A lower limit of quantification (LLOQ) for each PCIS signal was set at either 1% of the mean PCIS signal intensity during infusion (at isocratic conditions) or 10 times the mean noise measured over the first 0.5 min of the plasma injections (when the PCIS solution was still diverted to waste), whichever was lowest. The number of data points below LLOQ of the smoothed signal between 10 and 14 min were counted for each PCIS concentration.