What are the other Names for this Condition? (Also known as/Synonyms)

• Adult Respiratory Distress Syndrome
• Non-Cardiac Pulmonary Edema
• Non-Cardiogenic Pulmonary Edema

What is Acute Respiratory Distress Syndrome? (Definition/Background Information)

• Acute Respiratory Distress Syndrome (ARDS) is an acute lung condition caused by acute lung inflammation that leads to decreased oxygen saturation (hypoxemia) levels in blood
• Acute Respiratory Distress Syndrome is defined as acute hypoxemic respiratory failure due to lung inflammation from pneumonia or sepsis/inflammation in another organ of the body, and without accompanying heart failure
• It is the most serious type of injury to the lungs and usually happens within a week of injury to the lung or other major parts of the body
• Common triggers for Acute Respiratory Distress Syndrome are sepsis (infection and or toxins in the blood), pneumonia, aspiration of stomach contents into the lung, trauma, pancreatitis, and inhalation of toxic material
• For a diagnosis of Acute Respiratory Distress Syndrome, the characteristic clinical and radiological features, as well as an oxygenation ratio (PaO2/FiO2) of less than 300 mmHg must be present
• Despite availability of best treatment options, the prognosis of Acute Respiratory Distress Syndrome is mostly guarded. The death rate can be very high, particularly when ARDS occurs due to sepsis

Who gets Acute Respiratory Distress Syndrome? (Age and Sex Distribution)

• Acute Respiratory Distress Syndrome is seen worldwide and it affects nearly 2 million people worldwide. In the US, around 150,000 individuals are diagnosed with it every year
• There is no racial or ethnic preference observed
• Both males and females can develop ARDS
• Even though it can occur in any age group, the elderly succumb to ARDS more often, mainly due to certain pre-existing or associated illnesses

What are the Risk Factors for Acute Respiratory Distress Syndrome? (Predisposing Factors)

The risk factors of Acute Respiratory Distress Syndrome (ARDS) include:

• Any major insult (injury/serious illness) to the body increases one’s risk of ARDS such as pneumonia and septic shock
• Many individuals who develop ARDS may have already been hospitalized for another illness such as pneumonia
• Individuals with a history of alcoholism are at a higher risk of developing ARDS, due to the risk of aspiration of stomach contents (vomitus)
• Inflammation of the pancreas (acute pancreatitis) commonly from alcoholism or gallstones can cause ARDS

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Acute Respiratory Distress Syndrome? (Etiology)

Although the exact mechanism of Acute Respiratory Distress Syndrome is not completely understood, the condition normally develops from acute infection, sepsis, or inflammation leading to acute lung injury. Many of the risk factors associated with ARDS can cause this lung condition.

Acute Respiratory Distress Syndrome can cause lung injury in two ways:

• Direct lung injury (injury that affects the lung directly) from factors such as:
  • Pneumonia, SARS infection
  • Harmful fumes and smoke
  • Inhaling vomitus (usually occurs when the individual is unconscious or semi-unconscious)
  • Trauma to the lung
  • Drowning incident
  • Oxygen injury (toxicity)
  • Fat embolism (condition where a fat particle blocks the artery)
•  Indirect lung injury (injures the lungs secondary to an illness) from factors such as:
  • Sepsis (a condition where certain bacteria infect the circulating blood)
  • Blood transfusions
  • Chest or head injury
  • Pancreatitis (infection or inflammation of the pancreas)
  • Drug reaction, due to aspirin, opioids, or chemotherapy
  • Perforated bowel
  • Burn injury

Following the insult to the lung from any cause, functional units of the lung (capillary endothelial and alveolar cells responsible for oxygen-carbon dioxide exchange) are damaged. This damage progresses to an accumulation of fluid in and around the alveoli (the site where oxygen enters the lungs from the bronchial airways), which results in decreased oxygen in blood.

What are the Signs and Symptoms of Acute Respiratory Distress Syndrome?

The signs and symptoms of Acute Respiratory Distress Syndrome include:

• Shortness of breath that develops within 1-2 days
• Rapid breathing or difficulty in breathing
• Coughing
• Confusion
• Tiredness
• Other signs and symptoms may depend on the cause of the condition. For example, individuals may develop respiratory or urinary symptoms of infection and fever before ARDS develops

How is Acute Respiratory Distress Syndrome Diagnosed?

The diagnosis tools used for Acute Respiratory Distress Syndrome (ARDS) may include:

• Thorough evaluation of the individual’s medical history and a complete physical examination
• During history taking, the physician may want to know the following:
  • History of ARDS predisposing factors such as infection symptoms, immunosuppression, abdominal pain, inhalation of chemicals, vaping etc., blood transfusion, exposure to Covid 19 infection etc.
  • When the symptoms began and whether they are becoming worse
  • List of prescription and over-the-counter medications currently being taken
  • About one’s personal and family history
• A physical examination may reveal the following:
  • Breathing difficulty, low oxygenation, and respiratory failure
  • Low blood pressure or shock state
  • Abnormal sounds from the lung (crackles)
  • Severe low  oxygen in blood (measured by a pulse oximeter) in spite of high concentration of oxygen supplementation by facemask or high flow oxygen
• Arterial blood gas test is done to measure the level of oxygen in blood:
  • A low level of oxygenation ratio (PaO2/FiO2 < 300 mmHg) is typically  indicative of Acute Respiratory Distress Syndrome
  • Based on oxygenation ratio, ARDS is classified as severe (<100), moderate (100-200), and mild (200-300)
• Chest X-ray may reveal any fluid buildup in the lungs
• Other tests are based on the predisposing (causative) factors of ARDS and may include:
  • Electrocardiogram test to track the electrical activity within the heart
  • Echocardiogram test to reveal any abnormalities with the structure and function of the heart
  • Troponin and BNP (Brain Natriuretic Peptide) to evaluate the heart
  • Lactic acid for sepsis
  • Blood, respiratory, and urine cultures for evaluation of infection

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Acute Respiratory Distress Syndrome?

Acute Respiratory Distress Syndrome (ARDS) is a severe injury to the lung. Individuals recovering out of this lung insult may have complications that could include:

• Ventilator dependence: Individuals may need to be on ventilator support for a long period of time
• Oxygen toxicity can occur in individuals on mechanical ventilation for long periods. This toxicity may affect the central nervous system and the lungs
• Pulmonary fibrosis or lung scarring following ARDS: This makes exchange of oxygen difficult because of stiff lungs
• The affected individuals are at risk for clot formation in the deeper veins of the leg (DVT). This is due to immobility or lying in the hospital bed due to illness for a long time. These clots may break away, travel, and block blood flow to the lungs (pulmonary embolism) and further complicate recovery
• Cognitive dysfunction or delirium, which is characterized by confusion, problems with thinking, memory, reasoning, etc., may occur. It may happen due to decreased oxygen levels in blood for long time periods and/or due to the effect of medications such as prolonged sedation
• Infections: The ventilator tubes (used for breathing assistance) inserted into the windpipe to assist in breathing can  increase risks of ventilator-associated pneumonia (VAP)
• Ventilator settings with high peep pressures can be a risk for pneumothorax (collapse of lung) or barotrauma (air in the mediastinum)
• Lung-related symptoms: Many individuals with ARDS have issues with breathing after the condition. Symptoms, such as difficulty breathing, increased sputum production, and cough, may be present for extended periods  during the recovery period

How is Acute Respiratory Distress Syndrome Treated?

Currently, a multidisciplinary treatment approach is necessary for Acute Respiratory Distress Syndrome (ARDS). The primary goal in treating ARDS includes:

• Treatment of the underlying causative factors
• Supportive treatment to improve blood oxygen levels and prevent complications

ARDS patients, most of the time, require oral breathing tube placement and mechanical ventilation in an intensive care (ICU) setup.

• Medical scientists have proposed optimal settings as to how the individual has to be ventilated. These settings can help the individuals recover from ARDS earlier and also help prevent complications such as lung injury from the ventilator itself
• The parameters may include tidal volume 4-6ml/kg, appropriate PEEP per ARDSNet protocol, SaO2 maintained above 88%

Several modes of ventilation settings are available to manage ARDS patients in the ICU:

• Prone positioning or placing patient flat on the chest helps improve oxygenation
• ECMO (Extracorporeal membrane oxygenation) is a method where blood is removed by tubes and oxygenated by machine, which helps improve oxygenation and provides rest for the lungs
• The fluid levels (intake and output) in the body should be carefully monitored and appropriately managed

The healthcare provider will recommend the best treatment options based upon each patient’s specific circumstances.

How can Acute Respiratory Distress Syndrome be Prevented?

Current medical research has not established a method of preventing Acute Respiratory Distress Syndrome.

What is the Prognosis of Acute Respiratory Distress Syndrome? (Outcomes/Resolutions)

The overall prognosis of Acute Respiratory Distress Syndrome (ARDS) is generally guarded, irrespective of the cause.

• Nearly 40% of the individuals with this respiratory condition succumb to it, especially in cases of severe ARDS.
• Complications of ARDS and survival depend on certain predisposing factors, such as the age of the individual, state of their health, associated medical conditions, risks for multi-organ failure and response to supportive treatment
• Individuals, who do survive, may have several residual complications, such as chronic ICU-related weakness, delirium from prolonged sedation in ICU, chronic respiratory failure and oxygen supplementation from lung fibrosis, renal failure needing dialysis, ventilator dependence and tracheostomy (surgical breathing tube in the neck)

Additional and Relevant Useful Information for Acute Respiratory Distress Syndrome:

Some individuals with Acute Respiratory Distress Syndrome seek counseling for their anxiety, depression, and stress. It is recommended for the individuals to talk to their healthcare provider, family, and friends, for support to help relieve the stress and anxiety.  

Supportive care is crucial for successful recovery from ARDS. Some approaches include:

• Medications that help with relaxation and relieve discomfort
• Monitoring the vital signs, including oxygen saturations
• IV fluids may be given to improve hydration and avoid kidney failure
• Nutritional support - many individuals with ARDS may experience malnutrition; hence, adequate nutrition may be given through a feeding tube