Effects of Invasive Mechanical Ventilation on the Right Ventricular Function

The goal of this observational study is to learn about the influence of mechanical ventilation on the right ventricular (RV) function. The primary focus is on methods which are routinely used to improve gas exchange in ventilated patients (positive end expiratory pressure \[PEEP\], inhalation of NO, prone positioning). The main questions it aims to answer are: * Effects of prone positioning, PEEP and inhalation of NO on RV-function * Are there determinants (clinical, laboratory, demographic, echocardiographic) for the right ventricular response to the above? RV-Function will be assessed with right ventricular pressure-volume loops recorded with a conductance catheter at * each PEEP-Level during titration of the best PEEP * before and every 5 minutes (for max. 45 minutes) after rotation to prone position * before and under continuous inhalation of NO (if required based on clinical grounds)