Atelectasis overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Assistant Editor-in-Chief: Somal Khan, M.D.

Overview

Atelectasis is defined as a state in which the lung, in whole or in part, is collapsed or without air. It is a condition where the alveoli are deflated, as distinct from pulmonary consolidation. Infant respiratory distress syndrome includes another type of atelectasis, and is described and discussed in its own article.

Classification

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), destruction, and scarring (fibrosis).

Pathophysiology

There are several types of atelectasis according to their underlying mechanisms or the distribution of alveolar collapse; resorption, compression, microatelectasis and contraction atelectasis.

Causes

The most common cause is post-surgical atelectasis, characterized by splinting, restricted breathing after abdominal surgery. Outside of this context, atelectasis implies some blockage of a bronchiole or bronchus, which can be within the airway (foreign body, mucus plug), from the wall (tumor, usually squamous cell carcinoma) or compressing from the outside (tumor, lymph node, tubercle). Another cause is poor surfactant spreading during inspiration, causing an increase in surface tension which tends to collapse smaller alveoli.

Risk Factors

Smokers and the elderly are at an increased risk.