Acute Respiratory Distress Syndrome (ARDS): Basic Summary

What is Acute Respiratory Distress Syndrome (ARDS)?

Acute Respiratory Distress Syndrome (ARDS) is a severe condition where the lungs fail to provide enough oxygen to the bloodstream due to widespread inflammation and fluid accumulation in the air sacs (alveoli).

It can result from direct lung injury or systemic illness. ARDS isn’t a standalone disease but a complication of underlying issues like pneumonia, sepsis, or trauma.

Globally, ARDS affects approximately 10% of patients in intensive care units, with mortality rates ranging from 30-40%, depending on its severity and the patient’s overall health.


How Does ARDS Occur?

Think of your lungs as sponges that expand and contract to deliver oxygen to your blood. In ARDS, this sponge-like system becomes waterlogged due to inflammation and fluid leakage into the alveoli.

Normally, a thin barrier separates the air in the lungs from the blood, allowing gas exchange. In ARDS, inflammation damages this barrier, leading to fluid buildup and impaired oxygen transfer.

For an analogy, imagine a balloon trying to inflate while submerged in water. No matter how much you try, it can’t expand properly. Similarly, ARDS limits the lungs’ ability to fill with air, causing severe oxygen deprivation.


What Are the Causes of ARDS?

ARDS stems from various direct and indirect injuries to the lungs. Here are the most common causes:

  1. Sepsis (30-50%): The leading cause of ARDS, sepsis is a life-threatening condition where the body’s response to infection damages its own tissues.
  2. Pneumonia (20-30%): Severe lung infections can directly inflame and damage the alveoli.
  3. Aspiration (15-20%): Inhaling substances like stomach acid or food into the lungs triggers inflammation.
  4. Trauma (10-15%): Severe injuries, especially to the chest, can result in ARDS.
  5. Inhalation Injuries: Exposure to toxic fumes or smoke damages lung tissue.
  6. Pancreatitis and Blood Transfusions: Both conditions can cause widespread inflammation, indirectly affecting the lungs.

Risk Factors

Certain factors increase the likelihood of developing ARDS, even in seemingly healthy individuals. Understanding these risks is crucial for early detection and prevention:

  1. Chronic Health Conditions: Those with heart disease, liver disease, or diabetes are more vulnerable.
  2. Smoking History: Long-term smoking damages lung tissue, making it susceptible to injury.
  3. Age: Older adults, especially over 65, have a higher risk due to decreased resilience.
  4. Alcohol Abuse: Chronic alcohol consumption weakens the immune system, increasing susceptibility to infections and ARDS.
  5. Prolonged Hospital Stays: Patients in intensive care, particularly those on mechanical ventilation, face higher risks.

Among these, sepsis and pneumonia are the most significant contributors to ARDS.


What Are the Symptoms of ARDS?

The hallmark symptoms of ARDS are rapid and progressive respiratory failure. These include:

  1. Severe Shortness of Breath (Dyspnea): Often described as gasping or feeling like you can’t catch your breath.
  2. Low Oxygen Levels (Hypoxemia): Causes bluish discoloration of lips and fingertips.
  3. Rapid Breathing (Tachypnea): A compensatory mechanism as the body struggles to get oxygen.
  4. Fatigue and Weakness: Oxygen deprivation impacts muscle function and energy levels.
  5. Coughing: Sometimes associated with frothy sputum due to fluid in the lungs.

These symptoms result from fluid-filled alveoli and the reduced capacity for oxygen exchange. Left untreated, ARDS can rapidly lead to organ failure and death.


Differential Diagnosis

Many conditions mimic ARDS, so careful evaluation is critical. The most common differential diagnoses include:

  1. Heart Failure: Fluid in the lungs (pulmonary edema) from heart dysfunction can resemble ARDS.
  2. Pulmonary Embolism: A blood clot in the lungs causes sudden shortness of breath, similar to ARDS.
  3. Pneumonia: Both conditions share overlapping symptoms, especially in the early stages.
  4. COVID-19-related ARDS: Differentiating between ARDS caused by COVID-19 and other causes requires a detailed history and testing.

Distinguishing ARDS from these conditions often requires imaging, lab tests, and a thorough clinical examination.


How to Diagnose ARDS?

Diagnosing ARDS involves a combination of clinical assessment, imaging, and lab tests.

  1. Gold Standard: Chest X-ray or CT Scan
    These tests reveal diffuse lung opacities or “white-out” patterns due to fluid accumulation. A CT scan offers more detailed imaging, helping to rule out other causes like a pulmonary embolism.
  2. Blood Oxygen Levels (Arterial Blood Gas)
    This test measures oxygen and carbon dioxide levels in the blood. A PaO2/FiO2 ratio (partial pressure of oxygen to inspired oxygen fraction) below 300 indicates ARDS severity.
  3. Exclusion of Other Causes
    Heart function tests, such as echocardiograms, help differentiate ARDS from heart-related lung issues.

Treatment of ARDS

Can ARDS Be Treated?
Yes, though ARDS requires immediate, intensive medical care. Treatment focuses on supporting breathing, managing the underlying cause, and preventing complications.

  1. Mechanical Ventilation (Gold Standard) Most patients with ARDS need ventilator support. Positive End-Expiratory Pressure (PEEP) helps keep alveoli open, improving oxygen delivery.
  2. Prone Positioning
    Lying patients on their stomach improves oxygenation by redistributing lung fluids and promoting better ventilation.
  3. Medications
    • Steroids: Reduce inflammation, especially in severe ARDS.
    • Antibiotics: Treat bacterial infections causing ARDS.
    • Sedatives: Help manage agitation and synchronize with ventilators.
  4. Extracorporeal Membrane Oxygenation (ECMO)
    In severe cases, ECMO bypasses the lungs, directly oxygenating the blood. It serves as a last resort for patients unresponsive to standard treatments.
  5. Supportive Care
    • Preventing infections with antibiotics and sterile techniques.
    • Managing fluid levels to avoid further lung congestion.

While most patients recover, ARDS survivors may face long-term challenges, including reduced lung function, fatigue, and mental health issues.


References

  1. Matthay, M. A., et al. (2019). “Acute Respiratory Distress Syndrome.” Nature Reviews Disease Primers.
  2. Fan, E., et al. (2018). “Acute Respiratory Distress Syndrome: Advances in Diagnosis and Treatment.” JAMA.
  3. ARDS Definition Task Force. (2012). “The Berlin Definition of ARDS.” JAMA.
  4. National Heart, Lung, and Blood Institute (NHLBI). “What Is ARDS?” Retrieved from nhlbi.nih.gov.
  5. MedlinePlus. “Acute Respiratory Distress Syndrome.” Retrieved from medlineplus.gov.
Subscribe
Notify of
guest
0 Comments
Oldest
Newest Most Voted
Inline Feedbacks
View all comments
Scroll to Top