Recruitment Manoeuvre - 10 Mark Answer (MD Exam)

Definition

• Murray & Nadel's Textbook of Respiratory Medicine, p. 264

Rationale / Why It Is Done

• Tidal volume is delivered to a small portion of the lung only
• Cyclic opening and closing of alveoli causes atelectrauma
• This worsens Ventilator-Induced Lung Injury (VILI)

Pathophysiology of Collapse (Why Alveoli Collapse)

1. Surfactant dysfunction in ARDS increases surface tension at the air-liquid interface
2. This causes alveolar collapse, intrapulmonary shunting, and hypoxemia
3. The closing pressure of an alveolus is much less than its opening pressure - so once re-opened, a moderate PEEP can keep it open

Methods / Techniques

1. Sustained Inflation (SI) - Most Common

• Ventilator is switched to CPAP mode
• Airway pressure raised to 30-40 cm H2O
• Held for 30-40 seconds
• Patient monitored for haemodynamic instability
• Then PEEP is set at an adequate level to maintain recruitment

2. Incremental PEEP (Staircase Recruitment Manoeuvre - SRM)

• PEEP is increased step-by-step (e.g., 10 → 15 → 20 → 25 → 30 cm H2O) every 2 minutes
• Peak inspiratory pressure is kept at 15 cm H2O above PEEP throughout
• Maximum PEEP reached = 40 cm H2O
• Then PEEP is gradually reduced until SpO2 drops by 1% (this is the derecruitment point)
• Final PEEP is set 2-4 cm H2O above the derecruitment point
• This method is better tolerated haemodynamically than sustained inflation

3. Extended Sigh Manoeuvre (eSigh)

• Prolonged, slow inflation to a lower peak pressure over a longer duration
• Less haemodynamic compromise than sustained inflation
• Equally effective in improving lung aeration

4. Pressure-Controlled Ventilation with Progressive PEEP

• Stepwise increases in both PEEP and peak inspiratory pressure
• Allows continued ventilation while recruiting

5. Prone Positioning

• Considered a form of recruitment manoeuvre
• Redistributes collapsed dependent zones and improves V/Q matching

Indications

• Moderate to severe ARDS (PaO2/FiO2 < 200 mmHg) with persistent hypoxemia
• ARDS within the first 1 week (before fibro-proliferative phase)
• Hypoxemia refractory to conventional PEEP (PEEP > 10 cm H2O)
• Post-intubation or post-suction de-recruitment

Contraindications

Monitoring During the Procedure - When to STOP

• Systolic BP drops by > 20% despite vasopressors/fluids
• Oxygen saturation falls significantly
• Signs of barotrauma appear (sudden rise in airway pressures, haemodynamic collapse)
• New arrhythmia develops

Complications

1. Haemodynamic compromise - high intrathoracic pressure reduces venous return and cardiac output
2. Barotrauma - pneumothorax, pneumomediastinum
3. Volutrauma / Overdistension - of already-aerated alveoli
4. Hypoxia during the manoeuvre itself
5. Derecruitment - alveoli re-collapse rapidly if PEEP is not maintained afterward

Evidence (Current Status)

• ART Trial (2017): High PEEP + aggressive RM strategy was associated with increased 28-day mortality - raised serious safety concerns
• PHARLAP Trial: Did not show benefit in outcome measures
• Cochrane Review: RMs may improve short-term oxygenation but no consistent mortality benefit has been demonstrated
• RMs appear more beneficial in extrapulmonary ARDS (e.g., sepsis) than in pulmonary ARDS (e.g., pneumonia)

Key Principle - Open Lung Strategy

Recruit + Maintain

• RM opens collapsed alveoli
• Adequate PEEP (set just above the derecruitment point) prevents cyclic collapse
• Low tidal volume (6 mL/kg IBW) limits overdistension

Summary Table