From the Guidelines
The Acute Respiratory Distress Syndrome (ARDS) criteria are defined by the Berlin Definition, which requires four key elements for diagnosis, as recently reinforced by the 2024 American Thoracic Society clinical practice guideline 1. First, the onset must be 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) that cannot be fully explained by effusions, 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 of 5 cmH2O PEEP or CPAP. ARDS severity is classified as mild (PaO2/FiO2 200-300 mmHg), moderate (PaO2/FiO2 100-200 mmHg), or severe (PaO2/FiO2 < 100 mmHg), as outlined in the Berlin Definition and supported by recent studies 1.
Key considerations in managing ARDS include:
- Mechanical ventilation strategies that limit tidal volume (4–8 mL/kg predicted body weight) and inspiratory pressures, as recommended by the 2017 American Thoracic Society guideline 1 and reaffirmed in 2024 1.
- The use of higher PEEP without lung recruitment maneuvers as opposed to lower PEEP in patients with moderate to severe ARDS, suggested by the 2024 guideline 1.
- The recommendation against using prolonged lung recruitment maneuvers in patients with moderate to severe ARDS, based on moderate certainty of evidence 1.
- Early recognition and management are crucial, given the significant mortality (approximately 30-40%) associated with ARDS, as highlighted in recent reviews 1.
The most recent and highest quality study, the 2024 American Thoracic Society clinical practice guideline 1, provides the foundation for these recommendations, emphasizing the importance of evidence-based practice in managing ARDS to improve patient outcomes.
From the Research
ARDS Criteria
The diagnostic criteria for Acute Respiratory Distress Syndrome (ARDS) include:
- Onset within one week of a known insult or new or worsening respiratory symptoms 2
- Profound hypoxemia
- Bilateral pulmonary opacities on radiography
- Inability to explain respiratory failure by cardiac failure or fluid overload 2
Classification of ARDS
The Berlin definition proposes three categories of ARDS based on the severity of hypoxemia:
- Mild (200 mm Hg<Pao2/Fio2≤300 mm Hg)
- Moderate (100 mm Hg<Pao2/Fio2≤200 mm Hg)
- Severe (Pao2/Fio2 ≤100 mm Hg) 3
Key Features of ARDS
Some key features of ARDS include:
- Rapidly progressive dyspnea, tachypnea, and hypoxemia 2
- Noncardiogenic pulmonary edema 2
- Inflammatory cell accumulation in the alveoli and microcirculation of the lung 2
- Damage to the vascular endothelium and alveolar epithelium, leading to pulmonary edema, hyaline membrane formation, decreased lung compliance, and decreased gas exchange 2
Diagnosis and Management
The diagnosis of ARDS is based on a combination of clinical, hemodynamic, and oxygenation criteria 4 The management of ARDS is supportive and includes: