Bedside personalized methods based on electrical impedance tomography or respiratory mechanics to set PEEP in ARDS and recruitment-to-inflation ratio: a physiologic study

Background Various Positive End-Expiratory Pressure (PEEP) titration strategies have been proposed to optimize ventilation in patients with acute respiratory distress syndrome (ARDS). We aimed to compare PEEP titration strategies based on electrical impedance tomography (EIT) to methods derived from respiratory system mechanics with or without esophageal pressure measurements, in terms of PEEP levels and association with recruitability.Methods Nineteen patients with ARDS were enrolled. Recruitability was assessed by the estimated Recruitment-to-Inflation ratio (R/I-est) between PEEP 15 and 5 cmH(2)O. Then, a decremental PEEP trial from PEEP 20 to 5 cmH(2)O was performed. PEEP levels determined by the following strategies were studied: (1) plateau pressure 28-30 cmH(2)O (Express), (2) minimal positive expiratory transpulmonary pressure (Positive P(L)e), (3) center of ventilation closest to 0.5 (CoV) and (4) intersection of the EIT-based overdistension and lung collapse curves (Crossing Point). In addition, the PEEP levels determined by the Crossing Point strategy were assessed using different PEEP ranges during the decremental PEEP trial.Results Express and CoV strategies led to higher PEEP levels than the Positive P(L)e and Crossing Point ones (17 [14-17], 20 [17-20], 8 [5-11], 10 [8-11] respectively, p < 0.001). For each strategy, there was no significant association between the optimal PEEP level and R/I-est (Crossing Point: r(2) = 0.073, p = 0.263; CoV: r(2) < 0.001, p = 0.941; Express: r(2) < 0.001, p = 0.920; Positive P(L)e: r(2) = 0.037, p = 0.461). The PEEP level obtained with the Crossing Point strategy was impacted by the PEEP range used during the decremental PEEP trial.Conclusions CoV and Express strategies led to higher PEEP levels than the Crossing Point and Positive P(L)e strategies. Optimal PEEP levels proposed by these four methods were not associated with recruitability. Recruitability should be specifically assessed in ARDS patients to optimize PEEP titration.