What are the guidelines for managing Acute Respiratory Distress Syndrome (ARDS)?

ARDS Management Guidelines

For patients with ARDS, implement a lung-protective ventilation strategy with tidal volumes of 4-8 mL/kg predicted body weight, maintain plateau pressure <30 cmH₂O, and adjust PEEP based on ARDS severity. 1

Diagnosis and Classification

ARDS is characterized by:

• Severe dyspnea, tachypnea, and refractory hypoxemia despite oxygen therapy
• Decreased lung compliance and increased airway resistance
• Diagnosis confirmed by PaO2/FiO2 ratio ≤300 mmHg with bilateral infiltrates on chest radiography
• No cardiac dysfunction as the primary cause 1

ARDS severity classification:

Severity	PaO2/FiO2 Value
Mild	201-300 mmHg
Moderate	101-200 mmHg
Severe	≤100 mmHg

The Lung Injury Score (LIS) can assess disease severity, with an initial score >3.5 correlating with only 18% survival rate 1.

Ventilation Strategy by ARDS Severity

Mild ARDS (PaO2/FiO2 201-300 mmHg):

• Lung-protective ventilation (4-8 mL/kg PBW)
• Low PEEP strategy (5-10 cmH₂O)
• Conservative fluid management 1

Moderate ARDS (PaO2/FiO2 101-200 mmHg):

• Lung-protective ventilation (4-8 mL/kg PBW)
• Higher PEEP strategy
• Consider corticosteroids
• Consider neuromuscular blockers
• Conservative fluid management 1

Severe ARDS (PaO2/FiO2 ≤100 mmHg):

• Lung-protective ventilation (4-8 mL/kg PBW)
• Higher PEEP strategy
• Prone positioning >12 hours/day
• Neuromuscular blockers
• Corticosteroids
• Consider VV-ECMO in selected patients
• Conservative fluid management 1

Key Ventilator Parameters

1. Tidal Volume Calculation:

   • Males: PBW (kg) = 50 + 0.91 × (height [cm] − 152.4)
   • Females: PBW (kg) = 45.5 + 0.91 × (height [cm] − 152.4) 1

2. Driving Pressure:

   • Formula: DP = Plateau pressure (Pplat) - PEEP
   • Target: <15 cmH₂O (optimal 13-15 cmH₂O) 1

3. PEEP Management:

   • Minimum 5 cmH₂O for all ARDS patients
   • Set to maximize alveolar recruitment while avoiding overdistention 1
   • For more severe ARDS, higher PEEP is recommended 2

4. Plateau Pressure:

   • Maintain <30 cmH₂O
   • Monitor at least once per shift and after ventilator changes 1

Monitoring and Assessment

• Regular assessment of tidaling to ensure adequate ventilation
• Calculate driving pressure and target <15 cmH₂O
• Target PaO2 between 70-90 mmHg or SaO2 between 92-97% to avoid both hypoxemia and hyperoxia
• Monitor for permissive hypercapnia, which is generally well-tolerated but requires careful observation 1
• Central venous pressure monitoring to assess right ventricular function 1

Advanced Strategies

• Prone Positioning: Recommended for severe ARDS for >12 hours/day 1
• Neuromuscular Blockade: Consider for moderate to severe ARDS 1
• Extracorporeal CO2 Removal: May allow for very low tidal volumes (≈3 mL/kg) in severe ARDS, potentially further reducing ventilator-induced lung injury 3
• VV-ECMO: Consider for selected patients with severe ARDS unresponsive to conventional therapy 1

Common Pitfalls to Avoid

• Failing to differentiate ARDS from cardiogenic pulmonary edema
• Overlooking the underlying cause of ARDS
• Delaying diagnosis
• Misinterpreting radiographic findings
• Not recognizing ARDS early 1
• Using excessive tidal volumes (evidence shows mortality reduction from 39.8% to 31.0% with 6 mL/kg vs 12 mL/kg) 4

Long-term Considerations

ARDS survivors are at risk for:

• Diminished functional capacity
• Mental illness
• Decreased quality of life 1, 5

Regular follow-up care is essential for these patients to address these potential complications.