acute respiratory distress syndrome (ARDS)

acute respiratory distress syndrome

A normal alveolus (left) and a damaged injured alveolus in the acute phase of acute respiratory distress syndrome (right).

Acute respiratory distress syndrome (ARDS) is breathing failure that can occur in critically ill persons with underlying illnesses. It is not a specific disease. Instead, it is a life-threatening condition that occurs when there is severe fluid buildup in both lungs. The fluid buildup prevents the lungs from working properly – that is, allowing the transfer of oxygen from air into the body and carbon dioxide out of the body into the air.


In ARDS, the capillaries (tiny blood vessels) in the alveoli of the lungs are damaged because of an infection, injury, blood loss, or inhalation injury. Fluid leaks from the blood vessels into the alveoli. While some alveoli fill with fluid, others collapse. When this happens, the lungs can no longer fill properly with air and they become stiff. Without air entering the lungs properly, the amount of oxygen in the blood drops. When this happens, the person with ARDS must be given extra oxygen and may need the help of a breathing machine.


Breathing failure can occur very quickly after the condition begins. It may take only 1 or 2 days for fluid to build up. The process that causes ARDS may continue for weeks. If scarring occurs, this will make it harder for the lungs to take in oxygen and get rid of carbon dioxide.


In the past, only about 4 out of 10 people who developed ARDS survived. But today, with good care in a hospital's intensive or critical care unit, many people (about 7 out of 10) with ARDS survive. Although many people who survive ARDS make a full recovery, some survivors have lasting damage to their lungs.


Causes ARDS

The causes of acute respiratory distress syndrome (ARDS) are not well understood. It can occur in many situations and in persons with or without a lung disease.


There are two ways that lung injury leading to ARDS can occur: through a direct injury to the lungs, or indirectly when a person is very sick or has a serious bodily injury. However, most sick or badly injured persons do not develop ARDS.

Direct lung injury

A direct injury to the lungs may result from breathing in harmful substances or an infection in the lungs. Some direct lung injuries that can lead to ARDS include:


  • Severe pneumonia (infection in the lungs)
  • Breathing in vomited stomach contents
  • Breathing in harmful fumes or smoke
  • A severe blow to the chest or other accident that bruises the lungs

    Indirect lung injury

    Most cases of ARDS happen in people who are very ill or who have been in a major accident. This is sometimes called an indirect lung injury. Less is known about how indirect injuries lead to ARDS than about how direct injuries to the lungs cause ARDS. Indirect lung injury leading to ARDS sometimes occurs in cases of:


  • Severe and widespread bacterial infection in the body (sepsis)
  • Severe injury with shock
  • Severe bleeding requiring blood transfusions
  • Drug overdose
  • Inflamed pancreas

    It is not clear why some very sick or seriously injured people develop ARDS, and others do not. Researchers are trying to find out why ARDS develops and how to prevent it.


    Who is at risk?

    Acute respiratory distress syndrome (ARDS) usually affects people who are being treated for another serious illness or those who have had major injuries. In the United States, it affects about 150,000 people each year. ARDS can occur in people with or without a previous lung disease. People who have a serious accident with a large blood loss are more likely to develop ARDS. However, only a small portion of people who have problems that can lead to ARDS actually develop it.


    In most cases, a person who develops ARDS is already in the hospital being treated for other medical problems. Some illnesses or injuries that can lead to ARDS include:


  • Serious, widespread infection in the body (sepsis)
  • Severe injury (trauma) and shock from a car crash, fire, or other cause
  • Severe bleeding that requires blood transfusions
  • Severe pneumonia (infection of the lungs)
  • Breathing in vomited stomach contents
  • Breathing in smoke or harmful gases and fumes
  • Injury to the chest from trauma (such as a car accident) that causes bruising of the lungs
  • Nearly drowning
  • Some drug overdoses

    Signs and symptoms

    The major signs and symptoms of acute respiratory distress syndrome (ARDS) are:


  • Shortness of breath
  • Fast, labored breathing
  • A bluish skin color (due to a low level of oxygen in the blood)
  • A lower amount of oxygen in the blood

    Doctors and other health care providers watch for these signs and symptoms in patients who have conditions that might lead to ARDS. People who develop ARDS may be too sick to complain about having trouble breathing or other related symptoms. If a patient shows signs of developing ARDS, doctors will do tests to confirm that ARDS is the problem.


    ARDS is often associated with the failure of other organs and body systems, including the liver, kidneys, and the immune system. Multiple organ failure often leads to death.



    Doctors diagnose acute respiratory distress syndrome (ARDS) when:


  • A person suffering from severe infection or injury develops breathing problems.
  • A chest X-ray shows fluid in the air sacs of both lungs.
  • Blood tests show a low level of oxygen in the blood.
  • Other conditions that could cause breathing problems have been ruled out.

    ARDS can be confused with other illnesses that have similar symptoms. The most important is congestive heart failure. In congestive heart failure, fluid backs up into the lungs because the heart is weak and cannot pump well. However, there is no injury to the lungs in congestive heart failure. Since a chest X-ray is abnormal for both ARDS and congestive heart failure, it is sometimes very difficult to tell them apart.



    Patients with acute respiratory distress syndrome (ARDS) are usually treated in the intensive or critical care unit of a hospital. The main concern in treating ARDS is getting enough oxygen into the blood until the lungs heal enough to work on their own again. The following are important ways that ARDS patients are treated.


    Extra oxygen

    The main treatment is giving a higher concentration of oxygen than that found in normal air – that is, enough to raise blood levels of oxygen to safe levels. This can sometimes be done with a face mask. A face mask can deliver oxygen at a concentration of 40–60 percent. As the ARDS progresses over hours or days, the patient may need a higher level of oxygen than a face mask can give.


    If the patient becomes tired from breathing so hard, it may become necessary to connect the patient to a breathing machine (ventilator). This can be done by placing a tube through the mouth or nose into the windpipe (trachea) in a procedure called endotracheal intubation (or just intubation) and connecting the tube to the ventilator. Sometimes the connecting tube is inserted through a surgical opening in the neck (this procedure is called a tracheotomy). The breathing machine can be set to help or completely control breathing. It will deliver the minimum amount of air every minute. If the extra oxygen and help with breathing are not enough, the breathing machine can be set to Positive End Expiratory Pressure (PEEP) to maintain the surface for gas exchange.


    PEEP keeps some air in the lungs at the end of each breath. It helps keep the air sacs open instead of collapsing. The setting on the breathing machine can be adjusted to fit the needs of the patient. Other settings on the breathing machine control the number of breaths per minute (rate control) and the amount of air the ventilator uses to inflate the lungs in each breath (tidal volume).



    Many different kinds of medicines are used to treat ARDS patients. Some kinds of medicines often used include:


  • Antibiotics to fight infection
  • Pain relievers
  • Drugs to relieve anxiety and keep the patient calm and from "fighting" the breathing machine
  • Drugs to raise blood pressure or stimulate the heart
  • Muscle relaxers to prevent movement and reduce the body's demand for oxygen

    Other treatment

    With breathing tubes in place, ARDS patients cannot eat or drink as usual. They must be fed through a feeding tube placed through the nose and into the stomach. If this does not work, feeding is done through a vein. Sometimes a special bed or mattress, such as an airbed, is used to help prevent complications such as pneumonia or bedsores. If complications occur, the patient may require treatment for them.




    With treatment:


  • Some patients recover quickly and can breathe on their own within a week or so. They have the best chance of a full recovery.
  • Patients whose underlying illness is more severe may die within the first week of treatment.
  • Those who survive the first week but cannot breathe on their own may face many weeks on the breathing machine. They may have complications and a slow recovery if they survive.

    Recovering from ARDS

    Some people who survive acute respiratory distress syndrome (ARDS) heal quickly and recover completely in a relatively short time. Some are able to have the breathing tube and breathing machine removed in a week or so. Survivors often recover much of their lung function in the first 3–6 months after leaving the hospital, and they continue to recover for up to a year or more.


    Others recover more slowly, however. Some ARDS survivors never recover completely, and they have continuing problems with their lungs. Every case is different. People who are younger and healthier when they develop ARDS are more likely to recover quickly than those who are older or who have more health problems.


    ARDS patients who survive the first week but cannot breathe on their own may have to be on a breathing machine for several weeks or longer. These patients often develop complications, such as infections or air leaks (see the next section on Complications of ARDS). While some of these patients will die, others will get better and be able to breathe on their own again. Their recovery is usually slow, and they may have continuing problems.


    After leaving the hospital, ARDS survivors need to visit a doctor during recovery to check how well their lungs are doing. Doctors use lung function tests to check the lungs. Spirometry is the most commonly used lung function test. It involves taking a deep breath and blowing hard into a plastic tube. The doctor will also do an oxygen saturation (oximetry) test or a blood test to check the amount of oxygen in the blood.


    After going home from the hospital, the ARDS survivor may need only a little or a lot of help. While recovering from ARDS at home, a person may:


  • Need to use oxygen at home or when going out of the home, at least for a while
  • Need to have physical, occupational, or other therapy
  • Have shortness of breath, cough, or phlegm (mucus)
  • Have hoarseness from the breathing tube in the hospital
  • Feel tired and not have much energy
  • Have muscle weakness

    Possible Complications

    Anyone who stays in the hospital for a long time can get complications. Common complications in ARDS patients are infections with hospital-acquired bacteria and leaks of air out of the lungs into other body spaces.


  • Bacterial infections. The lungs or other parts of the body may become infected. These infections are usually treated with antibiotics after a test to see what kind of bacteria is causing the infection.

  • Air leaks. Leaks of air through holes in the lungs are caused by pressure from the breathing machine that is needed to be sure the patient gets enough air, and from the very stiff lungs. Air from the injured lungs may enter the space between the lungs and the lining around the lungs (the pleura) and cause a pneumothorax (collapsed lung). Treatment involves using a chest tube and suction to remove the air and help the lungs reinflate. Air may also enter the space between the membranes that line the abdomen (pneumoperitoneum) or the soft tissue under the skin (subcutaneous emphysema). These are not usually treated.

    Each complication is treated as it arises. Careful hand washing by hospital staff and visitors helps reduce infections, and new breathing machine methods help reduce air leaks.


    For family and friends

    While your family member or friend is in the hospital being treated for ARDS, you may feel a lot of stress. One day the patient may seem to be recovering, and the next day things may take a turn for the worse. It can be a scary experience to see someone you care about on a breathing machine.


    Several doctors work together to give care to your family member or friend. These doctors are often specialists who are treating different concerns of the patient. For example, an infectious disease specialist might be involved to help make sure that the initial infection or an infectious complication is properly treated. A lung specialist may be adjusting the settings on the breathing machine, and a kidney specialist may be required if kidney failure occurs. These doctors talk to each other regularly to make sure that care is given in a coordinated manner.


    There are some things you can do to help, even though you may feel very helpless:


  • Talk to the doctors, nurses, and other health care providers. Ask questions about the patient's condition and care, and ask how you can support your loved one.

  • Talk to the patient, even if he or she is in a drug-induced sleep. Talk about fun things you did together and laugh with them about silly things that you did. Many survivors say they were, at some level, aware of the people and things around them. They also recall dreams they had while in the drug-induced sleep. The dreams can be calming or frightening. Talking to the patient about happy and fun things may help make the dreams more positive.

  • Ask the hospital staff if you can put family photos near the patient, play music at low volume, or rub lotion into the patient's feet and hands. Many survivors are aware of people and things around them. This may help to trigger their senses of hearing, touch, and seeing. Leave fears and worries at the door. Always go outside the patient's room to talk with the doctor or nurse about the patient's condition. Make sure everyone is encouraging and hopeful while with the patient. The patient may sense stress in their presence.

  • Keep a journal or record of events for the patient to read after leaving the hospital. ARDS survivors want to know every detail of what happened while they were asleep.

  • Remember to take care of yourself, too. Try to get enough rest and sleep, eat well, and get some exercise. Call on other family members and friends to sit with the patient so you can have a break. Your very sick loved one will need your strength and support over what may be a long recovery period.

    The family members and friends of people who have had ARDS often are deeply affected by the experience. The "roller-coaster ride" of emotions while the ARDS patient is in the hospital is exhausting and stressful. Caring for the ARDS survivor at home can also be stressful and tiring. Ask for help from others or your health care providers if you need it. Most hospitals have individuals such as social workers who can help family members cope with these issues.