Absorption Atelectasis

What Is it, Causes, and More

Author: Anna Hernández, MD

Editors: Ahaana Singh, Ian Mannarino, MD, MBA

Illustrator: Abbey Richard

Copyeditor: Joy Mapes

What is absorption atelectasis?

Absorption atelectasis refers to a loss of lung volume caused by the resorption of air within the alveoli, the small air sacs of the lungs. 

Atelectasis is a common complication of surgeries that involve general anesthesia, but it can also occur as a result of other conditions. Most individuals who undergo a chest or upper abdominal surgery will develop some degree of postoperative pulmonary atelectasis, which, if left untreated, increases risk of more severe pulmonary complications, such as impaired blood oxygenation and respiratory failure.

How does absorption atelectasis occur?

Absorption atelectasis occurs when small pockets of air remain trapped within non-ventilated alveoli. The oxygen and carbon dioxide within these alveoli are gradually reabsorbed into the pulmonary circulation, which causes the alveoli to collapse, and subsequently, collapse of a portion of the lung. 

Absorption atelectasis often happens due to a blockage of the airways between the alveoli and the trachea, the tube that carries air to and from the lungs. Common causes of airway obstruction include mucus plugs, foreign objects, or tumors, all of which prevent the entry of fresh air into the lungs. 

In the absence of airway obstruction, absorption atelectasis can occur in individuals who receive high concentrations of supplemental oxygen. This is frequently the case for individuals undergoing general anesthesia. During 100% oxygen delivery, most of the air within the lungs is washed out and replaced with oxygen, which is readily absorbed into the pulmonary capillaries. The rapid diffusion of oxygen may lead to insufficient amounts of air left inside the alveoli to keep them inflated, resulting in collapse of the alveolar walls. Blood that flows through areas of the lung containing these collapsed alveoli will encounter no oxygen to absorb.

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How can you reduce the risk of absorption atelectasis?

Preventing absorption atelectasis begins by addressing any potentially problematic respiratory conditions before a surgical procedure, including advising individuals to stop smoking in the weeks prior to surgery. Individuals with an increased risk of developing postoperative pulmonary complications may benefit from preoperative physical therapy aimed at strengthening the breathing muscles, such as inspiratory muscle training and specific exercise programs. In addition, some physicians recommend using the lowest concentration of oxygen possible during the perioperative period in order to minimize the risk of postoperative pulmonary atelectasis. During surgery, intraoperative ventilation with positive end-expiratory pressure, or PEEP, can help reduce alveolar collapse by maintaining a set positive pressure within the airways. This ensures that a small amount of air is always left in the alveoli at the end of the expiration to support the alveolar walls.

How is absorption atelectasis diagnosed and treated?

Respiratory symptoms, such as shortness of breath, coughing, or chest pain, may suggest atelectasis. However, not all cases will present with symptoms, and diagnosis generally requires confirmation by demonstrating signs of lung collapse in a chest X-ray or computerized tomography (CT) scan. 

Treatment of absorption atelectasis focuses on addressing any underlying causes. With postoperative pulmonary atelectasis, supportive measures include ensuring adequate pain control after the surgery and encouraging the individual to walk around as soon as possible, practice deep-breathing exercises, and cough to break down existing mucus plugs. In some individuals with poor oxygen saturation, mechanical ventilation with continuous positive airway pressure, or CPAP, may be useful to reduce postoperative pulmonary atelectasis.

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Related links

Anatomy of the lungs and tracheobronchial tree
Pleural effusion, pneumothorax, hemothorax, and atelectasis: Pathology review
Postoperative evaluation: Clinical practice
Preoperative evaluation: Clinical practice

Resources for research and reference

Brodie L. Atelectasis and the cardiac surgery patient. British Journal of Cardiac Nursing. 2012;7(1):10-16. doi:

Randtke MA, Andrews BP, Mach WJ. Pathophysiology and prevention of intraoperative atelectasis: a review of the literature. Journal of PeriAnesthesia Nursing. 2015;30(6):516-527. doi:

‌Ray K, Bodenham A, Paramasivam E. Pulmonary atelectasis in anaesthesia and critical care. Continuing Education in Anaesthesia Critical Care & Pain. 2014;14(5):236-245. doi: