Table 1

Used indices and their derivation

Pulsatility index((peak systolic – end diastolic velocities)/mean flow velocity)
Resistance index((peak systolic – end diastolic velocities)/peak systolic velocities)
ConductanceVTI x CSA x HR/BW/100 mm Hg BP=mL/min/kg BW/100 mm Hg
VmaxMaximum 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.