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 (PEEP _INCREMENTAL ) or by stepwise decrease after a lung recruiting manoeuvre (PEEP _DECREMENTAL ). 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 PEEP _INCREMENTAL or PEEP _DECREMENTAL strategy to match the lowest ∆P. In the PEEP _INCREMENTAL group, PEEP was stepwise titrated from ZEEP up to 16 cm H ₂ O, whereas in the PEEP _DECREMENTAL group PEEP was decrementally titrated, starting from 16 cm H ₂ O, 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 PEEP _INCREMENTAL and from 45 [37-58]% to 33 [25-45]% in the PEEP _DECREMENTAL group (both p < 0.001 vs baseline). The resulting ∆P, however, was lower in the PEEP _DECREMENTAL than in the PEEP _INCREMENTAL group (8 [7-11] vs 10 [9-11] cm H ₂ O; p = 0.03). In the PEEP _DECREMENTAL group the PaO ₂ / FIO ₂ ratio increased significantly after intervention (from 140 [99-176] to 186 [152-243], p < 0.001). Both the PEEP _INCREMENTAL and the PEEP _DECREMENTAL strategies were able to decrease intraoperative shunt, but only PEEP _DECREMENTAL improved oxygenation and lowered intraoperative ΔP.Clinical trial number NCT03635281; August 2018; "retrospectively registered".
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