What are the recommended modes of ventilation for patients requiring mechanical ventilation?

Recommended Modes of Ventilation for Mechanical Ventilation

Volume-cycled ventilation using assist-control mode is the most appropriate initial ventilation strategy for most patients with acute respiratory failure, with pressure-targeted modes being beneficial alternatives in specific clinical scenarios. 1

Primary Ventilation Modes

Volume Control Ventilation (VCV)

• Sets a fixed tidal volume and inspiratory time
• Ventilator generates whatever pressure needed to deliver this volume
• Advantages:
  • Guarantees consistent tidal volume delivery
  • Provides reliable minute ventilation
  • With high fixed flow rates (75 L/min), can adequately reduce work of breathing 2
• Best used with:
  • Low tidal volumes (6 mL/kg predicted body weight) 3
  • Decelerating flow pattern when available 4

Pressure Control Ventilation (PCV)

• Sets inspiratory pressure with variable volume delivery
• Advantages:
  • Limits maximum airway pressure
  • Compensates for air leaks
  • Decelerating flow pattern may improve gas distribution 5, 1
• Considerations:
  • May result in variable tidal volumes
  • Requires close monitoring to ensure adequate ventilation

Pressure-Regulated Volume Control (PRVC)

• Hybrid mode combining aspects of both VCV and PCV
• Automatically adjusts pressure to achieve target tidal volume
• Caution: May deliver excessive tidal volumes in some patients 2

Ventilation Parameters for Lung Protection

Tidal Volume

• Target 6 mL/kg predicted body weight for patients with acute lung injury/ARDS 3, 1
• Can use 6-10 mL/kg PBW for patients without ARDS 1
• Calculate predicted body weight:
  • Males: PBW (kg) = 50 + 0.91 × (height [cm] − 152.4)
  • Females: PBW (kg) = 45.5 + 0.91 × (height [cm] − 152.4) 1

Airway Pressures

• Maintain plateau pressure ≤30 cmH2O 5, 1
• Target driving pressure <15 cmH2O 1

PEEP (Positive End-Expiratory Pressure)

• Apply adequate PEEP to prevent alveolar collapse 1
• For mild ARDS (PaO2/FiO2 200-300 mmHg): 5-10 cmH2O 5, 1
• For moderate-severe ARDS (PaO2/FiO2 <200 mmHg): Higher PEEP may be required 5, 1
• In patients with cirrhosis or hemodynamic instability: Use low PEEP strategy (<10 cmH2O) to avoid compromising venous return 5

Ventilation Strategy by Clinical Scenario

For ARDS/Acute Lung Injury

1. Use lung-protective ventilation:

   • Low tidal volume (6 mL/kg PBW) 3
   • Plateau pressure <30 cmH2O 1
   • Appropriate PEEP based on severity 1
   • Consider permissive hypercapnia 5

2. For severe ARDS (PaO2/FiO2 ≤100 mmHg):

   • Consider prone positioning for >12 hours/day 1
   • Consider neuromuscular blockade for up to 48 hours 1

For Patients with Cirrhosis/ACLF

1. Use lung-protective ventilation with:

   • Low tidal volume (6 mL/kg PBW)
   • Low plateau pressure (<30 cmH2O)
   • Low PEEP strategy for mild ALI to minimize risk of impairing venous return 5

2. For moderate-severe ALI in cirrhosis:

   • Higher PEEP may be required with careful hemodynamic monitoring 5

For Hypercapnic Respiratory Failure

1. Consider bi-level ventilation:
   • Set inspiratory pressure (IPAP) and expiratory pressure (EPAP)
   • Difference between IPAP and EPAP provides ventilatory assistance 5
   • Full face mask typically most suitable interface 5

Common Pitfalls to Avoid

1. Excessive tidal volumes: Even during pressure-targeted modes, monitor and adjust to maintain target volumes of 6 mL/kg PBW for ARDS 2

2. Inadequate flow rates in VCV: Use high flow rates (75 L/min) or decelerating flow patterns to reduce work of breathing 2, 4

3. Excessive PEEP in hemodynamically unstable patients: High PEEP can impede venous return and worsen hypotension, especially in patients with vasodilation 5

4. Focusing only on oxygenation: Balance oxygenation goals with prevention of ventilator-induced lung injury

5. Overlooking patient-ventilator synchrony: Asynchrony increases work of breathing and can worsen outcomes

The evidence strongly supports that lung-protective ventilation with low tidal volumes significantly reduces mortality in ARDS patients (31.0% vs 39.8%, p=0.007) 3. While both pressure and volume modes can be effective, the key is adherence to lung-protective principles rather than the specific mode chosen.