ObjectivePulse transit time (PTT) refers to the time it takes a pulse wave to travel between Outdoor Sectional two arterial sites.PTT can be estimated, amongst others, using the electrocardiogram (ECG) and photoplethysmogram (PPG).Because we observed a sawtooth artifact in the PTT while using standard patient monitoring equipment for ECG and PPG, we explored the reasons for this artifact.
MethodsPPG and ECG were simulated at a heartrate of both 100 and 160 beats per minute while using a Masimo PPG post-processing module and a Philips patient monitor setup at the neonatal intensive care unit.Two different post-processing modules were used.PTT was defined as the difference between the R-peak in the ECG and the point of 50% increase in the PPG.
ResultsA sawtooth artifact was seen in all simulations.Both length (59.2 to 72.
4 s) and amplitude (30.8 to 36.0 ms) of the sawtooth were dependent on the post-processing module used.
Furthermore, the absolute PTT value differed up to 250 ms depending on post-processing module and heart rate.The sawtooth occurred because the PPG wave continuously showed a minimal prolongation during the length of the sawtooth, followed by a Motor Parts sudden shortening.Both artifacts were generated in the post-processing module containing Masimo algorithms.
ConclusionPost-processing of the PPG signal in the Masimo module of the Philips patient monitor introduces a sawtooth in PPG and derived PTT.This sawtooth, together with a large module-dependent absolute difference in PTT, renders the thus-derived PTT insufficient for clinical purposes.