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
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
2. PERFUSION LIMITED —
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
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
1. Pulmonary hemorrhage
4. Left to right shunt
2. Pulmonary artery obstruction