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

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 H 2 O/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.