What is the difference between Acute Respiratory Distress Syndrome (ARDS) and Interstitial Lung Disease (ILD)?

From the Guidelines

Acute Respiratory Distress Syndrome (ARDS) and Interstitial Lung Disease (ILD) are distinct respiratory conditions with different causes, onset patterns, and treatments, with ARDS being an acute, life-threatening condition and ILD being a chronic disorder causing progressive scarring of lung tissue. The key differences between ARDS and ILD lie in their pathophysiology, clinical presentation, and management strategies. ARDS is characterized by rapid onset of widespread inflammation in the lungs, typically developing within hours to days after a triggering event such as sepsis, pneumonia, trauma, or aspiration, as described in the American Thoracic Society guideline 1. In contrast, ILD comprises a group of chronic disorders that cause progressive scarring of lung tissue over months to years, often resulting from environmental exposures, autoimmune diseases, or unknown causes.

Causes and Risk Factors

• ARDS is often triggered by conditions such as sepsis, pneumonia, trauma, or aspiration, leading to an inflammatory response and lung injury.
• ILD, on the other hand, can result from various factors including environmental exposures, autoimmune diseases, or unknown causes, with conditions like idiopathic pulmonary fibrosis, sarcoidosis, and hypersensitivity pneumonitis being common forms of ILD.

Clinical Presentation and Diagnosis

• ARDS presents with severe breathing difficulty, low blood oxygen levels, and fluid buildup in the air sacs (alveoli), requiring immediate intensive care.
• ILD is characterized by progressive scarring of lung tissue, leading to symptoms such as dry cough, dyspnea on exertion, and fatigue, with diagnosis often involving pulmonary function tests (PFTs) and high-resolution computed tomography (HRCT) of the chest, as recommended in the 2023 American College of Rheumatology guideline 1.

Treatment and Management

• ARDS management involves immediate intensive care, often with mechanical ventilation using low tidal volumes, PEEP, and prone positioning, as outlined in the American Thoracic Society guideline 1.
• ILD treatment depends on the specific type but may include corticosteroids, immunosuppressants, or antifibrotics for long-term management, with the 2023 American College of Rheumatology guideline 1 providing recommendations for the treatment of ILD in people with systemic autoimmune rheumatic diseases.

Outcomes and Prognosis

• ARDS has a mortality rate of 30-40%, but survivors can recover substantial lung function.
• ILD typically causes irreversible lung damage with a more gradual but progressive decline in respiratory function, emphasizing the importance of early diagnosis and treatment to slow disease progression, as discussed in the context of pulmonary rehabilitation for ILD patients 1.

From the Research

Definition and Characteristics

• Acute Respiratory Distress Syndrome (ARDS) is defined as noncardiogenic pulmonary edema that manifests as rapidly progressive dyspnea, tachypnea, and hypoxemia 2.
• ARDS is characterized by pulmonary edema, refractory hypoxemia, diffuse pulmonary infiltrates, and altered lung compliance 3.
• Interstitial Lung Disease (ILD) is a heterogeneous group of diseases characterized by widespread fibrotic and inflammatory abnormalities of the lung 4.

Diagnostic Criteria

• ARDS diagnostic criteria include onset within one week of a known insult or new or worsening respiratory symptoms, profound hypoxemia, bilateral pulmonary opacities on radiography, and inability to explain respiratory failure by cardiac failure or fluid overload 2.
• ILD diagnosis involves a diagnostic work-up that includes investigations regarding ILD etiology, such as autoimmune screening and bronchoalveolar lavage 4.

Management and Treatment

• ARDS treatment is supportive and includes mechanical ventilation, prophylaxis for stress ulcers and venous thromboembolism, nutritional support, and treatment of the underlying injury 2.
• ILD management involves oxygen supplementation and ventilatory support titrated according to the severity of acute respiratory failure and patients' therapeutic options 4.
• Low tidal volume and high positive end-expiratory pressure improve outcomes in ARDS patients 3, 2, 5, 6.

Key Differences

• ARDS is a life-threatening form of respiratory failure that affects approximately 200 000 patients each year in the United States, resulting in nearly 75 000 deaths annually 6.
• ILD is a chronic condition with a poor prognosis, and acute respiratory failure is a common complication in advanced stages or following acute worsening of the underlying disease 4.
• The management and treatment of ARDS and ILD differ, with ARDS requiring mechanical ventilation and supportive care, and ILD requiring a personalized approach to manage acute respiratory failure and underlying disease 4, 2.