Acute respiratory distress syndrome (ARDS) occurs when lung swelling causes fluid to build up in the tiny elastic air sacs in the lungs. These air sacs, called alveoli, have a protective membrane, but lung swelling damages that membrane. The fluid leaking into the air sacs keeps the lungs from filling with enough air. This means less oxygen reaches the bloodstream, so the body's organs don't get the oxygen they need to work properly.

ARDS usually occurs in people who are already critically ill or have major injuries. People usually are severely short of breath — the main symptom of ARDS — within a few hours to a few days after the injury or infection that caused ARDS.

Many people who get ARDS don't survive. The risk of death gets higher with age and how severe the illness is. Of the people who survive ARDS, some fully recover. But others have lasting lung damage.

The seriousness of ARDS symptoms can vary depending on what's causing them and whether there is underlying heart or lung disease. Symptoms include:

• Severe shortness of breath.
• Labored and rapid breathing that is not usual.
• Cough.
• Chest discomfort.
• Fast heart rate.
• Confusion and extreme tiredness.

Most people who get ARDS already are in a hospital for another condition. Many are critically ill. People are especially at risk if they have an infection, such as sepsis or pneumonia. They're also at higher risk if they have COVID-19, especially if they also have metabolic syndrome.

People who have alcohol use disorder or who use recreational drugs or smoke ― lifestyle habits that can harm the lungs ― are at higher risk of getting ARDS. Having a history of alcohol, drug or tobacco use also raises the risk of ARDS.

ARDS can cause other medical problems while in the hospital, including:

• Blood clots. Lying still in the hospital while you're on a ventilator can make it more likely that you'll get blood clots, particularly in the deep veins in your legs. If a clot forms in your leg, a portion of it can break off and travel to one or both of your lungs, where it can block blood flow. This is called a pulmonary embolism.
• Collapsed lung, also called pneumothorax. In most people with ARDS, a breathing machine called a ventilator brings more oxygen into the body and forces fluid out of the lungs. But the pressure and air volume of the ventilator can force gas to go through a small hole in the very outside of a lung and cause that lung to collapse.
• Infections. A ventilator attaches to a tube inserted in your windpipe. This makes it much easier for germs to infect and injure your lungs.
• Scarred and damaged lungs, known as pulmonary fibrosis. Scarring and thickening of the tissue between the air sacs in the lungs can occur within a few weeks of the start of ARDS. This makes your lungs stiffer, and it's even harder for oxygen to flow from the air sacs into your bloodstream.
• Stress ulcers. Extra acid that your stomach makes because of serious illness or injury can irritate the stomach lining and lead to ulcers.

Thanks to better treatments, more people are surviving ARDS. But many survivors end up with potentially serious and sometimes lasting effects:

• Breathing problems. After having ARDS, many people get most of their lung function back within several months to several years, but others may have breathing problems for the rest of their lives. Even people who do well usually have shortness of breath and fatigue and may need extra oxygen at home for a few months.
• Depression. Most ARDS survivors also report going through a period of depression, which can be treated.
• Problems with memory and thinking clearly. Sedatives and low levels of oxygen in the blood can lead to memory loss and learning problems after ARDS. In some people, the effects may get better over time. But in others, the damage may last for the rest of their lives.
• Tiredness and muscle weakness. Being in the hospital and on a ventilator can cause your muscles to weaken. You also may feel very tired after treatment.

There's no specific test for ARDS. Healthcare professionals base the diagnosis on physical exams, chest X-rays and oxygen levels. It's also important to rule out other diseases and conditions, such as certain heart problems that can lead to similar symptoms.

Imaging

A chest X-ray can show which parts of your lungs, and how much of the lungs, have fluid in them and whether your heart has gotten bigger. Another test called a CT scan combines X-ray images taken from many directions and creates cross-sectional views of internal organs. CT scans can give detailed information about the structures within the heart and lungs.

Lab tests

A test using blood from an artery can measure your oxygen level. Other types of blood tests can check for symptoms of infection or other medical conditions. If your healthcare professional thinks that you have a lung infection, secretions from your airway may be tested to find the cause of the infection.

Heart tests

Because the symptoms of ARDS are like those of certain heart problems, your healthcare professional may recommend heart tests such as:

• Electrocardiogram. This painless test, which also is known as an ECG, tracks the electrical activity in your heart. During the test, a healthcare professional attaches several wired sensors to your body.
• Echocardiogram. This test uses sound waves to create pictures of the heart. It shows how blood moves through the heart chambers and heart valves, and whether there are changes in the structures of your heart.

The first goal in treating ARDS is to improve the levels of oxygen in your blood. Without oxygen, your organs can't work properly.

Oxygen

To get more oxygen into your bloodstream, your healthcare professional likely will use:

• Extra oxygen. For milder symptoms or as a short-term treatment, oxygen may be delivered through a mask that fits tightly over your nose and mouth.
• Mechanical ventilation. Most people with ARDS need the help of a machine to breathe. A mechanical ventilator pushes air into your lungs and forces some of the fluid out of the air sacs.

Extracorporeal membrane oxygenation (ECMO)

ECMO may be an option for severe ARDS when other treatment options, such as mechanical ventilation, don't work. ECMO takes over for the heart, lungs or both for a limited time while the lungs rest and heal. This treatment can help when the body can't provide the tissues with enough oxygen.

The ECMO machine is an artificial heart and lung, removing blood from the body through tubes and pumping the blood through the artificial lung. This process removes carbon dioxide and adds oxygen. Then the machine pumps the blood back into the body. Because of the risks involved, it's important to discuss the pros and cons of ECMO with your healthcare team.

Prone positioning

For some people with ARDS, positioning on the stomach — what's known as a prone position — during mechanical ventilation may make more oxygen available to the lungs.

Fluids

Carefully managing the amount of IV fluids given to people with ARDS is very important. Giving too much fluid can make more fluid build up in the lungs. Giving too little fluid can strain the heart and other organs, leading to shock.

Medication

People with ARDS usually get medicine to:

• Prevent and treat infections.
• Ease pain and discomfort.
• Prevent blood clots in the legs and lungs.
• Reduce gastric acid reflux as much as possible.
• Help them feel calm or less anxious.

Lung transplant

When other treatments don't help, lung transplant may be an option for some carefully chosen people who have ARDS. Usually, these are people who were healthy before they developed severe ARDS. Because lung transplant is such a hard process, it should be done at a center that has highly skilled, experienced surgeons and transplant teams.

If you're recovering from ARDS, these suggestions can help protect your lungs:

• Quit smoking. If you smoke, seek help to quit. Also, stay away from secondhand smoke whenever you can.
• Get vaccinated. Getting the flu, also called influenza, shot every year, as well as the pneumonia vaccine as often as recommended, can lower your risk of lung infections.
• Attend pulmonary rehabilitation. Many medical centers now offer pulmonary rehabilitation programs that include exercise training, education and counseling to help you learn how to get back to your usual activities and get to your ideal weight.

Recovery from ARDS can take time, and you're likely to need plenty of support. Although everyone's recovery is different, being aware of common challenges that others with the condition have had can help.

Consider these tips:

• Ask for help. Be sure you have help with everyday tasks until you know what you can manage on your own. This is particularly important when you come home from the hospital.
• Join a support group. There are support groups for people with lifelong lung problems. Discover what's available in your community or online and consider joining others with similar experiences.
• Seek professional help. If you have symptoms of depression, such as hopelessness and loss of interest in your usual activities, tell your healthcare professional or contact a mental health professional. Depression is common in people who have had ARDS, and treatment can help.