The Accuracy of Plateau and Driving Pressures During Assisted and Spontaneous Ventilation Depends on the Degree of Inspiratory Effort and Duration of the Inspiratory Hold

Abstract

Background:

Plateau pressure (P_plat) is routinely monitored during mechanical ventilation to assess the risk of ventilator-induced lung injury. Although P_plat is classically measured during controlled ventilation with a constant-flow pattern, it is increasingly applied during decelerating flow modes and in the presence of spontaneous respiratory effort. Uncertainty persists regarding the accuracy of P_plat for determining static respiratory system compliance (C_RS) and the inspiratory hold duration required to obtain reliable measurements across varying flow patterns, levels of effort, and lung conditions.

Methods:

We conducted a combined bench and clinical study. Using an ASL 5000 lung simulator, we compared measured versus set C_RS across 3 pediatric age ranges, simulated lung conditions, levels of inspiratory effort, and 3 ventilation modes (volume-controlled continuous mandatory ventilation, pressure-controlled continuous mandatory ventilation with adaptive targeting, and pressure support ventilation) and determined the time required to achieve steady P_plat. In parallel, we performed a secondary analysis of airway pressure waveforms from children with pediatric ARDS enrolled in a lung- and diaphragm-protective ventilation trial to define the minimum inspiratory occlusion time required for reliable P_plat measurement during passive and spontaneous breathing.

Results:

Across all bench conditions, C_RS derived from driving pressure and tidal volume (V_T) slightly overestimated set C_RS (median bias 0.09 mL/cm H₂O/kg [95% CI 0.06–0.16]). Bias increased with greater inspiratory effort, without meaningful differences among ventilation modes after stratification by effort. Time to steady P_plat increased progressively with higher effort (passive 0 [0–400] ms; moderate: 300 [200–400] ms; high: 500 [380–800] ms; P < .001). In patient data, steady P_plat was achieved within 500 ms under passive conditions but exceeded 1,500 ms during high effort.

Conclusions:

During both constant and decelerating flow modes of ventilation, P_plat combined with V_T and PEEP provided a reliable measure of C_RS. However, as spontaneous respiratory effort increases, the time to achieve a steady P_plat was prolonged, and C_RS derived from P_plat may be overestimated.