Acute Respiratory Distress Syndrome (ARDS)

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is acute respiratory distress syndrome (ARDS)?

Acute respiratory distress syndrome (ARDS) is a life-threatening lung condition. Severe inflammation causes tiny blood vessels in the lungs to leak fluid. The fluid fills the lung’s air sacs (alveoli). This prevents the air sacs from functioning normally. The air sacs can no longer get fresh oxygen into the blood and remove carbon dioxide from it efficiently. As a result, organs and tissues do not get enough oxygenated blood. ARDS can be mild, moderate or severe.

ARDS mainly affects people who are critically ill in the hospital. It occurs in response to severe injury, trauma or illness. Examples include sepsis, severe pneumonia, and major head or chest trauma. People can develop ARDS regardless if they have had lung problems in the past.

ARDS typically develops within a few hours to a couple of days after the injury or illness. The main ARDS symptom is severe shortness of breath. However, people are often too sick to communicate their symptoms. Healthcare providers caring for the person may notice clues, such as rapid breathing, fast heart rate, and low blood pressure.

Patients with ARDS typically receive supportive medical care until the lungs heal. This usually means mechanical ventilation to take over the work of breathing. Medications can help reduce inflammation and remove fluid from the lungs. Antibiotics can treat any underlying infection if necessary.

ARDS can progress to respiratory failure and other organ failures. Sadly, ARDS is fatal in up to 50% of people who develop it. Those who survive may have lingering lung problems and other issues, but some people fully recover.

What are the symptoms of acute respiratory distress syndrome?

Acute respiratory distress syndrome symptoms typically start soon after the underlying injury or illness. The time frame can range from just a few hours to a couple of days. However, it can be hard for people to communicate their symptoms because they are too sick.

Common symptoms and signs of ARDS are:

  • Bluish tinge to the lips, skin and nails due to very low oxygen levels

  • Cough, which may produce a white or pink frothy sputum

  • Fever, fatigue and confusion

  • Low blood pressure

  • Rapid breathing and heart rate

  • Severe shortness of breath and labored breathing

ARDS symptoms are similar to several other conditions, including pneumonia and heart problems. Many of the vital sign changes are also common to other medical conditions. 

In addition, there is no single test that can identify ARDS. So, doctors have to rely on several tests to rule out other conditions to diagnose ARDS. This may include heart tests, chest X-rays, and other imaging exams.


What causes acute respiratory distress syndrome?

Acute respiratory distress syndrome is the result of severe inflammation. The inflammation causes tiny blood vessels in the lungs to become “leaky.” Fluid finds its way out of these blood vessels and into the alveoli—or air sacs. As the air sacs fill with fluid, breathing becomes difficult. The lungs are not able to provide enough oxygen for the rest of the body to function normally.

There are direct and indirect underlying causes of the inflammation at the root of ARDS. Direct causes, which have a primary effect on the lungs, include:

  • Aspiration, which is inhaling stomach contents

  • Near drowning

  • Severe pneumonia

  • Smoke or chemical fume inhalation

  • Trauma to the chest and lungs

Indirect causes, which have a secondary effect on the respiratory system, include:

  • Blood transfusions

  • Brain injury or trauma

  • Burns

  • Medication reactions

  • Pancreatitis

  • Sepsis

What are the risk factors for acute respiratory distress syndrome?

Acute respiratory distress syndrome mostly affects people who are already in the hospital due to another injury or illness. Often, they are already in critical condition.

It is difficult to predict who will develop ARDS and who will not. It is possible to develop ARDS even if you have never had any past lung problems. However, a number of factors may contribute to the risk of developing ARDS. Risk factors for ARDS may include:

Reducing your risk of acute respiratory distress syndrome

It is difficult to prevent ARDS because it is a reaction to a serious injury or illness. However, you may be able to lower your risk of ARDS by:

  • Getting vaccines to prevent lung infections, including the pneumonia vaccine and an annual flu shot 

  • Maintaining a healthy weight

  • Quitting smoking

  • Seeking treatment for alcohol abuse

How is acute respiratory distress syndrome treated?

Acute respiratory distress syndrome treatment is supportive. There is no specific treatment that will resolve ARDS. The goal of supportive treatment is to provide enough oxygen to the body’s tissues and allow the lungs to heal. It requires care in an ICU (intensive care unit). Treatment may include:

  • Fluid management to remove fluid from the lungs and prevent fluid buildup. This aspect of care requires a careful balance. Eliminating or limiting too much fluid can cause problems with blood pressure and organs, such as the heart and kidneys.

  • Medications to control fluid, treat infection, relieve pain, maintain blood pressure, and prevent blood clots

  • Nutrition support to feed the person using a temporary feeding tube

  • Oxygen therapy to increase the amount of oxygen in the blood. In mild ARDS, this may involve supplemental oxygen through a mask. However, ARDS usually requires mechanical ventilation. A machine will do the work of breathing while the lungs heal. This approach require sedation. In some cases, ECMO (extracorporeal membrane oxygenation) is necessary. ECMO circulates blood outside the body to add oxygen and remove carbon dioxide.

  • Prone positioning to place the person face down, which can improve oxygen levels

What are the potential complications of acute respiratory distress syndrome?

Acute respiratory distress syndrome causes complications in some cases. This can include collapsed lung—or pneumothorax—which is like a balloon popping and deflating. ARDS can also cause pulmonary fibrosis, which is scarring and thickening of the tissue around the air sacs. Pulmonary fibrosis makes the lungs stiff and breathing difficult. Other organ damage can occur as well. This includes damage to the brain, heart, kidneys and liver.

ARDS is unpredictable. Some people will have mild cases and recover quickly. Others will have it for weeks or months. Some will develop complications, while others will not. Up to 50% of people with ARDS will not survive despite good medical care. The risk of dying from ARDS is higher with more severe disease and older age.

For those patients who recover, long-term problems may persist. This includes breathing problems, depression, fatigue, muscle weakness, and problems with memory or thinking.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jul 10
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  3. ARDS. Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/ards/symptoms-causes/syc-20355576 
  4. What Is Acute Respiratory Distress Syndrome? American Thoracic Society. https://www.thoracic.org/patients/patient-resources/resources/acute-respiratory-distress-syndrome.pdf