What is atelectasis?
Atelectasis is the collapse of part or all of a lung by blockage of the air passages (bronchus or bronchioles), or by very shallow breathing. Atelectasis is a process whereby a segment of lung is not ventilated and becomes "collapsed." This process can occur for several different reasons including "compression" of a lung segment (like from an effusion pushing
on the tissue), obstruction of a bronchiole (tumor, post-operative or mucus plug), and contraction (scarring of lung). Most often atelectasis is secondary to a mucus plug that occludes a bronchiole segment.
Atelectasis may be an acute or chronic condition. In acute atelectasis, the lung has recently collapsed and is primarily notable only for airlessness. In chronic atelectasis, the affected area is often characterized by a complex mixture of airlessness, infection, widening of the bronchi (bronchiectasis (see Bronchiectasis), destruction, and scarring (fibrosis). People who smoke have a greater risk of developing atelectasis. Atelectasis can result from an obstruction (blockage) of the airways that affects tiny air scas called alveoli. Each alveoli is held open by complex walls called alveolar walls. These walls, along with a substance called surfactant that is produced by the lung, help keep the alveoli open and filled with air. When healthy people breathe, air travels all the way down the bronchial tubes to the alveoli. It is through these walls that gases like oxygen are transferred into the blood. When the airways are blocked by a mucous "plug," foreign object, or tumor, the alveoli are unable to fill with air and collapse of lung tissue can occur in the affected area. Atelectasis is a potential complication following surgery, especially in individuals who have undergone chest or abdominal operations resulting in associated abdominal or chest pain during breathing. Congenital atelectasis can result from a failure of the lungs to expand at birth. This congenital condition may be localized or may affect all of both lungs.