What does plateau pressure indicate on a ventilator (Ventilator- Assisted Breathing Machine)?

Plateau Pressure on Ventilator: Clinical Significance and Implications

Plateau pressure is a critical measurement that reflects alveolar distending pressure and lung compliance, with values above 30 cmH₂O indicating increased risk of ventilator-induced lung injury and mortality in mechanically ventilated patients.

Definition and Measurement

Plateau pressure is measured during an end-inspiratory pause (occlusion) on the ventilator, when there is no airflow. It represents:

• The static pressure in the alveoli at the end of inspiration
• The true distending pressure applied to the lungs and chest wall
• A key indicator of lung compliance and risk for barotrauma

Plateau pressure is obtained by performing an end-inspiratory hold maneuver (typically 0.5-2 seconds) on the ventilator, which temporarily stops airflow and allows pressure equilibration throughout the respiratory system 1.

Clinical Significance

1. Assessment of Lung Compliance

• Plateau pressure helps calculate respiratory system compliance (tidal volume divided by driving pressure)
• Lower compliance (higher plateau pressure for given volume) indicates stiffer lungs or chest wall
• Helps distinguish between different causes of respiratory failure

2. Risk Stratification

• Plateau pressure >30 cmH₂O is associated with increased mortality in ARDS 1, 2
• Values correlate with risk of ventilator-induced lung injury through overdistention
• Can predict weaning outcomes and ventilator dependency

3. Guiding Ventilator Management

Plateau pressure is essential for:

• Calculating driving pressure (ΔP = Plateau pressure - PEEP)
• Adjusting tidal volumes to maintain lung-protective ventilation
• Determining optimal PEEP settings
• Assessing response to recruitment maneuvers

Clinical Applications

ARDS Management

In patients with ARDS, plateau pressure guides critical ventilator adjustments:

• Target plateau pressure <30 cmH₂O to minimize ventilator-induced lung injury 1, 2
• If plateau pressure exceeds 30 cmH₂O despite low tidal volumes (6 mL/kg PBW), further reduce tidal volume to as low as 4 mL/kg PBW 1
• Higher plateau pressures may be acceptable in patients with very stiff chest walls, but should be approached with caution 1

Driving Pressure Calculation

Driving pressure (ΔP) = Plateau pressure - PEEP

• Driving pressure <15 cmH₂O is associated with improved survival 2, 3
• More predictive of mortality than plateau pressure or tidal volume alone 3
• Can be measured during both controlled and assisted ventilation 3

Assessing Patient Effort

During assisted ventilation modes:

• Plateau pressure can help estimate inspiratory muscle effort 4
• The difference between end-inspiratory occlusion plateau pressure and airway pressure before occlusion (PMI) correlates with inspiratory effort 4
• Can be used to titrate pressure support levels appropriately

Common Pitfalls and Considerations

1. Measurement accuracy issues:

   • Patient-ventilator asynchrony can affect readings
   • Insufficient inspiratory hold time may lead to inaccurate measurements
   • Active patient breathing efforts can invalidate plateau pressure readings

2. Interpretation challenges:

   • High plateau pressures may reflect chest wall stiffness rather than lung pathology
   • Patients with active breathing efforts generate higher transalveolar pressures for a given plateau pressure 1
   • Esophageal pressure monitoring may be needed to distinguish between lung and chest wall contributions

3. Patient-specific factors affecting plateau pressure:

   • Body mass index (higher BMI associated with elevated plateau pressures) 5
   • Race (non-white patients may have higher plateau pressures for the same tidal volume) 5
   • Severity of lung injury (more severe disease correlates with higher plateau pressures) 5

Practical Algorithm for Using Plateau Pressure

1. Measure plateau pressure regularly (at least once per shift and after ventilator changes)
2. If plateau pressure >30 cmH₂O:
   • Reduce tidal volume (target 4-6 mL/kg PBW)
   • Consider increasing respiratory rate to maintain minute ventilation
   • Accept permissive hypercapnia if not contraindicated
3. Calculate driving pressure (Plateau pressure - PEEP)
   • Target <15 cmH₂O
   • If elevated despite low tidal volumes, consider adjusting PEEP
4. Monitor trends in plateau pressure to assess:
   • Disease progression/improvement
   • Response to interventions (recruitment, positioning, medications)
   • Readiness for weaning

Plateau pressure remains one of the most important parameters to monitor in mechanically ventilated patients, particularly those with ARDS, as it directly relates to patient outcomes and guides lung-protective ventilation strategies.