Abstract Background ARDS is characterized by heterogeneous regional ventilation, with areas of collapse coexisting with overdistension. Both contribute to ventilator-induced lung injury. The ARDSNet PEEP-FiO2 table remains widely used but does not consider the balance between these opposing phenomena. In this analysis, we aimed to quantify the magnitude of collapse and overdistension and evaluate their impact on key physiological variables, including respiratory system compliance and oxygenation. Methods All patients were ventilated according to the low ARDSNet PEEP- FiO2 table for 30 minutes. A standardized lung recruitment maneuver was then performed, followed by a decremental PEEP titration guided by electrical impedance tomography (EIT). Collapse and overdistension were estimated at each step using the EIT titration tool. The PEEP level corresponding to equal proportions of collapse and overdistension was defined as the individualized EIT-based PEEP. Then, patients were randomized to receive ventilation guided either by the EIT-based PEEP strategy or by the ARDSNet PEEP-FiO2 table. Results 85 patients were analyzed, each undergoing both ventilation strategies in a crossover design. The EIT-guided approach resulted in higher individualized PEEP levels compared with ARDSNet (14 11-16 cmH2O vs 10.5 10-14 cmH2O, p 0.001). Despite the higher PEEP, the percentage of collapse was markedly lower during the EIT-guided phase than during the ARDSNet phase (4.9 3.5-7.1 vs 18.6 9.4-27.3, p 0.001). Percentage of overdistension also significantly reduced with EIT-guided titration (7.4 5.3-9.0 vs 10.5 6.4-19.6, p 0.001), The EIT-guided strategy improved respiratory system compliance by 8 mL/cmH2O on average (p 0.001), consistent with a more homogeneous and protective lung inflation pattern, as demonstrated in figure 1. In addition, patients managed with the EIT-guided or extended protection strategy achieved oxygen independence earlier than those in the ARDSNet group (log-rank p = 0.044). Prone positioning was less frequently required with EIT (70% vs 89.7%, p = 0.045). Conclusion EIT-guided PEEP titration, despite slightly higher PEEP levels, effectively reduced both collapse and overdistension, improving oxygenation and reducing the need for prone positioning. These findings support individualized, physiology-based PEEP adjustment to enhance lung protection in ARDS. Figure 1. PEEP (A), Respiratory system compliance (B), collapse (C) and overdistension (D) differences between the ARDSNet and the electrical impedance tomography (EIT) strategies. Change in PEEP after EIT assessment varied widely. On average, a higher PEEP was selected with EIT when compared to the ARDSNet strategy. Despite higher PEEP, Respiratory compliance, collapse and overdistension significantly reduced with the EIT strategy. This abstract is funded by: Fapesp
Alcala et al. (Fri,) studied this question.