With Sigh , oxygenation improved ( p < 0.001 vs no-Sigh ) , end-expiratory lung volume of nondependent and dependent regions increased ( p < 0.01 vs no-Sigh ) , Vtnondep showed a trend to reduction , and Vtdep significantly decreased ( p = 0.11 and p < 0.01 vs no-Sigh , respectively ) .