Lungs, Bronchial Airways and Cystic Fibrosis We all breathe air in and out of our lungs through a system of bronchial airways.  These airways are a complex system of tubes that become smaller as they reach deeper into our lungs.  We all have mucus coating these bronchial airways.  The mucus acts like 'fly paper" and catches the dust and germs in the air that we must breathe.  The mucus moves like a slow river outward toward the back of the throat where it collects.  When there is enough we clear our throats and swallow the mucus along with the dust and germs.  The mucus is swept outward along the bronchial airways by tiny hair-like structures called cilia that beat rapidly like miniature whips to move the mucus and debris out of the lungs.  The cilia beat in a very thin liquid layer that sits just below the mucus layer.  The mucus layer slides along on this liquid layer being pushed along by the beating cilia.  This system works quite well to keep our lungs free of dust and germs and the infections that they might cause. People with cystic fibrosis have a problem that causes their bronchial mucus to move too slowly.  It moves so slowly that the germs have time to multiply and cause an infection in the lungs.  Researchers have learned that there does not seem to be enough liquid in this liquid layer under the mucus.  As a result, the cilia cannot beat effectively, if at all.  As infection and inflammation develops even more mucus is produced and the airways begin to become partially blocked leading to air trapping, and then completely clogged leading to small areas of collapsed lung called atelectasis.  Eventually the cf patient may have a fever, breathing becomes difficult and antibiotics are required to fight the infection.  To clear the airways of mucus chest physical therapy is used to loosen the mucus and open the clogged airways.  Chest physical therapy involves physical techniques to dislodge bronchial airway mucus and to open up clogged airways in the various segments of the tracheo-bronchial tree.  The loosened mucus can then be more easily coughed out by the patient. Cystic fibrosis is a genetic disease for which there is not yet a cure.  The most debilitating and life threatening complications of cf result from the thick and copious mucus secretions in the airways of the lungs.