Learn About ARDS | American Lung Association

Learn About ARDS

Acute respiratory distress syndrome (ARDS) is a rapidly progressive disease occurring in critically ill patients. The main complication in ARDS is that fluid leaks into the lungs making breathing difficult or impossible.

Key Facts

  • ARDS occurs when there is trauma to the lungs, either directly or indirectly.
  • Most people who get ARDS are already in the hospital for trauma or illness.
  • ARDS causes fluid to leak into the lungs, making it difficult to get oxygen into the blood.
  • ARDS can be associated with an acute medical problem or procedure.

What Is ARDS?

ARDS is a buildup of fluid in the tiny air sacs in your lungs called alveoli. This means less oxygen can get to your organs, which is very dangerous. ARDS occurs when there is significant trauma that either affects the lungs directly or indirectly. Some examples of trauma include sepsis (a blood infection), breathing in smoke from a house fire, near-drowning, severe pneumonia, major trauma, and shock from any cause. Your body responds to this trauma with an inflammatory reaction that releases numerous natural molecules into the bloodstream. Normally, this inflammatory reaction would be protective and help you fight infection or heal from an injury. However, in some people, these inflammatory molecules lead the smallest blood vessels in the lungs to leak fluid. Fluid leaves these small vessels and goes into the alveoli. The alveoli fill with this fluid making it difficult for oxygen to get into the bloodstream.

How ARDS Affects Your Body

The fluid that leaks into the lungs makes it very difficult to breathe and leads to low oxygen in the blood, or hypoxemia. The fluid in the lungs makes the lungs stiff and difficult to inflate. This increases the work it takes to breathe and get air into your lungs. When the body can't carry out the work of breathing and has low oxygen levels, it causes respiratory failure. In order to improve the amount of oxygen and reduce the work of breathing, most ARDS patients will be placed on a ventilator to support them while the lungs heal. If the inflammation and fluid in the lung(s) persist, some patients will go on to develop scarring in the lungs. This is known as the fibrotic stage of ARDS. It is during this stage that the lung can "pop" and deflate, leading to a collapsed lung, also called a pneumothorax.

How Serious Is ARDS?

There are about 200,000 cases of ARDS each year in the United States. Most people who get ARDS are already in the hospital in critical condition from some other health complication or trauma. ARDS is a very serious disease and even with the best medical care between 30 and 50 percent of those diagnosed with ARDS die of it. Those surviving the disease will often have long hospital stays. One of the biggest problems with this disease is that many patients develop additional complications while they are in the intensive care unit. Some of these complications include pneumonia, collapsed lungs, other infections, severe muscle weakness, confusion, and kidney failure.

This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.


    This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.


    Approved by Scientific and Medical Editorial Review Panel. Last reviewed April 1, 2016.

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