The purpose of this study is to assess whether circulating Angiotensin (Ang) II and Ang (1-7) levels are associated with right ventricular (RV) dysfunction in mechanically ventilated subjects. It is also designed to further characterize the subject population for severity of RV dysfunction. This study will investigate the association of renin-angiotensin system (RAS) peptides and markers of RV function, as measured by echocardiography, in subjects requiring acute mechanical ventilation. Maximum 150 subjects will be enrolled for the study and they will be evaluated over three days period using standard of care investigations, including trans-thoracic echocardiography (TTE) and/or trans-esophageal echocardiography (TOE) echocardiography. The maximum total duration of this study for subjects is 28 days.