Atelectasis is the partial or complete collapse of lung tissue, specifically the tiny air sacs called alveoli. When these sacs deflate, they can no longer exchange oxygen and carbon dioxide with your bloodstream, which means less oxygen reaches your organs and tissues. It ranges from a small, barely noticeable patch to the collapse of an entire lobe, and it is one of the most common complications after surgery.
How Lung Collapse Happens
Your lungs contain millions of alveoli, grape-like clusters where oxygen passes into your blood and carbon dioxide passes out. Atelectasis occurs when something prevents these sacs from staying inflated. The result is a section of lung that essentially goes offline: blood still flows past those alveoli, but no fresh air meets it. If enough tissue is affected, your blood oxygen level drops.
There are several distinct ways this can happen, and they fall into a few categories based on the underlying mechanism.
Resorptive (obstructive) atelectasis is the most common type. Something blocks an airway, whether it’s a mucus plug, an inhaled object, or a tumor. The air already trapped beyond the blockage gradually absorbs into the bloodstream, and with no new air flowing in, the alveoli collapse flat.
Compression atelectasis occurs when something outside the lung pushes inward. A mass in the chest wall, a collection of fluid between the lung and rib cage (pleural effusion), or even a significantly enlarged heart can squeeze air out of the alveoli.
Relaxation (passive) atelectasis happens when the normal negative pressure that keeps the lung expanded is lost. A pneumothorax (air leak into the chest cavity) or a large pleural effusion separates the two layers of tissue that normally hold the lung open, and the lung partially deflates like a balloon losing suction against a wall.
Cicatrization (scarring) atelectasis results from severe lung scarring, often from diseases like tuberculosis or necrotizing pneumonia. The scar tissue contracts and physically prevents the alveoli from opening fully.
Common Causes and Risk Factors
Surgery is the single biggest risk factor, especially operations involving the chest or abdomen. Pulmonary complications occur in an estimated 9 to 40 percent of patients after major abdominal surgery, and that figure climbs as high as 69 percent after cardiothoracic procedures. Atelectasis is the most frequently encountered of these complications. General anesthesia contributes because it relaxes the breathing muscles, reduces lung volume, and can impair the natural surfactant that keeps alveoli open.
Outside the operating room, common culprits include mucus plugs (especially in people with asthma, cystic fibrosis, or chronic bronchitis), tumors that press on or grow into airways, inhaled foreign objects (more common in young children), and prolonged bed rest or shallow breathing from rib fractures or pain. Obesity increases risk because extra weight on the chest wall compresses the lower lung zones, particularly when lying flat.
What Atelectasis Feels Like
Small areas of collapse often produce no symptoms at all. Middle lobe syndrome, where part of the right middle lobe collapses, is frequently discovered on imaging done for another reason. When symptoms do appear, they typically include shortness of breath, a feeling of not being able to take a full breath, and sometimes a dry, hacking cough.
Larger or rapidly developing collapse is more dramatic. You may notice a fast heart rate, rapid breathing, and a noticeable dip in energy. In severe cases, blood pressure can drop, fever can develop, and oxygen levels can fall low enough to cause confusion or bluish discoloration of the lips and fingertips. Slowly developing atelectasis tends to be far more subtle, producing only mild breathlessness that you might chalk up to deconditioning or fatigue.
How It’s Diagnosed
A chest X-ray is usually the first step. Collapsed lung tissue appears as a dense, white area, and the surrounding structures often shift toward the affected side. The trachea (windpipe) and heart may visibly pull in that direction, and the diaphragm on the affected side may appear elevated.
On physical exam, a doctor may hear diminished or absent breath sounds over the collapsed area and notice dullness when tapping on the chest. Chest movement on the affected side is often visibly reduced compared to the other side. A CT scan provides a more detailed picture and can help distinguish atelectasis from pneumonia or a mass, which sometimes look similar on a plain X-ray.
Treatment and Recovery
Treatment depends entirely on the cause and the size of the collapse. For many post-surgical patients, the fix is straightforward: deep breathing exercises, coughing, and getting out of bed as soon as safely possible. These simple measures re-expand the collapsed alveoli by increasing airflow and clearing mucus.
Chest physiotherapy, sometimes called chest percussion, involves rhythmic tapping on the chest wall over the collapsed area to loosen and mobilize mucus. This can be done by a respiratory therapist using cupped hands or with mechanical devices like an air-pulse vibrator vest or a handheld oscillating tool. It’s particularly helpful when thick secretions are the problem.
When someone is too weak to cough effectively or has low oxygen levels after surgery, continuous positive airway pressure (CPAP) can help. The device delivers a steady stream of pressurized air through a mask, gently splinting the airways open and coaxing collapsed tissue back into service.
If a mucus plug or foreign object is causing the blockage and simpler methods haven’t worked, a bronchoscopy may be needed. During this procedure, a thin, flexible tube is guided through the mouth or nose and into the airways, allowing the doctor to suction out mucus or remove whatever is blocking airflow. When a tumor is responsible, it can sometimes be treated or reduced during the same procedure.
Potential Complications
Most cases of atelectasis resolve without lasting damage, especially when caught early. The main concern with persistent collapse is low blood oxygen, or hypoxemia. When alveoli stay deflated, oxygen simply can’t reach the bloodstream in that region of the lung, and if a large enough area is involved, the rest of the lung may not be able to compensate.
Collapsed lung tissue is also more vulnerable to infection. Stagnant mucus and poor ventilation create a favorable environment for bacteria, so untreated atelectasis can progress to pneumonia. This is one reason hospitals emphasize early mobilization and breathing exercises after surgery. In rare, severe cases where a large portion of the lung remains collapsed and oxygen levels stay critically low, respiratory failure can develop.
Prevention After Surgery
An incentive spirometer is the most widely used prevention tool in hospitals. It’s a simple handheld plastic device with a mouthpiece and a chamber that measures how deeply you inhale. The goal is to take slow, deep breaths that fully expand your lungs, then hold each breath for at least five seconds. The recommended frequency is at least 10 breaths every hour while you’re awake. A yellow marker on the side of the device tracks your best effort, giving you a target to work toward with each session.
Beyond the spirometer, the most effective prevention strategies are also the simplest: sitting upright rather than lying flat, walking as soon as your surgical team gives the go-ahead, and managing pain well enough that you can take deep breaths without splinting. If you smoke, quitting before a planned surgery meaningfully reduces the risk of postoperative lung complications, including atelectasis.