Acute Respiratory Distress Syndrome

What Is Acute Respiratory Distress Syndrome?

Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a serious lung condition that causes low blood oxygen. People who develop ARDS are usually ill due to another disease or a major injury.

In ARDS, fluid builds up inside the tiny air sacs of the lungs, and surfactant breaks down. Surfactant is a foamy substance made by your body that keeps your lungs fully expanded so you can breathe. The fluid buildup and lack of surfactant that happen because of ARDS prevent the lungs from properly filling with air and moving enough oxygen into the bloodstream and throughout the body. The lung tissue may scar and become stiff.

What causes acute respiratory distress syndrome?

Damage to the lung’s air sacs (called alveoli) causes ARDS. Fluid from tiny blood vessels leaks through the damaged walls of the air sacs and collects, limiting the lungs’ normal exchange of oxygen and carbon dioxide. The damage also causes inflammation that leads to the breakdown of surfactant — a liquid that helps keep your air sacs open.

The air sacs may become damaged as a result of an illness, such as a lung infection, or breathing in smoke. Other illnesses or injuries may trigger inflammation that damages the air sacs. To understand ARDS, you may also want to read about how the lungs work.

Speak with your doctor if you have any symptoms of ARDS. Your doctor will diagnose ARDS based on your medical history, a physical exam, and test results.

What raises the risk of ARDS?

You may have an increased risk of ARDS because of an infection, environmental exposures, lifestyle habits, or another medical condition. Risk factors can vary depending on your age, overall health, where you live, and the healthcare setting in which you receive care.

When diagnosing ARDS, doctors will use information about causes and risk factors to tailor a treatment that improves oxygen levels and treats underlying causes.

Infection: Infections are the most common risk factors for ARDS. The most common are flu or other virus, such as respiratory syncytial virus and SARS-CoV-2, the virus responsible for COVID-19. 

Other infections may include:

  • Pneumonia
  • Sepsis, a condition in which bacteria infect the bloodstream
  • Uterine infection in the mother, affecting a newborn’s lungs

Environment: Being exposed to air pollution for weeks or months can make you more vulnerable to ARDS.


Lifestyle habits: Habits that harm the health of your lungs increase your risk of ARDS. These include:

  • Heavy alcohol use
  • Overdose of illegal drugs
  • Smoking

Family history and genetics: The gene you inherit may put you at an increased risk for ARDS. These genes play a role in how the lungs respond to damage.

Other medical conditions or procedures

Other medical conditions, injuries, or medical procedures can raise your risk for ARDS. These may include:

  • Inhaling vomit, smoke, chemical fumes, or water during a near drowning
  • Injury: An injury from a blow, burn, or broken bone can lead to ARDS. A broken bone, for example, can lead to a fat embolism, a clot of fat that blocks an arteries.
  • Lung or heart surgery or being placed on a heart-lung bypass machine or ventilator
  • Pancreatitis, a condition in which the pancreas (a gland that releases enzyme and hormone) becomes infected
  • Reaction to medicines, such as those used to treat cancer or arrhythmia

Newborn lung conditions can raise your baby’s risk of neonatal ARDS. These conditions include pneumonia and a condition where the unborn baby passes stool while still in the womb and then inhales the stool into his or her lungs. Your baby is also at higher risk for ARDS if they did not get enough oxygen during delivery.


Difficulty breathing is usually the first symptom of acute respiratory distress syndrome (ARDS). Other symptoms may vary depending on how serious the underlying cause is. ARDS may take several days to develop, or it can rapidly get worse. Complications may include blood clots, infections, additional lung problems, or organ failure.

Warning signs that you are developing or are at risk for ARDS may include:

  • Shortness of breath
  • Fast breathing, or taking lots of rapid, shallow breaths
  • Fast heart rate
  • Coughing that produces phlegm
  • Blue fingernails or blue tone to the skin or lips
  • Extreme tiredness
  • Fever
  • Crackling sound in the lungs
  • Chest pain, especially when trying to breathe deeply
  • Low blood pressure
  • Confusion

To help diagnose ARDS, your doctor may ask you about any medical conditions or recent events that could be considered risk factors. For example, traveling could be a risk factor because of potential exposure to infections that are more common in certain geographic areas.

Your doctor will also ask about your symptoms and whether you have a heart problem, such as heart failure, or another condition that can cause symptoms similar to those for ARDS.

Physical exam

Your doctor will examine you for signs of ARDS. This exam may include:

  • Listening to your lungs through a stethoscope for abnormal breathing sounds, such as crackling
  • Listening to your heart for a fast heart rate
  • Checking for signs that you are having difficulty breathing, such as using muscles in your chest to help you breathe
  • Examining your skin or lips for a bluish tone, which can signal a low blood oxygen level
  • Examining your body for swelling or other signs of extra fluid, which may be linked to heart or kidney problems
  • Measuring your blood pressure and oxygen levels

Diagnostic tests and procedures

To diagnose ARDS, your doctor may have you undergo some of the following tests and procedures. Different tests may be appropriate for different ages and can include:

  • Blood tests measure 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. To confirm the cause of your symptoms, your doctor may also check your blood for signs of infection or a heart problem, or to see how well other organs are working.
  • Other tests of blood oxygen levels, such as pulse oximetry, that do not require collecting a blood sample may be done. For these tests, a sensor is attached to the skin or placed on a hand or foot.
  • Lung imaging tests, such as a chest X-ray or computerized tomography (CT) scan, create detailed images of your lungs.
  • Lung biopsy may be done if other tests do not confirm a diagnosis.

The goal of treatment for ARDS is to improve oxygen levels and treat the underlying cause. Oxygen therapy is the main treatment for ARDS. Other treatments aim to prevent complications and make you comfortable.

Oxygen therapy: Oxygen therapy is a treatment that delivers oxygen for you to breathe. You can receive oxygen therapy from tubes resting in your nose, a face mask, or a tube placed in your trachea (windpipe). You may need oxygen therapy if you have a condition that causes your blood oxygen levels to be too low.

Oxygen therapy can be given for a short or long period of time in the hospital, in another medical setting, or at home. Oxygen poses a fire risk, so you should never smoke or use flammable materials when using oxygen. You may experience side effects from this treatment, such as a dry or bloody nose, tiredness, and morning headaches. Oxygen therapy is generally safe.

Other breathing support: Depending on how serious your symptoms are, your doctor may suggest a device or machine to support your breathing:

  • Noninvasive ventilation, such as use of bilevel positive airway pressure (BiPAP) or continuous positive airway pressure (CPAP) machines, which are electronic breathing devices that help keep your airways open by blowing air through a face mask.
  • ventilator may help restore your blood oxygen levels. Some people transition from a ventilator to portable oxygen therapy. Risks from being on a ventilator include pneumonia and pneumothorax (collapsed lung).

Medicines: Your doctor may recommend medicines to relieve symptoms, treat the underlying cause, or prevent complications from being in a hospital:

  • Acid-reducing medicines prevent stress ulcers, which can cause bleeding in the intestines.
  • Antibiotics treat or prevent infections. If you are on a ventilator, your healthcare team may do tests, such as lung fluid lab tests or CT scans, to look for signs of new infection.
  • Blood thinners stop blood clots from forming or growing larger. Heparin is a common blood thinner for adults.
  • Muscle relaxants help prevent coughing or gagging while on a ventilator or reduce the amount of oxygen your body needs.
  • Sedatives help relieve anxiety, make it easier to breathe on a ventilator, or lower your body’s oxygen needs. Sometimes your doctor may pair a sedative with another medicine to make delivering the oxygen easier. Complications vary depending on the sedative used, the dose, and how long it is used. They can include depression, post-traumatic stress disorder (PTSD), problems with thinking or memory, or a delay in removing the ventilator.
Other treatments

Your doctor may recommend other treatments, including the following:

  • A feeding tube can ensure you get enough of the right nutrients while you are on a ventilator.
  • Blood transfusions treat low hemoglobin levels. Hemoglobin carries oxygen in the blood, so a transfusion can improve the delivery of oxygen to the body’s organs.
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  • Extracorporeal membrane oxygenation (ECMO) or a similar device helps when ventilation alone cannot deliver enough oxygen or while a patient waits for a lung transplant. ECMO works like an artificial lung, removing carbon dioxide and pumping oxygen-rich blood back into the body.
  • Fluid management through an intravenous (IV) line helps restore fluid levels if needed. Low fluid levels in your blood vessels can prevent oxygen from getting to your organs. If you have too much fluid in the lungs, your doctor may give you medicines that help your body get rid of the extra fluid.
  • Lying facedown helps get more oxygen to your lungs.
  • Physical therapy maintains muscle strength and prevent sores from forming. Movement may help shorten the time you are on a ventilator and improve recovery after you leave the hospital.



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