The lung system is responsible for supplying oxygen to the blood and expelling waste gasses.
The lungs contain the narrower passage ways, or bronchioles,which carry air to the functional unit of the lungs, the alveoli.
There, in the thousands of tiny alveolar chambers, oxygen is transferred through
the membrane of the alveolar walls to the blood cells in the capillaries
Likewise, waste gases diffuse out of the blood cells into the air in the alveoli, to be expelled upon exhalation.
The pleural membranes help provide lubrication (mucus) for the respiratory organs so that they are not chafed during respiration.
It was formerly believed that the bacteria were the primary cause of airway
destruction; it is now believed that the white blood cells, especially the
long viscous strands of DNA from the cell nuclei, are the principle cause
of airway clogging and damage.
It is those strands that DNAse seeks to chop
So thats why you have to do all those nebs , also some of us must inhale antibiotics like TOBI and COLIMYCINE , to prevent growth of those nasty bacteria .