What Is Acute Respiratory Distress Syndrome (ARDS)?

Acute respiratory distress syndrome (ARDS) is a type of severe and life-threatening lung problem. ARDS isn’t a disease in itself. Rather, a variety of medical situations can lead to it. People who are critically ill or who have sustained a significant injury may be at risk of ARDS. People with ARDS are often unable to breathe on their own, and so need support from a ventilator to stay alive.

ARDS was first characterized in 1967. When it affects children, the syndrome sometimes is called pediatric acute respiratory distress syndrome (PARDS). Though medical developments have lowered the mortality rate in people with ARDS, between 20% and 40% of people with ARDS die from its complications.

Young man connected to a ventilator mask
Juanmonitor / E+ / Getty Images 

ARDS Symptoms

Potential symptoms of ARDS include:

  • Severe shortness of breath
  • Rapid breathing
  • Bluish-colored extremities
  • Drowsiness
  • Confusion

Other symptoms may be present, depending on the underlying cause of ARDS. For example, people with ARDS due to infection may have symptoms like fever.

People with ARDS also have hypoxemia, a lower than normal level of oxygen in the blood. This can easily be estimated with a pulse oximeter, a device that clips onto your finger.

If untreated, people with ARDS quickly develop respiratory failure, in which levels of oxygen in the blood become life-threateningly low. This can cause further complications, like brain damage, irregular heartbeat, and liver damage. Ultimately, most deaths from ARDS occur from the failure of multiple organs.

Causes

Understanding the causes of ARDS the underlying dysfunction in the lungs as well as the triggers and risk factors.

What’s Happening in the Lungs

The small sacs of the lungs, the alveoli, play a critical role in life. Normally, they work to take fresh oxygen into your blood (from the air you breathe in) and remove extra carbon dioxide from your blood (transporting it into air you breathe out). The cells of the body require enough oxygen to survive, but too much carbon dioxide causes problems too.

ARDS occurs when the lungs rapidly collect fluid due to inflammation in the area. Some sort of trigger sets this inflammation in process. Inflammatory cells come to the region and may damage the lung’s lining. Small blood vessels in the lungs may start to leak, and blood clots may form in some of the remaining vessels. A portion of the cells lining the alveoli die.

Because of all this, the alveoli start to fill with fluid and dead cells. Then they can’t do their normal job of bringing fresh oxygen into the blood and removing carbon dioxide from it. This leads to the life-threatening symptoms of ARDS.

ARDS Triggers

ARDS doesn’t develop on its own. Instead, it is set off by a triggering event that causes lung inflammation hours or days after the initial problem.

The most common cause of ARDS is pneumonia, which can be caused by different types of infections by viruses, bacteria, or other pathogens. This includes COVID-19, the disease caused by the novel coronavirus, which leads to pneumonia and symptoms from ARDS in some people.

Other potentially triggering situations include the following:

  • Severe burns
  • Pancreatitis
  • Drug overdose
  • Physical trauma
  • Near drowning
  • Pulmonary vasculitis
  • Inhalation injury (from toxic fumes)
  • Stomach contents inhaled into the airways (gastric aspiration)
  • Sepsis (from lung infection or another infection)

Risk Factors

Certain factors seem to increase the risk of developing ARDS if you experience a potential trigger. They include:

  • Chronic alcohol abuse
  • Smoking (personally or through secondhand smoke)
  • Exposure to inhaled environmental pollutants
  • Exposure to noxious chemicals
  • Vitamin D deficiency

Children are less likely to develop ARDS than adults and less likely to die if it does happen. Generally, older adults are at greater risk compared to younger ones.

Diagnosis

The diagnosis of ARDS can be tricky, as its symptoms can mimic those of some other medical situations that aren’t as serious and don’t require the same rapid treatment. It’s important that ARDS be correctly diagnosed as quickly because most people with ARDS need support on a ventilator, as soon as possible.

Clinicians need to diagnose not just ARDS but the underlying condition that triggered the event, like pneumonia. Sometimes that’s obvious, but other times it requires more digging. Other causes of symptoms must be ruled out. For example, untreated congestive heart failure might cause some symptoms similar to ARDS.

It’s also important to distinguish simple pneumonia from ARDS, because they can have some very similar symptoms and signs. Pneumonia is one cause of ARDS. In pneumonia, low levels of oxygen will usually go away if a person is given supplemental oxygen. In ARDS, that usually isn’t the case.

As always, a person’s medical history and exam are the starting point for diagnosis. That includes recent symptoms, like shortness of breath and fever, as well as a person’s existing medical conditions. The physical exam also often reveals important clues about what might be causing a person’s symptoms.

Lab Tests

Certain basic laboratory tests might help in diagnosing ARDS and its underlying cause. These also give some basic information about how the rest of the body is impacted. Some of these might include:

It’s also important to check for infection. For example, if an infectious cause is suspected, a person might need to give a blood sample and that can be cultured in a lab to identify the specific pathogen.

Sputum samples and urine samples might be needed, depending on the context. Testing for COVID-19 infection through a blood or sputum sample may also be necessary, depending on the situation.

Imaging

Imaging is an important part of diagnosing ARDS. Chest ultrasound, X-ray, and/or CT scan might be used. On imaging, the doctor can see fluffy patches in the lungs that shouldn’t normally be there, from the inflammatory fluid filling the lung’s air sacs. Echocardiography also might be needed to rule out heart problems as a cause.

Follow-up Tests

If an underlying cause of the ARDS hasn’t been found, additional testing may be needed. This might include tests like bronchoalveolar lavage, which collects fluid from deep in the lung airways for analysis. In unusual cases, a small tissue from the lung (lung biopsy) might be needed to make the diagnosis.

Treatment

Unfortunately, we don’t have great treatments for ARDS itself. The body needs to be given time and support as it recovers.

Supportive Breathing Treatments

Treatment for ARDS focuses on keeping a person alive while they heal. A mainstay of this is ventilator treatment.

Most people with ARDS will need support on a ventilator. This machine helps people breathe when they can’t do this effectively on their own, allowing them to take in oxygen and get rid of carbon dioxide.

A tube is placed into the person’s mouth and goes down their windpipe (or into a hole surgically made in their neck). This tube is connected to the ventilator. The ventilator then can blow air (sometimes containing extra oxygen) into the person’s lungs and remove exhaled air.

While this is happening, the person is sedated to keep them comfortable. Sometimes they are also given medication to keep them physically paralyzed, particularly if their ARDS is severe.

The individual needs to stay on the ventilator until they can successfully breathe on their own. It’s important to regularly assess whether this is possible, because being on a ventilator poses its own health risks, including infection and further lung damage. A person shouldn’t be kept on a ventilator more than is necessary.

Extracorporeal membrane oxygenation (ECMO) is another ventilatory support method that can be tried, especially if traditional mechanical ventilation isn’t working well. This treatment uses a pump to circulate a person’s blood through an artificial lung outside their body.

This artificial lung adds oxygen and removes carbon dioxide before the blood is returned to the body. ECMO might be particularly beneficial for people with severe ARDS.

Patients with ARDS are often placed in a prone position (belly down), which may allow the lungs to work more effectively.

Other Supportive Care

Treatment with a ventilator requires care in an intensive care unit (ICU). While there, the individual will need to receive other support to keep them comfortable and help prevent other problems. Some of these supports include:

  • Careful management of fluids given intravenously
  • Feeding through a tube connected to the stomach (nasogastric or orogastric tubes)
  • Pain medication
  • Medications to prevent blood clots from lack of patient movement
  • Medications like proton pump inhibitors to help prevent stress ulcers
  • Regular patient repositioning (to prevent pressure sores)

Other medications may be needed as well, depending on the context. For example, someone with very low blood pressure due to sepsis might need a medication to help raise their blood pressure.

Targeting Underlying Causes

It’s also important to address any underlying causes of ARDS, if this is possible. For example, a person with ARDS from bacterial pneumonia needs targeted antibiotics to address the infection. Unfortunately, in many situations we don’t have treatments to address the root cause that triggered ARDS.

Targeting ARDS

Corticosteroids have sometimes been used to treat people with ARDS, but it’s not clear that they help much.

Inhaled nitric oxide may be helpful for some patients who aren’t doing well with standard treatments, but again, this is not completely clear. Another treatment, surfactant, is also sometimes used, but it is not currently recommended except for newborn infants.

Scientists have studied other drugs to help reduce symptoms from ARDS, but we don’t have additional direct treatments as of now.

After ARDS

People who do survive ARDS may experience some long-term side effects. Many people will lose weight and muscle mass, and thus might need help with daily skills. Some people experience cognitive problems (from reduced oxygen to the brain) that might last for months after going home.

Post-traumatic stress disorder occurs in some people as well. Some individuals experience shortness of breath and a reduced ability to exercise. However, many people who develop ARDS eventually return to near normal lung function within six to 12 months.

ARDS from COVID-19

Many people are concerned about ARDS resulting from the COVID-19 pandemic. The majority of people experience only manageable symptoms from COVID-19. However, in some people, the infection sets off a large amount of inflammation, called a cytokine storm. This may serve as the trigger for ARDS.

Currently, treatment for ARDS from COVID-19 is similar to the treatment of ARDS from other causes. Every day, clinicians are learning more about the specific characteristics of lung disease from COVID-19 and how they might be optimally managed.

Researchers are scrambling to identify specific treatments that might help target the virus itself or which might help reduce symptoms from ARDS. Some very early studies have suggested that corticosteroids may help patients with ARDS from COVID-19, but more data is needed to confirm its role.

A Word From Verywell

Acute respiratory distress syndrome (ARDS) is a life-threatening medical situation. It’s natural to feel scared and overwhelmed if a loved one is suffering from ARDS. Fortunately, health professionals have more tools than ever to maximize the chance of recovery. Highly trained medical professionals will work hard to give your loved one the best possible chance. 

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