What is the recommended initial setting for pressure support (PS) ventilation in patients requiring mechanical ventilation?

Initial Pressure Support Ventilation Settings in Mechanical Ventilation

For patients requiring mechanical ventilation, the recommended initial pressure support (PS) setting is 5-8 cmH2O rather than no pressure support (T-piece or CPAP). 1

Evidence-Based Rationale

The American College of Chest Physicians/American Thoracic Society (CHEST/ATS) clinical practice guideline provides a conditional recommendation with moderate certainty of evidence for using inspiratory pressure augmentation of 5-8 cmH2O for spontaneous breathing trials (SBTs) and initial ventilation settings 1.

Benefits of Initial PS at 5-8 cmH2O:

• Higher success rates: Conducting SBTs with pressure augmentation is more likely to be successful (84.6% vs 76.7%) 1
• Better extubation outcomes: Produces a higher rate of extubation success (75.4% vs 68.9%) 1
• Potential mortality benefit: Associated with a trend toward lower ICU mortality (8.6% vs 11.6%) 1
• Decreased work of breathing: Compensates for the imposed work of breathing from the endotracheal tube and ventilator circuit 2

Physiological Basis

Pressure support ventilation provides several physiological advantages:

• Overcomes the resistance of the endotracheal tube
• Reduces the work of breathing imposed by the ventilator circuit
• Improves patient comfort compared to volume-controlled ventilation 3
• Provides a more balanced pressure and volume change form of muscle work 4

Clinical Application Algorithm

1. Initial setting: Begin with PS 5-8 cmH2O with PEEP of 5 cmH2O 1, 5
2. Assessment: Monitor patient comfort, respiratory rate, tidal volume, and work of breathing
3. Titration: Adjust as needed based on:
   • Patient comfort
   • Respiratory rate (target 12-25 breaths/min)
   • Tidal volume (target 6-8 mL/kg ideal body weight)
   • Work of breathing indicators (use of accessory muscles, paradoxical breathing)

Special Considerations

• Endotracheal tube size: Smaller tubes create more resistance, potentially requiring higher PS settings
• Patient factors: Underlying lung disease, respiratory muscle strength, and overall clinical status may necessitate adjustments
• Duration of ventilation: For patients ventilated >72 hours, careful assessment of RSBI is important when considering extubation 6

Common Pitfalls to Avoid

1. Insufficient pressure support: May lead to increased work of breathing, respiratory muscle fatigue, and failed SBTs
2. Excessive pressure support: Can cause over-assistance, respiratory muscle deconditioning, and asynchrony
3. Ignoring patient comfort: Patient comfort during PS ventilation correlates with better outcomes 3
4. Fixed settings: Failing to reassess and adjust PS based on changing patient conditions

Monitoring and Adjustment

• Regularly assess patient-ventilator synchrony
• Monitor respiratory rate, tidal volume, and minute ventilation
• Evaluate signs of respiratory distress or excessive work of breathing
• Consider measuring imposed work of breathing if available 2

This recommendation for initial PS settings of 5-8 cmH2O places high value on reducing the duration of mechanical ventilation and maximizing the probability of extubation success 1.