The main goal of the present study is to document and compare the effect of lung protective conventional mechanical ventilation (CMV) and of different HFO strategies (already clinically tested in trials with conflicting results) on right ventricular performance as determined by TEE. More specifically, we intend to compare high-PEEP, lung protective CMV with a "high" mPaw/no cuff leak, high-frequency HFO strategy, and a "high" mPaw with cuff leak, "low" frequency HFO strategy with and without TGI.