Two methods of setting positive end-expiratory pressure in acute lung injury: An experimental computed tomography volumetric study

This study was conducted to observe effects of two methods of setting positive end-expiratory pressure (PEEP) based on the pressure-volume (PV) curve. After lung injury was induced by oleic acid in six mongrel adult dogs, the inflation PV curve was traced and the lower inflection point (LIP) was measured. The 'PEEP_INF' was defined as LIP+2 cmH₂O. After recruitment maneuver to move the lung physiology to the deflation limb of PV curve, decremental PEEP was applied. The lowest level of PEEP that did not result in a significant drop in PaO₂ was defined as the 'PEEP _DEF'. Arterial blood gases, lung mechanics, hemodynamics, and lung volumes (measured on computed tomography during end-expiratory pause) were measured at PEEP of 0 cmH₂O, PEEP_INF and PEEP _DEF sequentially. The median PEEP_INF was 13.4 cm H ₂O (interquartile range, 12.5-14.3) and median PEEP_DEF was 12.0 cm H₂O (10.0-16.5) (p=0.813). PEEP_DEF was associated with significantly higher PaO₂ and lung volumes, and significantly lower shunt fraction and cardiac index when compared to PEEP_INF (p<0.05). Setting the PEEP based on the deflation limb of the PV curve was useful in improving oxygenation and lung volumes in a canine lung injury model.