What are the recommended advanced ventilator modes and settings for critically ill patients?

Advanced Ventilator Modes for Critically Ill Patients

For critically ill patients, lung-protective ventilation strategies using low tidal volumes (4-8 mL/kg predicted body weight) with plateau pressures <30 cmH2O are strongly recommended as the primary ventilation approach, regardless of the specific ventilator mode selected. 1, 2

General Principles of Mechanical Ventilation

• Use standard full-featured ventilators rather than basic flow generators for optimal control and monitoring in critically ill patients 2
• Implement lung-protective ventilation strategies to prevent ventilator-induced lung injury 2, 3
• Monitor pressure-time and flow-time scalars to optimize ventilator synchrony 2
• Regularly measure peak inspiratory pressure, plateau pressure, mean airway pressure, and PEEP 2

Initial Ventilator Settings

Volume and Pressure Parameters

• Set tidal volume at 4-8 mL/kg predicted body weight 1, 2, 3
• Maintain plateau pressure <30 cmH2O 1, 2
• For patients with moderate to severe ARDS, use higher PEEP strategy (>10 cmH2O) 1, 2
• For patients with mild ARDS or non-ARDS respiratory failure, use lower PEEP strategy (5-10 cmH2O) 1, 2
• Adjust respiratory rate to maintain pH >7.20 (typically 20-35 breaths/min) 2, 3

Oxygenation and Ventilation Targets

• Maintain SpO2 between 92-97% when PEEP <10 cmH2O 1, 2
• Target SpO2 between 88-92% when PEEP ≥10 cmH2O 1, 2
• Maintain PaO2 >55 mmHg 2
• Target PaCO2 between 35-45 mmHg for healthy lungs, but permissive hypercapnia is acceptable in ARDS 2, 3
• Keep pH >7.20 1, 2

Recommended Ventilator Modes

For ARDS Patients

• Volume-controlled ventilation with low tidal volumes is strongly recommended as the primary mode 1, 3
• Pressure-controlled ventilation may be used as an alternative if plateau pressure can be maintained <30 cmH2O 2
• For refractory hypoxemia, consider airway pressure release ventilation (APRV) which has shown reduced risk of excessive tidal volumes 4

For Non-ARDS Respiratory Failure

• Volume-controlled or pressure-controlled modes are appropriate with lung-protective settings 2, 3
• Pressure support ventilation with guaranteed volume can help prevent excessive tidal volumes during spontaneous breathing 4

Advanced Strategies for Refractory Hypoxemia

• Implement prone positioning for 12-16 hours for moderate to severe ARDS 1, 2
• Consider recruitment maneuvers in patients with persistent hypoxemia, but avoid staircase (incremental PEEP) recruitment maneuvers 1
• For severe refractory hypoxemia despite optimizing ventilation and other rescue strategies:
  • Consider trial of inhaled pulmonary vasodilators 1
  • Consider venovenous ECMO if available or refer to an ECMO center 1

Neuromuscular Blockade Considerations

• Use intermittent boluses of neuromuscular blocking agents as needed rather than continuous infusion 1
• Consider continuous neuromuscular blockade infusion (up to 48 hours) only for:
  • Persistent ventilator dyssynchrony
  • Need for ongoing deep sedation
  • Prone ventilation
  • Persistently high plateau pressures 1

Special Patient Populations

Patients with Liver Disease/ACLF

• Use low tidal volume strategy (6 mL/kg PBW) and low plateau pressure (<30 cmH2O) 1
• For mild acute lung injury (PaO2/FiO2 200-300 mmHg), use low PEEP strategy (<10 cmH2O) to minimize risk of impairing venous return 1
• For moderate-severe acute lung injury (PaO2/FiO2 <200 mmHg), higher PEEP may be required with careful hemodynamic monitoring 1

Intubated COVID-19 Patients

• Use low tidal volume ventilation (4-8 mL/kg predicted body weight) 1
• Target plateau pressures <30 cmH2O 1
• Use higher PEEP strategy for moderate to severe ARDS 1
• Implement conservative fluid strategy 1
• Consider prone ventilation for 12-16 hours 1

Monitoring and Adjustments

• Measure PCO2 in arterial or capillary blood samples 1
• Consider transcutaneous CO2 monitoring 1
• Measure end-tidal CO2 in all ventilated patients 1
• Measure SpO2 continuously 1
• Perform daily extubation readiness testing 1, 2

Common Pitfalls to Avoid

• Excessive tidal volumes (>8 mL/kg) increase risk of ventilator-induced lung injury 1, 3
• Inadequate PEEP can lead to atelectasis and worsen hypoxemia 5
• Hyperoxia (SpO2 >97%) is associated with increased mortality and should be avoided 2
• Low tidal volume ventilation with insufficient PEEP (e.g., 5 cmH2O) results in poor oxygenation and compliance 5
• Excessive PEEP (e.g., 25 cmH2O) does not improve oxygenation or compliance 5
• Ventilator asynchrony increases work of breathing and may require adjustment of flow settings or sedation 6

By following these evidence-based recommendations for advanced ventilator management, clinicians can optimize outcomes for critically ill patients requiring mechanical ventilation while minimizing the risk of ventilator-induced lung injury.