Acute Respiratory Distress Syndrome (ARDS)

Last Updated 10/25/2022

Author:Nathaniel Marchetti, DO, FCCP

About Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a fast-moving disease that happens in those who are critically ill. The main challenge of ARDS is that fluid leaks into the lung. This makes breathing difficult or even impossible.

Key facts about ARDS
  • ARDS occurs rapidly and leads to lung failure.
  • Most people with ARDS will be on a mechanical ventilator, also known as life support.
  • The main problem in ARDS is that fluid leaks into the lung. This makes it difficult to breathe, and lungs cannot get oxygen into the blood

ARDS occurs when there is an injury to the body. This could be any number of injuries, such as pneumonia, breathing stomach contents into the lung, trauma, swelling (also called inflammation) of the pancreas, any serious infection, smoke inhalation from a house fire, reactions to medication, near drowning, or even blood transfusions.

These injuries result in an inflammatory reaction. This releases body chemicals into the bloodstream. Typically, this reaction would protect the body and help fight infection or heal from an injury. However, in some people these inflammatory chemicals will cause the smallest blood vessels in the lungs to leak fluid.

Fluid leaves these small vessels and goes into the tiny air sacs in our lungs, called alveoli. These tiny air sacs fill with fluid, which then prevents oxygen from getting into the bloodstream.

How ARDS affects your body

The fluid in the lung makes it difficult for you to breath and leads to low oxygen in the blood. This is called hypoxemia. Initially, hypoxemia can be overcome by using oxygen therapy. The fluid in the lungs makes the lung stiff and difficult to inflate. This stiffness increases the amount of work it takes you to breathe and get air into your lungs. The increased work of breathing and low oxygen level are known as respiratory failure.

To improve the amount of oxygen in their blood and reduce the work of breathing, many people are placed on a ventilator to support them while their lung heals. If the inflammation and fluid in the lung grow, some people develop scarring in the lung. This is known as the fibrotic stage of ARDS. During this stage, the lung can “pop” and deflate, leading to a collapsed lung—known as a pneumothorax.

How serious is ARDS?

There are about 200,000 cases of ARDS each year in the United States.

ARDS is a serious disease. The chances of dying from this disease are around 30% to 50%.

Those who survive will often have long hospital stays.

One of the biggest problems is that many people will develop 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.

Symptoms of ARDS

Early on, ARDS may be diagnosed as pneumonia or fluid in the lungs resulting from heart disease, called pulmonary edema. However, your health care provider may suspect ARDS if you don’t get better or have one of the known causes of ARDS.

Symptoms of ARDS include:

  • Shortness of breath, which is usually severe
  • Cough
  • Fever
  • Fast heart rates and rapid breathing
  • Chest pain, especially with inhaling
  • Some people have low oxygen levels. They may have bluish nails and lips from the severely decreased oxygen levels in the blood

What causes ARDS

The causes of ARDS are divided into 2 categories:

  • Direct injuries to the lung. Direct injuries to the lung include pneumonia, breathing stomach contents into the lung, near drowning, lung bruising from trauma (such as a car accident), and smoke inhalation from a house fire.
  • Indirect injuries to the lung. Indirect injuries to the lung include inflammation of the pancreas, severe infection (also known as sepsis), blood transfusions, burns, and reactions to medication.

Fortunately, most people with these problems will not develop ARDS. It isn’t known why some will. In those who develop ARDS, the inflammatory reaction designed to help us heal goes out of control. This leads to fluid leaking from the smallest blood vessels into the lung.

What are the risk factors for ARDS?

It isn’t clear who will develop ARDS, but a few factors may increase the risk of ARDS:

  • A history of cigarette smoking
  • Oxygen use for a preexisting lung condition
  • Recent high-risk surgery
  • Obesity
  • Low protein in the blood
  • Alcohol abuse
  • Recent chemotherapy

Diagnosing ARDS

Your health care provider diagnoses ARDS based on:

  • Symptoms
  • Vital signs
  • Chest X-ray images when there are known risk factors, such as pneumonia or trauma

No single test can confirm a diagnosis of ARDS.

People with ARDS have sudden shortness of breath and low oxygen in the blood. They often require high amounts of oxygen. The chest X-ray often shows fluid in both lungs.

It is important that there is no evidence of heart disease because heart disease can also cause fluid to accumulate in the lungs.

ARDS will often worsen in the first few days before the lung begins to heal.

When should you see your health care provider?

Most people who develop ARDS are in the hospital, but some may not be.

Call your health care provider if you have had recent injury to your chest or lungs and:

  • Experience shortness of breath;
  • Have new cough; or
  • Have a fever.

Treating ARDS

There is no cure for ARDS. Treatment focuses on supporting you while your lung heals. The goal of this supportive care is to keep enough oxygen in the blood to prevent further damage to the body. It is also important to treat whatever caused ARDS in the first place. This treatment must be done safely, without leading to other problems. Another important part of care is to prevent and manage complications related to being in an intensive care unit (ICU).

Ventilator support

All people with ARDS will require oxygen therapy. Even 100% oxygen is usually not enough, and you may need to be placed on a ventilator. A ventilator is a machine that will deliver breaths through a tube inserted into the windpipe, called the trachea. While the ventilator is needed to support you, the settings must be carefully chosen to avoid causing more injury to the lung. The size of the breath (called the tidal volume) set on the ventilator is important: It must be kept low to avoid damaging the lungs even more. Low tidal volumes have been shown to improve survival from ARDS. The amount of oxygen given through the ventilator is set to the lowest possible level.

Prone positioning

People in the hospital are typically in bed on their backs. However, we now know that having people lie face down, or prone, can help improve oxygen levels in their blood. This prone position can increase survival in patients with ARDS. This complicated task takes an entire team to accomplish, and some people maybe too sick for it. There are specialized beds designed to help position people in the ICU facedown. Although these specialized beds help, they are not absolutely necessary.

Sedation and medications to prevent movement

It is uncomfortable, even painful to be on a ventilator. This pain can lead to restlessness and agitation, which in turn can lead to high pressures in the lung or cause oxygen levels to drop even further. To stay comfortable while you’re on a ventilator, you may need sedation.

Your care team wants you to be able to interact with them and your loved ones. However, this is not often possible when you have ARDS because you may require deep sedation. Medications called paralytics can temporarily prevent you from moving. One research study suggested that using these medications may improve the outcomes of ARDS. Because side effects related to these medications are significant, this treatment is not always necessary.

Fluid management

ARDS is a problem of fluid leaking into the lungs, not too much fluid in the body. However, most health care providers will try to keep patients with ARDS on the dry side. They may order medication called diuretics to increase urine output. These medications must be used carefully: Too much fluid removal can lead to low blood pressure or kidney problems.

Extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a complicated treatment. It takes blood outside the body and forces it through a membrane. The membrane adds oxygen and removes carbon dioxide and then returns the blood to the body. This high-risk therapy has many complications. Talk to your health care provider about whether this treatment would help you.

Future treatments

Much of the current research on ARDS focuses on preventing it in patients who are at risk. Future studies aimed at preventing ARDS will start in the near future.

Managing ARDS

Often, you require a ventilator for longer periods. Although there is no set time, after about 7 to 14 days a doctor may need to place a tube through your throat directly into your trachea (called tracheostomy). This is done only if your health care team believes that it would take longer than 2 weeks to remove you from the ventilator. A tracheostomy isn’t permanent and can easily be removed once you no longer need the ventilator.

It’s important to note that even in people with severe lung damage, the lung can heal. Even the sickest people can recover lung function if they survive the initial illness. Most people won’t require oxygen long term. Those who survive ARDS often have lengthy hospitalization because of the severe weakness that can develop during the illness. This weakness improves with time and physical therapy, but some weakness can last for as long as a year. Most people find the weakness more a problem than any breathing issue.

Recovering from ARDS

ARDS is a serious disease that’s frightening for both patients and families to endure. Outcomes tend to be better in younger patients, trauma patients, and when the ARDS resulted from a blood transfusion. Most people won’t die from severe low oxygen levels in the blood. However, the chance of dying increases dramatically if other organs begin to fail, including the liver and kidney, or if you experience severely decreased blood pressure.


Facing ARDS may cause fear, anxiety, depression, and stress for both you and your loved ones. Joining a support group may help you adjust to your condition. You can see how other people who have the same symptoms have coped with them. Talk to your health care provider about local support groups, or check with an area medical center.

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

The American Lung Association recommends that patients and caregivers join its Living with Lung Disease support community to connect with others facing this disease. You can also call the American Lung Association’s Lung Helpline at 1-800-LUNGUSA to talk to a trained lung professional. They can help answer your questions and connect you with support.

Learn more about ARDS at:

Questions to ask your health care provider

Because most people who develop ARDS are already hospitalized, their caregivers must advocate for them and talk with their health care team. If you have a loved one with ARDS, you may find it helpful to ask your health care providers the following questions:

  • What is the difference between lung injury and ARDS?
  • What is the outlook for survival and getting out of the hospital after ARDS? Just how sick is my family member?
  • My family member requires sedation to help ventilation. What are the risks of this?
  • If my family member has a sudden onset of ARDS and is able to be discharged from the hospital, how long until they fully recover?
  • What are the chances that my family member will be able to recover to their previous level of activity?
  • What do the health care providers caring for my family member mean by FIO2 and PEEP?
  • If someone requires mechanical ventilation, how long does it take to be taken off of it?
  • What are the main risks and side effects of mechanical ventilation?
  • Should my family member be taking medications?