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GuyScharf: DeVilbiss BLUE (DV6x) support in OSCAR 1.2.1 - current status

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Status of DeVilbiss BLUE (DV6x) importer in OSCAR 1.2.1 Alpha - as of 4/15/2021

The primary criteria for determining status is comparison of OSCAR with DeVilbiss' SmartLink program. Overall, DeVilbiss DV64 support in OSCAR 1.2.1 is greatly improved though has not been completely checked out. Event flags and AHI calculations are now correct with only minor differences. I especially want to thank Heyns for the reverse engineering work he has done on DV64 data files.

From a user viewpoint, the major improvements in this development version are:

  • OSCAR now reports separate sessions rather than entire days. This fixes lots of calculation problems.
  • Event flags are now correct (or close to it).
  • Many minor fixes.

These notes are cursory and intended both as a guide to knowing what data is thought to be reliable and as a programmer checklist of things to be done.

Restrictions

The DeVilbiss BLUE (DV6x) importer is fully supported with these exceptions:

  • Backups are incomplete; only the latest information from the SD card is retained. The data files are organized as rolling buffers. To fully implement backup, we would need to copy selected data from the rolling buffers to backup files. This feature is designed but has not been implemented as we need multiple SD card images from the same machine to test this capability. Work on this is postponed until we have a user who can help with testing.
  • Importing multiple years of data is relatively slow. This will be corrected when we implement the complete backup mechanism.
  • Daily summary file is not processed. When we handle it, we will be able to show summary data from the first use of the machine. All other files are rolling buffers with limited memory (the daily summary file is limited too, but can hold 20 years of data).

Machine Identification (Daily page, upper left corner)

All data is believed to be correct for the currently supported models. Model names are provided for DV64E, DV64D, and DV63E machines. "DV6xx - Unknown product" is shown for a product code that is not recognized and that needs to be validated.

Events

  • Date, Start, and End times usually match. Every once in a while there is a major discrepancy. Cause has not yet been investigated but is probably related to session identification.
  • AHI - OSCAR and SmartLink agree.
  • Periodic Breathing - not fully checked.
  • Large Leak - DeVilbiss reports leaks as large only when rate exceeds 95 lpm, so they will be exceptionally rare. I have not seen one to determine whether the graphs are marked properly or theĀ % time is calculated properly. SmartLink has a field named "% Poor Mask Fit" which I suspect is what OSCAR calls "large leak percentage." When we get large leak data, we will confirm that.
  • Non-Responding Event - have not seen one to check.
  • Clear Airway - OSCAR and SmartLink agree.
  • Obstructive - OSCAR and SmartLink differ slightly but not significantly. For example, with 4 OA events in 6 hours, OSCAR reports OAI as 0.66 while SmartLink reports it as 0.80. But 4 events in 6 hours should be a rate of 0.66. AHI is calculated as CAI + OAI + HI. In OSCAR, the numbers total to AHI correctly. In SmartLink, they total to slightly higher than reported AHI. Cause of difference is unknown but has been minor in the examples seen.
  • Hypopnea - OSCAR and SmartLink agree.
  • Expiratory Puff - Not explored fully.
  • Flow Limitation - DeVilbiss reports flow limitations as four severity levels: none, mild, moderate, and severe. Severe flow limitations are flagged in the events graph. Flow limitations are also shown in a flow limitations graph with values of 0, 1, 2, or 3 corresponding to the DeVilbiss severity levels. The flow limitations graph is available only with high-resolution data so is not shown if high resolution data is not available.
  • RERA - RDI should equal AHI + RERA. In SmartLink we have to computer RERA = RDI - AHI. OSCAR has been observed to report a somewhat higher RERA value (example 2.0 instead of 1.5). Reason for this is unknown.
  • Leak Flag - not used and has been removed.

Statistics

  • Pressure - 95% and Max values match. Median value in OSCAR is slightly less than Average value in SmartLink.
  • Minute Vent - Minute vent is a product of tidal volume and breath rate. SmartLink does not compute this.
  • Resp Rate - OSCAR and SmartLink agree.
  • Leak Rate - OSCAR numbers, given median vs average, are similar to SmartLink in days examined.
  • Total Leaks - Uncertain what exactly leak rate vs total leaks is in data recorded by DV6x series.
  • Snore - Not yet examined.
  • Insp. Time and Exp. Time - calculated by OSCAR
  • Tidal Volume - Tidal volume is recorded in the DV6x series data.
  • Time over leak redline -- This is the time over the leak "redline" as defined in File/Preferences/CPAP. Since the DV6x machines apparently leak at a higher rate, and report total rather than just unintended leak, you should adjust the leak redline in the Preferences dialog to a value that has meaning to you.

Machine Settings

Data reported here matches SmartLink and known machine settings. We need to add additional machine settings data.

Pressure settings are not shown for some days. This appears to happen on days when the first session is just a few seconds long and probably contains minimal data. To be investigated.

Session Information

SmartLink doesn't report sessions as such, but they can be assessed by visual examination of the graphs. Generally there is good agreement between OSCAR and SmartLink plots, with a few wild exceptions. These have yet to be explored.

Event Flags Graph

By visual examination, this graph matches SmartLink's graphs. SmartLink's graphs are in much lower resolution, so we cannot compare detail.

Events do not seem to line up well with the flow graph. The misalignment varies from event to event and is not predictable. OSCAR makes a slight adjustment to the event's start time that, overall, seems to get the events closer to where they belong in the flow graph. (The adjustment made is to move the event flag left by one-half of the event's duration.)

The duration of the events often does not look right when comparing with the flow graph. However, OSCAR is reporting the duration recorded by the DV6x CPAP machine. Further work on these two issues is postponed until more information is available.

Graphs

By visual inspection, OSCAR graphs match SmartLink graphs, with the proviso that SmartLink graphs are much lower resolution so are hard to compare.

SmartLink reports session end time when the per-minute data stops, while OSCAR reports session end time as when the high-resolution data stops. This can result in OSCAR reporting a session lasting a minute or so longer than SmartLink. A different session length can result in slightly different calculated index values.

We don't fully understand the leak rate graph and what numbers the machine is reporting. However, OSCAR's summary numbers seem to agree with SmartLink, so this may be a question of understanding rather than a problem to be fixed.

Snore graph is built from event flags and resolution is not known. The graph has values of 0, 1, 2, or 3 with 3 indicating the greatest severity.

DeVilbiss DV6x machines retain only 100 hours (~10 days) of high-resolution data. If importing data more than 100 hours old, the flow graph is not shown as we have no older flow data. The pressure graph is high-resolution when that data is available, otherwise it is at lower resolution (1 Hz instead of 25 Hz). Low-resolution pressure graph is currently not shown on the day when high-resolution data begins, leaving a gap in the pressure graph at the beginning of that day.

Resources

With thanks to ArchAngle, the DeVilbiss Intellipap AutoAdjust Clinical Overview contains lots of good general tech info on CPAP. http://www.devilbisshealthcare.com/files/IntelliPAP%20AutoAdjust%20Clinical%20Overview_LT-2089.pdf




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