Measuring Plateau Pressure Without Inspiratory Hold Maneuver
No, plateau pressure (Pplat) cannot be accurately measured without an inspiratory hold maneuver in mechanically ventilated patients. The inspiratory hold is the standard and necessary technique to obtain a true plateau pressure by allowing equilibration of pressures throughout the respiratory system 1, 2, 3.
Why the Inspiratory Hold is Essential
Plateau pressure requires zero flow conditions to accurately reflect end-inspiratory alveolar pressure, which can only be achieved by occluding the airway at end-inspiration 1, 2.
The inspiratory hold maneuver allows pressure equilibration between the proximal airway and alveoli, eliminating the resistive component of airway pressure 1.
Without the hold, the measured pressure includes both elastic recoil pressure and resistive pressure from ongoing gas flow, making it impossible to isolate true alveolar distending pressure 2, 3.
Alternative Approaches and Their Limitations
End-Inspiratory Occlusion During Assisted Ventilation
In patients on pressure support ventilation, an end-inspiratory occlusion can estimate inspiratory muscle effort but this is fundamentally different from measuring plateau pressure 4.
The difference between the end-inspiratory occlusion plateau and pre-occlusion airway pressure (called PMI) reflects muscle pressure, not lung distending pressure 4.
This technique requires the patient to be relaxed during the occlusion for reliable interpretation 5.
Reliability Concerns During Patient-Triggered Breaths
Recent evidence shows that 92% of inspiratory holds during assisted ventilation can be classified as readable or unreadable based on specific waveform characteristics 5.
Readable plateaus are characterized by: a short time from airway peak to plateau pressure, and a stable, longer plateau duration 5.
Unreadable plateaus occur with: ongoing muscular activity, higher inspiratory effort, and unstable pressure tracings 5.
Even when attempting plateau measurement during assisted breaths, active muscle contraction makes the measurement unreliable and does not represent true alveolar pressure 5.
Clinical Implications
For lung-protective ventilation targeting Pplat ≤30 cmH₂O, the inspiratory hold maneuver remains mandatory 1, 3.
Modern ventilators have built-in inspiratory hold buttons that make this measurement straightforward in controlled ventilation modes 1, 2.
In patients with spontaneous breathing efforts, adequate sedation or neuromuscular blockade may be necessary to obtain reliable plateau pressure measurements 5.
Important Caveats
Transpulmonary pressure (airway pressure minus esophageal pressure) provides more accurate assessment of lung distending pressure than plateau pressure alone, particularly in patients with elevated intra-abdominal pressure or chest wall stiffness 6, 7.
Plateau pressure can be misleading: it may underestimate lung stress in atelectasis and overestimate it with elevated intra-abdominal pressure 7.
Driving pressure (Pplat - PEEP) is a stronger predictor of outcomes than plateau pressure alone, with values >15 cmH₂O being particularly concerning 1, 3.
The stress index (shape of the pressure-time curve) may identify injurious ventilation even when plateau pressure appears acceptable, with values >1.05 suggesting overdistension 8.