What Is Acute Respiratory Distress Syndrome?

Acute respiratory distress syndrome (ARDS) is a severe lung condition that can cause life-threatening respiratory failure. ARDS can be caused by various factors, including trauma, infections, and inhalation injuries. Effective treatment involves providing supportive care, such as administering supplemental oxygen, utilising mechanical ventilation and prescribing medication.

Overview 

Acute respiratory distress syndrome (ARDS) is a common lung condition that can cause life-threatening respiratory failure in critically ill patients. ARDS is associated with the acute onset of pulmonary oedema (when fluid builds up in the tiny air sacs (alveoli) of the lungs). Once the lungs are full of fluid, gas exchange is restricted. This can reduce the oxygen in the blood, leading to organ failure. ARDS can be caused by various factors, including trauma, infections, and inhalation injuries.¹

Causes and risk factors of ARDS

What can cause ARDS?

ARDS can be caused by a wide range of factors,¹ including:

• Infections, including viral or bacterial infections and pneumonia
• Pulmonary aspiration: when material (e.g. food and drink) from the stomach, mouth or oesophagus is accidentally inhaled into the lungs
• Trauma, such as severe injuries to the chest or head
• Inhalation injuries: when the airways and lungs are exposed to irritants like chemical fumes
• Pancreatitis: inflammation of the pancreas
• Drug overdose
• Blood transfusions: transfusion-associated acute lung injury is usually related to fresh frozen plasma, red blood cell or platelet transfusions
• Transplantation or surgery: including after cardiopulmonary bypass, lung resection, and lung transplants
• Near drowning: occurs with both fresh or salt water
• Smoke inhalation: can cause direct injury to the lungs

How does ARDS develop?

The exact cause of ARDS is not well understood. However, it is believed that after an injury to the lungs, the immune system reacts by releasing large amounts of inflammatory chemicals called cytokines.² 

These cytokines can damage the alveoli (tiny air sacs) and capillaries (tiny blood vessels) in the lungs, allowing fluid to leak in. 

Additionally, ARDS involves a loss of surfactant (fluid that stops the alveoli collapsing) and the accumulation of dead cells, debris and inflammatory fluid in the alveoli.  

A combination of these steps can lead to the following:

• Decreased pulmonary compliance, or the ability of lungs to stretch and expand
• Clotting in the alveolar capillaries, which causes microthrombi (tiny blood clots)
• Impaired gas exchange, making it difficult for oxygen to pass from the alveoli to the bloodstream
• Respiratory failure, where the oxygen supply does not meet the demand of the body due to impaired gas exchange²

If not treated, ARDS will eventually lead to organ failure due to a lack of oxygen and blood supply, resulting in death.

Risk factors for ARDS 

Aside from the aforementioned clinical causes of ARDS, several risk factors can increase the likelihood of developing ARDS,^3,4 including:

• Age: the older someone is, the higher their risk of developing ARDS
• The extent of injury: a more severe injury is associated with a higher risk of developing ARDS
• Chronic alcohol abuse: this is linked to a 2-3x higher risk of developing ARDS, the reason for which is unknown. However, some studies think that it may be due to a reduced antioxidant capacity in the lungs
• History of smoking
• Hypoalbuminemia: the loss of albumin, a protein that helps keep blood inside blood vessels
• Obesity

Signs and symptoms of ARDS 

The symptoms of ARDS can vary depending on the patient and the severity of the condition, but common symptoms include:⁵

• Severe dyspnea (shortness of breath)
• Rapid, shallow breathing
• Tiredness
• Drowsiness
• Confusion 
• Feeling faint 

Management and treatment for ARDS

Treatment for patients can involve supportive care and medication. A physician will assess the situation and take the best course of action. The underlying cause of ARDS is usually treated to prevent further complications, using effective management options such as:⁶

• Corticosteroids
• Extracorporeal membrane oxygenation (ECMO): a machine that supplies oxygen to the blood outside the body
• Fluid management strategy: patients may undergo a conservative (which involves receiving diuretics, sometimes in combination with an albumin solution or restricted fluid intake) or liberal fluid strategy (which involves receiving a lot of fluid and sometimes, diuretics) 
• Inhaled vasodilators: these help blood vessels expand
• Lung protective ventilation to keep lung volume and pressure balanced

Diagnosis of ARDS 

Diagnosis of ARDS is based on the patient's medical history, a physical examination and imaging tests such as an echocardiogram (an ultrasound of your heart and nearby blood vessels), X-rays or computed tomography (CT) scans. 

Since ARDS affects the lungs and their ability to sufficiently provide oxygen to the body, pulse oximetry or a blood test may be used to check blood oxygen levels. A blood test may also test for infection.⁵

Prevention of ARDS 

People can prevent ARDS by addressing underlying risk factors such as obesity, alcohol and tobacco use, and avoiding lung injury by staying safe around chemicals and smoke, for example. Additional steps include treating lung infections promptly.⁵

If you notice a decline in blood oxygen levels, e.g. while using a home pulse oximeter, you should consult healthcare services immediately. Thisis a medical emergency due to the risk of vital organs like the heart and brain being starved of oxygen.⁵

Complications of ARDS 

ARDS can cause potentially severe complications, including:

• Muscle weakness: patients that recover may experience nerve and muscle damage, which cause pain and weakness⁵
• Respiratory failure: when the body's demand for oxygen exceeds the respiratory system's oxygen supply, respiratory failure occurs^1,2
• Organ failure: low oxygen levels in the bloodstream means organs will receive less oxygenated blood, which may result in their failure^1,2
• PTSD and depression: patients may develop psychological conditions due to the traumatic experience of being critically ill with ARDS⁵
• Pulmonary hypertension (high blood pressure): ARDS can cause fluid to build up in the lungs, increasing blood pressure in the pulmonary artery, which takes blood from the lungs to the heart⁷

FAQs 

Can ARDS be cured? 

There is no specific cure for ARDS, but patients can expect to fully recover and regain lung function with appropriate treatment and management.⁶

Is ARDS contagious? 

ARDS itself is not contagious,⁶ although some contagious diseases like the flu can cause ARDS.⁵

Can smoking cause ARDS? 

Tobacco use can increase the risk of developing lung infections and cause injury to the lungs that may ultimately trigger ARDS, but it is not a direct cause of the condition.⁴

What can I expect if I have ARDS? 

If you have ARDS, you may experience various symptoms, such as shortness of breath, confusion, fatigue, and drowsiness, as your lungs will not be working at full efficiency. 

In hospital, patients can expect supportive care, such as mechanical ventilation and oxygen therapy, to help their lungs regain function and increase blood oxygen levels. 

Your treatment will depend on the underlying cause of ARDS. For example, you may be prescribed antibiotics if you have a bacterial infection. 

If the severity of ARDS is high, you may be hospitalised in the intensive care unit (ICU) to ensure ongoing monitoring and prompt treatment. 

Recovery can take weeks to months, with patients also reporting long-term complications.⁵

How common is ARDS? 

ARDS is a relatively rare condition, but it is very serious if it occurs. About 1 in 3 people who get it will die. However, death generally occurs due to the underlying cause rather than ARDS itself.⁵

When should I see a doctor?

If you experience a combination of symptoms associated with ARDS, including shortness of breath, low blood oxygen, shallow breathing or fatigue, you should immediately seek medical attention. With ARDS, it is essential to treat any underlying conditions, as prompt diagnosis and treatment can improve the chances of recovery.⁵

Summary 

ARDS is a severe lung condition that can cause life-threatening respiratory failure. ARDS is caused by various factors, including smoke inhalation, trauma, and infection. Symptoms include shortness of breath, shallow breathing, confusion and tiredness. 

Some people have risk factors for developing ARDS, such as old age or obesity. However, it is unclear whether the high mortality rate is caused by ARDS rather than underlying medical conditions.¹

Effective treatment for ARDS involves providing supportive care, such as oxygen therapy, mechanical ventilation and medication. The underlying cause of ARDS should be targeted during treatment and considered when taking preventative measures. 

Preventative measures include prompt treatment of lung infections and avoiding smoking. By detecting and treating the condition early, patients can improve their chances of survival and reduce their risk of long-term complications.¹