The three types of atelectasis are resorption (obstructive), compression, and contraction (cicatrization). Each type describes a different mechanism by which air sacs in the lung lose volume and partially or fully collapse. Understanding which type is involved matters because the underlying cause, and therefore the treatment approach, differs for each.
Resorption (Obstructive) Atelectasis
Resorption atelectasis is the most common type. It happens when something blocks an airway, cutting off the flow of fresh air to the tiny air sacs (alveoli) beyond the blockage. Once that connection is severed, the body’s bloodstream gradually absorbs the trapped gas that remains in those air sacs. With no new air coming in to replace it, the affected portion of lung deflates and collapses inward.
The blockage itself can come from several sources. A mucus plug is one of the most frequent culprits, especially after surgery when coughing and deep breathing are painful and less effective. Tumors growing inside an airway can also create an obstruction, as can an accidentally inhaled object, particularly in young children. In some cases, thick secretions from conditions like cystic fibrosis or severe pneumonia are enough to seal off a bronchial passage. The amount of lung that collapses depends on where the blockage sits. A plug in a main bronchus can take down an entire lobe, while one in a smaller branch may only affect a small segment.
Compression Atelectasis
Compression atelectasis works from the outside in. Instead of a blocked airway, something in the chest cavity presses on the lung tissue and physically squeezes air out of the alveoli. The lung doesn’t lose its airway connection; it simply can’t expand against the external pressure.
The most common causes are fluid or air accumulating in the space between the lung and the chest wall (the pleural space). A pleural effusion, where fluid builds up from heart failure, infection, or cancer, can compress the lower portions of a lung significantly. A pneumothorax, where air leaks into that same space, pushes the lung inward from the surface. Large tumors, an enlarged heart, or even a severely distended abdomen pushing the diaphragm upward can all generate enough pressure to cause compression atelectasis. The key distinction from resorption atelectasis is that the airways remain open. If the pressure source is removed, such as draining the fluid, the lung can often re-expand relatively quickly.
Contraction (Cicatrization) Atelectasis
Contraction atelectasis results from scarring within the lung itself. When lung tissue is damaged by disease or injury, the body replaces normal elastic tissue with stiff scar tissue (fibrosis). That scarring prevents the alveoli from opening properly during a breath. Instead of stretching and filling with air, the scarred region stays contracted and pulls surrounding tissue inward.
This type tends to be permanent or at least very difficult to reverse, because the underlying architecture of the lung has been structurally altered. Conditions that cause widespread lung scarring, such as pulmonary fibrosis, radiation therapy to the chest, or chronic infections like tuberculosis, are typical triggers. Unlike the other two types, contraction atelectasis doesn’t respond to clearing an airway or draining fluid. The damage is baked into the tissue itself.
How Atelectasis Feels
Symptoms depend heavily on how fast the collapse develops and how much lung is involved. A small area of atelectasis after surgery may produce no noticeable symptoms at all, or just a mild cough. Slowly developing atelectasis from a growing tumor might cause only subtle shortness of breath that worsens over weeks.
Rapid collapse of a large section of lung is a different story. When a major airway suddenly becomes blocked or a large pneumothorax develops, you can experience sharp pain on the affected side, sudden difficulty breathing, a fast heart rate, and in severe cases a bluish tint to the skin from low oxygen levels. A persistent dry, hacking cough can also develop, particularly when the middle lobe of the right lung is involved. On a physical exam, the affected side of the chest may move less during breathing, and breath sounds over the collapsed area are diminished or absent.
How Atelectasis Is Detected
A chest X-ray is the primary tool. Radiologists look for direct signs like a visible shift in the normal lung boundaries (fissures) and an opaque, white-out appearance where the collapsed tissue sits. Indirect signs add further evidence: the windpipe or heart may be pulled toward the collapsed side, the diaphragm on that side may sit higher than normal, and the ribs may appear crowded together. When an entire lung collapses, the whole side of the chest appears white on the X-ray, with the central structures of the chest shifted toward the affected side. That shift is actually a useful clue, because a massive fluid collection would push those structures the opposite direction.
How Atelectasis Is Managed
Treatment targets the underlying mechanism. For resorption atelectasis, the goal is to clear the blockage. That might mean suctioning mucus, performing a bronchoscopy to remove an object or plug, or treating a tumor that’s compressing an airway. For compression atelectasis, removing the external pressure is key: draining pleural fluid or releasing trapped air from the chest cavity. Contraction atelectasis has the fewest treatment options, since the scarring is generally irreversible. Management focuses on treating the underlying fibrotic disease and supporting breathing.
Prevention plays a major role, especially around surgery. Postoperative atelectasis is extremely common, with pulmonary complications occurring in an estimated 9 to 40% of major abdominal surgeries and up to 69% of cardiothoracic procedures. Incentive spirometry, a handheld device that encourages slow, deep breaths with visual feedback, is the most widely used tool for prevention and treatment in hospital settings. Positive airway pressure therapies that gently push air into the lungs are also effective but require more specialized equipment. Early mobilization after surgery, pain control that allows comfortable deep breathing, and coughing exercises all help keep the airways open and the alveoli inflated.