PSV+Sigh group settings. Similarly, PSV in this group will be set with the same protective targets of the PSV group (see above) and cyclic pressure control phase at 30 cmH2O for 3 seconds delivered once per minute (i.e., Sigh) will be added. PSV+Sigh is an easy to implement ventilation mode and, for the present study, the investigators will use high performance ICU ventilators already available in each clinical unit. Briefly, ventilators will be switched to biphasic positive airway pressure mode (e.g., BiPAP on Drager ventilators, SIMV-PC on Maquet and GE, DuoPAP on Hamilton) with the lower pressure level set at clinical PEEP and the higher pressure level set at 30 cmH2O with a 3-second inspiratory time and then a 57-second expiratory time. This Sigh rate of one per minute can be obtained by virtually all the already available high performance ICU ventilators, thus, even though a lower Sigh rate might be regarded as more physiological, we choose the 1/min rate for feasibility and costs related to the future large RCT. FiO2 will be left as selected before the pre-randomization Sigh test.