Atelectasis is the partial or complete collapse of lung tissue. It happens when the tiny air sacs in your lungs, called alveoli, deflate or fill with fluid, reducing the amount of oxygen that reaches your blood. It is one of the most common lung complications after surgery, affecting roughly 9 to 40% of patients after major abdominal operations and up to 69% after cardiothoracic procedures. Collapsed lung tissue has been found in about 90% of people under general anesthesia.
How Lung Tissue Collapses
Your lungs contain millions of alveoli, grape-like clusters where oxygen passes into the bloodstream. These air sacs stay open thanks to a combination of air pressure inside them and a slippery coating called surfactant that keeps their walls from sticking together. Atelectasis occurs when something disrupts that balance through one of three basic mechanisms: pressure from outside the lung squeezing the air sacs shut, a blockage preventing air from reaching them, or a breakdown in the surfactant coating that normally keeps them inflated.
When air can no longer flow into a section of alveoli, the oxygen already trapped inside gets absorbed into the blood within minutes to hours. With nothing left to hold the air sacs open, they collapse inward. The affected area of lung essentially goes offline, unable to participate in gas exchange. If enough tissue is involved, blood oxygen levels drop noticeably.
Obstructive vs. Nonobstructive Types
Atelectasis falls into two broad categories based on what triggers the collapse.
Obstructive atelectasis happens when something physically blocks an airway. Mucus plugs are the most common culprit, especially after surgery when coughing is painful and secretions build up. Tumors, inhaled foreign objects (particularly in children), and blood clots can also block airways. Once blocked, the air trapped beyond the obstruction absorbs into the bloodstream, and the downstream lung tissue deflates. Children are especially vulnerable because their lungs have fewer backup pathways for air to reroute around a blockage. Adults with chronic lung disease, by contrast, tend to have extensive collateral airways that make this type less likely.
Nonobstructive atelectasis covers everything else. The most common form is compression atelectasis, where something outside the lung pushes inward and squeezes air sacs shut. Fluid buildup around the lung, a collapsed lung (pneumothorax), abdominal swelling, or a tumor pressing on lung tissue can all cause this. Another form involves surfactant breakdown: when the coating inside alveoli stops working properly, surface tension pulls the walls together and the air sacs stick shut. This is what happens in acute respiratory distress syndrome in adults and respiratory distress syndrome in premature newborns. Lung scarring from conditions like tuberculosis or pulmonary fibrosis can also permanently collapse sections of tissue.
Why Surgery Is the Most Common Trigger
General anesthesia is by far the leading cause of atelectasis. Computed tomography studies show that collapsed lung tissue appears in approximately 90% of people during anesthesia, whether they are breathing on their own or on a ventilator, and regardless of whether the anesthetic is inhaled or injected. Anesthesia relaxes the muscles that normally keep the chest wall expanded, reduces the volume of air remaining in the lungs between breaths, and suppresses the natural deep-breathing and sighing reflexes that periodically re-expand alveoli throughout the day.
The type of surgery matters too. Abdominal and chest operations carry the highest risk because pain at the incision site makes patients reluctant to take deep breaths or cough afterward. One study of pediatric patients undergoing gastrointestinal surgery found radiographic evidence of atelectasis in about 25.6% on the first day after their procedure. High concentrations of supplemental oxygen during surgery also contribute: oxygen absorbs into the blood much faster than nitrogen, so when alveoli are filled with oxygen-rich gas, they deflate more quickly once airflow slows.
What Atelectasis Feels Like
Small areas of atelectasis often cause no symptoms at all and may only show up incidentally on a chest X-ray. When a larger portion of lung is involved, the most common signs are shortness of breath and a feeling that you can’t get a full breath. You may notice rapid, shallow breathing and a faster heart rate as your body tries to compensate for lower oxygen levels. Some people develop a mild cough, though this is not always present.
In more significant cases, oxygen levels in the blood drop enough to cause fatigue, confusion, or a bluish tint to the lips and fingertips. If atelectasis develops after surgery, it typically appears within the first 24 to 48 hours and may initially be mistaken for the general grogginess of recovery. Persistent atelectasis that goes unaddressed can lead to pneumonia, because collapsed, mucus-filled lung tissue creates an ideal environment for bacteria to grow. In severe or widespread cases, it can progress to respiratory failure.
How It Shows Up on Imaging
Chest X-rays are usually the first tool used to spot atelectasis. The hallmark signs include a visible area of increased density (whiteness) where the lung has collapsed, reduced volume in the affected lobe, and a shift of nearby structures toward the collapsed area. The diaphragm on the affected side may appear elevated, and the spaces between the ribs may look narrower.
CT scans provide more detail and are especially useful when the X-ray findings are ambiguous or when a specific type called rounded atelectasis needs to be distinguished from a lung mass. On CT, rounded atelectasis appears as a soft-tissue-density lesion hugging the outer surface of the lung, with blood vessels and airways curving into it in a distinctive pattern called the “comet tail” sign. Air-filled bronchi visible within the collapsed tissue (air bronchogram) and thickening of the adjacent lining of the lung are also typical. These features help doctors differentiate atelectasis from a tumor without needing a biopsy.
Treatment and Recovery
Treatment depends on the cause and size of the collapse. For post-surgical atelectasis, which is the scenario most readers will encounter, the cornerstone is getting the lungs re-expanded through a combination of breathing exercises, movement, and pain control.
An incentive spirometer, the clear plastic device you breathe into after surgery, encourages slow, deep inhalation that helps pop collapsed air sacs back open. The standard regimen is about ten deep breaths every hour while you’re awake. But the device alone is not enough. Evidence shows that it works best when combined with directed coughing, deep breathing exercises, adequate pain management to make those deep breaths possible, and getting out of bed as early as your surgical team allows. Simply sitting upright increases the amount of air your lungs hold at rest, which directly counteracts the collapse.
For atelectasis caused by a mucus plug, chest physiotherapy (positioning, percussion, and vibration to loosen secretions) and suctioning can clear the blockage. When fluid or air around the lung is the cause, draining the fluid or releasing the trapped air treats the atelectasis by removing the external pressure. If a tumor is blocking an airway, treating the tumor itself is necessary to restore airflow.
In hospital settings, positive-pressure breathing devices like CPAP or BiPAP may be used to deliver a continuous stream of pressurized air that forces collapsed tissue open. For patients on a ventilator, clinicians use specific techniques like positive end-expiratory pressure and lung recruitment maneuvers to re-inflate affected areas.
Reducing Your Risk Before and After Surgery
If you’re preparing for a planned surgery, learning to use an incentive spirometer before the operation gives you a head start. Patients who practice preoperatively tend to use the device more effectively afterward, when pain and fatigue make it harder to focus on technique.
After surgery, the most effective prevention strategy combines several approaches:
- Deep breathing exercises: Ten slow, full breaths with the incentive spirometer every hour while awake.
- Early movement: Getting out of bed and walking as soon as your care team says it’s safe. Even sitting upright in a chair helps.
- Pain control: Uncontrolled pain makes you breathe shallowly. Staying ahead of pain, ideally with approaches that minimize heavy sedatives, protects your breathing.
- Directed coughing: Controlled coughing helps clear mucus from the airways. Splinting your incision with a pillow reduces discomfort.
During anesthesia itself, surgical teams take steps like using the lowest effective oxygen concentration, applying positive end-expiratory pressure, and performing lung recruitment maneuvers to minimize collapse while you’re under. These measures won’t eliminate post-surgical atelectasis entirely, but they significantly reduce its severity.