Breathing System (Biology)

The mucus layer in the nose is used to secret mucus which is for filering dust & wetting the incoming air . It also contains some enzymes to kill bacteria . However when the underlining get swollen , it simply broads the amount of air passing through , more severely you breath with no air , since amount of air decreased , there will be less oxygen diffused into the blood in the lung not in the mucus layer which is in the nose .

mucus layer would become much thicker -> Diffusion Distance for Oxygen in the air sac INCREASES -> Rate of Diffusion of Oxygen Decrease -> Less Oxygen replenish