Acute Respiratory Distress Syndrome: Symptoms, Causes & Treatment

Breathing difficulty after a severe infection, injury or medical condition should never be ignored. In some people, the lungs can become severely inflamed and filled with fluid, making it difficult for oxygen to enter the bloodstream. This serious condition is called acute respiratory distress syndrome, commonly known as ARDS. 

ARDS can develop within hours or over a few days. It is usually triggered by another illness, such as pneumonia or sepsis, rather than occurring on its own. Because oxygen levels can fall quickly, ARDS requires urgent medical evaluation and is often treated in a hospital intensive care unit. 

This guide explains ARDS symptoms, ARDS causes, how doctors diagnose it and the main approaches used for ARDS treatment. 

What Is Acute Respiratory Distress Syndrome? 

Acute respiratory distress syndrome is a serious form of lung injury that causes dangerously low blood oxygen levels. The tiny air sacs in the lungs, called alveoli, normally fill with air and allow oxygen to pass into the blood. 

In ARDS, inflammation damages the walls of these air sacs. Fluid then leaks into them, while a substance called surfactant may break down. Surfactant helps keep the air sacs open. When it is reduced, the lungs may become stiff and less able to expand. 

As a result: 

• The lungs become harder to inflate. 
• Oxygen has difficulty moving into the bloodstream. 
• Breathing becomes fast and tiring. 
• Other organs may not receive enough oxygen. 
• Severe cases may lead to respiratory failure or organ damage. 

According to the National Heart, Lung, and Blood Institute, ARDS can develop at any age and may worsen very quickly. 

ARDS is not the same as the respiratory distress syndrome seen in premature newborns. It is also different from a simple episode of breathlessness caused by anxiety, mild asthma or temporary exertion. 

Acute Respiratory Distress Syndrome Symptoms 

The first sign of ARDS is often sudden or worsening shortness of breath. However, symptoms can vary depending on the underlying cause and how severely the lungs are affected. 

Common acute respiratory distress syndrome symptoms include: 

• Severe difficulty breathing 
• Fast, shallow breathing 
• A feeling of not getting enough air 
• Low oxygen levels 
• Fast heartbeat 
• Cough, sometimes with phlegm 
• Bluish lips, fingers or skin 
• Extreme tiredness or weakness 
• Fever or chills 
• Chest discomfort, especially during deep breathing 
• Confusion, unusual sleepiness or difficulty staying alert 
• Crackling, bubbling or rattling sounds while breathing 
• Low blood pressure in severe cases 

A person with ARDS may appear frightened or exhausted because breathing requires a great deal of effort. They may use the muscles of the neck, chest or abdomen to breathe. Some people become confused because the brain is not receiving enough oxygen. 

When Are ARDS Symptoms an Emergency? 

Seek emergency medical help if someone has: 

• Severe or rapidly worsening breathlessness 
• Blue or grey lips, face or fingertips 
• Confusion, fainting or difficulty waking up 
• Chest pain with breathing difficulty 
• Inability to speak full sentences because of breathlessness 
• Very fast breathing or extreme exhaustion 
• A falling or unusually low oxygen reading on a pulse oximeter 

Do not wait for a routine laboratory appointment if ARDS is suspected. The person may need oxygen, imaging and monitoring in a hospital. 

ARDS Causes and Risk Factors 

ARDS causes are linked to injury or inflammation in the lungs. Sometimes the damage begins directly in the lungs. In other cases, a severe illness elsewhere in the body triggers widespread inflammation that affects the lungs. 

Direct Lung Injury 

Common direct causes of ARDS include: 

• Severe pneumonia 
• Viral infections, including influenza or COVID-19 
• Breathing in smoke or toxic chemical fumes 
• Inhaling vomit or stomach contents 
• Near-drowning 
• Serious chest injury 
• Lung infection caused by bacteria, viruses or fungi 
• Blood transfusion-related lung injury in rare cases 

Pneumonia is one of the most common triggers. A severe infection can fill the lungs with inflammatory fluid and reduce oxygen exchange. 

Indirect Causes of ARDS 

ARDS may also develop because of a serious condition affecting the whole body. These causes include: 

• Sepsis, or a dangerous response to infection 
• Severe pancreatitis 
• Major burns or trauma 
• Shock or very low blood pressure 
• Serious blood loss 
• Fat embolism after a major bone fracture 
• Certain medicine reactions or drug overdoses 
• Complications after major surgery 
• Severe infections affecting multiple organs 

Who Has a Higher Risk of ARDS? 

ARDS can affect anyone, but the risk may be higher in people who: 

• Have a severe infection or pneumonia 
• Smoke tobacco 
• Drink heavily 
• Have chronic lung disease 
• Have a weakened immune system 
• Have recently experienced major trauma or surgery 
• Have sepsis, pancreatitis or severe burns 
• Have been exposed to smoke, chemical fumes or polluted air 
• Have received prolonged mechanical ventilation 
• Have certain inherited or genetic risk factors 

Having one of these risk factors does not mean that a person will definitely develop ARDS. It simply means that doctors may monitor breathing and oxygen levels more closely. 

How Is Acute Respiratory Distress Syndrome Diagnosed? 

There is no single blood test that confirms ARDS. Doctors diagnose it by combining the person’s symptoms, medical history, physical examination, oxygen measurements and imaging results. 

1. Medical History and Physical Examination 

The doctor may ask: 

• When did the breathing problem begin? 
• Was there a recent infection, injury or surgery? 
• Has the person inhaled vomit, smoke or chemicals? 
• Is there a history of heart or lung disease? 
• Are there symptoms of sepsis, such as fever, confusion or very low blood pressure? 

During examination, the doctor may check breathing rate, heart rate, blood pressure, skin colour and lung sounds. Crackling sounds may suggest fluid or inflammation in the lungs, although this finding alone cannot confirm ARDS. 

2. Pulse Oximetry 

A pulse oximeter is a small device placed on the finger or ear. It estimates the amount of oxygen in the blood without taking a blood sample. 

Doctors may use repeated readings to monitor whether oxygen levels are improving or falling. Readings can sometimes be affected by cold fingers, poor circulation, movement, nail products or device limitations. A reading should always be interpreted along with symptoms and medical examination. 

3. Arterial Blood Gas Test 

An arterial blood gas, or ABG, measures oxygen, carbon dioxide and acidity in a sample of arterial blood. It helps doctors understand how effectively the lungs are transferring oxygen into the blood. 

ABG testing is generally performed in a hospital because it requires an arterial blood sample and is used for urgent clinical decisions. 

4. Chest X-Ray or CT Scan 

A chest X-ray may show widespread white or cloudy areas in both lungs. A CT scan can provide more detailed images and may help identify pneumonia, fluid, lung injury or other causes of breathing difficulty. 

Imaging also helps doctors rule out conditions that may look similar to ARDS, such as heart failure-related fluid buildup, a collapsed lung or a blood clot in the lung. 

5. Blood and Other Laboratory Tests 

Doctors may order blood tests to: 

• Look for infection or inflammation 
• Check blood cell counts 
• Assess kidney and liver function 
• Measure electrolytes 
• Check clotting status 
• Identify signs of sepsis 
• Evaluate whether the heart may be involved 
• Monitor the effects of treatment 

Blood cultures, sputum testing, urine testing or respiratory virus testing may be used to identify the underlying infection. 

6. Heart Tests 

Heart failure can also cause fluid in the lungs and low oxygen levels. Doctors may use an electrocardiogram, echocardiogram or other heart-related tests to determine whether the breathing problem is primarily due to the heart. 

ARDS Treatment: How Is ARDS Managed? 

ARDS treatment focuses on two main goals: 

1. Improving oxygen levels and supporting breathing. 
2. Finding and treating the underlying cause. 

Treatment must be personalised according to the person’s age, health, oxygen level, cause of ARDS and response to therapy. 

Oxygen Therapy 

Oxygen is usually the first treatment. It may be given through: 

• Nasal prongs 
• A face mask 
• High-flow nasal oxygen 
• Non-invasive ventilation 
• A breathing tube connected to a ventilator 

The medical team continuously monitors oxygen levels, breathing effort and blood gas results. 

Mechanical Ventilation 

If oxygen therapy is not enough, a ventilator may be needed. A breathing tube is placed into the windpipe, and the machine supports breathing. 

Modern ARDS treatment generally uses lung-protective ventilation. This means the ventilator is carefully adjusted to reduce further injury to already fragile lungs. The American Thoracic Society recommends lower tidal-volume ventilation and controlled airway pressures for patients with ARDS. 

Ventilator treatment can be lifesaving, but it may also have risks, including infection, blood clots, muscle weakness and lung injury. These risks are closely monitored in intensive care. 

Prone Positioning 

Prone positioning means placing a patient on their stomach under careful medical supervision. This position may improve oxygen movement through the lungs in moderate or severe ARDS. 

Patients on ventilators may remain in the prone position for several hours at a time. A trained healthcare team must manage the breathing tube, lines and pressure points safely. 

Treating the Underlying Cause 

The treatment depends on what triggered ARDS. For example: 

• Antibiotics may be used for bacterial pneumonia or sepsis. 
• Antiviral treatment may be considered for selected viral infections. 
• Treatment for pancreatitis may be required. 
• Fluids, medicines and infection control are used for sepsis or shock. 
• Special treatment may be needed after chemical inhalation or aspiration. 
• Surgery or trauma care may be required after serious injury. 

Antibiotics and other medicines should only be used when prescribed. Taking medicines without medical guidance can delay the correct treatment or cause harmful side effects. 

Medicines and Supportive Care 

Doctors may use medicines to: 

• Reduce inflammation in selected cases 
• Prevent blood clots 
• Control pain or anxiety 
• Help the patient tolerate a ventilator 
• Treat infections 
• Manage blood pressure 
• Remove excess fluid when appropriate 

ECMO for Severe ARDS 

Extracorporeal membrane oxygenation, or ECMO, is an advanced treatment used in selected cases when the lungs cannot provide enough oxygen despite other treatments. 

ECMO temporarily works like an artificial lung. It removes carbon dioxide, adds oxygen to the blood and returns the blood to the body. It is available only in specially equipped hospitals and involves important risks. 

Nutrition and Physical Therapy 

Patients with ARDS may need nutritional support through a feeding tube, especially if they remain on a ventilator. Physical therapy can help reduce muscle weakness and stiffness during recovery. 

Even after the lungs improve, the body may remain weak after a long ICU stay. Gradual rehabilitation, breathing exercises and follow-up care can support recovery. 

Possible Complications of ARDS 

ARDS can affect more than the lungs. Possible complications include: 

• Respiratory failure 
• Pneumonia or other hospital-acquired infections 
• Blood clots 
• Kidney problems 
• Muscle weakness 
• Pressure injuries from prolonged bed rest 
• Confusion or memory problems 
• Anxiety, depression or post-traumatic stress 
• Scarring or reduced lung function 

The risk of complications depends on the severity of ARDS, the underlying illness, treatment duration and general health. 

Recovery After ARDS 

Recovery can take days, weeks or several months. Some people recover most of their lung function, while others may experience continuing breathlessness, tiredness, weakness or reduced exercise tolerance. 

After leaving the hospital, a person may need: 

• Follow-up visits with a physician or pulmonologist 
• Pulmonary rehabilitation 
• Breathing and strengthening exercises 
• Nutritional support 
• Emotional or psychological support 
• Review of medicines and oxygen requirements 
• Repeat tests if advised by the doctor 

Family members should understand that recovery is not always immediate. A patient who survived a critical illness may need patience and practical support while returning to normal activities. 

Can ARDS Be Prevented? 

Not every case of ARDS can be prevented, but some steps may lower the risk: 

• Keep vaccinations up to date as advised by a doctor. 
• Avoid smoking and second-hand smoke. 
• Seek prompt medical care for severe pneumonia or infection. 
• Follow safety precautions around chemicals, fumes and smoke. 
• Avoid misuse of alcohol, medicines and recreational drugs. 
• Manage chronic heart, lung and metabolic conditions. 
• Follow medical advice after surgery or a major injury. 
• Treat infections early rather than delaying care. 

Prevention is especially important for people with chronic lung disease or weakened immunity.

Conclusion 

Acute respiratory distress syndrome is a serious condition in which inflammation and fluid buildup prevent the lungs from supplying enough oxygen to the body. The most important ARDS symptoms include severe breathlessness, fast breathing, low oxygen levels, blue lips or skin, confusion and extreme tiredness. 

ARDS causes often include pneumonia, sepsis, severe infection, aspiration, trauma, pancreatitis and smoke or chemical exposure. Diagnosis involves a combination of clinical examination, oxygen monitoring, blood tests and chest imaging. ARDS treatment may include oxygen, mechanical ventilation, prone positioning, medicines, fluid management and advanced support such as ECMO in selected cases. 

If breathing difficulty is severe or worsening, seek emergency care immediately. Early treatment of the underlying illness and careful hospital monitoring can improve the chance of recovery. 

Medical Disclaimer: This article is for general awareness and does not replace consultation with a qualified doctor. Do not delay emergency care or start treatment based only on information read online.