What Are The Three Types Of Atelectasis? Key Information

Atelectasis is the partial or complete collapse of part of a lung. The three main types are obstructive atelectasis, compressive atelectasis, and adhesive atelectasis. Each type has a different cause, and understanding which one is present matters because the underlying problem — a blockage, external pressure, or loss of surfactant — determines how it is treated.

What Are The Three Types Of Atelectasis?

The three types are classified by what is preventing the alveoli from staying open. Alveoli are the tiny air sacs where gas exchange happens. When they collapse, that section of lung can no longer do its job.

Obstructive atelectasis happens when something blocks the airway. Air already in the alveoli gets absorbed into the bloodstream, and because no new air can get in, the sacs collapse. This is the most common type.

Compressive atelectasis happens when something outside the lung pushes against it. The pressure physically squeezes the lung tissue and forces air out of the alveoli. Fluid, air, a tumor, or an enlarged organ in the chest can all do this.

Adhesive atelectasis happens when the alveoli lose the substance that keeps them from sticking shut. That substance is surfactant, a natural mixture of lipids and proteins that reduces surface tension inside the lungs. Without enough of it, the smallest air sacs collapse even when the airway is open and nothing is pressing on the lung.

What Causes Obstructive Atelectasis?

Anything that plugs an airway can cause it. The blockage can sit in a large bronchus or deep in the smaller airways.

Common causes include:

• Mucus plugs, which are especially common after surgery or in people with cystic fibrosis, severe asthma, or chronic bronchitis
• Inhaled objects, more often in children but possible in adults
• Tumors growing into or pressing on an airway
• Enlarged lymph nodes
• Blood clots after trauma or surgery

One detail that surprises many people: when an airway is blocked, the trapped air is absorbed into the blood within hours. The lung tissue does not collapse because of suction from outside. It collapses because the air inside simply disappears and nothing replaces it. This is why obstructive atelectasis can develop fairly quickly.

In adults, a new case of obstructive atelectasis — especially without an obvious cause like recent surgery — sometimes points to an underlying lung tumor. This does not mean every case is cancer. It means the cause needs to be identified, not assumed.

What Causes Compressive Atelectasis?

In compressive atelectasis, the problem is outside the lung. Something in the chest cavity takes up space and pushes the lung inward.

Causes include:

• Pleural effusion — fluid collecting between the lung and the chest wall
• Pneumothorax — air trapped in the pleural space
• An enlarged heart or enlarged lymph nodes
• A mass or tumor in the chest
• An elevated diaphragm, which can happen after abdominal surgery or with certain conditions
• Severe scoliosis or other chest wall deformities

The mechanism is straightforward. The chest cavity has a fixed volume. When something else fills part of that space, the lung has less room and gets squeezed. The alveoli empty and stay empty until the pressure is relieved.

This is why treating compressive atelectasis usually means treating the underlying problem. Draining a pleural effusion or removing air from the pleural space often allows the lung to re-expand on its own. If the cause is a mass, the atelectasis resolves only when the mass is addressed.

What Causes Adhesive Atelectasis?

Adhesive atelectasis is tied to surfactant. Surfactant is produced by special cells in the alveoli called type II pneumocytes. It lines the inside of each air sac and lowers surface tension, which is what keeps the sacs from collapsing every time you exhale.

When surfactant is low or its function is impaired, the alveoli stick together and collapse. This type is seen in a few specific situations:

• Acute respiratory distress syndrome (ARDS), where surfactant production and function are both disrupted
• Neonatal respiratory distress syndrome, which affects premature infants whose lungs have not yet produced enough surfactant
• Pulmonary embolism, where blood flow is blocked and surfactant production in that area drops
• Prolonged shallow breathing, such as after surgery or with certain pain conditions

Adhesive atelectasis is different from the other two types because there is no physical blockage and no external pressure. The airway is open. The problem is at the level of the alveolus itself.

How Do The Three Types Differ?

The table below summarizes the core differences. It is meant as a reference, not a diagnostic tool.

In practice, more than one type can be present at the same time. A person recovering from major surgery might have obstructive atelectasis from mucus plugging and adhesive atelectasis from shallow breathing. Clinicians often treat both at once.

What Are The Symptoms Of Atelectasis?

Small areas of atelectasis may cause no symptoms at all. When symptoms do appear, they depend on how much lung tissue is affected and how quickly it developed.

Common symptoms include:

• Shortness of breath
• Rapid, shallow breathing
• Cough
• Chest pain, especially with deep breaths
• Low oxygen levels, which may show up on a pulse oximeter

Large areas of collapse can cause noticeable drops in blood oxygen. In severe cases, the skin, lips, or fingernails may look blue — a sign called cyanosis that requires urgent medical attention.

One important point: atelectasis itself is not an infection. But collapsed lung tissue can trap mucus and create conditions where pneumonia is more likely to develop. This is one reason why preventing and treating atelectasis matters, especially after surgery.

How Is Atelectasis Diagnosed?

Chest X-ray is usually the first imaging test. It can show areas of increased density, a shifted trachea or mediastinum, or an elevated hemidiaphragm — all signs that part of the lung has collapsed.

CT scan gives more detail and can often show the specific cause, such as a mucus plug, a tumor, or a pleural effusion. When the cause is not clear from imaging, a bronchoscopy may be done. This involves passing a thin, flexible tube with a camera into the airways to look for blockages directly.

Blood tests and pulse oximetry help assess how much the collapse is affecting oxygen levels. These are supportive tests, not diagnostic ones for atelectasis itself.

How Is Atelectasis Treated?

Treatment depends entirely on the type and cause. There is no single approach that works for all three.

For obstructive atelectasis, the goal is to clear the blockage. Techniques may include:

• Deep breathing exercises and incentive spirometry
• Chest physiotherapy and controlled coughing
• Bronchoscopy to remove a mucus plug or foreign object
• Treating the underlying tumor or lymph node enlargement

For compressive atelectasis, the goal is to remove the pressure. This might mean draining a pleural effusion with a needle or chest tube, or removing air from the pleural space in pneumothorax.

For adhesive atelectasis, treatment focuses on the underlying condition. In premature infants, surfactant replacement therapy is a well-established treatment. In ARDS, management centers on supporting breathing and treating the cause of lung injury.

In all types, supplemental oxygen may be used if blood oxygen levels are low. Positive pressure ventilation — either non-invasive or mechanical — can help keep alveoli open when breathing efforts alone are not enough.

What works for one type does not necessarily work for another. Incentive spirometry helps with obstructive and adhesive atelectasis by encouraging deep breaths. It does not fix a lung that is being compressed by a large pleural effusion.

Can Atelectasis Be Prevented?

Some causes cannot be prevented. A tumor or a premature birth is not something a person can control. But certain situations carry a higher risk, and steps can reduce it.

After surgery, the risk of atelectasis is well documented. General anesthesia and pain medications can suppress deep breathing and coughing. This allows mucus to build up and alveoli to collapse. Established preventive measures include:

• Using an incentive spirometer as instructed
• Getting out of bed and moving as soon as it is safe
• Doing deep breathing exercises regularly
• Staying hydrated to keep mucus thinner
• Using pain control that allows for deep breaths without excessive sedation

For people with chronic lung conditions, keeping underlying disease well managed reduces the risk of mucus plugging and airway obstruction. For children, keeping small objects out of reach prevents the kind of inhaled foreign body that can block an airway.

When Should You See A Doctor?

Shortness of breath that is new, worsening, or severe needs medical attention. The same goes for chest pain with breathing, coughing up blood, or a drop in oxygen levels.

Atelectasis can develop quickly, especially after surgery or with a sudden illness. It is not something to wait out if breathing is getting harder.

In many cases, atelectasis is mild and resolves with treatment. In others, it signals a more serious underlying problem that needs to be found and addressed. The three types exist because the causes are different — and so are the solutions.