What is a recruitment maneuver in mechanical ventilation (MV)?

Recruitment Maneuver in Mechanical Ventilation

A recruitment maneuver is a transient elevation in airway pressure applied during mechanical ventilation to open collapsed lung units and increase the number of alveoli participating in tidal ventilation, thereby improving oxygenation and lung mechanics. 1

Types of Recruitment Maneuvers

There are several types of recruitment maneuvers that can be used in mechanical ventilation:

• Continuous positive airway pressure (CPAP): Application of sustained high pressure (30-40 cmH2O) for 30-40 seconds 1, 2
• Pressure control recruitment maneuver (PCRM): Using a combination of PEEP (e.g., 15 cmH2O) with pressure control above PEEP (e.g., 35 cmH2O) for 2 minutes 1, 3
• Incremental PEEP elevation: Progressive increases in PEEP at constant driving pressure 1
• Vital capacity maneuver: Resembles manual recruitment but delivered through ventilator circuit 1
• Intermittent sighs: Periodic delivery of breaths with higher airway pressure 1

Physiological Effects and Benefits

Recruitment maneuvers provide several potential benefits:

• Reopening of collapsed alveoli: Helps reverse atelectasis that commonly occurs during general anesthesia and in ARDS 1
• Improved oxygenation: Increases PaO2/FiO2 ratio by reducing intrapulmonary shunt 1
• Enhanced lung compliance: Improves respiratory mechanics by increasing the functional lung volume 2, 3
• Reduced need for rescue therapy: In ARDS patients, recruitment maneuvers can reduce the need for rescue interventions 1
• Prevention of atelectrauma: May reduce injury from repetitive opening and closing of alveoli 1

Clinical Application and Recommendations

When implementing recruitment maneuvers, consider the following:

• Patient selection: Most beneficial in patients with recruitable lung tissue, particularly in early ARDS or after disconnection from the ventilator circuit 1
• Timing: Should be performed after a disconnection from the circuit and whenever the patient's SpO2 is consistently ≤94% 1
• Pressure settings: Use the lowest effective pressure and shortest effective time to minimize risks 1
• PEEP maintenance: After recruitment, adequate PEEP levels should be maintained to prevent derecruitment 1, 3
• Monitoring: Continuous hemodynamic and SpO2 monitoring before and during the recruitment maneuver is essential 1

Potential Complications and Contraindications

Recruitment maneuvers are not without risks:

• Hemodynamic instability: Can cause hypotension requiring vasopressor support 1
• Barotrauma: Risk of pneumothorax or other forms of air leaks 1
• Increased intracranial pressure: Particularly concerning in patients with brain injury 1
• Reduced cerebral perfusion pressure: May occur due to decreased mean arterial pressure 1
• Transient hypoxemia: Paradoxical desaturation can occur during the maneuver 1

Special Considerations in Neurological Patients

In patients with acute brain injury or elevated intracranial pressure:

• Type of recruitment maneuver matters: Pressure control recruitment maneuvers (PCRM) appear safer than continuous positive airway pressure recruitment maneuvers (CRM) in patients with aneurysmal subarachnoid hemorrhage 1
• Timing considerations: In subarachnoid hemorrhage patients, recruitment maneuvers may have different effects on ICP depending on the post-bleed day 1
• Monitoring requirements: Close monitoring of ICP and cerebral perfusion pressure is essential 1

Evidence on Mortality and Outcomes

The impact of recruitment maneuvers on mortality remains controversial:

• ICU mortality: Some evidence suggests reduced ICU mortality with recruitment maneuvers as part of an open lung ventilation strategy 4
• 28-day and hospital mortality: No consistent difference has been demonstrated 4
• Combination with other strategies: Most positive outcome studies used recruitment maneuvers as part of a comprehensive lung-protective ventilation strategy 1, 4

Practical Implementation

For optimal implementation of recruitment maneuvers:

• Ventilator-driven maneuvers are preferred over manual techniques to avoid loss of positive pressure when switching back to ventilator circuit 1
• Ensure adequate hemodynamic stability before performing the maneuver 1
• Avoid in patients with contraindications such as hemodynamic instability, pneumothorax, or severe emphysema 1, 5
• Consider individual patient characteristics such as BMI, positioning, and abdominal conditions when determining appropriate pressure and duration 1

Recruitment maneuvers should be viewed as one component of a comprehensive lung-protective ventilation strategy rather than an isolated intervention 1, 4.