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Atelectasis is the reduction or absence of air in part or all of a lung. It may be an acute or chronic condition.


Atelectasis may or may not show signs and symptoms depending upon the extent of lung tissue which has collapsed. If a major segment of lung tissue is involved the patient will present the following symptoms:

In severe cases of atelectasis, acute respiratory failure may occur [6].

  • However, the incidence of fever, defined as temperature or 38.0 degrees C fell from 37 to 21 to 17%. When defined as temperature or 38.5 degrees C, the daily incidence of fever fell daily from 14 to 3 to 1%.[ncbi.nlm.nih.gov]
  • A study of 100 post-op patients followed with serial chest X-rays and temperature measurements showed that the incidence of fever decreased as the incidence of atelectasis increased.[en.wikipedia.org]
  • […] with postoperative fever however, there is controversy regarding whether or not atelectasis actually causes fever infant respiratory distress syndrome Treatment Management approach treatment is specific to the underlying cause and aims to re-expand the[medbullets.com]
Foreign Body Aspiration
  • Causes Intraluminal mucus (e.g. postoperative, asthma, cystic fibrosis) foreign body aspiration Mural bronchial carcinoma Extramural peribronchial lymphadenopathy aortic aneurysm About Dr Chris Nickson An oslerphile emergency physician and intensivist[lifeinthefastlane.com]
  • It is commonly caused by the mucous plugs accompanying asthma, chronic bronchitis, bronchiectasis, postoperative states, and foreign body aspiration.[sharinginhealth.ca]
  • Causes of this could include: Intraluminal pathology: sputum plug, foreign body, aspiration Mural pathology: eg. carcinoma Extramural pathology: eg. peribronchial lymphadenopathy, an enlarged left atrium, etc.[derangedphysiology.com]
  • body aspiration resorptive atelectasis of an entire lung ("collapsed lung") can result from complete obstruction of the right or left main bronchus passive (relaxation) atelectasis occurs when contact between the parietal and visceral pleura is disrupted[radiopaedia.org]
  • Treatment includes maintaining coughing and deep breathing and treating the cause.[merckmanuals.com]
  • The RTX respirator is a biphasic external cuirass-style ventilator that supports both inspiration and expiration at various cycle rates and pressures, as well as allowing application of the vibration and cough modes.[ncbi.nlm.nih.gov]
  • Periodic deep breaths, which people take unconsciously, and coughing also help keep alveoli open. Coughing expels any mucus or other secretions that could block the airways leading to the alveoli.[merck.com]
  • Coughing, percussion on affected side will loosen mucus accumulation. Deep breathing exercises are done with spirometry.[symptoma.com]
  • It commonly occurs during and after surgery because you can't cough. Drugs given during surgery make you breathe less deeply, so normal secretions collect in the airways.[mayoclinic.org]
Pleural Effusion
  • RESULTS: 23% of the patients had changes in the lung related to pleural effusion, atelectasis or pneumonia/pneumonitis.[ncbi.nlm.nih.gov]
  • A pleural effusion or pneumothorax causes relaxation or passive atelectasis. Pleural effusions affect the lower lobes more commonly than pneumothorax, which affects the upper lobes.[emedicine.medscape.com]
  • With rapid, extensive atelectasis, dyspnea or even respiratory failure can develop. With slowly developing, less extensive atelectasis, symptoms may be mild or absent. Pneumonia may cause cough, dyspnea, and pleuritic pain.[merckmanuals.com]
  • We report the case of an 11-year-old boy investigated for persistent cough and dyspnea with complete left lung atelectasis mimicking pneumonia. CT and MRI showed an endobronchial mass of the left main bronchus.[ncbi.nlm.nih.gov]
  • In the chronic form, the patient may experience no symptoms other than gradually developing dyspnea and weakness. X-ray examination may show a shadow in the area of collapse.[healthcentral.com]
Bronchial Breath Sounds
  • When the doctor listens to the lungs through a stethoscope (ausculation), diminished or bronchial breath sounds may be heard.[encyclopedia.com]
Painful Cough
  • BACKGROUND: Atelectasis is an important prognostic factor that can cause pleuritic chest pain, coughing or dyspnea, and even may be a cause of death.[ncbi.nlm.nih.gov]
  • The symptoms of atelectasis include: Difficulty breathing Rapid breathing Chest pain Coughing. Diagnosis and Treatment Atelectasis is routinely diagnosed using a chest X-ray to visualize the lungs and surrounding areas.[innerbody.com]
  • Atelectasis and Pneumothorax Lungs Pain Trouble breathing Faintness Cyanosis Mucus plug Tumor Inhaled foreign object Physical trauma to the lung Wound Overview Atelectasis and pneumothorax are conditions in which the lung or part of the lung collapses[nm.org]
  • Symptoms In acute atelectasis in which there is sudden obstruction of the bronchus, there may be dyspnea and cyanosis, elevation of temperature, a drop in blood pressure, or shock.[healthcentral.com]
  • The heart rate and breathing rate may increase, and sometimes the person may look bluish (a condition called cyanosis ) because oxygen levels in the blood are low.[merck.com]
  • CLINICAL PRESENTATION Rapidly developing atelectasis: Chest pain on the affected side, Dyspnoea, and Cyanosis. Hypotension, tachycardia, fever, and shock may also occur.[respiratoryupdates.wordpress.com]
  • May have no signs and symptoms or they may include: cough, but not prominent; chest pain (not common); breathing difficulty (fast and shallow); low oxygen saturation; pleural effusion (transudate type); cyanosis (late sign); increased heart rate.It is[en.wikipedia.org]
  • Hypotension, tachycardia, fever, and shock may also occur. Slowly developing atelectasis is usually asymptomatic sometimes causes minor symptoms.[respiratoryupdates.wordpress.com]
  • Small number of affected alveoli or slowly manifesting atelectasis asymptomatic or minimal symptoms Large number of affected alveoli or rapid onset acute dyspnea, chest pain, tachypnea, tachycardia, and cyanosis Dull percussion note, diminished breath[amboss.com]
  • .  Marked respiratory distress  Dyspnea, tachycardia,  Tachypnea, pleural pain, and central cyanosis  Difficulty breathing in the supine position  Anxious 12.[slideshare.net]


Diagnosis is mainly based on plain chest radiography as often the patient may show no signs and symptoms.

A complete physical examination should be done along with a few basic laboratory tests. Physical examination may reveal absence of breath sounds on the affected side of the hemi thorax. On percussion, dullness maybe demonstrated. Chest expansion may be reduced.

Oximetry may reveal low levels of oxygen. Chestradiographs show distinct signs of atelectasis. Usual radiological signs of collapse on chest x-ray result from airlessness of the lung causing opacification [7] and shrinkage.

Each segment or lobe of the lung when collapsed has a particular pattern of blurring normal boundaries (silhouette sign). Middle lobe or lingular lobe collapse causes blurring of the right and left heart border. Upper lobe collapse may obliterate the superior mediastinal border. However, in complete upper lobe collapse, prolapse of the apical segment of the lower lobe can restore the silhouette of the mediastinal boundaries, the luftsichel sign. A collapse of the whole lung [8] results in opacification and shift of mediastinal structures to the same side. Lower lobe collapse does not obliterate cardiac borders and causes a retrocardiac triangular opacity when completely collapsed [9].

CT scan findings are similar to those seen on chest radiographs but in transaxial planes.

Pleural Effusion
  • RESULTS: 23% of the patients had changes in the lung related to pleural effusion, atelectasis or pneumonia/pneumonitis.[ncbi.nlm.nih.gov]
  • A pleural effusion or pneumothorax causes relaxation or passive atelectasis. Pleural effusions affect the lower lobes more commonly than pneumothorax, which affects the upper lobes.[emedicine.medscape.com]


The main objective of the treatment is to treat and remove the underlying cause. Small areas of collapse can resolve without treatment.

Treatment mainly includes:

  • Chest physiotherapy that aims at improving breathing especially post-surgery to inflate the collapsed lung. Coughing, percussion on affected side will loosen mucus accumulation [10]. Deep breathing exercises are done with spirometry. Postural drainage should be done wherein the head should be positioned lower than the chest allowing mucus to drain out of the lungs.
  • Medications mainly antibiotics should be given to treat any chronic infection. Bronchodilators should be administered for easier breathing.
  • Bronchoscopy should be done for clearing of airways, by suctioning the mucus or to remove any small obstruction. Bronchoscopy can also be useful for removal of any small tumours of the lung.
  • Continuous positive pressure (CPAP) may be useful for low oxygen levels.


The mortality and morbidity of atelectasis mainly depends on the underlying primary pathology.

The collapsed part of the lung usually inflates once obstruction has been resolved or the cause been removed. Some amount of residual scarring or damage may be present [4].

It can be life threatening especially in premature babies, infants and patients with underlying respiratory problems. Thus, the morbidity and complications depends upon the extent of lung tissue collapse.

Certain complications can occur due to atelectasis e.g. pneumonia, hypoxemia and scarring.


The exact etiology is uncertain. Depending upon the type of collapse, atelectasis can be obstructive or non-obstructive. Most common cause of atelectasis is post cardiac surgery.

Obstructive atelectasis is due to an obstruction in the airways. This occurs due to resorption of air distal to the obstruction. The site of obstruction could be central or peripheral. Main causes of blockage are:

  • Mucus accumulation post-surgery which results in an inability to cough, resulting in a collection of mucus and secretions. Anaesthesia and other drugs given during surgery can also cause mucus accumulation.
  • Foreign body inhalation like small objects, peanuts and small toys, mainly inhaled accidentally by children [1].
  • Lung tumours or any space occupying lesion.
  • Mucus plugs may also accumulate in cystic fibrosis and asthma [2].

Non obstructive atelectasis can occur due to different reasons as follows:

Compressive collapse occurs from relaxation of the lung due to pleural disease like pleural effusion, pneumothorax and hydropneumothorax.

  • Any inflammation of the lungs which can occur from any type of pneumonia can cause temporary atelectasis.
  • Adhesive collapse is where there is an abnormality in the surfactant resulting in collapse of the lungs [3].


Atelectasis has no racial predilection, affects men and women equally. The mean age of clinical onset of this condition is around 60 years. It also occurs in premature babies and mainly presents as Acute Respiratory Distress Syndrome (ARDS). There is a high incidence of atelectasis in asbestos workers. Post-surgery atelectasis improves well.

Sex distribution
Age distribution


The factors maintaining normal lung expansion are the balance of mechanical and surface forces. The chest wall physio-mechanically coupled by forces through the pleurae is essential for normal lung expansion.The surfactant lining the alveoli aids ventilation via normal and collateral pathways and is essential for maintenance of lung inflation.

Disruption of these properties can lead to lung instability and collapse. It can occur due to resorption of gas distal to an airway obstruction. Relaxation of the lung due to uncoupling of lung and chest wall forces by fluid (pleural effusion) or gas (pneumothorax) and loss of surfactant in ARDS can cause atelectasis.

In an obstructed lobe, the oxygen is consumed raising the partial pressures of other gases above the normal. These gases dissolve in the blood and get absorbed eventually reducing the volume of the affected lobe. During resolution of pneumonia or post-operative conditions, secretions and mucus collect in the central bronchi. Due to a diminished cough reflex and reduced diaphragmatic motion and pain there is absorption of air distal to obstruction.

Shrinkage due to lung collapse results in compensatory hyperinflation. In a collapsed lung unit there is no ventilation, but perfusion continues producing a shunt effect. This results in hypoxemia which cannot be corrected by oxygen therapy. Refractory hypoxemia is therefore the basic pathophysiological abnormality.

Expansion of collapsed lobe can occur after the obstruction is removed as ventilation is restored.


Atelectasis can be prevented by certain modifications in posture and habits. Smoking should be stopped. Small objects and toys should not be given to children to prevent obstruction.

Post-surgery deep breathing exercises should be done along with posture changes for easy drainage of mucus. Coughing should be encouraged post-surgery. In case of pain in chest, pain medication should be given. Position of lying down should not remain constant and frequently altered. Ambulation should be encouraged.


Atelectasis is the total or incomplete collapse of a part of the lung or the entire lung. This results in failure of expansion of the lungs due to deflated alveoli. It is a condition which results in airlessness with shrinkage of the lungs.

It can be congenital (atelectasis neonatorum) due to an inborn failure of lungs to expand and usually presents in premature babies. It can be acquired anytime during the lifetime wherein there is absorption of air secondary to obstruction, compression, contraction or surfactant loss.

Atelectasis occurs mainly secondary to other respiratory problems like cystic fibrosis, lung tumours, foreign body inhalation, pneumothorax and chest injuries. Atelectasis is frequently known as lung collapse and is the commonest complications post-surgery.

If only a small segment of the lung has collapsed, there may be no signs and symptoms. If not treated timely, it can cause severe complications as the oxygen supply to the body reduces.

Patient Information

Atelectasis is a medical condition where a part of or the entire lung tissue collapses resulting in reduced gaseous exchange. This leads to reduced oxygen levels in the body. Atelectasis results from either an obstruction in the airways or after a surgical operation. It can also occur if there is some external pressure from other tissues on the lungs.

It usually occurs secondary to some respiratory problem .In premature babies too, atelectasis can occur. The main cause for atelectasis is mucus accumulation in the lung thus resulting in no air in the air sacs which lead to reduced gaseous exchange. Most common conditions which cause atelectasis are any obstruction like tumours, or any foreign objects, any chronic infections in the lungs and trauma to the chest. Post surgery there is a high chance of developing atelectasis due to reduced coughing reflex.
Majority of the cases show no signs and symptoms unless a large segment of lung tissue is involved. There may be difficulty in breathing, chest pain and low fever.

A medical care provider will be able to confirm the condition by a physical examination as well as may advice to do a chest X-ray. Chest X-ray will confirm the diagnosis as atelectasis is very prominent on a radiograph. CT scan may be needed.

Treatment mainly involves removal of the cause of atelectasis, thus enabling the inflation of the lung. Chest physiotherapy should be done regularly for removal of the mucus. Deep breathing techniques are advised. Post-surgery posture should be frequently changed for easy drainage of any secretions. Coughing should be encouraged. Medications may be given for an infection.
Bronchoscopy is done to clear the air passages and remove any obstruction if present. If treatment not administered on time it can lead to severe complications which can ultimately lead to respiratory failure. Post any operation, proper care should be taken to avoid accumulation of secretions and postural modifications should be done. Patient should be encouraged to walk as much as possible.

The outlook depends on the primary cause, but with prompt treatment and removal of any obstruction atelectasis has a good recovery.



  1. Priftis KN, Mermiri D, Papadopoulou A, Anthracopoulos MB, et al. The role of timely intervention in middle lobe syndrome in children. Chest. 2005 Oct;128(4):2504-10.
  2. Hendriks T, de Hoog M, Lequin MH, Devos AS, Merkus PJ. DNase and atelectasis in non-cystic fibrosis pediatric patients. Crit Care. 2005 Aug;9(4):R351-6.
  3. Franken EA Jr, Klatte EC. Atypical (peripheral) upper lobe collapse. Ann Radiol (Paris). 1977 Jan-Feb;20(1):87-93.
  4. Reinius H, Jonsson L, Gustafsson S, et al. Prevention of atelectasis in morbidly obese patients during general anesthesia and paralysis: a computerized tomography study. Anesthesiology. 2009 Nov;111(5):979-87.
  5. Mavros MN, Velmahos GC, Falagas ME. Atelectasis as a cause of postoperative fever: where is the clinical evidence? Chest. 2011 Aug;140(2):418-24.
  6. Chen HA, Lai SL, Kwang WK, Liu JC, et al. Middle lobe syndrome as the pulmonary manifestation of primary Sjogren's syndrome. Med J Aust. 2006 Mar 20;184(6):294-5.
  7. Herold CJ, Kuhlman JE, Zerhouni EA. Pulmonary atelectasis: signal patterns with MR imaging. Radiology. 1991 Mar;178(3):715-20.
  8. Proto AV. Lobar collapse: basic concepts. Eur J Radiol. 1996 Aug;23(1):9-22.
  9. Woodring JH, Reed JC. Radiographic manifestations of lobar atelectasis. J Thorac Imaging. Spring 1996;11(2):109-44.
  10. Pryor JA. Physiotherapy for airway clearance in adults. Eur Respir J. 1999 Dec;14(6):1418-24.

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Last updated: 2019-07-11 22:29