How do you recruit lungs in a patient with acute respiratory distress syndrome (ARDS)?

Lung Recruitment Strategies in ARDS

For patients with moderate to severe ARDS, higher PEEP without prolonged lung recruitment maneuvers is recommended as the primary strategy for lung recruitment.

Understanding Lung Recruitment in ARDS

Acute Respiratory Distress Syndrome (ARDS) is characterized by:

• Inflammatory lung injury with bilateral pulmonary infiltrates
• Impaired oxygenation
• Atelectasis that exacerbates lung injury during mechanical ventilation

Atelectasis in ARDS:

• Reduces the size of the lung available for tidal ventilation
• Amplifies stress at the interface between atelectatic and aerated lung
• Causes cyclic tidal recruitment and derecruitment, worsening injury 1

Recommended Lung Recruitment Strategies

1. Higher PEEP Strategy (First-Line Approach)

Higher PEEP without prolonged lung recruitment maneuvers is the preferred approach for lung recruitment in moderate to severe ARDS 1.

• Target PEEP levels:

  • Moderate ARDS (PaO₂/FiO₂ 101-200 mmHg): Higher titrated PEEP
  • Severe ARDS (PaO₂/FiO₂ ≤100 mmHg): Higher titrated PEEP 2

• Benefits of higher PEEP:

  • Reduces mortality in moderate/severe ARDS (RR, 0.77; 95% CrI, 0.60-0.96) 1
  • Improves oxygenation (PaO₂/FiO₂ ratio 63.7 mm Hg higher) 1
  • Prevents cyclic opening/closing injury
  • Decreases intrapulmonary shunting 1

• Implementation:

  • Start PEEP at 5 cmH₂O and titrate based on oxygenation response
  • For moderate/severe ARDS, use higher PEEP levels (typically 15-25 cmH₂O) 1
  • Monitor for hemodynamic compromise and barotrauma

2. Recruitment Maneuvers (Second-Line Approach)

While the 2017 ATS guideline suggested using recruitment maneuvers (RMs) 1, the 2024 updated guideline now recommends against using prolonged lung recruitment maneuvers (PEEP >35 cmH₂O for >60 seconds) in patients with moderate to severe ARDS 1.

However, short recruitment maneuvers may still be considered in specific situations:

• Types of acceptable recruitment maneuvers:

  • Brief application of continuous positive airway pressure (30-40 cmH₂O)
  • Progressive incremental increases in PEEP at constant driving pressure
  • Brief high driving pressures 1

• When to consider short RMs:

  • Severe refractory hypoxemia despite optimized PEEP 1
  • After disconnection from the ventilator
  • After endotracheal suctioning

• Cautions:

  • Monitor hemodynamics closely during RMs
  • Avoid RMs in hemodynamically unstable patients 2
  • Discontinue if deterioration in blood pressure or oxygenation occurs 1

Additional Lung-Protective Strategies

1. Prone Positioning

• Strongly recommended for severe ARDS (PaO₂/FiO₂ ≤100 mmHg) 1
• Maintain for 12-16 hours per day 2
• Improves oxygenation and mortality in severe ARDS

2. Neuromuscular Blockade

• Consider in early severe ARDS 1
• Particularly useful for:
  • Persistent ventilator dyssynchrony
  • Prevention of excessive transpulmonary pressure 2
• Limit to short-term use (≤48h) to minimize ICU-acquired weakness 2

3. Lung-Protective Ventilation

• Use low tidal volumes (4-8 mL/kg predicted body weight)
• Maintain plateau pressure ≤30 cmH₂O
• Target driving pressure (plateau pressure - PEEP) minimization 2
• Consider permissive hypercapnia (pH >7.2) 2

Monitoring During Lung Recruitment

• Oxygenation (PaO₂/FiO₂ ratio)
• Respiratory system compliance
• Hemodynamic parameters (blood pressure, heart rate)
• Signs of barotrauma (pneumothorax, subcutaneous emphysema)
• Driving pressure (plateau pressure - PEEP)

Common Pitfalls to Avoid

1. Using prolonged high-pressure recruitment maneuvers - The 2024 ATS guideline strongly recommends against prolonged LRMs (PEEP >35 cmH₂O for >60s) due to potential harm 1

2. Applying recruitment maneuvers in hemodynamically unstable patients - RMs can cause significant hemodynamic compromise 1, 2

3. One-size-fits-all approach to PEEP - PEEP should be individualized based on severity of ARDS and response to therapy 1

4. Ignoring driving pressure - High driving pressures can worsen ventilator-induced lung injury even with appropriate PEEP 2

5. Failing to reassess after recruitment - Continuous monitoring is essential to ensure sustained benefit and detect complications 2

Conclusion

The optimal approach to lung recruitment in ARDS has evolved with recent evidence. Higher PEEP without prolonged lung recruitment maneuvers is now the preferred strategy for moderate to severe ARDS, with careful monitoring for hemodynamic effects and barotrauma. Brief recruitment maneuvers may be considered in specific situations, but prolonged high-pressure maneuvers should be avoided.