| The heartbeat in the Primus airway signals |
2026-10-19 |
current |
A pilot in 30 recordings for a heartbeat-locked route from the Primus to the SNUADC. Airway pressure shows the heartbeat in 9% of windows only. CO₂ shows a heartbeat-locked trace in 60% of windows, tight to 20 ms, but its lag does not follow the Primus drift, so it cannot time the Primus. Closed as a clock route. |
| Gaps and unbroken segments in every waveform |
2026-10-19 |
draft |
Every gap and every unbroken segment in the 6,388 recordings, per waveform. The curves are not smooth: a cliff at about 18 s in every device marks the recorder's pauses, SNUADC segments stop at 5 hours, Primus segments at about 2.0 hours and BIS segments at about 2.3 hours (each device's correction cycle), and BIS's short gaps grow with the time since the last one (clock resynchronisations, not lost data). |
| The Primus stamp step at each airway-pressure pause |
2026-10-19 |
current |
Measured directly at 2,491 pauses in 1,021 recordings: where CO₂ carries on through the AWP pause (74%), the Primus stamps barely step (median −1 ms, p10–p90 −164 to +187 ms, close to the no-pause controls); where CO₂ stops too (26%), they step by up to seconds. No step undoes the drift built up since the last pause. |
| What each break in the stamps is |
2026-10-19 |
draft |
Every step between waveform records in the release, sorted by mechanism: written twice, a SNUADC clock reset, interleaved streams, a pause shared by every device, whole messages, less than a message, or a fraction of a message beyond whole ones. A continuity test with controls shows which classes lose data: shared pauses and most longer SNUADC gaps do; steps under one message, and SNUADC's lone one-message steps, mostly do not. |
| Records out of order at SNUADC resets, and where the lost time goes |
2026-10-17 |
current |
At every SNUADC reset the five records after it are written out of order: two continue the old timing and three start the new. Put back in order, the waveform runs on with no samples missing; the 18–20 ms lost at each reset goes missing inside the last old-timing record, and an extra zero sample follows. |
| Drug effects as a clock check |
2026-10-13 |
current |
Infusion pumps, the rapid infuser and the cerebral oximeter share no waveform with the reference. Drug effects that follow infusions at plausible delays (propofol to BIS in about 2 minutes, fluid to CVP in about 30 s) bound their clocks to well within a minute of the recorder. |
| What the lab timestamp marks |
2026-10-13 |
current |
VitalDB's lab time is a per-specimen timestamp: not the draw, and not the result. Blood gases are stamped 3–12 minutes after the draw, central-lab panels about 8–24 minutes after it, and the result follows a turnaround the release does not record. |
| Closing loops in the timing graph |
2026-10-13 |
current |
Where two independent routes reach the same clock, the offsets around the loop must sum to zero. Three measured loops close within their noise; the BIS loop closes up to a constant latency; the proposed EMR loop is not a loop at all. |
| The cardiac artefact in the BIS EEG |
2026-10-12 |
current |
The BIS EEG carries a weak electrical trace of every heartbeat. Too weak for beat-by-beat matching, it shows clearly when averaged on the ECG's R peaks, and gives a second SNUADC–BIS timing reference that agrees with the bursts to about 16 ms. |
| Anaesthesia record times are rounded up |
2026-10-12 |
current |
Anaesthesia start and end entered on a 5-minute mark sit 90–290 s later, against device markers, than entries typed to the minute. Rounding up to the next 5 minutes fits every one of 11 markers better than rounding to the nearest or down. |
| Shared bursts between the ECG and the EEG |
2026-10-12 |
current |
Electrocautery and muscle bursts appear in both the SNUADC ECG and the BIS EEG. Cross-correlating their envelopes gives the offset between the two devices' stamps every 10 minutes: about −0.8 s, in a sawtooth that follows both clocks' corrections. |
| SpO₂ and pulse rate latency from step events |
2026-10-12 |
current |
SpO₂ cannot be recomputed from one plethysmogram, so its timing comes from events that change the PLETH abruptly. SpO₂ lags the recorded PLETH by about 4 s and then smooths over roughly 10–20 s. |
| The Primus ventilator against SNUADC, by breaths |
2026-10-12 |
open |
Each breath shows in the Primus airway pressure and, through the chest, in SNUADC's central venous pressure. Tracking that lag puts the Primus on the SNUADC timeline to about 55 ms over the whole release, with a line per stretch between its AWP pauses (49 ms in the pilot). At scale it measures the Primus drifting a median +104 ppm against the recorder PC between its AWP pauses, with steps at the pauses that do not reset it. |
| Arterial line accesses in the pressure waveform |
2026-10-11 |
current |
Flushes, zeroing and blood draws leave clear signatures in the arterial pressure. A detector finds them in the waveform alone (about one access per hour) and matches 77% of lab draws to an access within 15 minutes, against 26% for random times. |
| Clock corrections in every file |
2026-10-11 |
current |
A scan of all 6,388 files for the jumps where the recorder re-synchronises a device's stamps. Each device type has its own correction signature; only SNUADC and BIS correct clearly enough to measure their drift. |
| Arterial pressure as a check on the PPG correction |
2026-10-11 |
current |
Arterial pressure is sampled by the same converter but has no frame and no sawtooth, so every PPG slip leaves ECG→ABP unchanged. Against it, detected slips are 97–100% real and tier A leaves about 2 ms of drift mid-tooth. |
| Where the PPG sawtooth stops |
2026-10-11 |
current |
In some stretches no slip comes although several were due. The PPG delay there is flat, not hidden: the monitor keeps framing, and only the content's drift against the frames has stopped. |
| The PPG's 30 Hz frame clock |
2026-10-10 |
current |
ECG and PPG fiducials resolve to one 2 ms sample, but PPG fiducials taken on raw samples lock to a hidden 33.3 ms frame grid. Scanning for it finds the oximeter's frame clock to about 1 ppm, a fixed fingerprint of each recording setup. |
| 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. |