Atelectasis: Symptoms, Causes, Diagnosis & Treatment — Complete Guide
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What Is Atelectasis?
Atelectasis is the collapse of a lung or part of a lung when the tiny air sacs, called alveoli, lose air. It is one of the most common breathing complications after surgery and can also result from a mucus plug, an inhaled object, a tumor, or fluid around the lung. Most cases are treatable, and mild cases may clear alone. [1]
What the research says
Most anesthetized patients develop atelectasis. A review in Anesthesiology reports that atelectasis occurs in the dependent parts of the lungs of most patients who are anesthetized, and that it is linked to reduced lung compliance and impaired oxygenation, with effects that can persist into the postoperative period. (Duggan & Kavanagh, Anesthesiology, 2005) [3]
Ventilator settings during surgery can lower the risk. In a network meta-analysis of randomized trials, low-tidal-volume ventilation with moderate PEEP plus recruitment maneuvers reduced atelectasis compared with conventional ventilation (odds ratio 0.36, 95% credible interval 0.16–0.87), as did high PEEP plus recruitment maneuvers (OR 0.41, 0.15–0.97). (Deng et al., Br J Anaesth, 2020) [4]
Evidence for incentive spirometry is still limited. A Cochrane review of 12 trials (1,834 participants) found no statistically significant benefit of incentive spirometry for preventing postoperative pulmonary complications after upper abdominal surgery, but the evidence was low quality and the authors call for larger, well-designed trials. (do Nascimento Junior et al., Cochrane Database Syst Rev, 2014) [5]
At a Glance: Atelectasis Summary
What it is: Collapse of a lung or part of a lung (a lobe) when the air sacs (alveoli) lose air.
Most common setting: One of the most common breathing complications after surgery.
Two mechanisms: Obstructive (blocked airway) and nonobstructive (pressure from outside the lung).
Symptoms: Often no clear signs; difficulty breathing, rapid weak breathing, wheezing, coughing.
When to act: Always seek care for breathing trouble; emergency help if breathing suddenly becomes difficult.
Key tests: Chest X-ray, CT scan, oximetry, chest ultrasound, bronchoscopy.
Main treatments: Chest physiotherapy (incentive spirometer, percussion), mucus-loosening medicines, bronchoscopy/surgery, breathing tube, CPAP.
Serious complications: Low blood oxygen (hypoxemia), pneumonia, respiratory failure.
What Is Atelectasis?
Atelectasis (at-uh-LEK-tuh-sis) is the collapse of a lung or part of a lung — also known as a lobe. It happens when the tiny air sacs within the lung, called alveoli, lose air. When enough air sacs deflate, the affected portion of the lung can no longer expand normally, and breathing becomes harder.
Atelectasis is one of the most common breathing complications after surgery. It is also a possible complication of other respiratory problems, including cystic fibrosis, lung tumors, chest injuries, fluid in the lung, and respiratory weakness. You may also develop it if you breathe in a foreign object.
The condition makes breathing hard, particularly if you already have lung disease. Treatment depends on what is causing the collapse and how severe it is.
Atelectasis vs. Pneumothorax: What's the Difference?
The definition of atelectasis is broader than pneumothorax (noo-moe-THOR-aks). A pneumothorax happens when air leaks into the space between your lungs and chest wall, causing part or all of a lung to collapse. In other words, a pneumothorax is one of several causes of atelectasis — not a separate condition with the same definition.
What are the symptoms of atelectasis?
Atelectasis often causes no noticeable symptoms, though some people develop breathing problems such as wheezing or coughing. Many small areas of collapse produce no symptoms you would notice. If you do have signs, they may include:
Having a hard time breathing
Rapid, weak breathing
Wheezing
Coughing
When to see a doctor: Always get medical attention right away if you have a hard time breathing. Other conditions besides atelectasis can make it hard to breathe, so getting the right diagnosis and treatment matters. If your breathing suddenly becomes difficult, get emergency medical help.
What causes atelectasis, and what are its two mechanisms?
Atelectasis develops through one of two mechanisms. A blocked airway can cause it — this is called obstructive atelectasis. Pressure from outside the lung can also cause it — this is called nonobstructive atelectasis.
General anesthesia — the sleep-like state produced with medicines before a procedure or surgery — is a common cause of atelectasis. It changes your regular pattern of breathing and affects the exchange of lung gases, which can cause the air sacs to lose air. Nearly everyone who has major surgery has some amount of atelectasis. It often occurs after heart bypass surgery.
Causes of Obstructive Atelectasis (Blocked Airway)
When a blocked airway causes atelectasis, it may be due to:
Mucus plug. A mucus plug is a buildup of sputum or phlegm in your airways. It commonly occurs during and after surgery because you cannot cough and the drugs given during surgery make you breathe less deeply — so mucus that would usually move out of your lungs builds up instead. Suctioning the lungs during surgery helps clear them, but sometimes mucus still builds up. Mucus plugs are also common in children, people with cystic fibrosis, and during severe asthma attacks.
Foreign body. Atelectasis is common in children who have inhaled an object into their lungs, such as a peanut or part of a small toy.
Tumor inside the airway. A growth, which may or may not be cancer, can narrow or block the airway.
Causes of Nonobstructive Atelectasis (Outside Pressure)
Possible causes of atelectasis due to pressure from outside the lung include:
Injury. Chest trauma, such as from a fall or car accident, can cause you to avoid taking deep breaths due to pain, leading to the squeezing of your lungs.
Pleural effusion. A buildup of fluid in the space between the lining of your lungs and the inside of your chest wall.
Pneumonia. Various types of this lung infection can cause atelectasis.
Pneumothorax. Air leaking into the space between your lungs and chest wall causes some or all of a lung to collapse.
Scarring of lung tissue. Injury, lung disease, or surgery could cause scarring.
Tumor. A large tumor can press against the lung and force air out of it.
In short: a blocked airway (mucus plug, foreign body such as a peanut or toy part, or a tumor inside the airway) causes obstructive atelectasis, while pressure from outside (chest injury, pleural effusion, pneumonia, pneumothorax, lung scarring, or a large tumor) causes nonobstructive atelectasis. General anesthesia and major surgery are a shared trigger for both.
Atelectasis Risk Factors: Who Is Most Likely to Develop It?
Atelectasis is more likely after recent chest or stomach surgery or general anesthesia, and with lung disease, weak breathing muscles, long bed rest or smoking.
Any condition that makes it hard to swallow
Needing to stay in bed over a long time without enough changes of position
Lung disease, such as asthma, bronchiectasis, or cystic fibrosis
Recent surgery in the stomach area or chest
Recent general anesthesia
Weak breathing muscles due to muscular dystrophy, spinal cord injury, or another neuromuscular condition
Medicines that may cause weak breathing
Pain or injury that makes it painful to cough or causes weak breathing, including stomach pain or a broken rib
Smoking
If you have recently had surgery or are facing surgery while you have lung disease or weakened breathing muscles, you are in the highest-risk group — and it is worth discussing prevention with your doctor before your procedure.
What are the complications of atelectasis?
Atelectasis can usually be treated when only a small area is affected, especially in adults. But left unaddressed, atelectasis can lead to serious complications:
Low blood oxygen (hypoxemia). Atelectasis makes it harder for your lungs to get oxygen to the air sacs.
Pneumonia. Your risk of pneumonia continues until the atelectasis goes away. Mucus in a collapsed lung may lead to infection.
Respiratory failure. Loss of a lobe or a whole lung, especially in an infant or someone with lung disease, can be life-threatening.
This is exactly why sudden or severe breathing difficulty should always trigger immediate medical care — the cause may be atelectasis, or it may be something else entirely, and only proper diagnosis can tell.
How can atelectasis be prevented?
Atelectasis in children is often caused by a blockage in the airway. To lower the risk, keep small objects out of the reach of children.
In adults, atelectasis most commonly occurs after major surgery. If you are scheduled for surgery, talk with your doctor about ways to lower your risk. Some research shows that certain breathing exercises and muscle training may lower the risk of atelectasis after some surgeries.
How Is Atelectasis Diagnosed?
A doctor's examination and a plain chest X-ray may be all that is needed to diagnose atelectasis. But other tests may be done to confirm the source of symptoms or figure out the type or severity of the collapse [2].
Doctor's exam + chest X-ray: Often enough to diagnose atelectasis on its own.
CT scan: Better than an X-ray at finding the cause and type of atelectasis.
Oximetry: A small device on your finger measures your blood oxygen level and shows how severe the atelectasis is.
Chest ultrasound: Uses sound waves and a small hand-held device on the chest to find causes such as pneumothorax and pleural effusion.
Bronchoscopy: A flexible, lighted tube down your throat lets the doctor see what is causing a blockage (mucus plug, tumor, or foreign body) — and can also remove the blockage.
How is atelectasis treated, from deep breathing to surgery?
Treatment of atelectasis depends on the cause. Mild atelectasis may go away without treatment. Sometimes medicines are used to loosen and thin mucus. If the condition is due to a blockage, you may need surgery or other treatments [2].
Chest Physical Therapy (Chest Physiotherapy)
Chest physical therapy is a group of airway clearance techniques. They help you breathe deeply after surgery to expand collapsed lung tissue. It is best to learn these techniques before surgery. They include:
Deep-breathing exercises with an incentive spirometer. You breathe deeply using a hand-held device called an incentive spirometer, followed by deep coughing to help clear your lungs. This gets rid of mucus and other secretions and can help your lung return to its larger size.
Positioning. Your body is positioned so your head is lower than your chest, allowing mucus to drain better from the bottom of your lungs.
Percussion. Tapping on your chest over the collapsed area loosens mucus. You can also use mechanical mucus clearance devices, such as an air pulse vibrator vest or a hand-held instrument.
Surgery and Bronchoscopy
Suctioning mucus or performing a bronchoscopy can get rid of airway blockages. During bronchoscopy, the doctor gently guides a flexible tube down your throat to clear your airways.
If a tumor is causing atelectasis, treatment may involve removing or shrinking the tumor during the bronchoscopy, which may include surgery. Other cancer treatments, such as chemotherapy or radiation, may or may not be needed.
Breathing Treatments
In some cases, a breathing tube may be needed. Continuous positive airway pressure (CPAP) may help people who are too weak to cough and have low oxygen levels (hypoxemia) after surgery.
How should you prepare for an atelectasis appointment?
Unless you need emergency care, you are likely to first see your family doctor. But in some cases, when you call to set up an appointment, you may be referred right away to a pulmonologist — a doctor who specializes in lung conditions.
What You Can Do
To prepare for your appointment, make a list of:
Symptoms you are having, including any that don't seem related to why you scheduled the appointment
When the symptoms began and what you were doing at the time
All medicines, vitamins, or supplements you are taking
Questions for your doctor
Questions to Ask Your Doctor
What is likely causing my symptoms or condition?
What kinds of tests do I need?
What treatment do you recommend?
What are my treatment options?
I have other health conditions — how can I best manage them together?
Are there any diet or activity restrictions?
Do you have any brochures or other printed material that I can have?
What websites do you recommend?
What to Expect From Your Doctor
Your doctor is likely to ask you several questions, including:
When did you start having symptoms?
Do you always have symptoms, or do they come and go?
How severe are your symptoms?
Have you had a fever?
What, if anything, makes you feel better?
What, if anything, makes your symptoms worse?
Take a family member or friend with you to your appointment, if possible, to help you remember everything that is said.
Frequently Asked Questions About Atelectasis
What does atelectasis mean?
Atelectasis is the collapse of a lung or part of a lung (a lobe) that happens when the tiny air sacs (alveoli) lose air. It is one of the most common breathing complications after surgery.
Can atelectasis go away on its own?
Yes — mild atelectasis may go away without treatment. However, cases caused by a blockage may require bronchoscopy, surgery, or other treatments to remove the cause.
What are the symptoms of atelectasis?
There may be no clear signs at all. When symptoms appear, they can include having a hard time breathing, rapid weak breathing, wheezing, and coughing. Always seek care for breathing trouble, and get emergency help if breathing suddenly becomes difficult.
How is atelectasis diagnosed?
A doctor's exam and a plain chest X-ray may be enough. CT scans, oximetry (a finger device measuring blood oxygen), chest ultrasound, and bronchoscopy can identify the cause, type, and severity of the collapse.
What is the treatment for atelectasis after surgery?
Chest physical therapy is the core treatment: deep-breathing exercises with an incentive spirometer, deep coughing, head-lower-than-chest positioning, and percussion to loosen mucus. For blockages, bronchoscopy or surgery removes the cause; CPAP or a breathing tube may help those with low oxygen.
How do I prevent atelectasis?
In children, keep small objects out of reach to prevent inhaled foreign bodies. Before major surgery, ask your doctor about lowering your risk — breathing exercises and muscle training may reduce the chance of atelectasis after some surgeries.
Is atelectasis life-threatening?
A small area of atelectasis, especially in adults, usually can be treated. But complications can include low blood oxygen, pneumonia, and respiratory failure — and loss of a lobe or a whole lung can be life-threatening in an infant or someone with existing lung disease.
Conclusion
Atelectasis is more common than most people realize — nearly everyone who undergoes major surgery has some degree of it. The three lessons to keep:
It is silent but serious. Atelectasis can produce no symptoms at all, which is why any breathing difficulty deserves prompt medical attention.
It has two clear mechanisms. Either an airway is blocked (mucus plug, object, tumor) or pressure from outside squeezes the lung down (injury, fluid, air leak, scarring).
It is usually treatable. From an incentive spirometer to bronchoscopy, the tools to reopen the lung are well established — especially when treatment starts early.
This guide covers everything you need to understand the condition, recognize the warning signs, and walk into your appointment prepared. If your breathing troubles come with asthma, read our complete guide to asthma — asthma attacks can trigger the mucus plugs that obstruct the airways.
This article is for general informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment.
Related Reading
Chest Physiotherapy (Chest PT): Techniques, Uses and Benefits explains chest physiotherapy for clearing mucus.
References
Mayo Clinic Staff. Atelectasis - Symptoms and causes. Mayo Clinic. November 8, 2023. https://www.mayoclinic.org/diseases-conditions/atelectasis/symptoms-causes/syc-20369684
Mayo Clinic Staff. Atelectasis - Diagnosis and treatment. Mayo Clinic. November 8, 2023. https://www.mayoclinic.org/diseases-conditions/atelectasis/diagnosis-treatment/drc-20369688
Duggan M, Kavanagh BP. Pulmonary atelectasis: a pathogenic perioperative entity. Anesthesiology. 2005;102(4):838-854. PMID: 15791115. DOI: 10.1097/00000542-200504000-00021.
Deng QW, Tan WC, Zhao BC, et al. Intraoperative ventilation strategies to prevent postoperative pulmonary complications: a network meta-analysis of randomised controlled trials. Br J Anaesth. 2020;124(3):324-335. PMID: 32007240. DOI: 10.1016/j.bja.2019.10.024.
do Nascimento Junior P, Módolo NSP, Andrade S, et al. Incentive spirometry for prevention of postoperative pulmonary complications in upper abdominal surgery. Cochrane Database Syst Rev. 2014;2014(2):CD006058. PMID: 24510642. DOI: 10.1002/14651858.CD006058.pub3.
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