Physiological effects of two driving pressure-based methods to set positive end-expiratory pressure during one lung ventilation

During one-lung ventilation (OLV), titrating the positive end-expiratory pressure (PEEP) to target a low driving pressure (∆P) could reduce postoperative pulmonary complications. However, it is unclear how to conduct PEEP titration: by stepwise increase starting from zero PEEP (PEEPINCREMENTAL) or by stepwise decrease after a lung recruiting manoeuvre (PEEPDECREMENTAL). In this randomized trial, we compared the physiological effects of these two PEEP titration strategies on respiratory mechanics, ventilation/perfusion mismatch and gas exchange. Patients undergoing video-assisted thoracoscopic surgery in OLV were randomly assigned to a PEEPINCREMENTAL or PEEPDECREMENTAL strategy to match the lowest ∆P. In the PEEPINCREMENTAL group, PEEP was stepwise titrated from ZEEP up to 16 cm H2O, whereas in the PEEPDECREMENTAL group PEEP was decrementally titrated, starting from 16 cm H2O, immediately after a lung recruiting manoeuvre. Respiratory mechanics, ventilation/perfusion mismatch and blood gas analyses were recorded at baseline, after PEEP titration and at the end of surgery. Sixty patients were included in the study. After PEEP titration, shunt decreased similarly in both groups, from 50 [39–55]% to 35 [28–42]% in the PEEPINCREMENTAL and from 45 [37–58]% to 33 [25–45]% in the PEEPDECREMENTAL group (both p < 0.001 vs baseline). The resulting ∆P, however, was lower in the PEEPDECREMENTAL than in the PEEPINCREMENTAL group (8 [7–11] vs 10 [9–11] cm H2O; p = 0.03). In the PEEPDECREMENTAL group the PaO2/ FIO2 ratio increased significantly after intervention (from 140 [99–176] to 186 [152–243], p < 0.001). Both the PEEPINCREMENTAL and the PEEPDECREMENTAL strategies were able to decrease intraoperative shunt, but only PEEPDECREMENTAL improved oxygenation and lowered intraoperative ΔP. Clinical trial number NCT03635281; August 2018; “retrospectively registered”.