) between systemic capillaries & cells
2) alveoli and pulmonary capillaries
CO2 is 6mmHg
O2 is 60mmHg
• The reason why O2 require 60mmHg to get it into the cells and CO2 only require 6mmHg to get it into the blood is because of
Fiks law, the diffusion constant term, and the solubility of CO2 is 20X more then O2
An increase in altitude leads to a
Decrease in:
- atmospheric pressure
- PO2 in air
- PO2 in alveoli
- PO2 in arterial blood
Limitation:
This means that equilibration does not occur between the PO2 in the pulmonary capillary blood and alveolar gas.
Kind of limitations
Perfusion and diffusion limitation
Something that causes a perfusion limitation (example)
if there’s a reduction in blood flow to the lungs causing the partial pressure of O2 leaving the lungs to be less then the partial pressure going into the aveoli, its perfusion.
At rest,
an increase in diffusion would cause ?
A decrease in diffusion would cause?
No limitation
No limitation
During exercise,
An increase in blood flow would cause?
A decrease in diffusion AND increase in blood flow would cause?
- no limitation
- DIFFUSION LIMITATION
At high altitude,
A decrease in diffusion would cause ?
A diffusion limitation.
