LAUSR

BACKGROUND Superobesity and laparoscopic surgery promote negative end-expiratory transpulmonary pressure, which causes atelectasis formation and impaired respiratory mechanics. We hypothesized that end-expiratory transpulmonary pressure differs between fixed and individualized PEEP strategies, and mediates their effects on respiratory mechanics, end-expiratory lung volume, gas-exchange, and hemodynamic parameters in superobese patients. METHODS In this prospective, non-randomized crossover study including 40 superobese patients (body mass index 57.3 ± 6.4 kg·m-2) undergoing laparoscopic bariatric surgery, PEEP was set according to A) a fixed level of 8 cmH2O (PEEPEmpirical), (B) the highest respiratory system compliance (PEEPCompliance) or (C) an end-expiratory transpulmonary pressure targeting 0 cmH2O (PEEPTranspul) at different surgical positioning. The primary endpoint was end-expiratory transpulmonary pressure at different surgical positioning, secondary endpoints were respiratory mechanics, end-expiratory lung volume, gas-exchange, and hemodynamic parameters. RESULTS Individualized PEEPCompliance compared to fixed PEEPEmpirical resulted in higher PEEP (supine, 17.2 ± 2.4 vs. 8.0 ± 0.0 cmH2O; supine with pneumoperitoneum, 21.5 ± 2.5 vs. 8.0 ± 0.0 cmH2O; and beach chair with pneumoperitoneum; 15.8 ± 2.5 vs. 8.0 ± 0.0 cmH2O; P < 0.001 each) and less negative end-expiratory transpulmonary pressure (supine, -2.9 ± 2.0 vs. -10.6 ± 2.6 cmH2O; supine with pneumoperitoneum, -2.9 ± 2.0 vs. -14.1 ± 3.7 cmH2O; and beach chair with pneumoperitoneum, -2.8 ± 2.2 vs. -9.2 ± 3.7 cmH2O; P < 0.001 each). Titrated PEEP, end-expiratory transpulmonary pressure and lung volume were lower with PEEPCompliance compared to PEEPTranspul (P < 0.001 each). Respiratory system and transpulmonary driving pressure, and mechanical power normalized to respiratory system compliance were reduced using PEEPCompliance compared to PEEPTranspul. CONCLUSIONS In superobese patients undergoing laparoscopic surgery, individualized PEEPCompliance may provide a feasible compromise regarding end-expiratory transpulmonary pressures compared to PEEPEmpirical and PEEPTranspul, since PEEPCompliance with slightly negative end-expiratory transpulmonary pressures improved respiratory mechanics, lung volumes, and oxygenation while preserving cardiac output.