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Acute Respiratory Distress Syndrome (ARDS) Overview  

Acute respiratory distress syndrome (ARDS) is a type of severe lung injury that develops rapidly within a few hours or days in patients with infections such as pneumonia, COVID-19, and sepsis or other serious medical conditions. It is an acute lung injury that usually occurs in people who are ill from a serious medical condition and admitted to the hospital. 

ARDS is a life-threatening condition of the respiratory system. It is a serious lung condition that can lead to acute respiratory failure without prompt and aggressive treatment in the intensive care unit (ICU). Most patients with ARDS require mechanical ventilation support and medical care from a multidisciplinary team of specialists in critical care medicine.

ARDS Stats and Facts

• ARDS affects about 3 million people globally and 200,000 people in the U.S. each year.

• ARDS is the underlying cause of 1 in 4 people requiring mechanical ventilation.

• ARDS is responsible for 1 in 10 ICU admissions. 

• Approximately two-thirds of patients who died from COVID-19 had ARDS.

Importance in Critical Care

Acute respiratory distress syndrome is a life-threatening acute lung injury that can result in lung damage, respiratory failure, and multi-organ failure. Many patients with ARDS require life support with a ventilator to help them breathe. Yet, despite extensive research and advances in treatments for acute lung injury, ARDS remains under-diagnosed. Experts estimate that about 2 out of 5 cases of ARDS are missed by clinicians. As a result, ARDS remains undertreated and has a high mortality rate of up to 40%.

Common Causes of ARDS

Pathophysiology: ARDS Mechanisms

According to the National Heart, Lung, and Blood Institute, acute respiratory distress syndrome (ARDS) is a lung injury that develops in critically ill patients who are in the hospital receiving treatment for a serious infection, illness, or injury. 

In people with ARDS, fluid leaks into the alveoli (tiny air sacs) in the lungs. This prevents the air sacs from filling with air, which leads to hypoxia (dangerously low blood oxygen levels). 

As a result, pulmonary artery vasoconstriction occurs (narrowing of the blood vessels supplying blood to the lungs). The body tries to redirect blood away from the affected alveoli and poorly-ventilated portions of the lungs towards unaffected and better-ventilated parts of the lungs. This can lead to pulmonary hypertension (high blood pressure in the lungs) and lung damage. Without prompt and aggressive treatment, ARDS can cause diffuse alveolar damage. 

In addition, vital organs such as the heart, brain, kidneys, and gastrointestinal tract do not get enough oxygen to function properly. Consequently, people with ARDS can develop life-threatening medical complications and multiple organ failure.

Pulmonary ARDS (Lung-Related Causes)

• Pneumonia (infection and inflammation of the lungs caused by bacteria, viruses, or fungi)

• Aspiration pneumonia (breathing in a foreign object such as food into the airway)

• SARS-CoV-2 infection (COVID-19)

• Inhalation of toxic gases or chemical fumes

• Ventilator-induced lung injury

• Lung trauma or injuries

• Cardiovascular surgery

• Drowning or near drowning

• Fat embolism (a condition in which fat particles enter the bloodstream and block blood flow)

• Pulmonary vasculitis (inflammation of blood vessels in the lungs that can lead to damage of lung tissue)

Extrapulmonary ARDS (Non-Lung-Related Causes)

• Sepsis or septicemia (a life-threatening condition in which the body has an exaggerated response to infection)

• Transfusion-related acute lung injury (TRALI) due to an immune response to donor blood after a blood transfusion

• Chest trauma

• Pancreatitis

• Burns

• Drug reactions

• Drug overdose, for example, from opioids or cocaine

• Non-cardiogenic shock (a condition in which cardiac function is normal but the heart does not fill properly with blood)

• Cardiopulmonary bypass (a procedure in which a machine temporarily takes over heart and lung function during surgery)

Risk Factors for Developing ARDS

ARDS typically develops in people who are in hospital for serious infections, illnesses, or injuries. Risk factors for ARDS include:

• Older age (above 65 years).

• Underlying lung disease.

• Smoking.

• Substance use disorders.

Common ARDS Symptoms

• Dyspnea (severe shortness of breath). This can feel like breathlessness, difficulty breathing, air hunger, tightening in the chest, or a feeling of suffocation.

• Tachypnea (rapid breathing above the normal respiratory rate in adults which is 12 to 20 breaths per minute).

• Labored breathing (increased effort to breathe).

• Noisy breathing (clicking, rattling, or bubbling sounds while breathing).

• Tachycardia (fast heartbeat).

• Cyanosis (bluish discoloration of the fingertips and lips due to low blood oxygen levels).

Diagnostic Criteria 

A diagnosis of ARDS is made if a person has: 

• Acute onset of lung injury (develops within a week).

• Bilateral lung infiltrates (substances denser than air, such as fluid, blood, or pus) are seen on chest X-ray or computed tomography (CT) scan in both lungs.

• Non-cardiogenic pulmonary edema (too much fluid in the lungs).

• Hypoxemia (low blood oxygen level)

Healthcare providers classify ARDS as mild, moderate, or severe or as exudative, proliferative, or fibrotic. These classifications are based on the blood oxygen levels, the amount of fluid buildup and inflammation in the lungs, the amount of scarring in the lung tissue, and the repair needed to regain normal lung function.

Diagnostic Tests: How Do Doctors Diagnose ARDS?  

Healthcare providers can make a diagnosis of ARDS based on symptoms, physical exam, and diagnostic tests, such as: 

• Chest X-ray

• Blood tests to measure blood oxygen level, complete blood count, and others

• Pulse oximetry (a fingertip sensor) for continuous measurement of oxygen levels

• Electrocardiogram (ECG or EKG) to evaluate electrical activity of the heart

• Echocardiogram (ultrasound of the heart) to assess heart function

• CT Scan for more detailed images of the lungs

• Sputum culture to diagnose infections in the lungs and airways

Differentiating From Other Respiratory Conditions

A life-threatening lung injury such as acute respiratory distress syndrome (ARDS) can cause many of the same or similar symptoms as chronic lung and heart conditions. Diagnostic tests can help specialists in intensive care med identify the cause of the symptoms.

Treatment and Management  

Initial Management Strategies

The immediate treatment for acute respiratory distress syndrome consists of raising blood oxygen levels to prevent organ damage. This is achieved with a mechanical ventilator, a breathing machine that can provide breathing support. High-flow nasal cannula oxygen therapy may be sufficient in some patients who don’t have severe disease.

Medications used by specialists in intensive care medicine to treat ARDS may include:

• Early neuromuscular blockade.

• Sedatives to reduce discomfort and help in tolerating mechanical ventilation.

• Anticoagulants (blood thinners) to prevent blood clots.

• Diuretics (water pills) to remove excess fluid from the body.

• Antibiotics to treat lung infections.

Mechanical Ventilation Techniques  

Various mechanical ventilation techniques are used in patients with ARDS, such as:

• Low tidal volumes

• Low plateau pressures to minimize barotrauma using low FiO2

• Optimization of positive end-expiratory pressure (PEEP) 

• Prone positioning

• Fluid management

• Extracorporeal membrane oxygenation (ECMO) for patients with severe ARDS who don’t respond to conventional mechanical ventilation 

• Non-invasive ventilation

• Esophageal pressure monitoring

• Recruitment maneuvers

Supportive Treatments and Therapies

• Mobility exercises and physical therapy to maintain muscle strength

• Pulmonary rehabilitation to increase lung capacity and strengthen the lungs

Recovery and Long-Term Outcomes  

Rehabilitation Process Post-ARDS

It can take several weeks to months for your lungs to regain function and for you to recover fully from acute respiratory distress syndrome (ARDS). A supervised pulmonary rehabilitation program, consisting of breathing exercises and breathing techniques, can help to relieve symptoms like shortness of breath and help you perform activities of daily living with minimal assistance. 

Potential Long-Term Effects on Health  

Potential complications of acute respiratory distress syndrome include:

• Pneumothorax (collapsed lung)

• Pleural effusion (buildup of fluid in the space between the lungs and chest wall)

• Pulmonary fibrosis (scarring of the lung tissue)

• Multiple organ failure

• Deep vein thrombosis (blood clot in a leg)

• Delirium (confusion)

• Muscle weakness

• Stress ulcers

• Mental health conditions such as anxiety, depression, and post-traumatic stress disorder (PTSD) 

Research and Future Directions In Treatment

ARDS is a life-threatening lung injury in which fluid leaks into the air sacs in the lungs. There is no known cure for ARDS.

Recent research on acute respiratory distress syndrome (ARDS) reported by the clinical trials network includes: 

• Research on lysolipid levels. Lysolipids are a byproduct of the body’s immune response to bacteria and viruses. They can reduce the amount of surfactant (a substance made of fats and proteins) that is necessary for lung inflation. 

• Researchers in respiratory medicine are studying how different levels of inflammation affect ARDS prognosis and trying to identify subgroups of patients who may respond better to certain treatments. 

• Scientists are investigating personalized ventilator therapies in mechanically ventilated patients with ARDS. They are looking at ways to use CT scans to detect strain on lung tissue from ventilators. 

• Some studies have found that steroids may reduce 3-month mortality rates, but others have found that steroids may be detrimental in late ARDS. 

• A meta-analysis found that recruitment maneuvers are unlikely to improve clinical outcomes for unselected ARDS patients. 

• Edesa Biotech, Inc. is developing Paridiprubart, an anti-TLR4 monoclonal antibody, as a treatment for hospitalized COVID-19 patients with ARDS. 

• A secondary analysis of the HARP-2 study found that patients with high baseline plasma IL-18 levels had an increased risk of 28-day mortality. 

Frequently Asked Questions  

What Is Life Expectancy With ARDS?

Life expectancy with ARDS depends on various factors, including the person’s underlying health status, medical history, and severity of lung injury. 

ARDS is a life-threatening condition, but it is not always fatal. About 50% to 75% of patients survive ARDS if they receive prompt treatment in intensive care units. Survival rates are lower when diagnosis and treatment are delayed, and other organs have begun to fail when treatment is begun. Also, the prognosis (outlook) is poorer in patients who have severe lung damage from a direct lung injury, such as severe pneumonia, compared to those who have indirect damage, for example, from a blood transfusion.

Can You Fully Recover From ARDS?

You can fully recover from ARDS, but it can be 6-12 months before your lungs recover completely and you regain normal lung function. 

What Are The 5 P's of ARDS Treatment?

The five P's of ARDS treatment are:

• Perfusion: Ensuring there is enough oxygen in the blood and throughout the body.

• Positioning: Placing the patient in the prone position (on their belly).

• Protective lung ventilation: Using mechanical ventilator support.

• Protocol weaning: Gradually reducing ventilator support until the patient can breathe on their own and be ventilator-free.

• Prescription Medications: Using medications as needed, such as blood thinners to prevent blood clots and steroids to reduce inflammation.