Recent data from large trials of high-frequency high frequency oscillation (HFO) without a cuff leak vs, lung-protective conventional ventialtion (CMV) failed to show any HFO-related benefit with respect to outcome. A possible explanation is that HFO increases the probability of right ventricular dysfunction due to the combination of high mean airway pressures (mPaws) and hypercapnia. In contrast, available preliminary data on low-frequency HFO-tracheal gas insufflation (TGI) with cuff leak vs. CMV are suggestive of an HFO-TGI related benefit. Low-frequency HFO-TGI with a cuff leak is associated with relatively low mean tracheal pressures and adequate control of PaCO2. Thus, the investigators intend to test the hypothesis that low frequency HFO +/- TGI with a cuff leak is associated with better right ventricular function relative to high-frequency HFO without a cuff leak.