What is the recommended approach for a recruitment maneuver in patients requiring mechanical ventilation (MV)?

Recruitment Maneuvers in Mechanical Ventilation

Primary Recommendation

Recruitment maneuvers may be conditionally recommended in patients with moderate or severe ARDS, but should be applied selectively with careful patient selection and close monitoring, as aggressive recruitment strategies have not demonstrated mortality benefit and carry significant risks. 1

Evidence-Based Approach to Recruitment Maneuvers

When to Consider Recruitment Maneuvers

The American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine provides a conditional recommendation for recruitment maneuvers in moderate or severe ARDS (low confidence in effect estimates), indicating uncertainty about the balance of benefits and harms. 1

Patient selection is critical - recruitment maneuvers are most beneficial in patients with:

• Early ARDS (within first few days) with recruitable lung tissue 2
• Low chest wall elastance (EstW <6 cm H₂O/L) 2
• Low lung elastance (EstL <24 cm H₂O/L) 2
• After disconnection from the ventilator circuit 3
• SpO₂ consistently ≤94% despite optimization of other ventilator parameters 3

Contraindications and High-Risk Scenarios

Do not perform recruitment maneuvers in patients with:

• Hemodynamic instability requiring vasopressor support 3
• Pneumothorax or other air leak syndromes 3
• Severe emphysema 3
• Elevated intracranial pressure (particularly in traumatic brain injury or subarachnoid hemorrhage) 1
• Late ARDS (>7 days of mechanical ventilation) 2
• High chest wall elastance (impaired chest wall mechanics) 2

Recommended Technique

The safest and most studied approach uses:

• Continuous positive airway pressure (CPAP) of 35-40 cm H₂O for 40 seconds 3, 4
• Alternatively, stepwise incremental PEEP elevation with pressure control ventilation 3, 5
• FiO₂ of 1.0 during the maneuver 5, 2

After recruitment, PEEP titration is essential:

• Set PEEP 2 cm H₂O above the lower inflection point (Pflex) or collapsing pressure 4, 5
• Maintain adequate PEEP to prevent derecruitment 3
• Typical post-recruitment PEEP ranges from 13-15 cm H₂O 6, 5

Monitoring Requirements

Continuous monitoring before, during, and after recruitment maneuvers must include:

• Hemodynamic parameters (mean arterial pressure, cardiac output) 3, 2
• Oxygen saturation (SpO₂) 3
• In neurological patients: intracranial pressure and cerebral perfusion pressure 1
• Respiratory mechanics (plateau pressure, compliance) 5

Expected Outcomes and Response Assessment

Responders typically demonstrate:

• ≥50% increase in PaO₂/FiO₂ ratio within 2 hours 2
• Improved static compliance 5
• Sustained oxygenation improvement at 120 minutes post-maneuver 6

Non-responders are characterized by:

• Longer duration of mechanical ventilation (>7 days) 2
• Higher lung elastance (EstL >28 cm H₂O/L) 2
• Higher chest wall elastance (EstW >10 cm H₂O/L) 2

Important Caveats and Pitfalls

The evidence reveals critical limitations:

The 2021 European Respiratory Review guideline notes that "enrichment based on severe hypoxemia has proven insufficiently effective for an 'open lung approach' with high PEEP and aggressive recruitment maneuvers" in recent trials. 1 This represents a shift away from routine aggressive recruitment strategies.

Heterogeneous responses are common - approximately 50% of patients do not respond to recruitment maneuvers with improved oxygenation, and these non-responders experience significant hemodynamic compromise (31% decrease in cardiac output, 19% decrease in mean arterial pressure). 2

Complications occur frequently:

• Transient hypoxemia during the maneuver 3, 7
• Hemodynamic instability requiring vasopressor support 3, 7
• Barotrauma risk (though not significantly increased in controlled trials) 1
• Decreased respiratory system compliance in some patients 7

Special Populations

In patients with aneurysmal subarachnoid hemorrhage and severe ARDS:

• Recruitment maneuvers with ICP monitoring may be reasonable as rescue therapy for life-threatening hypoxemia 1
• Pressure control recruitment maneuvers appear safer than continuous positive airway pressure techniques 3
• Close monitoring of cerebral perfusion pressure is mandatory 3

Integration with Lung-Protective Ventilation

Recruitment maneuvers should never be used in isolation but rather as part of a comprehensive lung-protective strategy that includes:

• Low tidal volume (4-8 mL/kg predicted body weight) 1
• Plateau pressure ≤30 cm H₂O 1
• Higher PEEP in moderate-severe ARDS 1
• Prone positioning >12 hours/day for severe ARDS 1

The combination of recruitment maneuvers with low tidal volume ventilation and appropriate PEEP has been associated with improved ICU survival (62% vs 29%) compared to conventional ventilation in selected patients. 4

Practical Implementation Algorithm

1. Confirm indication: Moderate-severe ARDS with SpO₂ ≤94% despite optimized ventilator settings 3
2. Screen for contraindications: Hemodynamic instability, pneumothorax, elevated ICP, late ARDS 3, 2
3. Assess recruitability: Early ARDS (<7 days), low chest wall elastance preferred 2
4. Prepare monitoring: Arterial line, continuous hemodynamics, SpO₂ 3
5. Perform maneuver: CPAP 40 cm H₂O for 40 seconds at FiO₂ 1.0 3, 4
6. Titrate PEEP: Set 2 cm H₂O above collapsing pressure 4, 5
7. Assess response: Check PaO₂/FiO₂ at 2 hours 6, 2
8. Monitor complications: Watch for hypotension, desaturation, barotrauma 3, 7