Smoking has many complex effects on the lungs. It paralyzes the ciliary hair cells lining the large airways for approxi mately one hour after one cigarette. In chronic smokers, the ciliary cells are destroyed. This increased production of mucous combined with reduced removal of the mucous increases the likelihood that a mucous plug will block or partially block a large airway, trapping the gas beyond the blockage. To add even further insult to injury, if a smoker stops smoking, the production of mucous actually increases for the first week.
Smoking increases the production of mucous in the nose and sinuses.
It also causes problems with the drainage of mucous from these areas. A large number of research projects have tried to determine if diving has any short or long term effects on the lungs. This is a measurement of small airways function and seems to correlate with the risk of suffering pulmonary barotrauma and arterial gas embolism. Therefore, diving might damage small airways but smoking definitely damages small airway function. Smoking has also been shown to cause the airways in the lungs to constrict, increasing breathing resistance threefold for up to 35 minutes after one cigarette.