The authors showed that the optimal PEEP level was different for the dependent and non dependent region. Also, in their experimental study, Dargaville et al. demonstrated that ventral, medial and dorsal lung regions have different optimal selleckchem Imatinib Mesylate PEEP levels based on regional compliance values in both normal and surfactant depleted lungs. This was confirmed by our results, in which the best PEEP level for the non dependent and dependent regions were 5 and 15 cm H2O, respectively. In accordance with our previous studies, we found more ventilation of the dependent region at higher PEEP levels, as described by the parameter COV. COV describes the ventilation distribution in the ventral to dorsal direction and a value of 50% reflects an even distribution.

Thus, COV provides information about the optimal distribution of tidal volume to the Inhibitors,Modulators,Libraries non dependent and dependent regions at a certain PEEP level, but it does not give information about collapse or overdistention during a breath, as is seen Inhibitors,Modulators,Libraries with the intratidal gas distribution. The RVD was developed to assess the homogeneity of aeration of the lung regions during a slow inflation maneuver. It has been demonstrated in pigs that ALI lungs are more inhomogeneous compared with healthy lungs. however, application of higher PEEP levels improved the homogeneity of lung ventilation. In addition, the authors showed that the dependent region was slower inflated as compared with the non dependent region, indicating inhomogeneous ventilation of the dorsal lung parts. however, they used the standard deviations of the RVD index to create a ventilation homogeneity Inhibitors,Modulators,Libraries map.

In the present study we calculated the time needed to reach a threshold of 40% of the regional impedance change compared with the total inspiratory Inhibitors,Modulators,Libraries time and without the use of a slow flow Inhibitors,Modulators,Libraries inflation. We found that RVD values in both lung regions increased at each decremental PEEP step. Therefore, we were unable to detect the best PEEP level by means of RVD, with the used PEEP levels. However, Wrigge et al. described that RVD could only be used during a slow flow inflation maneuver with a tidal volume of 12 mL kg to describe tidal recruitment. Therefore, in the present study the results of the RVD are incorrect. Another index to describe homogeneous ventilation is the GI index, which quantifies the variation in tidal ventilation distribution and shows the lowest value in healthy patients and the highest value in patients with ARDS.

However, because this selleck chemical Bortezomib index describes homogeneity based on differences in measured impedance, the index value does not take into account the presence of atelectasis or overdistention and, therefore, we believe that this is not an appropriate index. Since, within our range of PEEP levels, we were unable to detect an optimal PEEP level based on the GI index and RVD index, it is possible that an optimum may have been found if higher PEEP levels had been applied than used in the present study. This study has some limitations.