Used indices and their derivation
| Index | Derivation |
| Pulsatility index | ((peak systolic – end diastolic velocities)/mean flow velocity) |
| Resistance index | ((peak systolic – end diastolic velocities)/peak systolic velocities) |
| Conductance | VTI x CSA x HR/BW/100 mm Hg BP=mL/min/kg BW/100 mm Hg |
| Vmax | Maximum velocity of Doppler flow (in cm/s) |
| Left/right ventricular output and peripheral artery blood flow | (VTI x CSA) x HR/BW = mL/kg/min VTI=Velocity time integral, area under the curve CSA: Cross-sectional area of the respective annulus of aorta (left), pulmonary artery (right), or peripheral artery; calculated as π x D/2 |
BW, birth weight; CSA, cross-sectional area; HR, heart rate; VTI, velocity time integral.