The results of all these three methods showed considerable inter-

The results of all these three methods showed considerable inter-patient variation, which suggests the use of an individualized PEEP selection sellectchem process. It has to be noted that the dynamic compliance and the compliance-volume curve method focus on the mechanics of the respiratory system, while the GI index focuses on a different aspect, namely the homogeneity of ventilation distribution. 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 (at least to dynamic compliance). In the analysis of dynamic compliance, due to the quasi-plateau phase in the compliance-pressure curves (Figure (Figure3),3), it is difficult to claim that the PEEP level where C = Cmax is superior to the level where C = Cmax �� 98%.

The difference between these two PEEP levels can be as large as 8 mbar. The PEEP selection using the compliance-volume curves is an enhancement of the dynamic compliance method. However, categorizing the compliance-volume curves is somehow complex and not intuitive. Therefore, another parameter to select PEEP in a different aspect is still needed. In addition, the GI index is superior to dynamic lung mechanics in spontaneously breathing patients where reliable lung mechanics are difficult to obtain.The quasi-static P/V curve has also been used to individualize the setting of a proper PEEP level. But how to generate and analyze the P/V curve is still under intense debate [18].

To set PEEP at the lower inflection point plus 2 cmH2O was shown to be appropriate by Takeuchi and colleagues in a lavage-injured sheep ARDS model [23]. But there is no physiological interpretation to support it and the lower inflection point may be difficult to identify accurately [24], especially in patients with a wide distribution of opening pressures. New findings indicate that it may be better to derive PEEP from the upper inflection point of the deflation limb of the P/V curve [25]. In order to obtain quasi-static P/V curves, a normal ventilation process has to be interrupted in order to perform respiratory maneuvers, such as low-flow or super-syringe inflation. These maneuvers may be harmful to the patients due to hyper-inflation.

Besides using lung mechanics, there are other studies on open-lung PEEP selection using blood gas analysis [26-29] and imaging techniques [8,9,30], both of which are difficult Dacomitinib to implement as a continuous bedside monitoring tool. Blood gas analysis provides a way to titrate PEEP but it is an invasive and discontinuous method. Recently, more and more studies on PEEP selection use imaging techniques. CT is the gold standard for assessment of tidal volume distribution in injured lungs [4].

Leave a Reply

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>