Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening lung injury that causes fluid to build up in the tiny air sacs of your lungs, leading to dangerously low oxygen levels in your blood. This serious condition usually develops within hours to days after a major illness or injury, and requires immediate intensive care treatment.

Table of contents

• What is acute respiratory distress syndrome?
• What causes ARDS?
• Symptoms and development
• How is ARDS diagnosed?
• Treatment options
• Recovery and living with ARDS
• Outlook and prognosis

What is acute respiratory distress syndrome?

Acute respiratory distress syndrome (ARDS) is a serious lung condition that happens when fluids build up in the small air sacs in your lungs, called alveoli (the tiny balloon-like structures where oxygen enters your blood)^[1]. This fluid buildup prevents your lungs from filling up with air properly and causes critically low oxygen levels in your blood, a condition called hypoxia (when your body doesn’t get enough oxygen)^[1].

When ARDS develops, it prevents vital organs such as your brain, heart, kidneys, and stomach from getting the oxygen they need to work properly^[1]. At a microscopic level, ARDS is associated with damage to the blood vessels in your lungs and widespread injury to the alveoli^[5].

The average person has close to 500 million alveoli in their lungs. Each of these is responsible for two critical tasks: moving oxygen into the blood and removing carbon dioxide from the blood^[8]. When lung injury occurs, fluid leaks into the spaces between tiny blood vessels called capillaries and the alveoli. Pressure on the alveoli increases, and eventually fluid gets inside them too, causing them to collapse^[8].

Healthcare providers typically classify ARDS as mild, moderate, or severe based on how much oxygen is in your blood compared to how much oxygen needs to be given to achieve healthy levels^[1]. According to medical definitions, ARDS is characterized by rapid onset, fluid buildup in both lungs shown on imaging, and low oxygen levels that cannot be explained by heart failure^[5].

• Lungs
• Alveoli (air sacs)
• Capillaries (small blood vessels in the lungs)

What causes ARDS?

ARDS is always caused by an injury to the lungs, whether from illness or trauma. It usually affects people who are already seriously ill or have experienced major injuries^[8]. The most common cause of ARDS is sepsis, which happens when you have a serious infection in your lungs or other organs that spreads throughout your body^[1].

Direct causes that affect the lungs include:

• Pneumonia (lung infection)^[1]
• Aspiration pneumonia, which occurs when you breathe stomach contents, vomit, or food into your lungs^[1]
• Breathing in smoke or toxic chemical fumes^[1]
• Drowning or near drowning^[1]
• Chest injuries that bruise the lungs^[8]

Indirect causes that occur elsewhere in the body but ultimately harm the lungs include:

• Sepsis from infections anywhere in the body^[1]
• Receiving more than 15 units of blood in a short period of time^[1]
• COVID-19 infection, which can develop into severe ARDS^[1]
• Severe pancreatitis (inflammation of the pancreas)^[1]
• Major injuries, severe burns, or accidents^[1]
• Drug overdose from substances like cocaine and opioids^[1]

ARDS affects approximately 200,000 people in the United States and 3 million people worldwide every year^[1]. It causes around 10% of all intensive care unit admissions and is the reason at least 25% of people need a breathing machine in hospital settings^[1].

Symptoms and development

The main symptom of ARDS is severe shortness of breath^[2]. Other symptoms include:

• Fast and labored breathing^[1]
• Rapid heart rate^[1]
• Bluish color of fingernails and lips due to low oxygen in the blood^[1]
• Cough^[2]
• Confusion and extreme tiredness^[2]

ARDS tends to develop within a few hours to a few days of the event that caused it, and it can worsen very quickly^[1]. People usually become severely short of breath within this timeframe after the original injury or illness^[2].

ARDS typically happens when a person is already in the hospital receiving treatment for another serious condition^[1]. However, if you are not hospitalized and experience symptoms of ARDS, you should get medical attention immediately by calling emergency services or going to the nearest emergency department^[2].

Healthcare providers sometimes classify ARDS into three stages based on inflammation levels and the body’s repair process: exudative (early fluid buildup), proliferative (healing phase), and fibrotic (scarring). Not all people progress to the third stage^[1].

How is ARDS diagnosed?

There is no single specific test for ARDS. Healthcare professionals base the diagnosis on physical examinations, medical history, oxygen levels, and imaging studies^[15]. It is also important to rule out other diseases and conditions, such as heart problems, that can cause similar symptoms^[15].

Diagnostic tests may include:

Imaging tests: A chest X-ray can show which parts of your lungs have fluid in them and whether your heart has gotten bigger^[15]. A CT scan combines X-ray images taken from many directions to create detailed views of structures within the heart and lungs^[15].

Blood tests: A test using blood from an artery measures your oxygen level. Other blood tests can check for signs of infection or other medical conditions^[15].

Heart tests: Because ARDS symptoms are similar to certain heart problems, your doctor may recommend heart tests. An electrocardiogram (ECG) tracks the electrical activity in your heart using sensors attached to your body. An echocardiogram uses sound waves to create pictures of the heart and show how blood moves through it^[15].

Your doctor may also review your medical history and test secretions from your airway if a lung infection is suspected^[1].

Treatment options

ARDS is a life-threatening condition that must be treated in the intensive care unit (ICU) of a hospital^[1]. The main goal of treatment is to improve oxygen levels and treat the underlying cause^[11].

Oxygen therapy is the main treatment for ARDS. You can receive oxygen through tubes resting in your nose, a face mask, or a tube placed in your windpipe^[11]. Most people with ARDS need to be placed on a ventilator, which is a machine that helps you breathe until your lungs can work properly again^[1].

Depending on how serious your symptoms are, your doctor may suggest:

• Noninvasive ventilation using special breathing machines that blow air through a face mask to help keep your airways open^[11]
• Mechanical ventilation using a ventilator, which is the standard treatment to support breathing^[11]
• Prone positioning, which means lying on your stomach, can improve oxygen levels in severe cases^[11]

Other important treatments include:

Medicines: Your doctor may prescribe antibiotics if an infection is present, pain medications, and possibly corticosteroids (medicines that reduce inflammation)^[11].

Fluid management: Careful control of fluids is essential to avoid fluid overload while ensuring your organs get enough blood flow^[8].

Treatment of the underlying cause: Because infection is often the underlying cause of ARDS, early administration of appropriate antibiotics is essential. In some cases, removing infected lines, draining fluid collections, or surgical treatment may be necessary^[17].

In select, severe cases where standard treatments are not working, patients may need extracorporeal membrane oxygenation (ECMO), which is a machine that helps with gas exchange outside the body, allowing the lungs to rest^[13].

The only treatment proven to improve survival in ARDS is a mechanical ventilation strategy using low volumes of air with each breath^[17].

Recovery and living with ARDS

Recovery after leaving the hospital can take many weeks or months, particularly for older adults^[18]. The longer you were on a ventilator, the longer it may take to recover your strength and return to familiar routines^[18].

After ARDS, you will need regular follow-up care with your healthcare team. Your doctor may recommend:

• Keeping regular appointments to monitor your recovery^[18]
• Taking all medicines regularly as prescribed^[18]
• Working with physical therapists or other healthcare providers to regain strength^[18]
• Lung function tests to check how well your lungs are working^[18]
• Tests to measure muscle strength and physical capacity^[18]

Many survivors experience challenges after hospitalization. Common issues include:

• Muscle weakness or wasting from prolonged bed rest^[19]
• Ongoing shortness of breath that may require continued use of oxygen at home^[7]
• Psychological problems such as depression, anxiety, or post-traumatic stress disorder^[19]

A multi-disciplinary rehabilitation program involving physical therapists, occupational therapists, psychologists, and respiratory therapists can help with recovery and improve quality of life^[19]. Your doctor can help you manage these problems and suggest additional resources^[18].

Outlook and prognosis

ARDS is dangerous and carries a high risk of death. Even with the best care, about 40% of people with ARDS die^[23]. With treatment, an estimated 60% to 75% of those who have ARDS survive the disease^[8].

Of those who survive ARDS, some fully recover, but others have lasting lung damage^[2]. Long-term effects can include shortness of breath, muscle weakness, and pain^[6]. The risk of death increases with age and the severity of the illness^[2].

Patients with ARDS are at risk for complications during treatment, including pneumothorax (collapsed lung), infections from intravenous lines, blood clots, bleeding, and muscle weakness^[17]. Careful attention to preventing these complications is an important part of treatment^[17].