Purpose: To assess the correlation between inferior vena cava echocardiographic indices and central venous pressure, right atrial pressure and thus to practice, assessment of inferior vena cava, as a guide for the status of right side of the heart. Materials and Methods: In this descriptive cross-sectional study, a total of (60) patients (males and females) with their age ranging between (18–80) years were admitted to the respiratory care unit. Echocardiographic assessment of inferior vena cava hemodynamics (IVC expiratory, IVC inspiratory diameters and IVC collapsibility index) were carried out. In addition to the standard echocardiography examination, right heart function measurements (Tricuspid Annular Plane Systolic Excursion and right atrial area), in spontaneously and mechanically ventilated, patients were done. Findings: Both IVCe and IVCi diameters showed strong negative correlation with collapsibility index, (r= -0.920 for IVCe and r= -0.964 for IVCi) (P<0.001). There was a positive correlation between TAPSE and IVC-CI (r=0.857, P<0.001). Moreover, RA area was negatively correlated with collapsibility index (r = -0.892, P <0.001). IVC-CI in mechanically ventilated patients (40.11± 1.782) compared to spontaneous breathing (48.91± 1.811) (P <0.001) Implications to Theory, Practice and Policy: There was a linear relationship of IVC collapsibility index with TAPSE but an inverse relation with RA area. Evaluation of IVC diameter and its collapsibility index was an easy and non-invasive method to estimate CVP and RAP and so evaluate right heart performance of critically ill patients. Its use is more helpful in patients who are spontaneously breathing than those who are mechanically ventilated. The study tried to find an estimate predictor of right atrial pressure.