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.