L6 Gas diffusion across the repiratory membrane Flashcards Preview

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Flashcards in L6 Gas diffusion across the repiratory membrane Deck (11):
1

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

2

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

3

What are the components of respiratory unit/lobule ?

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

4

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

5

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)

6

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

2. PERFUSION LIMITED —

7

Which gas transfer will be affected in the fibrosis ?

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

8

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

9

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

10

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

11

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