Originally Posted by MJAID
In FA, under obstructive lung diseases, it mentions that airways close prematurely at high lung volumes. Is this just because of the increased collapsing pressure(in other words elastic recoil)? Also, why is FEV 1 reduced more than FVC in COPD?
It's been a long time since I've considered this stuff, but I think you're right. Emphysema (due to smoking) causes destruction of elastin. Elastin, in turn, is important for elastic recoil. Without elastin, the lungs collapse more easily.
Lung collapse causes difficulty with exhalation. Of note, rate of exhalation has nothing to do with total lung volume (FVC). FCV might be intact. But without elastin, the air may be in the lungs, but it's difficult to expel it. That's why FVC is impaired, but FVC might be unchanged or less impaired. Note that all the air in the lungs will probably be expelled eventually, but, again, it takes time.
I've focused on emphysema but I think the same applies to the other COPD diseases (bronchiectasis).