What are the Acute Respiratory Distress Syndrome (ARDS) criteria to diagnose?

From the Guidelines

The diagnosis of Acute Respiratory Distress Syndrome (ARDS) is based on the Berlin Definition criteria, which requires four key elements to be present, as outlined in the most recent and highest quality study 1. First, the onset must be acute, occurring within one week of a known clinical insult or new/worsening respiratory symptoms. Second, bilateral opacities must be present on chest imaging (X-ray or CT scan) that cannot be fully explained by effusions, lung collapse, or nodules. Third, respiratory failure cannot be fully explained by cardiac failure or fluid overload. Fourth, there must be impaired oxygenation with a PaO2/FiO2 ratio ≤ 300 mmHg with a minimum PEEP or CPAP of 5 cm H2O. ARDS severity is classified based on the PaO2/FiO2 ratio: mild (200-300 mmHg), moderate (100-200 mmHg), and severe (<100 mmHg). When evaluating a patient with suspected ARDS, it's essential to obtain arterial blood gases while the patient is on a known FiO2, perform appropriate imaging, and rule out cardiogenic pulmonary edema, typically through echocardiography, as recommended by 1 and 1. The Berlin Definition improved upon the older American-European Consensus Conference definition by removing the term "acute lung injury," adding a minimum PEEP requirement, and better stratifying disease severity, which correlates with mortality risk, as noted in 1 and 1. Key points to consider in the diagnosis and management of ARDS include:

• The importance of early recognition and diagnosis, as emphasized in 1
• The need for careful consideration of the underlying cause of respiratory failure, as discussed in 1 and 1
• The role of imaging and laboratory tests in supporting the diagnosis, as outlined in 1 and 1
• The importance of monitoring and adjusting ventilatory support to minimize the risk of ventilator-induced lung injury, as recommended in 1 and 1

From the Research

Diagnostic Criteria for Acute Respiratory Distress Syndrome (ARDS)

The diagnostic criteria for ARDS include:

• Onset within one week of a known insult or new or worsening respiratory symptoms 2
• Bilateral pulmonary opacities on radiography 2, 3
• Inability to explain respiratory failure by cardiac failure or fluid overload 2, 3
• Profound hypoxemia, defined as a PaO2/FiO2 ratio < 300 mmHg 4, 3
• A minimum level of positive end-expiratory pressure and mutually exclusive PaO2/FiO2 thresholds were chosen for the different levels of ARDS severity (mild, moderate, severe) 3

ARDS Severity Levels

The Berlin Definition of ARDS categorizes patients into different severity levels based on the PaO2/FiO2 ratio:

• Mild ARDS: 201-300 mmHg 3
• Moderate ARDS: 101-200 mmHg 3
• Severe ARDS: ≤ 100 mmHg 3

Importance of Imaging in ARDS Diagnosis

Imaging, including chest radiography and computed tomography (CT), plays a crucial role in the diagnosis of ARDS:

• Bilateral diffuse infiltration on chest X-ray is a key diagnostic criterion 2, 3, 5
• CT can be useful in the diagnosis and management of ARDS, particularly in determining the extent of lung injury 5