From Echocardiography in ICU
The subcostal echographic window is probably the most useful window in intubated patients. You can visualize and assess the function of all cardiac structures, and the inferior vena cava (IVC) diameter to evaluate the patient's volume status. It is also the best view to estimate a pericardial effusion. Unfortunately the echographic planes are not suited to the Doppler examination and it will not be possible to quantitate valvular disease nor to calculate hemodynamic parameters.
You can start with the subcostal 4 chamber and then move to the IVC views.