Call for Update: S9 Data Skew Issue

Nord wrote: I'm guessing you still have it Oscar...

Nord

You described it perfectly. I have never reformatted my card so it slowly gets worse and worse. My firmware is SX474-0601, if it determined to be a firmware issue is there a way to update it or are we just stuck.

-SWS wrote:

Nord wrote: The skew "issue" begins at about 4 or 5 mask sessions after formatting and gets progressively worse.

Nord, by "mask sessions" do you refer to mask-fit sessions? If so, that might explain why I see no skew. I only ran the mask-fit session once during initial machine setup. I don't bother with that part of the routine.

perhaps this new firmware has a solution. Let me know if you see the same skew with 10 second viewing...

No skew in 10-second view... But I only have 13 nights worth of data---and so far I don't run mask-fit sessions. Thanks for the input, Nord.

Can others pin the data skew down to mask-fit sessions? If so, can you experimentally avoid the skew by refraining from mask-fit sessions?

Your 13 nights of Detailed Data should be enough to see the skew issue... that's at least 13 mask sessions and if that's the number then my guess would be a skew of approx 10 seconds...

That is the Flow Data would start at 22:00:00 and the Flow Limitation or Pressure data would start at 22:00:15...

Nord

I have notice the skew issue in my 29th days of usage. It last 2-3 days and back to normal. I have used the S9 for 3 months, never format my SD card.

Okay... per the above firmware discussion, are there any S9 users with firmware version SX474-0602 who have also discovered the data skew?

oscar98 wrote:

Nord wrote: I'm guessing you still have it Oscar...

Nord

You described it perfectly. I have never reformatted my card so it slowly gets worse and worse. My firmware is SX474-0601, if it determined to be a firmware issue is there a way to update it or are we just stuck.

Hi Oscar...

If the newest Firmware does correct the skew...
then it could probably be updated by DLing from the Internet File by ResMed and copying to the S9.

Firmware on my Garmin GPS is updated regularly by SD card... it call shipping the product before it works perfectly.

Nord

Nord wrote: Your 13 nights of Detailed Data should be enough to see the skew issue... that's at least 13 mask sessions and if that's the number then my guess would be a skew of approx 10 seconds...

That is the Flow Data would start at 22:00:00 and the Flow Limitation or Pressure data would start at 22:00:15...

Nord

Okay, thanks for that explanation, Nord. My flow-limitation and pressure data graph lines begin 13 seconds after my detailed flow graph begins. And yet my OA, CA, and H markers DO NOT reflect that same lag or data skew in the magnified window panes below. Perhaps the SX474-0602 firmware update fixed that latter part of the problem.

-SWS wrote:

Nord wrote: Your 13 nights of Detailed Data should be enough to see the skew issue... that's at least 13 mask sessions and if that's the number then my guess would be a skew of approx 10 seconds...

That is the Flow Data would start at 22:00:00 and the Flow Limitation or Pressure data would start at 22:00:15...

Nord

Okay, thanks for that explanation, Nord. My flow-limitation and pressure data graph lines begin 13 seconds after my detailed flow graph begins. And yet my OA, CA, and H markers DO NOT reflect that same lag or data skew in the magnified window panes below. Perhaps the SX474-0602 firmware update fixed that latter part of the problem.

Unfortunately I don't think the Firmware really dealt with that issue then...
If the skew is still happening in the beginning... then it happens for "events" as well... it just takes longer to show up.

The Data Flow skew is easier to see when it starts. Thats why I point to it for an indicator. You can now watch your events and you will notice that they do not line up. At first only a second or two... then all of a sudden you will have an event 1 minute after the S9 was shut down...

Sorry to be the bearer of bad news.
We are not alone, I fully believe that every S9 skews data... but it is not noticed by some, not cared about by others.
When some of us noticed this earlier and started talking about it here, it may have been too early for everybody to accept... certainly ResMed rejects the idea too.
And S9's are selling well due to all the positive press. And there is good reason.
As I've always said... I love my S9... I just wish it worked right.

Nord

Nord wrote: If the skew is still happening in the beginning... then it happens for "events" as well... it just takes longer to show up.

Well, so far the event markers don't show right-shifting on mine. Rather, at session 13 they sit properly oriented as they did on session 1---right at the end of the corresponding events.

I'll keep an eye on both the start-of-graph lines (currently skewed) as well as the event markers (currently unskewed). If/when the event markers skew, then I'll report that new skew back to this thread.

Still looking for data skew observations from S9 users with that newer SX474-0602 firmware version...

Is this a problem with the Elite and AutoSet machines?

Thanks,

Evb

Nord wrote:The skew "issue" begins at about 4 or 5 mask sessions after formatting and gets progressively worse.

If you set the Detailed session in ResScan to compare looking the starting point for Flow and then Pressure ( or any other data line in the detailed area)... use 10 second viewing.
It will show up beginning at 1st and second mask session with no difference then by 4th or 5th mask session will show 2 or 3 seconds difference.
By the time you get to 12th session the difference will be 15 to 20 seconds and sometimes you will be missing 1 or 2 minutes of Flow Data or your events will be displaced by 1 to 2 minutes.
I only go to about 20 masks sessions at most... then I re-format and we start over.

I have tried all variations that I can think of w/o success at changing the skew.

ResMed have not been helpful to solutions yet. Customer Service agreed with the problem then engineers denied there is any problem. I am still in discussion with them but...

BTW: SWS and DreamOn... perhaps this new firmware has a solution. Let me know if you see the same skew with 10 second viewing...
I'm guessing you still have it Oscar...

I have the newer SX474-0602 firmware version on my machine. I've used the machine for 9 days.

Okay, when I view the details in 10-second view, I see the following:

2nd DAY (I had tested the machine for a few minutes in the afternoon on the first day, so perhaps this is considered the third "mask session"?):
(AHI 0.7, 3 centrals + 3 hypopneas)

Start Times:
Flow - 11:11:45
Flow Limitation, Pressure & Minute Vent. - 11:11:46

End Times:
Flow - 07:19:45
Flow Limitation, Pressure & Minute Vent. - 07:19:44


9th DAY:
(AHI 0.6, 4 centrals + 1 hypopnea)

Start Times:
Flow - 11:00:58
Flow Limitation, Pressure & Minute Vent. - 11:01:02

End Times:
Flow - 06:28:58
Flow Limitation, Pressure, Minute Vent. - 06:29:00

The differences in start and end times aren't evident in 10-minute view. They can be seen slightly in 5-minute view. The event markers line up with flow in all views, including 10-second. The apnea/hypopnea markers are at the end of each event as indicated on the flow graph.

That graph provided by DreamDiver (posted by -SWS earlier in this thread) is in 5-minute view. The skewed events are quite evident there. I do not see that at all.

I'm an S9 newbie! How do you check which version of the firmware you have?

elizavb wrote:Is this a problem with the Elite and AutoSet machines?

Thanks,

Evb

Both...

Nord

DreamOn wrote:

Nord wrote:The skew "issue" begins at about 4 or 5 mask sessions after formatting and gets progressively worse.

If you set the Detailed session in ResScan to compare looking the starting point for Flow and then Pressure ( or any other data line in the detailed area)... use 10 second viewing.
It will show up beginning at 1st and second mask session with no difference then by 4th or 5th mask session will show 2 or 3 seconds difference.
By the time you get to 12th session the difference will be 15 to 20 seconds and sometimes you will be missing 1 or 2 minutes of Flow Data or your events will be displaced by 1 to 2 minutes.
I only go to about 20 masks sessions at most... then I re-format and we start over.

I have tried all variations that I can think of w/o success at changing the skew.

ResMed have not been helpful to solutions yet. Customer Service agreed with the problem then engineers denied there is any problem. I am still in discussion with them but...

BTW: SWS and DreamOn... perhaps this new firmware has a solution. Let me know if you see the same skew with 10 second viewing...
I'm guessing you still have it Oscar...

I have the newer SX474-0602 firmware version on my machine. I've used the machine for 9 days.

Okay, when I view the details in 10-second view, I see the following:

2nd DAY (I had tested the machine for a few minutes in the afternoon on the first day, so perhaps this is considered the third "mask session"?):
(AHI 0.7, 3 centrals + 3 hypopneas)

Start Times:
Flow - 11:11:45
Flow Limitation, Pressure & Minute Vent. - 11:11:46

End Times:
Flow - 07:19:45
Flow Limitation, Pressure & Minute Vent. - 07:19:44


9th DAY:
(AHI 0.6, 4 centrals + 1 hypopnea)

Start Times:
Flow - 11:00:58
Flow Limitation, Pressure & Minute Vent. - 11:01:02

End Times:
Flow - 06:28:58
Flow Limitation, Pressure, Minute Vent. - 06:29:00

The differences in start and end times aren't evident in 10-minute view. They can be seen slightly in 5-minute view. The event markers line up with flow in all views, including 10-second. The apnea/hypopnea markers are at the end of each event as indicated on the flow graph.

That graph provided by DreamDiver (posted by -SWS earlier in this thread) is in 5-minute view. The skewed events are quite evident there. I do not see that at all.

Hi DreamOn...

The amount of "Mask Events" or "Mask Sessions" is given to you in the "Summary Graphs" tab of the "Review Screen"... page 21 of the Clinical Manual.

All the "views" are of the same data given. The difference is that the 10 second view gives you a second by second accounting of what data has happened. In other words you are looking at the evidence with a magnifying glass... it is High Definition television.

The skewing starts with the areas that I pointed out at the beginning of each data trail. The skewing of "apnea events" happens at the same time but because it is micro seconds difference... you cannot see it. The S9 corrects to the nearest second by definition... so you will not see it yet after a fewer mask sessions. Formatting the SD card always starts the process over at "zero" skews.

Nord

Rebecca R wrote:I'm an S9 newbie! How do you check which version of the firmware you have?

Hi Rebecca...

It is given on the LCD screen. Check your S9 "Advanced Menu" (push Info and Setup buttons together) and go to last readout for SW (SoftWare).

Your S9 Clinical Manual.

Nord

-SWS wrote:DD, can you find any correlation between your machine's data skew and number of mask-fit sessions?

Sorry to hear about your frustrating experience with sleep studies.

I could probably take the time to sit down and measure, but I think others may have already done that. I'm still putting some distance between me and the problem.

There are four main files types in question: *BRP.edf, *PLD.edf, *EVE.edf, and *SAD.edf. The .crc files are 'sanity' check files, as far as I can tell, to make sure the numbers have not been tampered with upon uploading to ResScan.

*BRP.edf includes two very high resolution measurements at 25 Hz: Flow and Mask Pressure. This data is linear. These two measurements are either combined using an algorithm to produce what we see in ResScan, or one of them is simply dropped. I suspsect the former.

*PLD.edf includes eleven less-high resolution (1 Hz) data, which are linear. These include another different Mask Pressure measurement, Therapy pressure, Exp Pressure, Leak, RR, Vt, MV, Snore Index, FFL Index and two unlabeled indices or lines that seem to have something to do with lining up the *EVE.edf data (the next one.)

*EVE.edf includes all event data (point or 'marker' data on a timeline), including central, obstructive and unknown apneas and hypopneas. The shorter this file, the better we supposedly sleep.

*SAD.edf is for high-resolution oxygen and pulse data. ResMed suggests the data being measured is 1Hz data, even though the sensor they use is capable of 25(27?)Hz collection, including plethysmography, so I don't know what to believe on that one because I haven't seen any oximetry data in a *SAD.edf file yet.

Some of the data being measured is either not stored or not displayed by ResScan, even though the S9 measures it. Some of the data shown by ResScan graphs is created during the upload process, such as the AHI graph.

The three most important files for this are the *BRP.edf, *PLD.edf and *EVE.edf files. They have to be written to one at a time because the S9 has only one processor and can handle only one task at a time. Similarly, the data cannot be all read at identically the same time, but rather, darned close. It looks to me like the flow data takes precedence, since it writes most often. The 1Hz linear data is written next. The event (point data) data writes independently of either flow or linear data, only when events are noted by the software in the S9. Regardless of when the data is written, at least one variable is being held as a sort of changing global variable from mask-session to mask-session that affects the skew of the next data session. The currently writing session seems to either grab some variables from the their analogous files from the last mask session, or from a variable storage file that is used to alter the original write time of the current session. However it happens, those variables change from session to session, independently for each file type when they should be identical. Session begin-time ends up being different for each file in a mask session, with that difference in time growing in an asymptotic curve. The outcome is ever-increasing skew.

Data seen in the EDF browser are usually identical to what is seen in the data on ResScan, down to the second, so an independent audit of the data proves that ResScan is not introducing the problem. It already exists in the data as written by the S9 before it gets to ResScan. The SD cards provided by ResMed are their approved cards, so they cannot be the problem. Hence, the data skew must be either firmware- or hardware-based.