What is the recommended approach for proning in patients with severe Acute Respiratory Distress Syndrome (ARDS)?

Prone Positioning in Severe ARDS

For patients with severe ARDS, prone positioning should be implemented for more than 12 hours per day to reduce mortality. 1

Indications and Patient Selection

• Prone positioning is strongly recommended for:
  • Patients with severe ARDS (PaO₂/FiO₂ ratio ≤100 mmHg) 1, 2
  • Moderate ARDS patients (PaO₂/FiO₂ ratio 101-200 mmHg) may also benefit 1, 3
  • Should be initiated early in the course of ARDS (within 48 hours of diagnosis) 4

Implementation Protocol

1. Duration:

   • Maintain prone position for >12 hours per day 1, 2
   • Optimal duration appears to be 16-20 hours daily 4
   • Longer durations (>12h/day) have shown significant mortality reduction compared to shorter durations 5, 3

2. Timing:

   • Early initiation (<17 hours from diagnosis) is associated with better outcomes 6, 4
   • Continue prone positioning sessions daily until significant improvement in oxygenation is maintained in supine position

3. Concurrent Ventilation Strategy:

   • Use lung-protective ventilation with tidal volumes of 4-8 ml/kg predicted body weight 1, 2
   • Higher PEEP strategies (≥10 cmH₂O) should be used with prone positioning 2, 5
   • Target PaO₂ 70-90 mmHg and SpO₂ 92-97% 2

Physiological Benefits

Prone positioning improves outcomes through multiple mechanisms:

• Improves ventilation-perfusion matching 1
• Increases end-expiratory lung volume 1
• Decreases ventilator-induced lung injury through more uniform distribution of tidal volume 1, 7
• Enhances recruitment of dorsal lung regions 1, 7
• Improves lung mechanics and alveolar ventilation 1

Potential Complications and Management

Prone positioning is associated with certain complications that require monitoring:

• Endotracheal tube obstruction:

  • Higher risk with prone positioning (RR 1.76) 1
  • Ensure secure ETT fixation before turning
  • Confirm tube position after each position change

• Pressure sores:

  • Increased risk (RR 1.22) 1
  • Use appropriate padding for pressure points (face, shoulders, knees, iliac crests)
  • Perform regular skin assessments

• Other considerations:

  • Increased sedation requirements may limit early mobilization 1
  • Careful coordination required during turning procedures to prevent line displacement 4
  • No significant increase in barotrauma compared to supine positioning 1

Special Considerations

• ECMO patients:

  • Prone positioning can be considered in patients on VV-ECMO support 6
  • Early initiation of prone positioning in ECMO patients may improve survival 6

• Contraindications:

  • Unstable spine fractures
  • Open abdominal wounds
  • Hemodynamic instability
  • Increased intracranial pressure

Evidence Quality and Strength of Recommendation

The recommendation for prone positioning in severe ARDS is supported by:

• Strong recommendation with moderate-high confidence in effect estimates from the American Thoracic Society 1
• Multiple meta-analyses showing mortality benefit in severe ARDS 5, 3
• The PROSEVA trial and subsequent analyses demonstrating significant mortality reduction 7

While earlier studies showed physiological improvements without mortality benefit, more recent evidence focusing on longer durations (>12h/day), early implementation, and patients with more severe ARDS has demonstrated significant survival advantages 1, 4, 5, 3.