Abstract
IntroductionLung protective ventilation requires low tidal volume and suitable positive end-expiratory pressure (PEEP). To date, few methods have been accepted for clinical use to set the appropriate PEEP. The aim of this study was to test the feasibility of PEEP titration guided by ventilation homogeneity using the global inhomogeneity (GI) index based on electrical impedance tomography (EIT) images.MethodsIn a retrospective study, 10 anesthetized patients with healthy lungs mechanically ventilated under volume-controlled mode were investigated. Ventilation distribution was monitored by EIT. A standardized incremental PEEP trial (PEEP from 0 to 28 mbar, 2 mbar per step) was conducted. During the PEEP trial, "optimal" PEEP level for each patient was determined when the air was most homogeneously distributed in the lung, indicated by the lowest GI index value. Two published methods for setting PEEP were included for comparison based on the maximum global dynamic compliance and the intra-tidal compliance-volume curve.ResultsNo significant differences in the results were observed between the GI index method (12.2 ± 4.6 mbar) and the dynamic compliance method (11.4 ± 2.3 mbar, P > 0.6), or between the GI index and the compliance-volume curve method (12.2 ± 4.9 mbar, P > 0.6).ConclusionsAccording to the results, it is feasible and reasonable to use the GI index to select the PEEP level with respect to ventilation homogeneity. The GI index may provide new insights into the relationship between lung mechanics and tidal volume distribution and may be used to guide ventilator settings.
Highlights
Lung protective ventilation requires low tidal volume and suitable positive end-expiratory pressure (PEEP)
Starting at zero end-expiratory pressure (ZEEP), the global inhomogeneity (GI) index first decreased with the increase of PEEP indicating that ventilation was more homogenously distributed
We have found no significant differences among the optimal PEEP values selected by these three methods, which indicates that homogeneity of air distribution in the lung has been somehow related to the global lung mechanics
Summary
Lung protective ventilation requires low tidal volume and suitable positive end-expiratory pressure (PEEP). In the presence of lung injury, such as acute respiratory distress syndrome (ARDS), dependent lung regions are essentially nonaerated, while non-dependent regions remain partially aerated [1]. Under certain conditions both collapse of the dependent regions and overinflation of the non-dependent ones may occur, which may increase the risk of ventilator-induced lung injury [2]. Lung protective ventilation requires low tidal volume and a suitable positive end-expiratory pressure (PEEP) level to minimize. Increase of PEEP further prevents derecruitment in the dependent areas but may lead to overdistension in the non-dependent areas as well. To find a balance between these two aspects is one goal of setting PEEP
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