For more information, visit http://www.nhlbi.nih.gov/health/health-topics/topics/ards/

What Is ARDS?

ARDS, or acute respiratory distress syndrome, is a lung condition that leads to low oxygen levels in the blood. ARDS can be life threatening because your body's organs need oxygen-rich blood to work well.

People who develop ARDS often are very ill with another disease or have major injuries. They might already be in the hospital when they develop ARDS.

Overview

To understand ARDS, it helps to understand how the lungs work. When you breathe, air passes through your nose and mouth into your windpipe. The air then travels to your lungs' air sacs. These sacs are called alveoli (al-VEE-uhl-eye).

Small blood vessels called capillaries (KAP-ih-lare-ees) run through the walls of the air sacs. Oxygen passes from the air sacs into the capillaries and then into the bloodstream. Blood carries the oxygen to all parts of the body, including the body's organs.

In ARDS, infections, injuries, or other conditions cause fluid to build up in the air sacs. This prevents the lungs from filling with air and moving enough oxygen into the bloodstream.

As a result, the body's organs (such as the kidneys and brain) don't get the oxygen they need. Without oxygen, the organs may not work well or at all.

People who develop ARDS often are in the hospital for other serious health problems. Rarely, people who aren't hospitalized have health problems that lead to ARDS, such as severe pneumonia.

If you have trouble breathing, call your doctor right away. If you have severe shortness of breath, call 9–1–1.

Outlook

More people are surviving ARDS now than in the past. One likely reason for this is that treatment and care for the condition have improved. Survival rates for ARDS vary depending on age, the underlying cause of ARDS, associated illnesses, and other factors.

Some people who survive recover completely. Others may have lasting damage to their lungs and other health problems.

Researchers continue to look for new and better ways to treat ARDS.

Other Names for ARDS

Acute lung injury
Adult respiratory distress syndrome
Increased-permeability pulmonary edema
Noncardiac pulmonary edema

In the past, ARDS was called stiff lung, shock lung, and wet lung.

What Causes ARDS?

Many conditions or factors can directly or indirectly injure the lungs and lead to ARDS. Some common ones are:

Sepsis. This is a condition in which bacteria infect the bloodstream.
Pneumonia. This is an infection in the lungs.
Severe bleeding caused by an injury to the body.
An injury to the chest or head, like a severe blow.
Breathing in harmful fumes or smoke.
Inhaling vomited stomach contents from the mouth.

It's not clear why some very sick or seriously injured people develop ARDS and others don't. Researchers are trying to find out why ARDS develops and how to prevent it.

Who Is at Risk for ARDS?

People at risk for ARDS have a condition or illness that can directly or indirectly injure their lungs.

Direct Lung Injury

Conditions that can directly injure the lungs include:

Pneumonia. This is an infection in the lungs.
Breathing in harmful fumes or smoke.
Inhaling vomited stomach contents from the mouth.
Using a ventilator. This is a machine that supports breathing; however, the pressure from a ventilator sometimes can injure the lungs.
Nearly drowning.

Indirect Lung Injury

Conditions that can indirectly injure the lungs include:

Sepsis. This is a condition in which bacteria infect the bloodstream.
Severe bleeding caused by an injury to the body or having many blood transfusions.
An injury to the chest or head, such as a severe blow.
Pancreatitis (PAN-kre-ah-TI-tis). This is a condition in which the pancreas becomes irritated or infected. The pancreas is a gland that releases enzymes and hormones.
Fat embolism (EM-bo-lizm). This is a condition in which fat blocks an artery. A physical injury, like a broken bone, can lead to a fat embolism.
Drug reaction.

What Are the Signs and Symptoms of ARDS?

The first signs and symptoms of ARDS are feeling like you can't get enough air into your lungs, rapid breathing, and a low blood oxygen level.

Other signs and symptoms depend on the cause of ARDS. They may occur before ARDS develops. For example, if pneumonia is causing ARDS, you may have a cough and fever before you feel short of breath.

Sometimes people who have ARDS develop signs and symptoms such as low blood pressure, confusion, and extreme tiredness. This may mean that the body's organs, such as the kidneys and heart, aren't getting enough oxygen-rich blood.

People who develop ARDS often are in the hospital for other serious health problems. Rarely, people who aren't hospitalized have health problems that lead to ARDS, such as severe pneumonia.

If you have trouble breathing, call your doctor right away. If you have severe shortness of breath, call 9–1–1.

Complications From ARDS

If you have ARDS, you can develop other medical problems while in the hospital. The most common problems are:

Infections. Being in the hospital and lying down for a long time can put you at risk for infections, such as pneumonia. Being on a ventilator also puts you at higher risk for infections.
A pneumothorax (collapsed lung). This is a condition in which air or gas collects in the space around the lungs. This can cause one or both lungs to collapse. The air pressure from a ventilator can cause this condition.
Lung scarring. ARDS causes the lungs to become stiff (scarred). It also makes it hard for the lungs to expand and fill with air. Being on a ventilator also can cause lung scarring.
Blood clots. Lying down for long periods can cause blood clots to form in your body. A blood clot that forms in a vein deep in your body is called a deep vein thrombosis. This type of blood clot can break off, travel through the bloodstream to the lungs, and block blood flow. This condition is called pulmonary embolism.

How Is ARDS Diagnosed?

Your doctor will diagnose ARDS based on your medical history, a physical exam, and test results.

Medical History

Your doctor will ask whether you have or have recently had conditions that could lead to ARDS. For a list of these conditions, go to "Who Is at Risk for ARDS?"

Your doctor also will ask whether you have heart problems, such as heart failure. Heart failure can cause fluid to build up in your lungs.

Physical Exam

ARDS may cause abnormal breathing sounds, such as crackling. Your doctor will listen to your lungs with a stethoscope to hear these sounds.

He or she also will listen to your heart and look for signs of extra fluid in other parts of your body. Extra fluid may mean you have heart or kidney problems.

Your doctor will look for a bluish color on your skin and lips. A bluish color means your blood has a low level of oxygen. This is a possible sign of ARDS.

Diagnostic Tests

You may have ARDS or another condition that causes similar symptoms. To find out, your doctor may recommend one or more of the following tests.

Initial Tests

The first tests done are:

An arterial blood gas test. This blood test measures the oxygen level in your blood using a sample of blood taken from an artery. A low blood oxygen level might be a sign of ARDS.
Chest x ray. This test creates pictures of the structures in your chest, such as your heart, lungs, and blood vessels. A chest x ray can show whether you have extra fluid in your lungs.
Blood tests, such as a complete blood count, blood chemistries, and blood cultures. These tests help find the cause of ARDS, such as an infection.
A sputum culture. This test is used to study the spit you've coughed up from your lungs. A sputum culture can help find the cause of an infection.

Other Tests

Other tests used to diagnose ARDS include:

Chest computed tomography (to-MOG-rah-fee) scan, or chest CT scan. This test uses a computer to create detailed pictures of your lungs. A chest CT scan may show lung problems, such as fluid in the lungs, signs of pneumonia, or a tumor.
Heart tests that look for signs of heart failure. Heart failure is a condition in which the heart can't pump enough blood to meet the body's needs. This condition can cause fluid to build up in your lungs.

How Is ARDS Treated?

ARDS is treated in a hospital's intensive care unit. Current treatment approaches focus on improving blood oxygen levels and providing supportive care. Doctors also will try to pinpoint and treat the underlying cause of the condition.

Oxygen Therapy

One of the main goals of treating ARDS is to provide oxygen to your lungs and other organs (such as your brain and kidneys). Your organs need oxygen to work properly.

Oxygen usually is given through nasal prongs or a mask that fits over your mouth and nose. However, if your oxygen level doesn't rise or it's still hard for you to breathe, your doctor will give you oxygen through a breathing tube. He or she will insert the flexible tube through your mouth or nose and into your windpipe.

Before inserting the tube, your doctor will squirt or spray a liquid medicine into your throat (and possibly your nose) to make it numb. Your doctor also will give you medicine through an intravenous (IV) line in your bloodstream to make you sleepy and relaxed.

The breathing tube will be connected to a machine that supports breathing (a ventilator). The ventilator will fill your lungs with oxygen-rich air.

Your doctor will adjust the ventilator as needed to help your lungs get the right amount of oxygen. This also will help prevent injury to your lungs from the pressure of the ventilator.

You'll use the breathing tube and ventilator until you can breathe on your own. If you need a ventilator for more than a few days, your doctor may do a tracheotomy (tra-ke-OT-o-me).

This procedure involves making a small cut in your neck to create an opening to the windpipe. The opening is called a tracheostomy (TRA-ke-OS-to-me). Your doctor will place the breathing tube directly into the windpipe. The tube is then connected to the ventilator.

For more information, go to the Health Topics Oxygen Therapy article.

Supportive Care

Supportive care refers to treatments that help relieve symptoms, prevent complications, or improve quality of life. Supportive approaches used to treat ARDS include:

Medicines to help you relax, relieve discomfort, and treat pain.
Ongoing monitoring of heart and lung function (including blood pressure and gas exchange).
Nutritional support. People who have ARDS often suffer from malnutrition. Thus, extra nutrition may be given through a feeding tube.
Treatment for infections. People who have ARDS are at higher risk for infections, such as pneumonia. Being on a ventilator also increases the risk of infections. Doctors use antibiotics to treat pneumonia and other infections.
Prevention of blood clots. Lying down for long periods can cause blood clots to form in the deep veins of your body. These clots can travel to your lungs and block blood flow (a condition called pulmonary embolism). Blood-thinning medicines and other treatments, such as compression stocking (stockings that create gentle pressure up the leg), are used to prevent blood clots.
Prevention of intestinal bleeding. People who receive long-term support from a ventilator are at increased risk of bleeding in the intestines. Medicines can reduce this risk.
Fluids. You may be given fluids to improve blood flow through your body and to provide nutrition. Your doctor will make sure you get the right amount of fluids. Fluids usually are given through an IV line inserted into one of your blood vessels.

Living With ARDS

Some people fully recover from ARDS. Others continue to have health problems. After you go home from the hospital, you may have one or more of the following problems:

Shortness of breath. After treatment, many people who have ARDS recover close-to-normal lung function within 6 months. For others, it may take longer. Some people have breathing problems for the rest of their lives.
Tiredness and muscle weakness. Being in the hospital and on a ventilator (a machine that supports breathing) can cause your muscles to weaken. You also may feel very tired following treatment.
Depression. Many people who've had ARDS feel depressed for a while after treatment.
Problems with memory and thinking clearly. Certain medicines and a low blood oxygen level can cause these problems.

These health problems may go away within a few weeks, or they may last longer. Talk with your doctor about how to deal with these issues. Also, see the suggestions below.

Getting Help

You can take steps to recover from ARDS and improve your quality of life. For example, ask your family and friends for help with everyday activities.

If you smoke, quit. Smoking can worsen lung problems. Talk to your doctor about programs and products that can help you quit. Also, try to avoid secondhand smoke and other lung irritants, such as harmful fumes.

If you have trouble quitting smoking on your own, consider joining a support group. Many hospitals, workplaces, and community groups offer classes to help people quit smoking.

For more information about how to quit smoking, go to the Health Topics Smoking and Your Heart article and the National Heart, Lung, and Blood Institute's (NHLBI's) "Your Guide to a Healthy Heart." Although these resources focus on heart health, they include general tips on how to quit smoking.

Go to pulmonary rehabilitation (rehab) if your doctor recommends it. Rehab might include exercise training, education, and counseling. Rehab can teach you how to return to normal activities and stay active.

Your rehab team might include doctors, nurses, and other specialists. They will work with you to create a program that meets your needs.

Emotional Issues and Support

Living with ARDS may cause fear, anxiety, depression, and stress. Talk about how you feel with your health care team. Talking with a professional counselor also can help. If you're very depressed, your doctor may recommend medicines or other treatments that can improve your quality of life.

Joining a patient support group may help you adjust to living with ARDS. You can see how other people who have the same symptoms have coped with them. Talk to your doctor about local support groups or check with an area medical center.

Support from family and friends also can help relieve stress and anxiety. Let your loved ones know how you feel and what they can do to help you.

Clinical Trials

The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.

NHLBI-supported research has led to many advances in medical knowledge and care. However, many questions remain about various diseases and conditions, including ARDS.

The NHLBI continues to support research to learn more. For example, NHLBI-supported research on ARDS includes studies that explore:

The long-term outcomes for ARDS patients who receive breathing support from mechanical ventilators
Health outcomes and quality of life for ARDS patients who were enrolled in previous clinical research related to ARDS
New medicines and therapies for treating ARDS

Much of this research depends on the willingness of volunteers to take part in clinical trials. Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions.

For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.

By taking part in a clinical trial, you can gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.

If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.

If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.

For more information about clinical trials related to ARDS, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:

For more information about clinical trials for children, visit the NHLBI's Children and Clinical Studies Web page.

Links to Other Information About ARDS

NHLBI Resources

How the Lungs Work (Health Topics)
Oxygen Therapy (Health Topics)
Pneumonia (Health Topics)
Pulmonary Rehabilitation (Health Topics)
Ventilator/Ventilator Support (Health Topics)

Non-NHLBI Resources

Acute Respiratory Distress Syndrome (MedlinePlus)

Clinical Trials

Children and Clinical Studies
Clinical Trials (Health Topics)
Current Research (ClinicalTrials.gov)
NHLBI Clinical Trials
NIH Clinical Research Trials and You (National Institutes of Health)
ResearchMatch (funded by the National Institutes of Health)