Individualized PEEP to optimise respiratory mechanics during abdominal surgery: a pilot randomised controlled trial

Abstract Background Higher intraoperative driving pressures (ΔP) are associated with increased postoperative pulmonary complications (PPC). We hypothesised that dynamic adjustment of PEEP throughout abdominal surgery reduces ΔP, maintains positive end-expiratory transpulmonary pressures (Ptp_ee) and increases respiratory system static compliance (Crs) with PEEP levels that are variable between and within patients. Methods In a prospective multicentre pilot study, adults at moderate/high risk for PPC undergoing elective abdominal surgery were randomised to one of three ventilation protocols: (1) PEEP≤2 cm H2O, compared with periodic recruitment manoeuvres followed by individualised PEEP to either optimise respiratory system compliance (PEEPmaxCrs) or maintain positive end-expiratory transpulmonary pressure (PEEPPtp_ee). The composite primary outcome included intraoperative ΔP, Ptp_ee, Crs, and PEEP values (median (interquartile range) and coefficients of variation [CVPEEP]). Results Thirty-seven patients (48.6% female; age range: 47–73 yr) were assigned to control (PEEP≤2 cm H2O; n=13), PEEPmaxCrs (n=16), or PEEPPtp_ee (n=8) groups. The PEEPPtp_ee intervention could not be delivered in two patients. Subjects assigned to PEEPmaxCrs had lower ΔP (median8 cm H2O [7–10]), compared with the control group (12 cm H2O [10–15]; P=0.006). PEEPmaxCrs was also associated with higher Ptp_ee (2.0 cm H2O [-0.7 to 4.5] vs controls: -8.3 cm H2O [-13.0 to -4.0]; P≤0.001) and higher Crs (47.7 ml cm H2O [43.2–68.8] vs controls: 39.0 ml cm H2O [32.9–43.4]; P=0.009). Individualised PEEP (PEEPmaxCrs and PEEPPtp_ee combined) varied widely (median: 10 cm H2O [8-15]; CVPEEP=0.24 [0.14–0.35]), both between, and within, subjects throughout surgery. Conclusions This pilot study suggests that individualised PEEP management strategies applied during abdominal surgery reduce driving pressure, maintain positive Ptp_ee and increase static compliance. The wide range of PEEP observed suggests that an individualised approach is required to optimise respiratory mechanics during abdominal surgery. Clinical trial registration NCT02671721.