[1] It is a very common finding in chest X-rays and other radiological studies, and may be caused by normal exhalation or by various medical conditions.

The term uses combining forms of atel- + ectasis, from Greek: ἀτελής, "incomplete" + ἔκτασις, "extension".

May have no signs and symptoms or they may include:[3] It is a common misconception and pure speculation that atelectasis causes fever.

Factors also associated with the development of atelectasis include: age, presence of chronic obstructive pulmonary disease or asthma, and type of anesthetic.

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).

[13] Children are notably more susceptible to atelectasis due to poorly developed collateral airways, which protect against alveolar collapse by maintaining inflation.

[citation needed] It is usually associated with accumulation of blood, fluid, or air within the pleural cavity, which mechanically collapses the lung.

[15] This type occurs when either local or generalized fibrotic changes in the lung or pleura hamper expansion and increase elastic recoil during expiration.

[16] This type of atelectasis is due to lack of surfactant, as occurs in hyaline membrane disease of newborn or acute (adult) respiratory distress syndrome (ARDS).

The blocked, contracted lung may develop pneumonia that fails to resolve completely and leads to chronic inflammation, scarring, and bronchiectasis.

In atelectasis manifestations that result from the mucus plugging of the airways as seen in patients with cystic fibrosis and pneumonia, mucolytic agents such as acetylcysteine (NAC) is used.

[citation needed] The primary treatment for acute massive atelectasis is correction of the underlying cause.

In certain cases, the affected part of the lung may be surgically removed when recurring or chronic infections become disabling or bleeding is significant.