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 tiny air sacs within the lung, called alveoli, lose air.

Atelectasis is one of the most common breathing complications after surgery. It's also a possible complication of other respiratory problems, including cystic fibrosis, lung tumors, chest injuries, fluid in the lung and respiratory weakness. You may develop atelectasis if you breathe in a foreign object.

This condition can make breathing hard, particularly if you already have lung disease. Treatment depends on what's causing the collapse and how severe it is.

The definition of atelectasis is broader than pneumothorax (noo-moe-THOR-aks). Pneumothorax is when air leaks into the space between your lungs and chest wall, causing part or all of a lung to collapse. Pneumothorax is one of several causes of atelectasis.

There may be no clear signs of atelectasis. If you have any 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 it's important to get the right diagnosis and treatment. If your breathing suddenly becomes difficult, get emergency medical help.

A blocked airway can cause atelectasis. This is called obstructive atelectasis. Pressure from outside the lung also can cause atelectasis. This is called nonobstructive atelectasis.

General anesthesia — which brings on a sleeplike state with the use of 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. This can cause the air sacs in your lungs to lose air. Nearly everyone who has major surgery has some amount of atelectasis. It often occurs after heart bypass surgery.

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 can't cough. Drugs given during surgery make you breathe less deeply. So mucus that usually would move out of your lungs may build up in your airways. Suctioning the lungs during surgery helps clear them. But sometimes mucus still builds up. Mucus plugs also are 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.

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. This can lead to the squeezing of your lungs.
• Pleural effusion. This condition involves the buildup of fluid in the space between the lining of your lungs and the inside of your chest wall.
• Pneumonia. Various types of pneumonia, which is a lung infection, can cause atelectasis.
• Pneumothorax. This is when air leaks into the space between your lungs and chest wall, causing 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.

Factors that make you more likely to get atelectasis include:

• Any condition that makes it hard to swallow.
• Needing to stay in bed over a long time and not having 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 may make it painful to cough or cause weak breathing, including stomach pain or a broken rib.
• Smoking.

A small area of atelectasis, especially in adults, usually can be treated. These complications may come from atelectasis:

• 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.

Atelectasis in children is often caused by a blockage in the airway. To lower the risk of atelectasis, keep small objects out of the reach of children.

In adults, atelectasis most commonly occurs after major surgery. If you're 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.

A doctor's examination and plain chest X-ray may be all that's needed to diagnose atelectasis. But other tests may be done to confirm the source of symptoms or figure out the type or severity of atelectasis.

These tests include:

• CT scan. A CT may be better than an X-ray at finding the cause and type of atelectasis.
• Oximetry. This simple test uses a small device placed on one of your fingers to measure your blood oxygen level. It helps in finding out how severe the atelectasis is.
• Chest ultrasound. This test uses sound waves to create detailed images of structures inside your chest. A small, hand-held device is pressed against your chest and moved as needed to capture the images. It can find the causes of atelectasis, such as pneumothorax, where air leaks into the space between the lungs and chest wall, and pleural effusion, where fluid builds up around the lungs.
• Bronchoscopy. During this test, a flexible, lighted tube is placed down your throat. It allows your doctor to see what may be causing a blockage. Possible causes include a mucus plug, tumor or foreign body. This test also may be used to take out blockages.

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.

Chest physical therapy

Chest physical therapy, also called chest physiotherapy, is a group of airway clearance techniques. They help you breathe deeply after surgery to expand collapsed lung tissue. It's best to learn these techniques before surgery.

These techniques include:

• Doing deep-breathing exercises using a hand-held device called an incentive spirometer, followed by deep coughing to help clear your lungs. This technique can help get rid of mucus and other secretions. And it can help your lung go back to its larger size.
• Positioning your body so that your head is lower than your chest. This allows mucus to drain better from the bottom of your lungs.
• Tapping on your chest over the collapsed area to loosen mucus. This technique is called percussion. You also can use mechanical mucus clearance devices, such as an air pulse vibrator vest or a hand-held instrument.

Surgery

Suctioning mucus or doing 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 some people who are too weak to cough and have low oxygen levels, also called hypoxemia, after surgery.

Unless you need emergency care, you're 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. This is a doctor who specializes in lung conditions.

Here's some information to help you prepare for your appointment.

What you can do

To prepare for your appointment, make a list of:

• Symptoms you're having, including any that don't seem to be 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're taking.
• Questions for your doctor.

Questions to ask your doctor

Ask your doctor questions such as:

• 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?

Don't hesitate to ask other questions during your appointment if you don't understand something or need more information.

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.