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Obstructive vs Restrictive lung disease.

Why does obstructive lung disease cause expiratory problems and restrictive cause inspiratory problems?

So, with obstructive lung disease there is a problem with the conducting pathways right, so wouldn't it also be difficult to get the air into lungs as it would be to get them out?
Reply 1
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ax12
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Original post by MedStudentt
Why does obstructive lung disease cause expiratory problems and restrictive cause inspiratory problems?

So, with obstructive lung disease there is a problem with the conducting pathways right, so wouldn't it also be difficult to get the air into lungs as it would be to get them out?


The problem with obstructive diseases is that the airways collapse. With COPD you have destructive changes in the lungs and thickening of the airways which cause them to collapse earlier in expiration, so you end up unable to fully exhale. When the pressure in the lungs is greater during inspiration they are held open, so there isn't as much of a problem.

In restrictive diseases there is a problem with expanding the lungs, like with fibrosis reducing compliance or a chest wall deformity, so you don't get full inspiration, but you don't have problems breathing out.
Original post by ax12
The problem with obstructive diseases is that the airways collapse. With COPD you have destructive changes in the lungs and thickening of the airways which cause them to collapse earlier in expiration, so you end up unable to fully exhale. When the pressure in the lungs is greater during inspiration they are held open, so there isn't as much of a problem.

In restrictive diseases there is a problem with expanding the lungs, like with fibrosis reducing compliance or a chest wall deformity, so you don't get full inspiration, but you don't have problems breathing out.


But during inspiration isn't pressure in the lungs lower because you want the air to move in from an area of higher pressure in the atmosphere to an area of lower pressure in the lungs?

I get all of it, except that part. Confused :frown:
Reply 3
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ax12
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Original post by MedStudentt
But during inspiration isn't pressure in the lungs lower because you want the air to move in from an area of higher pressure in the atmosphere to an area of lower pressure in the lungs?

I get all of it, except that part. Confused :frown:


Yes, sorry, that bit was me thinking about people with COPD when they exhale, they often purse their lips to increase the back pressure to hold the airways open for longer.
Original post by ax12
Yes, sorry, that bit was me thinking about people with COPD when they exhale, they often purse their lips to increase the back pressure to hold the airways open for longer.


Okay, so am I right in thinking that during inspiration, the pressure in the lungs is more negative and the volume is increased within the lungs so the airways are wider allowing air to enter more easily?
Reply 5
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ax12
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Original post by MedStudentt
Okay, so am I right in thinking that during inspiration, the pressure in the lungs is more negative and the volume is increased within the lungs so the airways are wider allowing air to enter more easily?


Yes, the pressure is lower than the air, and the airways are being expanded.

On expiration when the muscles are contracting in the chest wall, the pressure around the airways is greater, causing them to collapse.

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