Abstract Rationale Optimizing positive end-expiratory pressure (PEEP) remains a clinical challenge, particularly in cases of asymmetrical lung injury, where one lung is more severely affected. Electrical Impedance Tomography (EIT) is a bedside imaging technique that provides real-time assessment of global and regional aeration and may help individualize PEEP in this context. Objectives To compare three EIT-based PEEP titration strategies—minimal overdistention, minimal collapse, and the best compromise (crossing-point)—in a non-to-low recruitable, asymmetrical lung injury model, evaluating their effects on respiratory mechanics, gas exchange, and hemodynamics. Methods Randomized experimental study in a porcine model. Asymmetrical lung injury was induced by selective left-lung surfactant lavage and high-stretch ventilation, while the right lung remained collapsed. After injury, bilateral ventilation was resumed, and a decremental PEEP trial guided by EIT was performed. Animals were randomized to: (1) Minimal-Overdistention (PEEP at 0-3% overdistention), (2) Crossing-Point (PEEP at collapse-overdistention intersection), or (3) Minimal-Collapse (PEEP at 0-3% collapse). Animals were ventilated for 12 hours, with periodic measurements of respiratory mechanics, gas exchange, and hemodynamics. Results Fifteen animals (n = 5/group) were studied. Post-injury overall PaO2/FiO2 was 178±52 and respiratory system compliance (CRS) 24±5 mL/cmH2O. The model presented low recruitability (median recruitment-to-inflation ratio 0.57IQR:0.39-0.94). Mean PEEP was 3±2cmH2O (Minimal-Overdistention), 9±2cmH2O (Crossing-Point), and 14±2cmH2O (Minimal-Collapse), p 0.001. After 12 hours, setting PEEP at minimal collapse resulted in higher CRS (24±3mL/cmH2O vs 15±3mL/cmH2Op = 0.003) and lower pulmonary shunt(p = 0.035) and cardiac output (5.1±0.5L/min vs. 7.9±2.4L/minp = 0.036), compared to Minimal-Overdistention. Lactate levels also tended to be higher in Minimal-Collapse(p = 0.089). Conclusion In this low-recruitable, asymmetrical lung injury model, setting PEEP to minimize collapse resulted in better respiratory mechanics and oxygenation; however, it was also associated with hemodynamic impairment, which might be a better indicator of high lung overdistention. Additional experiments and analyses are underway to confirm and expand these findings. This abstract is funded by: None
Sousa et al. (Fri,) studied this question.