Pulmonary atelectasis during low stretch ventilation: "open lung" versus "lung rest" strategy

) to limit transmu-ral pressure and levels of positive end-expiratory pressure (PEEP) sufficient toavoid tidal recruitment have been pro-posed to minimize VILI (2, 6).Several studies demonstrated the im-portance of the “lung rest” approach tominimize VILI (4, 8, 9). This strategy limitsvolume and pressure and applies moderatelevels of PEEP to obtain minimal oxygen-ation target eventually tolerating occur-rence of atelectasis (10, 11). Duggan et al(12) recently found that in rats receivinglow volume and zero PEEP, the develop-ment of atelectasis decreased survival andwas associated to ultrastructural evidenceof microvascular disruption. However, it isstill unclear whether “atelectasis-induced”lung injury might be due to the associ-ated shear stress on the boundary be-tween aerated and collapsed areas oratelectasis per se may promote lunginjury through the activation of intra-cellular pathways that may alter cellu-lar life span (12).In alternative to the “lung rest” ap-proach, the “open lung” strategy proposesto fully recruit the collapsed lung by thetransient application of high inflating pres-sure and high levels of PEEP to maintainthe lung recruited throughout the entirerespiratory cycle (7, 13). The expected ad-vantage is a reduction of the mechanicalstress on the boundary between atelectasisand aerated areas (14). Although only avariable percentage of lungs with acute re-spiratory distress syndrome could be re-cruited without greater lung injury by lead-ing to pulmonary hyperinflation (15),recent experimental data suggest that incomparison to the “lung rest” approach,