Rare devices against SNUADC¶
CardioQ, EV1000, Vigileo and Vigilance each get a link to the SNUADC timeline: beat matching for the CardioQ, mean arterial pressure alignment for the EV1000 and Vigileo, and a long-window fit for Vigilance's averaged heart rate.
| Date | 2026-10-13 |
| Status | current |
| Methods | One event, two clocks, Delays and averaging windows |
| Techniques | Beat matching |
| Clocks | CardioQ clock, SNUADC sample clock, Recorder PC clock |
| Devices | CardioQ, EV1000, Vigileo, Vigilance, SNUADC |
| Variables | CardioQ pressure and flow, EV1000 mean arterial pressure, Vigileo SV, CO and SVV, Vigilance continuous cardiac output, Arterial pressure (SNUADC), ECG lead II (SNUADC) |
Background¶
A few hundred cases carry haemodynamic monitors besides the main ones. Their stamps re-anchor irregularly or describe long averages, so each needs its own route to the reference.
Data¶
997 cases with at least one of the rarer haemodynamic monitors, each with SNUADC arterial pressure or ECG as the reference:
- CardioQ: 27 cases tried, 24 fitted.
- EV1000 mean arterial pressure: 588 tried, 579 fitted (stroke volume variation as a second signal: 67 of 589).
- Vigileo stroke volume variation: 343 tried, 25 aligned.
- Vigilance averaged heart rate: 63 cases; 52 fitted (11 lacked HR_AVG or ECG).
Method¶
- CardioQ: beats in its arterial pressure matched to SNUADC arterial pressure within each re-anchored stretch.
- EV1000, Vigileo: their mean pressure or stroke volume variation aligned with the same quantity computed from SNUADC arterial pressure, one offset per 30-minute window.
- Vigilance: its averaged heart rate fitted with long windows (mean and median over 32–4,096 beats or 30–3,600 s, exponential averages) against ECG R–R intervals, with the delay held at zero or above.
Results¶
- CardioQ: matched-beat MAD 0.24 s, R–R correlation 0.96 (24 cases); its stamps lag SNUADC by 0.4–4.4 s (p5–p95) and re-anchor about 40 times per case.
- EV1000: values sit a median 1.6 s (p25 0.9, p95 3.2 s; 579 cases) after the end of an assumed 20 s window; after alignment the residual SD is 0.25–2.4 s.
- Vigileo: aligned in only 25 of 343 cases (|offset| 4.7 s median, p95 26 s).
- Vigilance: a running median over 600–2,185 s (median 1,050 s, about 17 minutes), available 0–175 s after its window ends (median 51 s); 16 of 52 cases sit at zero delay.
| Parameter | Value | Status | From |
|---|---|---|---|
| CardioQ stamps behind SNUADC | 0.4–4.4 s (p5–p95); matched-beat MAD 0.24 s (24 cases) | measured | Rare devices against SNUADC |
Discussion¶
The three-way arterial pressure loop confirms the CardioQ and EV1000 links against each other (Closing loops in the timing graph). Vigilance values describe the last 10–36 minutes; alignment finer than minutes is not meaningful.
Limitations¶
Small samples; Vigileo alignment is weak and Vigilance's fit is a pilot.
Open questions¶
- Vigileo rarely aligns (unexplained phenomenon). Vigileo aligns in only 25 of 343 cases; whether its values are too smooth or its clock too unstable is not known.
- Vigilance: 13 cases or 52 (conflict between studies). 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.