Respiratory mechanics and mechanical power during low vs. high positive end-expiratory pressure in obese surgical patients - A sub-study of the PROBESE randomized controlled trial

Study objective: We aimed to characterize intra-operative mechanical ventilation with low or high positive end-expiratory pressure (PEEP) and recruitment manoeuvres (RM) regarding intra-tidal recruitment/derecruitment and overdistension using non-linear respiratory mechanics, and mechanical power in obese surgical patients enrolled in the PROBESE trial.Design: Prospective, two-centre substudy of the international, multicentre, two-arm, randomized-controlled PROBESE trial.Setting: Operating rooms of two European University Hospitals.Patients: Forty-eight adult obese patients undergoing abdominal surgery.Interventions: Intra-operative protective ventilation with either PEEP of 12 cmH(2)O and repeated RM (HighPEEP+RM) or 4 cmH(2)O without RM (LowPEEP).Measurements: The index of intra-tidal recruitment/de-recruitment and overdistension (%E-2) as well as airway pressure, tidal volume (V-T), respiratory rate (RR), resistance, elastance, and mechanical power (MP) were calculated from respiratory signals recorded after anesthesia induction, 1 h thereafter, and end of surgery (EOS).Main results: Twenty-four patients were analyzed in each group. PEEP was higher (mean +/- SD, 11.7 +/- 0.4 vs. 3.7 +/- 0.6 cmH(2)O, P < 0.001) and driving pressure lower (12.8 +/- 3.5 vs. 21.7 +/- 6.8 cmH(2)O, P < 0.001) during HighPEEP+RM than LowPEEP, while V-T and RR did not differ significantly (7.3 +/- 0.6 vs. 7.4 +/- 0.8 ml center dot kg(-1), P = 0.835; and 14.6 +/- 2.5 vs. 15.7 +/- 2.0 min(-1), P = 0.150, respectively). %E-2 was higher in HighPEEP+RM than in LowPEEP following induction (-3.1 +/- 7.2 vs. -12.4 +/- 10.2%; P < 0.001) and subsequent timepoints. Total resistance and elastance (13.3 +/- 3.8 vs. 17.7 +/- 6.8 cmH(2)O center dot l center dot s(-2), P = 0.009; and 15.7 +/- 5.5 vs. 28.5 +/- 8.4 cmH(2)O center dot l, P < 0.001, respectively) were lower during HighPEEP+RM than LowPEEP. Additionally, MP was lower in HighPEEP+RM than LowPEEP group (5.0 +/- 2.2 vs. 10.4 +/- 4.7 J center dot min(-1), P < 0.001).Conclusions: In this sub-cohort of PROBESE, intra-operative ventilation with high PEEP and RM reduced intra-tidal recruitment/de-recruitment as well as driving pressure, elastance, resistance, and mechanical power, as compared with low PEEP.

Automated summary

The study aimed to examine the impact of low or high positive end-expiratory pressure (PEEP) and recruitment manoeuvres (RM) on intra-tidal recruitment/derecruitment and overdistension in obese patients. The results showed that higher PEEP and RM reduced intra-tidal recruitment/derecruitment, driving pressure, elastance, resistance, and mechanical power.