Acute respiratory distress syndrome (ARDS) is a life-threatening medical condition where the lungs cannot provide enough oxygen for the rest of the body.

ARDS can affect people of any age and usually develops as a complication of a serious existing health condition. Consequently, most people have already been admitted to hospital by the time the symptoms of ARDS begin.

Symptoms and signs of ARDS can include:

• severe shortness of breath
• rapid, shallow breathing
• tiredness, drowsiness or confusion
• feeling faint

Medical emergency

Although most cases of ARDS begin in hospital, this is not always the case. For example, the condition may develop quickly due to an infection such as pneumonia or after somebody has accidentally inhaled their vomit.

If you notice any breathing problems in a child or adult, call 999 immediately and ask for an ambulance.

Why it happens

ARDS develops if the lungs become severely inflamed due to an infection or injury. The inflammation causes fluid from nearby blood vessels to leak into the tiny air sacs in your lungs, making breathing increasingly difficult.

The lungs may become inflamed due to:

• pneumonia or severe flu
• blood poisoning (sepsis)
• severe chest injury  
• accidental inhalation of vomit, smoke or toxic chemicals
• near drowning
• acute pancreatitis, where inflammation of the pancreas can spread throughout the body
• an adverse reaction to the transfusion of a blood product

How it’s diagnosed

There is no specific test to diagnose ARDS. A full assessment is needed to identify the underlying cause of ARDS and to rule out other conditions. This assessment is likely to include:

• a physical examination
• blood tests – to measure the amount of oxygen in the blood and check for an infection
• a pulse oximetry test – to measure how much oxygen is being absorbed in the blood, using a sensor attached to the fingertip, ear or toe
• a chest X-ray and a computerised tomography (CT) scan – to look for evidence of ARDS
• an echocardiogram – a type of ultrasound scan used to create a picture of the heart

Treating ARDS

If someone develops ARDS, they will probably be admitted to an intensive care unit (ICU) and put on a ventilator to assist their breathing.

In some cases, it may be possible to use an oxygen mask to supply them with oxygen. However, if they have severe ARDS, a tube is inserted down the throat and into the lungs through which oxygen is pumped.

Fluids and nutrients will be supplied through a tube that goes into the stomach through the nose.

The underlying cause of ARDS should also be treated. For example, if it was caused by a bacterial infection, you may be prescribed antibiotics to help fight the infection.

The amount of time you need to spend in hospital will depend on your individual circumstances and the cause of ARDS. Most people respond well to treatment within days, but it may be several weeks or months before someone with ARDS is well enough to leave hospital.

Complications

As ARDS is often the result of a serious health condition, about one in three people who develop it will die. However, most deaths are due to another problem caused by their illness, rather than ARDS itself.

For people who survive, the main complications are associated with nerve and muscle damage, causing problems such as weakness and pain. Some people also develop psychological problems, such as post-traumatic stress disorder (PTSD) and depression. The lungs themselves tend to be able to recover and long-term (chronic) lung failure after ARDS is rare.