Open questions¶

What the studies left open, gathered from every study and grouped by kind: results nobody can yet explain, explanations the evidence only weakly supports, assumptions the data cannot test, and places where two studies disagree. The last group lists checks still to run and decisions still to make. Settling any of them is a good way to contribute.

Unexplained phenomena¶

34 files whose records overlap throughout · Records out of order at SNUADC resets, and where the lost time goes
Mostly explained since: records written twice and two interleaved streams (Eight recordings store whole messages twice, In some recordings two unrelated streams are interleaved in one track); whether these account for all 34 is not checked (In 34 files the SNUADC records overlap throughout).
A residual of −13 ppm · SNUADC against the PC-stamped heart rate
On the corrected SNUADC line the ECG-to-HR delay still ramps by −13.0 ± 4.0 ppm. It may be the Solar8000's own processing, an error in the stamp model's rate, or the PC; a larger run (all step-mode cases without gaps) would narrow it. The whole-release run (The SNUADC clock through the Solar8000 numerics, whole release) cannot settle it: per recording it is too noisy, and in recordings under about 4 h its rate is biased toward zero.
About 50 s more than rounding · Anaesthesia record times are rounded up
The anaesthesia record times sit later than rounding alone explains. Documentation lag and an offset between the EMR clock and the recorder cannot be separated with these data.
Anaesthesia start ignores the 5-minute rule · How the anesthesia start time was charted
Why does anaesthesia start not follow the 5-minute rule the paper describes? Were there two entry methods, or a change of system partway through?
Is 150 mg a ceiling? · Rounding and heaping of propofol bolus
Is 150 mg a ceiling people write for any large dose, or are larger doses usually given as a second bolus and summed? The upper tail is right only in the first case. Adding 200 mg to the set did not pass BIC.
Long regular runs that may be paced · Paced ECG as an independent clock
About 40 cases have long regular runs (370–920 ms) whose interval wanders by about 1 ms between stretches. Whether they are paced is not settled.
Misfits at 90 mg and 130 mg · Rounding and heaping of propofol bolus
The misfits at 90 mg and 130 mg are unexplained.
Recordings that change correction mode partway · The stamp sawtooth model for SNUADC and BIS
Recordings that change correction mode partway still fail the model (p99 about 250 ms). Why a recording changes mode, and how to fit both parts, is open.
Recordings that never correct their clocks · Clock corrections in every file
Some recordings never correct their clocks within the 2 s test. Slower units, a third recorder mode, or both, could explain it. The shared bursts point to slower units (about −36 ppm where the BIS rate is known; Long SNUADC recordings with no correction at all); their drift units have not been compared with the rest. Followed up on The stamp sawtooth model for SNUADC and BIS.
The filler sample · Records out of order at SNUADC resets, and where the lost time goes
Why most resets hold one extra zero sample, a little after the gap, is not known.
The ventilation loop only partly closes · Closing loops in the timing graph
The ventilation loop only partly closes: its two physiological arms differ by 37–46 ppm.
Thoracic records are much finer than gynaecology's · Rounding and heaping of intraoperative urine output
Thoracic surgery charts urine output mostly to 10 or 5 mL, gynaecology and urology mostly to 50 or 100 mL, even at the same volumes. The model now lets the rounding propensities depend on department (it improves BIC by 87), but why they differ is not known: a urometer with fine graduations in some theatres and a drainage bag in others would explain it. The urology split rests on 41 records.
Twelve unmatched resets · Records out of order at SNUADC resets, and where the lost time goes
Twelve unmatched resets have small interleaved steps of 8–12 ms. Whether they are resets of a different size or something else is not known.
Vigileo rarely aligns · Rare devices against SNUADC
Vigileo aligns in only 25 of 343 cases; whether its values are too smooth or its clock too unstable is not known.
What event anaesthesia start marks · How the anesthesia start time was charted
Partly answered: device-marked induction (BIS loss of consciousness, else the propofol pump start) comes a median 14 minutes after the charted start (10th–90th percentile 6 to 25 minutes) in 2,913 cases (Post-induction hypotension, from the charted start and from the devices), so the charted time marks the start of anaesthesia care, not induction. Which event of care it records (arrival, monitoring, pre-oxygenation) is open.
What replaces the sawtooth · Where the PPG sawtooth stops
At the start and end of some recordings the PPG lag is not flat but ramps by several ms per minute against arterial pressure. Its cause is not known.
What sets the steps at the AWP pauses · The Primus ventilator against SNUADC, by breaths
Partly answered by The Primus stamp step at each airway-pressure pause (2,491 pauses): where CO₂ carries on through the AWP pause the stamps barely step (median −1 ms, p10–p90 −164 to +187 ms); the large steps, up to seconds, come where CO₂ stops too (26% of pauses). None undoes the drift built up. Open: what the stamps re-anchor to when both waveforms stop.
What the kidney-surgery colloid values record · Colloid container rules
What do the kidney-surgery values record: a different product, a fixed small dose, or albumin in grams? Until confirmed, values of 50 mL or less are flagged unit_uncertain at native resolution. The VitalDB team or local protocols would settle it.
What the Primus's small corrections correct · How often each device is corrected
The corrections imply 1–11 ppm, but breath matching measures the Primus drifting about +104 ppm against the recorder PC (Primus drift against the recorder PC, from breath matching), and the stamps also step at the AWP pauses by amounts unrelated to the drift built up. What the small steps correct, if not the drift, is open. (This replaces the earlier conflict between 1–11 ppm and the assumed 115 ppm, which breath matching settled.)
Where the sawtooth stops · Pulse arrival time in two correction steps
In some stretches no slip comes although several were due, and the delay is flat (Where the PPG sawtooth stops). The model treats the stretch before and after a pause as creep then hold, of unknown length, which leaves up to one frame of uncertainty there.
Which firmware ran · The SNUADC firmware
The deployed version, and which converter channel feeds which track, are not known.
Which unit is which device · Physical units, shared drift and time order
Units are inferred from drift alone, and busy ports carried several units. The physical boards behind each unit are not identified.
Why 12% of files run at a different slope · SNUADC stamp arithmetic
747 files sit between −0.90 and −0.55 ppm instead of −0.954, with no trend through the release. A different recorder build or a different stamp increment are the obvious candidates; comparing these files' header version, device list and correction mode with the rest would test it.
Why imputed op ends cluster in thoracic and non-general cases · Imputed times, conformance failures and exclusion rules
Imputed op ends are twice as common in thoracic surgery as in general surgery, and four to six times as common under sedation or spinal anaesthesia as under general anaesthesia. Cases without a charted op end are not spread at random; why these groups lack one (a different charting workflow, a different person recording, the operation's end not being marked) is not known, and the VitalDB team could say.
Why some PaO₂ records are whole numbers · Pre-operative PaO₂ decimal rule
Which of the two candidate explanations (two analysers or a manual transcription step) is behind the whole- number records is not known.
Why the artefact shows in only some cases · The cardiac artefact in the BIS EEG
A clear averaged artefact appears in 13 of 30 cases. What decides whether it is visible (electrode placement, signal quality, filtering) is not known.
Why the constant offset differs between modes · The stamp sawtooth model for SNUADC and BIS
The EEG lags the ECG by −0.80 s in step mode and −0.66 s in frequent mode after the model (whole release; −0.69 s in the pilot); why the constant differs between modes is not known.

Weakly supported hypotheses¶

A fixed-point stamp behind −0.954 ppm · SNUADC stamp arithmetic
A 0.2 s increment held at a resolution of 2⁻²⁰ s fits, but is unproven; the recorder's source or one controlled recording would settle it.
Analyte p as phosphorus · Heaping screen of all variables
The analyte coded p (16,440 results) is missing from lab_parameters.csv. Its median of 3.2 (IQR 2.7–3.8, p5–p95 1.9–5.0) fits phosphorus in mg/dL, the only common analyte with that range, but only the VitalDB team can confirm it.
The BIS constant as processing latency · Closing loops in the timing graph
The loop closes in drift and steps but leaves −0.80 s (step mode) or −0.69 s (frequent mode; −0.66 s over the whole release). A processing latency in the BIS is the working explanation; it fits the sign and size but has no direct evidence, and it does not explain why the constant differs between modes.
The recording PC sets the fast path · Two heart-rate delay groups, one poll apart
Some recordings get the Solar8000 heart rate one 2 s poll earlier, and on a given recording sometimes do not. The PC key predicts the group for 94% of cases, so the working explanation is the PC's polling path; what makes an early-majority PC deliver late in some recordings is not in the release.
Two firmware versions behind the reset order · Records out of order at SNUADC resets, and where the lost time goes
1,785 files write their reset clusters out of order and 820 in order, and no file does both. Two recorder or firmware versions would explain the clean split, but nothing in the release shows which file ran which; file headers and recording dates (hidden in the release) would tell.
Two out-of-range end times as 12-hour or date errors · How the anesthesia end time was charted
Two anaesthesia-end records lie at 720 and 1,441 minutes, outside the modelled range. A 12-hour clock slip and a one-day date error are the obvious explanations; neither is confirmed.
What the stamps re-anchor to when both waveforms stop · The Primus stamp step at each airway-pressure pause
Steps of up to seconds come where AWP and CO₂ stop together. A re-opened connection re-anchoring the stamps to the PC's arrival time is the working explanation; the recorder's message log around those gaps would test it.
Why 10 bits from a 12-bit converter? · Value resolution of every signal
Either the SNUADC used in the release was a 10-bit design, or a 12-bit converter's readings are reduced to 10 bits before they are sent (which the observed truncation would fit). The SNUADC firmware or the VitalDB team could settle it.
Why does the SNUADC appear to speed up when the BIS slows down? · When each device's clock is corrected, in every recording
Within a recording, the SNUADC and BIS drift deviations against the recorder PC are anticorrelated (r = −0.54, 133 recordings; shuffled null −0.01), the opposite of what a shared PC excursion would give. Candidates: a common factor acting on the two oscillators with opposite signs (temperature, on crystals of different cuts), or a coupling in how the two drifts are measured. Test against each recording's time course (temperature itself is not recorded; operating-room events and recording length are proxies) and in the joint clock model.

Untestable assumptions¶

Age as completed years · Blood products, age and ICU days
Age is taken as completed years (floor). The release documents only "years"; whole-number adults, infants in tenths of a year and the cap at 89 point to an exact age cut down, but the data cannot test it. Rounded age would shift every value by half a year.
Blood products in millilitres · Intraoperative fluid balance as a distribution
The release gives red cells and plasma in units. A unit's volume (typically 250–350 mL for red cells) is not recorded, so the balance leaves these cases out; an assumed range would bring them in with a wider distribution.
Every instrument within its calibration · Instrument accuracy and calibration
The atlas treats each instrument as accurate: no bias, no drift between calibrations, imprecision ignored. The release cannot test this. Calibration and quality-control records for every measuring device used in the VitalDB cases (laboratory analysers, monitors, infusion pumps, ventilators, scales and stadiometers) would replace the assumption with a measured accuracy for each variable. This is beyond the scope of this work, but the hospital will hold the records, and publishing them in a metrology atlas like this one would make every variable's uncertainty complete.
How ICU days are counted · Blood products, age and ICU days
The release does not say. The counts argue against calendar days touched (815 one-day stays against 98 two-day stays, where that rule would make 2 the commonest value), so the atlas reads them as nights in the ICU or completed days, which the data cannot tell apart. The VitalDB team could settle it.
Is 90 ms from radial artery to finger plausible? · One device delay for the PLETH across the release
With the global 385 ms, finger PAT exceeds radial-artery PAT by about 90 ms foot to foot. Published values for the radial-to-fingertip pulse transit (and for the volume pulse lagging the pressure pulse) would check the adopted 270 ms independently; a larger or smaller gap there would move the global delay by the same amount.
Is a recording without a BIS on the same PC as its key's other recordings? · Identifying the recording setup of every case
The assignment assumes that a recording made without a BIS used the same PC as the complete recordings that share its other ports. Validation hides the BIS of recordings that had one, so it cannot test this; a BIS-free recording on a PC kept only for such cases would be assigned to the wrong setup. Clock fingerprints would test it.
Is SaO₂ measured or calculated? · End-tidal to arterial CO₂, and pulse oximetry against blood gas, at the right moment
Many blood-gas analysers calculate SaO₂ from PO₂ and pH rather than measuring it by co-oximetry. Which was used decides whether SaO₂ − SpO₂ compares two measurements or a measurement with a model.
No time axis for era effects · How the anesthesia start time was charted
Resolution cannot be checked by era: case IDs are random (the release says so, and they are uncorrelated with anything dated), and dates are removed. The models assume rounding habits were constant over the years the data cover. Department makes no difference; emergency cases are rounded a little more often.
One PC key, one PC · Identifying the recording setup of every case
The register treats each PC key as one recorder PC. Two PCs cabled identically would share a key; the release cannot show it directly, though Two heart-rate delay groups, one poll apart found keys that separate their cases almost perfectly (purity 0.90–0.97), and clock fingerprints could find exceptions.
PC clock steps, not slews · Recorder PC clock steps and recording pauses
The analysis assumes the recorder PC's clock corrects in steps. Slow slewing would look like device drift and cannot be told apart from it with these data.
The adopted 0.27 s · Pulse arrival time in two correction steps
The global delay is the release's median stored delay to the pulse foot (655 ms) minus 0.27 s, a mean R-to-foot finger PAT for anaesthetised adults from studies that sampled ECG and PPG on one clock (The PPG hardware delay and the adopted pulse arrival time). Differences between patients and changes within a case are measured; the absolute level of every case moves with the adopted value. It implies a finger-minus-radial difference of about 90 ms foot to foot, which a literature value could check.
The PC-to-UTC link · Recovering the time of day
Every route from a device clock to UTC passes through the recorder PC's clock, which is assumed to have been kept on UTC by network time. The release holds no second, independent clock against which to test it, so this link is assumed, not measured.
The recorder PC's time zone · Recovering the time of day
Whether its Unix time was true UTC, or local time read as UTC, cannot be tested in the release.
Turnaround after the timestamp · What the lab timestamp marks
The release has no result times, so the turnaround from the lab timestamp to the result is assumed, not measured.
What plausible PAT range should be shown for anaesthetised adults? · Pulse arrival time in two correction steps
The figure shades 200–285 ms to the foot (shifted by 59 ms to the upstroke), the range of means in shared-clock studies of awake adults (The PPG hardware delay and the adopted pulse arrival time). That is a range of study averages, not of individual windows, and anaesthesia lengthens PAT by about 40 ms. A verified range for adults under anaesthesia, ideally of individual values, is still needed; Ruffolo et al. 2025 gives one for critically ill children.

Conflicts between studies¶

Does the setup still fix the drift on the whole release? · Identifying the recording setup of every case
The register's drifts come from the correction scan's cases (472 SNUADC step-mode and 1,627 BIS recordings, one duration-weighted rate per recording, including the −0.95 ppm stamp arithmetic). There the PC key puts 97% of SNUADC and 83% of BIS drifts within 3 ppm of their setup's median. Rerun on the whole release's correction intervals (When each device's clock is corrected, in every recording: 642 SNUADC and 1,939 BIS recordings), the same test gives 71% and 60% (against 25% and 17% for the release median). The setup still narrows the drift a great deal, but less than the register says; the difference may be the drift's variation within a recording (a median 3.5 ppm for the BIS), which a single interval does not average out. Which rate per recording the register should use is not decided.
How far does the SNUADC drift in frequent-correction mode? · SNUADC stamp arithmetic
Between corrections the frequent-mode stamps show only the −0.95 ppm of stamp arithmetic, which is why the real drift in that mode is put under about 1 ppm. But the small forward corrections that keep those stamps on the PC add up to more: about one an hour of +5 to +15 ms (SNUADC frequent-correction steps), and the correction scan's per-recording drift for the 82 frequent-mode recordings it could fit has a median of +2.7 ppm (10th percentile −0.9; Clock corrections in every file). The drift against the PC is what the corrections remove, so it may be a few ppm rather than under one. Not reconciled.
Rounded up or to the nearest: two studies disagree · Anaesthesia record times are rounded up
For anaesthesia start, the device markers here favour rounding up, but only by a small margin, while the value model, which compares the charted time with the recording start, prefers the nearest mark by 47 BIC points (How the anesthesia start time was charted). For anaesthesia end the two agree (rounded up). Operation start and end were not measured here; their value models give the nearest mark and rounding down (How the operation end time was charted, Bias in charted intervals), while the EMR timing entry (Anaesthesia record events) treats every 5-minute entry as rounded up. Not reconciled.
Vigilance: 13 cases or 52 · Rare devices against SNUADC
Vigilance fits differ between the two analyses (13 cases in the rare-device scan, 52 in the window study); the difference has not been reconciled.

Unfinished checks and decisions¶

A finer estimator for short recordings · The SNUADC clock through the Solar8000 numerics, whole release
Fitting the delay's slope directly in the likelihood (a delay that ramps within the recording), on a finer grid and without the first block, would remove the bias toward zero and let this route test recordings with no SNUADC reset.
A firmer central-lab lag · What the lab timestamp marks
Most central-lab samples are not drawn from the arterial line, so their access matches are mostly chance and their lag is only an estimate.
A guard on the reorder rule for overlapping files · Records out of order at SNUADC resets, and where the lost time goes
The reorder rule matches 115,487 coincidental clusters in the 34 overlapping files. None of them are in the current builds or fits, but before any full import the rule must detect these files and leave them alone, with a test on one of them.
Assigning the last 112 recordings to a setup · Identifying the recording setup of every case
Done for most: 521 of the 633 recordings without a full key are assigned with a posterior of at least 0.9 (99% right in validation, with the frame clock added). The remaining 112 have no matching key (51) or no fingerprint that separates their candidates; most lack a usable PLETH stretch for the frame clock. They take the release's values until another fingerprint is found.
Census figures without the anomalous files · Records out of order at SNUADC resets, and where the lost time goes
The census summary now leaves out the 34 anomalous files and counts them separately. The figures made before that change still include them, so they need re-exporting from the new summary, and the summary change needs committing in vitaldb-bench.
Do the ways of recognising a setup agree? · Identifying the recording setup of every case
Tabulate, per PC key, the drift units, the oximeter's frame clock, the PPG sawtooth rate and delay, the correction mode and the heart-rate delay group, to see whether they name the same setups and where a key hides two.
Does the value side depend on the setup? · Identifying the recording setup of every case
Only department has been tested for value-side habits (urine output is charted much more finely in thoracic surgery). The PC key is a finer grouping: rounding habits, analysers and devices may follow the theatre.
Epochs in time · One device delay for the PLETH across the release
Ruffolo et al. saw two offsets over two epochs. VitalDB has no recording dates; any other ordering of the cases in time (software versions in the file headers, say) would allow a sharper test than the case number.
Fit the missing time · What each break in the stamps is
For gaps that lose data, fit how many samples are missing (Does the waveform run on?) rather than testing only whether any are.
Frequent-correction mode on more cases · SNUADC against the PC-stamped heart rate
Frequent-correction mode is inconclusive on 7 cases (52 ± 40 ppm).
How much of the drift spread is the recorder PC's? · When each device's clock is corrected, in every recording
A joint model of the PC and every device clock (each drifting and corrected), fitted to all correction events at once, would separate the PC's corrections from the devices'; events seen by several devices at once (diathermy bursts, Shared bursts between the ECG and the EEG) would validate it.
Integer codes behind float signals · Value resolution of every signal
Signals sent as floats (BIS EEG, CardioQ, the numerics) may all start as integers from a converter of n bits, scaled once. Recover the integer and the scale for each (BIS EEG already fits 16 bits of 0.05 µV; CardioQ FLOW looks companded).
Lost data or a moved clock? · Message sizes and the steps between records
For SNUADC and BIS gaps that are not whole messages, test whether the waveform continues across the gap (no loss) or needs missing samples to fit (Does the waveform run on?). Partly answered by What each break in the stamps is: steps under one message run on (clock corrections), while about 70% of SNUADC fractional gaps and roughly a third of BIS fractional gaps lose data. What is left is fitting how much.
Monitor clock lines in six files only · Monitor clocks in the waveforms' spectral lines
The monitor clock lines were seen in six files; running these files through physiosync, and then a larger set, would settle whether they are general.
Most teeth cannot be corrected with confidence · Pulse arrival time in two correction steps
In 75 of 121 cases no tooth reached tier B, so the sawtooth stays in them. The likeliest causes, in order: the example gives the fit no creep-rate prior, although the rate is fixed per setup (The ECG→PPG delay is a sawtooth, the Recording setups page), so a tooth reaches tier A only if the recording has two full teeth that agree; 60-minute windows hold few full teeth (on up to 3 hours, cases with a confident tooth rose from 47% to 57% and confident teeth from 21% to 33%); tier C teeth (the most common) are fitted but not applied; and a simple PLETH fiducial produces false slips (some cases show 24–46 an hour against about 4). Setup priors and longer windows come first; the tier rules were tuned on injected sawtooths, not on recordings.
Pairing by the modal delay in the example itself · Pulse arrival time in two correction steps
Eight of 121 cases were paired one beat out (fast heart rates or doubled R peaks) and are left out of the cohort figures. The census pairs pulses by each segment's modal delay instead (One device delay for the PLETH across the release); using that pairing here would bring them back.
Per-setup drift in the uncertainty models · Physical units, shared drift and time order
Drift is known per setup far better than over the release (Device clock drift depends on the setup). The drift parameters now list per-setup values (by PC key), but the clock domains and the planner still use one value for all recordings. They should take a recording's setup when its ports are known, with the release range only as the fallback. The per-setup values come from the correction scan's cases; the whole-release correction steps (When each device's clock is corrected, in every recording) would give them for three to five times as many.
Recordings that failed the quality rule · One device delay for the PLETH across the release
Fast heart rates and noisy ECG make the modal delay ambiguous. A beat-to-beat pairing that uses the ECG's RR interval explicitly would bring most of the 600 back into the census.
Recordings without a SNUADC correction · The stamp sawtooth model for SNUADC and BIS
Giving the 1,096 recordings without a SNUADC correction their port's step-mode rate removed most of their drift (median −176 to −11 ms/h), but each still drifts at its own rate (p10–p90 −135 to +122 ms/h left). A per-recording rate cannot come from the stamps: with no correction they carry no information about the recorder PC (the census gives −1.0 ppm, the stamp arithmetic, for all of them). It needs a clock tied to the PC that shares events with the SNUADC (bursts against a BIS with whole teeth, in 122 recordings; calibration, so tested on held-out windows), or the setup's unit. Where the BIS has teeth the bursts imply the SNUADC drifts about −36 ppm rather than −63, the fast-BIS, slow-SNUADC pattern of When each device's clock is corrected, in every recording's open question.
Rounding or truncation in each numeric · Value resolution of every signal
Against the Primus's own waveforms (with the corrected gains), all 6,342 recordings favour rounding for ETCO₂ (where round and floor differ, 77% of numerics match round, 18% floor), PIP (61% / 32%) and mean airway pressure (62% / 28%). The match is not complete because the window does not reproduce the device's own computation, so the result is "likely". The Solar8000 ART numerics cannot be tested this way: the SNUADC copy of the arterial pressure differs from them by more than one step.
SaO₂ above 100 in the library · End-tidal to arterial CO₂, and pulse oximetry against blood gas, at the right moment
vitaldb-resolution treats a recorded SaO₂ of 100 like any other whole number, with the true value up to 100.475. A cap at 100 (a top-coded value, like the other reporting limits) would fix this at the source.
Separating the airway-to-CVP delay · The Primus ventilator against SNUADC, by breaths
The physiological delay from airway pressure to CVP is inside the measured offset and has not been separated.
Splitting a PC key into the units it carried · Identifying the recording setup of every case
A key is a PC's cabling, not its devices: the busiest key holds 755 recordings, its SNUADC's and BIS's drifts show more than one unit, and two keys hold two distinct oximeter frame clocks. Drift units and frame clocks could split a key into periods with one set of devices, which is what the per-setup delays and rates really belong to.
The maximum-likelihood smoother follows Ruffolo et al. in approach, not in detail · Pulse arrival time in two correction steps
The window length (30 s), the outlier floor (2%) and the error model's terms are this example's choices; the estimator has not been checked against the original implementation, or against injected PAT changes of known size.
The remaining backward steps · What each break in the stamps is
About 500 recordings per SNUADC channel and 3,850 for Primus AWP have backward steps none of the classes explains, mostly of a few samples.
Was op end imputed deliberately? · How the operation end time was charted
Was op end imputed from recording end deliberately? This is to be asked of the VitalDB team.
Was op end imputed deliberately? · Imputed times, conformance failures and exclusion rules
Was op end imputed from recording end deliberately? This is to be asked of the VitalDB team.
Where the imputed op ends are · How the operation end time was charted
Mapped on 18 October: thoracic surgery and cases under sedation or spinal anaesthesia have far more imputed op ends than the rest (Op end was filled in from the recording end in 537 cases). The model already excludes them; analyses that use op end should check whether their subgroup is one of these.
Which gaps lose data? · Gaps and unbroken segments in every waveform
Answered per class in What each break in the stamps is: shared pauses and most SNUADC gaps beyond one message lose data; sub-message steps and BIS resynchronisations do not.