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Dave,
I examined my events and can confirm no skew relative to the flow. HOWEVER:
I noted that the pressure on my S9 Autoset builds up after the event, not during. In a say 13 second event, the pressure starts to rise after the event is over at second #13 or 14. Should the pressure not rise DURING the event to counteract it?

Edit:
Some interesting data about the skew bug...
Regardless of data transfer best practices, a skew between flow and detailed data keeps appearing in my graphs.

• There is always a minimum of one second in offset between flow data and detailed data in the graphing detail pane.
• The skew first starts out showing the beginning and end of the flow offset by a number of seconds from all other detailed data.
• That number of seconds seems to almost double on a daily basis after a certain number of mask events.
• The offset is between flow (hi-res) data and detailed data. In contrast, detailed data seem to stay aligned with each other. However event data show a peculiar difference, possibly because they are point data rather than line data.
• At first, event data continues to line up correctly with flow data, even though line graphs of detailed data continue to skew wider and wider at the beginning and end of each mask event. After an unknown threshold of mask events, the skew begins to show up in the apnea/hypopnea event data graph as a massive skew between where it appears in flow and where it appears in event graphing.
• Skew lengths are not always predictable, other than that they grossly tend to get larger. For instance, sometimes the skew will be four seconds at the beginning of a mask event and six seconds at the end of the same mask event. Sometimes the skew will be opposite what it was at the beginning of the mask event.
• Here's one item that is predictable: Flow data must always start and stop on the same even numeral.
  • March 18th was the only day I found where start/stop times were actually odd, yet they remain the same numeral for start and stop:
  • March 18th Flow Data - Mask event start and stop times:
    • Mask event 1 - started at 18:55:55 and ended at 19:20:55
    • Mask event 2 - started at 00:48:51 and ended at 05:40:51
    • Mask event 3 - started at 06:11:55 and ended at 06:46:55
• Another item that is also always predictable: Detailed data must always start and stop on an even numeral, the last of which is always 2 seconds less than the first:
  • March 18th Detailed Data - Mask event start and stop times:
    • Mask event 1 - started at 18:56:06 and ended at 19:21:04 | 06 - 04=2
    • Mask event 2 - started at 00:49:38 and ended at 05:40:36 | 38 - 36=2
    • Mask event 3 - started at 06:12:46 and ended at 06:46:44 | 46 - 44=2
• March 18th - Flow minus FL start and stop time differences:
  • Event
    Mask event 1
    F - FL start | 11 sec
    F - FL stop | 9 sec
    
    Mask event 2
    F - FL start | 47 sec
    F - FL stop | -15 sec
    
    Mask event 3
    F - FL start | 51 sec
    F - FL stop | -11 sec
• March 18th is also the day when the skew shows up in the events.
  It's particularly interesting in that the first mask event shows no skew in event graphing, but the second mask event does.
  • March 18th Event graphing
    • Mask event 1 - no visible skew between flow and event graphs
    • Mask event 2 - about 11 seconds visible skew between flow and event graphs
    • Mask event 3 - no apneas - n/a
• Regardless of whether I lock the SD card when transferring the data to ResScan 3.10, the skew continues to grow.
• For some people, the skew does not appear to be happening. They may not be looking as closely, so I cannot say.
• The only way for me to temporarily reset the skew is to wipe the card and start again. Since the card is locked during data entry, forum members have (perhaps erroneously) concluded that the bug resides in the firmware of the S9.

First Mask Event - No Event Graph Skew


Same Day, Next Mask Event - Visible Skew

DreamDiver wrote: [*]There is always a minimum of one second in offset between flow data and detailed data in the graphing detail pane.

Agreed, I see this too

DreamDiver wrote: [*]The skew first starts out showing the beginning and end of the flow offset by a number of seconds from all other detailed data.

Agreed

DreamDiver wrote: [*]That number of seconds seems to almost double on a daily basis after a certain number of mask events.

Yes, this is what I've seen, it's almost doubling and then it gets to a point where it's so offset that you suddenly miss an hour of data twoards the end of the night but not within the last hour.

DreamDiver wrote: [*]The offset is between flow (hi-res) data and detailed data. In contrast, detailed data seem to stay aligned with each other. However event data show a peculiar difference, possibly because they are point data rather than line data.

I would concur with that

DreamDiver wrote: [*]At first, event data continues to line up correctly with flow data, even though line graphs of detailed data continue to skew wider and wider at the beginning and end of each mask event. After an unknown threshold of mask events, the skew begins to show up in the apnea/hypopnea event data graph as a massive skew between where it appears in flow and where it appears in event graphing.

Yes, it does seem to take a lot longer before you see the skew in the Events vs Flow data. That is where it really becomes evident.

DreamDiver wrote: [*]Regardless of whether I lock the SD card when transferring the data to ResScan 3.10, the skew continues to grow.

This to me still points at that it's not ResScan causing the problem - unless it was an import problem but I'm 100% sure it's not an import problem.

DreamDiver wrote: [*]For some people, the skew does not appear to be happening. They may not be looking as closely, so I cannot say.
[*]The only way for me to temporarily reset the skew is to wipe the card and start again. Since the card is locked during data entry, forum members have (perhaps erroneously) concluded that the bug resides in the firmware of the S9.

My gut feeling here is (and this is not to insult anyone so please people don't take this personally) but I think for the people that aren't seeing the skew they're not minutely going through the stats like a few of us. The skew is there for the most part and continues to grow. It might just be that some are really lucky for some reason to not have it skew, but I still don't know why it would affect some and not others.

The only other thing that I could see that might confirm why some people are seeing skews and some aren't is that if someone doesn't see a skew maybe they have not formatted their SD card. My SD card came with the config files pre-written to the card from what I can recall but I'm not 100% sure on this, I may have put it into the machine and powered it on quickly. Now if that's the case, it could be the way the original files are written at factory to the card vs how the S9 writes them, might be the reason why some don't see the problem if they haven't either formatted their card or used a new card. I'm prety sure I didn't receive the "do you want to erase card" message out of the factory, which you would see if the card didn't have the config files on the root directory of the SD card.

It's possible there's a difference in the way the files are written to the card between factory and how the S9 writes them.

Thanks
Dave

Bump to the top...

Nord

Repeat of Info to keep Thread in position:

Still Skewing Progressively...

Apr 13th... 1 - 7 Mask Sessions - Skewing up to 3 seconds... Missing No Data... Flow now starts on Odd Seconds...

Apr 14th... 8 - 20 Mask Sessions - Skewing up to 17 seconds... Missing 50 seconds and 46 seconds... Flow now starts on Odd Seconds... 1 Hypopnea out of position

Apr 15th... 21 - 23 Mask Sessions - Skewing up to 21 seconds... Missing 45 seconds and 43 seconds and 41 seconds... Flow now starts on Odd Seconds... 1 OA severely out of place

Nord

Nord,

Musings:

1. I wonder if the number of mask sessions relate to the skew. I have 1-2 sessions per night without a skew. Maybe the software isn't designed to handle that many sessions per night?

2. Also, try starting over with a clean card? You won't lose any data, since you have it on the old card.

3. Do you reset every day (unplug or push the left button)? I think that was discussed.

Newbie (< a month of analysis), who is enthusiastic about detailed S9 data, trying to help with a new (and perhaps naive) perspective.

gpk111 wrote:1. I wonder if the number of mask sessions relate to the skew. I have 1-2 sessions per night without a skew. Maybe the software isn't designed to handle that many sessions per night?

It's not related to the number of mask sessions per day, as I only have 1 mask session per day and receive the skew. That's not to say that it doesn't get worse with more mask sessions, but I've been very careful to not have more than 1 mask session a day.

I do however wonder...
1. How many people who have the Skew are using the H5i on a nightly basis?
2. Are you pre-heating the H5i for the entire time?
3. Are you pre-heating the H5i for part of the time?
4. Are you not pre-heating the H5i?

On several nights where I've seen the skew grow, I've realised that I've pre-heated the chamber but not for the full duration (was too tired to let it pre-heat entirely), and probably a pure co-incidence but wondering whether this might somehow be related. Most nights I don't pre-heat and start the S9 and let it heat up whilst using. I'm going to try and test this again.

I'm going to erase my card again to get back to a baseline without a skew. I've tried power cycling the S9 once the skew appears but it doesn't rectify the skew once it's in play, but power cycling for me at least on a nighly basis pre-skew seems to keep it at bay.

Thanks
Dave

dave21 wrote: I do however wonder...
1. How many people who have the Skew are using the H5i on a nightly basis?
2. Are you pre-heating the H5i for the entire time?
3. Are you pre-heating the H5i for part of the time?
4. Are you not pre-heating the H5i?

On several nights where I've seen the skew grow, I've realised that I've pre-heated the chamber but not for the full duration (was too tired to let it pre-heat entirely), and probably a pure co-incidence but wondering whether this might somehow be related. Most nights I don't pre-heat and start the S9 and let it heat up whilst using. I'm going to try and test this again.

I've only tried the pre-heating once and never looked back. I have not pre-heated since starting with the fresh class-4 card. Perhaps pre-heating partway may alter skew in some way, but skew is still happening regardless of preheating. I haven't changed the setting on the humidifier since setting it a couple months ago. It's pretty much set and forget.

gpk111 wrote:Nord,

Musings:

1. I wonder if the number of mask sessions relate to the skew. I have 1-2 sessions per night without a skew. Maybe the software isn't designed to handle that many sessions per night?

2. Also, try starting over with a clean card? You won't lose any data, since you have it on the old card.

3. Do you reset every day (unplug or push the left button)? I think that was discussed.

Newbie (< a month of analysis), who is enthusiastic about detailed S9 data, trying to help with a new (and perhaps naive) perspective.

Hi Gerry

1. I think that number of Mask Sessions "speeds up" the process of Skewing but we don't have evidence that it "causes" it... I intentionally had a large number of Mask Sessions to test.
We set up those differences initially to test skew - DreamDiver was only going to have 1 Mask Session per day... but the number doesn't prevent the skew - just delays it.

2. This was a "clean" formatted card as of the beginning of April 13th. Starting over with newly formatted card takes the skew back to 0 seconds... but it begins again.

3. My "process" to follow was... to NOT unplug or re-set the S9 if possible. But... my S9 was unplugged twice between the 13th and 14th out of necessity.

Thanks for the help Gerry... I wish I knew why your machine has been able to stay away from skews. We are not trying to examine the difference. Some people have managed to stay away from skewing for some unknown reasons. So far, nothing that we can see about the "process" that you follow is different from what some others follow who have skew. So... since some machines don't seem to skew... we have considered hardware differences as a possibility (if there are any)

Nord

DreamDiver wrote:

dave21 wrote: I do however wonder...
1. How many people who have the Skew are using the H5i on a nightly basis?
2. Are you pre-heating the H5i for the entire time?
3. Are you pre-heating the H5i for part of the time?
4. Are you not pre-heating the H5i?

On several nights where I've seen the skew grow, I've realised that I've pre-heated the chamber but not for the full duration (was too tired to let it pre-heat entirely), and probably a pure co-incidence but wondering whether this might somehow be related. Most nights I don't pre-heat and start the S9 and let it heat up whilst using. I'm going to try and test this again.

I've only tried the pre-heating once and never looked back. I have not pre-heated since starting with the fresh class-4 card. Perhaps pre-heating partway may alter skew in some way, but skew is still happening regardless of preheating. I haven't changed the setting on the humidifier since setting it a couple months ago. It's pretty much set and forget.

I, too, have only used the pre-heater infrequently. I have had some H5i problems and have tested my machine by using the pre-heater only at those times. Makes sense that power drain could affect "writing" by the S9. We haven't given that possibility enough thought yet maybe. That would be a whole "new" area.

Nord

I supplied my detailed manufacturing data on another thread. Sorry i can't be any more help.

Here's another thing to toss into the pot: what about power at the plug? Is it possible that a less-than-perfect power feed could be causing problems? I know we have brownouts in our neighborhood at least once a week - mostly due to trees touching power lines and grounding them during windy days/nights. Then at least once a month the power goes out completely for five seconds and then comes back on for no known reason - usually during the day.

Looking at my Kill-A-Watt EZ, some days it says the power coming to my socket is 117 or 116 volts - not really 120 volts we're supposed to have. Just now it reads as 120.8 volts. Five minutes ago, 119.8 volts. It's also 59.9 Hz - not 60Hz as is standard.

Considering the S9's brick is supposed to make the power perfectly uniform for the S9, perhaps this is barking up the wrong tree too.

Also considering how few people are seeing skew according to the quiz, it makes me wonder if a few of us just have bad S9's. I'm looking forward to Nord's latest findings with the new machine.

DreamDiver,
In theory, the S9 side of the brick supplies the power required by the S9, regardless of slight voltage variations. Having said that, the thread about battery back up implies that a near perfect back up power source is required to supply power to the brick.

by gpk111 on Thu Apr 08, 2010 10:20 am

John,
I would think the PC UPS system supplies whatever power the brick needs. I would also think that the brick is ultimately responsible for supplying as pure a sine wave as the flow generator and the humidifier are specced for. Yes?

_________________
Machine: S9 AutoSet™ CPAP Machine
Mask: Swift FX™ Nasal Pillow CPAP Mask with Headgear
Humidifier: S9™ Series Humidaire H5i™ Heated Humidifier with Climate Control
Additional Comments: ResScan v3.10

Gerry in Florida
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JohnBFisher

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Private message Reply with quote Re: Battery Backup Design
by JohnBFisher on Thu Apr 08, 2010 11:55 am

gpk111 wrote:
... I would think the PC UPS system supplies whatever power the brick needs. I would also think that the brick is ultimately responsible for supplying as pure a sine wave as the flow generator and the humidifier are specced for. Yes? ...

You would think so, wouldn't you? Well, in all previous versions of the ResMed humidifiers you would be wrong. A modified sine wave is not a problem with the xPAP unit. It's only a problem with the heated humidifier. Here's the guide for all previous units and associated humidifiers:

http://www.resmed.com/us/assets/documen ... lo_eng.pdf

But that guide has not been updated for the S9 unit. So, I reccomend:


To speak with a ResMed Representative call 800.424.0737 (Monday – Friday, 5:00am – 5:00pm PST).

_________________
Mask: Mirage Quattro™ Full Face CPAP Mask with Headgear
Humidifier: HumidAire 2i™ Heated Humidifier
Software: ResScan Version 3.7 Software
Additional Comments: User of CPAP/BiPAP/ASV for almost 20 years, currently use ResMed VPAP Adapt SV with EEP @ 10cm H2O (max @ 25cm H2O)

Nord wrote:[1. I wonder if the number of mask sessions relate to the skew. I have 1-2 sessions per night without a skew. Maybe the software isn't designed to handle that many sessions per night?

Personally I don't think the amount of mask sessions, in terms of mask sessions per day is causing the skew. What I think you've identified in your tests is that skews happen over time (which we already know). e.g. if you have 12 days worth of single session mask usage then you may see a skew. By having 12 mask sessions in a day is basically only advancing the onset to the point at that you are accelerating the amount of time (effectively folding it like a time warp) to get to that figure where you see the skew but quicker.

At least that's my understanding as to the mask sessions (although I may be proven wrong over time).

Thanks
Dave

My DME told me these units are guaranteed for a year. How about if those struck by the skew bug simply return the units to ResMed?

Am I missing something?