Figure 1

Mathematical analysis of the thermodilution curve. Panel a) Both algorithms rely on mean transit time (Mtt), the time required for half of the indicator to pass the thermistor in the femoral artery. Mtt divides the area under the curve (AUC) into two areas of the same size (AUC₁ and AUC₂). Panel b) Downslope time (Dst) is part of the PiCCO™ GEDV algorithm. It is the time of the temperature decay between two set points in the thermodilution curve, for example, 80% to 40%. Theoretically, the decay is mono-exponential, so it can be measured at any time point after the peak and be adjusted by a constant factor. Panel c) The VolumeView™ algorithm relies on maximum up-slope (S₁) and maximum down-slope (S₂) of the dilution curve. This approach may be less sensitive to early recirculation and thermal noise.