Positive end expiratory pressure guided by transpulmonary pressure on lung protection in pig model with acute respiratory distress syndrome

Abstract

Objective To investigate the effect of positive end expiratory pressure (PEEP) guided by transpulmonary pressure compared with the optimal oxygenation-directed PEEP on lung injury in a pig model with acute respiratory distress syndrome(ARDS) . Methods Twelve ordinary pigs were randomly divided into a transpulmonary pressure group (n=6) and an optimal oxygenation group (n=6) . Both groups were given invasive mechanical ventilation. Their hemodynamics was monitored, and catheterization of the right internal jugular vein was done to test CVP. The hemodynamics was stable 30 minutes after the operation. The pigs were given lung lavage with normal saline to induce ARDS. The optimal PEEP was set by transpulmonary pressure titration or optimal oxygenation after lung recruitment. Thereafter, ventilation continued for 4 hours. PVPI, EVLWI and respiratory mechanics changes were recorded before lung lavage with saline (PEEP 5 cmH2O) (Tbase), after stabilization of ARDS (PEEP 5 cmH2O) (T0) and after using optimal PEEP for 0, l, 2, 3 and 4 hours (T1-T4) . At the time of Tbase, T0 and T4, blood was collected to detect interleukin-1β and -6. At the end the experiment, the right upper, right lower ventral, right lower dorsal lung tissues were taken for immunohistochemical test of NF-ΚB, IL-1β and IL-6. Lung homogenates were prepared to detect myeloperoxidase (MPO) . At the same time, lung tissue was taken to observe pathological changes and record the lung wet/dry weight ratio (W/D) . Results The levels of PEEP, Pm, Paw-exp, and Ptrans-exp in the transpulmonary pressure group were significantly lower than those in the optimal oxygenation group (P 0. 05) . The pathological scores of the right upper, right lower dorsal, and right lung tissues were all significantly lower in the transpulmonary pressure group than those in the optimal oxygenation group (P>0. 05) . Conclusion PEEP guided by transpulmonary pressure can open the alveoli, reduce the inflammatory response, prevent the ventilator-associated lung injury, and then reach the effect of lung protection. Key words: Acute respiratory distress syndrom; Mechanical ventilation; Lung injury