The PLETH arrives about 0.4 s late¶
Raw R-to-PPG-foot pulse arrival time in VitalDB has a median of 0.64–0.71 s, about 0.4 s more than physiology: the monitor's buffering and filtering. One delay fits the whole release: no clusters by setup, SNUADC port or case order (One device delay for the PLETH across the release).
| Status | established: shown on many cases, with a control. |
| Devices | Solar8000 monitor |
| Variables | Plethysmogram (SNUADC) |
What it means¶
PAT and any ECG–PPG timing from VitalDB is mostly device delay unless that delay is removed. PLETH also lags ART by 0.40–0.53 s, depending on the fiducial.
What is done about it¶
One global delay, 385 ms (PPG hardware delay: the stored R-to-foot delay of 655 ms minus an adopted physiological PAT of 270 ms), is subtracted from every recording, which keeps the differences between patients.
Evidence¶
| Study | Date | Status | Summary |
|---|---|---|---|
| One device delay for the PLETH across the release | 2026-10-18 | current | The stored ECG-to-PLETH delay was measured in 5,536 recordings, to the foot and to the steepest upstroke of each pulse. It has one peak (655 ms to the foot, 715 ms to the upstroke, in the median recording), no clusters by recording setup or SNUADC port, and no shift along the case order: one global device delay, 385 ms with an adopted R-to-foot finger PAT of 270 ms, fits the whole release, as Ruffolo et al. found in their own data. |
| The PPG hardware delay and the adopted pulse arrival time | 2026-10-12 | current | VitalDB's raw ECG→PPG pulse arrival time is about 0.4 s longer than physiology. Splitting it into a hardware delay (one value for the release; One device delay for the PLETH across the release) and a physiological part needs an adopted value from studies that sampled ECG and PPG on one clock: about 270 ms for anaesthetised adults. |
| The PPG sawtooth and its correction | 2026-10-10 | current | The ECG→PPG delay creeps at 18–52 ppm and jumps up by one 33.3 ms frame at each slip, every 11–31 minutes. A tooth-by-tooth model removes it; where the correction is confident it is essentially exact on injected test data. |