Atelectasis

Atelectasis is a condition in which part of the lung becomes airless and collapses.

What is going on in the body?

The lungs are divided into large sections called lobes. Each lobe is divided into smaller segments. Each of these segments is composed of thousands of small air cavities. These tiny spaces are called alveoli, and they look somewhat like a honeycomb. 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 alveoli cannot stay open, atelectasis occurs. When that happens, the lung cannot pass oxygen to the blood.

What are the causes and risks of the condition?

There are several types of atelectasis.

Obstructive atelectasis occurs when something prevents air from reaching the alveoli. This blockage may be caused by:

Compressive atelectasis results when the air passages are closed from the outside. An enlarging lung tumor may press on the outside of the larger bronchial tubes, resulting in partial or complete closure.

Adhesive or congenital atelectasis results from the lack of surfactant. Surfactant is a protein found naturally in the lungs that helps with gas exchange in the alveoli. It also helps keep the lungs elastic. This type of atelectasis can be caused by congenital disorders such as hyaline membrane disease. Without surfactant, the alveolar walls alone cannot keep the alveoli open.

People are more at risk for atelectasis if they: