L6 Gas diffusion across the repiratory membrane Flashcards Preview

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Flashcards in L6 Gas diffusion across the repiratory membrane Deck (11):

What are the requirements for constant gas transfer in the blood ?

1. Constant diffusion across respiratory membrane ( by maintaining a constant lung pressure )

2. Constant perfusion of blood in pulmonary circulation


How the lung is maintaining his pressure constant ?

By not changing his volume a lot in one breath .. it takes 16 times to fully replace lung air with new air


What are the components of respiratory unit/lobule ?

1. Respiratory bronchiole
2. Alveolar duct
3. Atria
4. Alveoli


What are the components or respiratory membrane ?

1. This layer of fluid
2. Epithelium of the alveoli
3. Fused basement membrane
4. Endothelium of the capillaries


What does the rate of diffusion of a gas depends on :

1. Gas solubility in the membrane

2. Gas solubility in the blood

3. Difference in partial pressures between alveoli and Blood (P1-P2)

4. Thickness of the membrane.(T)

5. Surface of the membrane (A)


What is diffusion limited and what is perfusion limited ?

1. DIFFUSION LIMITED —> long equilibrium time
- CO has low solubility in the membrane but very high in the blood and Hb ... so it mainly depends on how much it will diffuse



Which gas transfer will be affected in the fibrosis ?

Oxygen mainly will be affected and will be changed from perfusion limited do diffusion limited


What is the time for blood to be oxygenated in the capillaries ?

0.75 s however, normally at rest you need only 1/3 (0.25) and the rest is reserve


What does the diffusion capacity depends on ?

1. Surface area
2. Thickness of membrane
3. Difference in the pressure
4. Perfusion
5. Hemoglobin in the blood


Why the DLCO has a wide range ? When it increase and when it decrease ?

As CO binds very tightly to Hb and any increase or decrease in Hb amounts will affect the percentage of DLCO

Increase :
1. Pulmonary hemorrhage
2. Polycythemia
3. LHF
4. Left to right shunt

Decrease :
1. Anemia
2. Pulmonary artery obstruction


What are the three main reasons which could lead to abnormal AaDO2?

1. Abnormal DLCO

2. Abnormal shunt ( anatomical or functional )

3. Ventilation / perfusion mismatch