ResMed S9 Data format and signals

[elliott2]

I have been using a peice of software (EDFBrowser) to look at the data from my ResMed S9 along with the ResScan and Sleephead. The software is pretty easy to use and navigate and it's really easy to view the data in different scales. When I open the folder that contains the data files I see four .edf files. The files have header data in them that describes the sample rate, signal limits, signal name, etc. On the _BRP.edf seems to contain the high sample rate (25HZ or 0.04 seconds/sample) data, the _EVE.edf file is the event data and the _PLD.edf is the low rate (0.5HZ or 2 seconds/sample) data.

The question I have is about the data in the low data rate (PLD.edf) file.
Most of the signals are pretty much self explanatory.
The signals that are shown in the header files are:

1. Mask Pressure - the calculated pressure at the mask
2. Therapy Pressur - the set point pressure
3. Exp Pressure - the expiration pressure when you exhale
4. Leak - the leak rate
5. RR - the respiration rate
6. Vt - the Tidal Volume
7. MV - the volume averaged over a minute
8. Snore Index - the calculated snore level
9. FFL Index - the free flow level or how closed up the breathing passage is.
10. (no label)
11. (no label0)

The last two signals do not have names but seem to coincide with the central apnea detection most of the time.
the signal 10 has a range of 0 to +2 (digital value 0 to 200)
the signal 11 has a range of -3 to +3 (digital value -120 to +120)

Does anyone know what these two signals are and how they relate to the other data in the file?
I can paste the header and signal files in ascii form if anyone is interested or needs them.
Thanks in advance.

[trish6hundred]

Hi elliott2,
WELCOME! to the forum.!
Hang in there for answers to your question.

[drgrimes]

Elliot, you are really getting into the nitty gritty of the data files.....deeper than I have been so I can't answer your questions about those two fields. Do you see the same data from those fields showing up in Rescan or Sleepyhead? Or I wonder if that data is used in some calculation or analysis but does not show up in an obvious way.

I have tried hard to understand the data structure and how things work, but I admit it is eluding me. There are some odd things that happen and I cannot figure a simple answer. Everytime I put my card in my laptop and open Rescan, it warns me that there is duplicate data and asks me whether I want to overwrite or discard. Well they don't tell you where it wants to write to....your card or files in the PC. I've tried it both ways and everthing is still there.

Then when I put the card back into my Autoset, it says it must rewrite my data card. When you answer no, you are stopped and cannot use the machine. SO the only answer is Yes, and when you say yes it says "erasing data card" which spooked me pretty good first time, but all the data was still there.

I have a feeling most forum members don't know or care about all this, but I do know lots of folks have concerns about losing their data, including me. I wish they (Rescan, Resmed, and/or our computers) would tell us what is being written over and discarded. So far it doesn't seem to matter much if you answer those questions wrong.

To get the answers to your questions I wonder if you can contact the makers of the Rescan software, or maybe Resmed, since they must have had a reason for having those two fields. Hope you find the answer.

[elliott2]

The way I deal with the data card on my machine is I shut the S9 off and remove the SD Card. I then slide the write protect switch to the locked or write protect position. I put it into my desktop via a usb adapter and copy the data from the card to a sub-directory called S9DataCard. I then dismount the SD Card, un-write protect it and put it back in the S9 machine, that way Windows, ResScan or anything else can not change the data card contents.

The S9DataCard directory has two sub-directories, SETTINGS and DATALOG. Each morning I copy four files (Identification.tgt and .crc and STR.edf and .crc) from the root directory of the SD Card to the S9DataCard directory, all of the files in the SETTINGS sub-directory of the SD Card and the eight new files for the previous nights session. I saw that all of the files changed in the SETTINGS directory and the four files in the root directory every day and the files in the DATALOG directory were not changing except for the added files. It looks to me like all of the files on the SD Card have a cyclic redundancy check (CRC) file associated with them to allow the system (the S9?) to verify the data is good and with out corruption. If a file is changed and the .crc file is not updated with a new crc value, the system will flag an error.

I then copy the files from the desktop to a thumb drive using the same procedures to use with ResScan. The thumb drive has the four files that were in the top level (root level) of the SC Card in it's top level and the other data goes in the SETTINGS and the DATALOG sub-directories. The thumb drive is what I use for ResScan to look at and when ResScan asks if I want to overwrite or discard the duplicate data I tell it to discard the duplicate data. This seems to preserve the full data set on the thumb drive so i have full high data sample rate data for all of the days. I've read that the S9 will overwrite data older then a week old and not preserve the high sample rate data (which is what I'm most interested in). I don't know if it does but when I copy and discard, the older files don't get updated. From what I understand the option to update or discard the data file has to do with the data going INTO ResScan and not to the card but i use the write protect procedure to be sure.

From what I've seen, ResScan requires a data card or equivalent (the thumb drive) to read the new data from, it will not read the data from a directory on the hard drive, or at least I have not been able to figure out how. SleepHead and EDFBrowser will read from the hard drive sub-directory without a problem.

To figure out what the label were for in the data files, I compared the data displayed in EDFBrowser to SleepyHead and ResScan. I didn't snap to what RR, MV, VT and FFL Index were until I looked and compared data and then it made sense. I have not found anything that seems to correlate to the signal 10 and 11 but using EDFBrowser you can see that they are related to events, I just not sure how and what the magnitudes are about.

Cheers,
Tim

[PaulaO2]

I have tried hard to understand the data structure and how things work, but I admit it is eluding me. There are some odd things that happen and I cannot figure a simple answer. Everytime I put my card in my laptop and open Rescan, it warns me that there is duplicate data and asks me whether I want to overwrite or discard. Well they don't tell you where it wants to write to....your card or files in the PC. I've tried it both ways and everthing is still there.

Overwrite: overwrites the data on from the card for dates that you have already downloaded. You may lose detailed data if over 30 days. You will lose flow rate if over 7 days.

Discard: skips over the data on the card for the dates you have already downloaded. The data remains in ResScan just like before and remains on the card just like before.

ResScan does not write to the card unless you are telling it to reset your settings. I think it can do that somewhere inside of it but I'm not sure where. I dislike ResScan so have never messed with it much.

Then when I put the card back into my Autoset, it says it must rewrite my data card. When you answer no, you are stopped and cannot use the machine. SO the only answer is Yes, and when you say yes it says "erasing data card" which spooked me pretty good first time, but all the data was still there.

Are you locking the card before you put it in your computer? You should be doing this. If not, something on your computer is writing something onto the card that the Autoset doesn't like. This could be anything from ResScan itself (which I doubt) or your antivirus software.

[drgrimes]

Tim, thanks for all the information. Everytime I open Rescan, I use a customized report that I created that creates a very detailed five page report. It creates a PDF file, and I save those daily ever since I started using the data capable machine. It's nice because I don't have to waste paper or time printing, but I have a nice backup of everything incase something goes wrong with SD card, Autoset, or my PC. I worry lots less now. Thanks again.
Darrell

[PaulaO2]

Elliot, one of them you don't have in your list is Inspiration time unless that is figured into the RR total?

I don't think it would be time, as in compliance.

This is way cool information!

You know, one person who may know what it means is Mark, the creator of SleepyHead. You can PM him here at this forum or contact him over at the SleepyHead section of SourceForge.

[jgjones1972]

drgrimes,

If you want to keep ALL of your old data stored on your pc in the ResScan files you must choose "discard" when asked during the download. The CPAP will only store 7 days of high resolution waveform data and 30 days of detailed data on the SD card - it will erase and replace the oldest data with new data regardless of how much space is still on the card. When when downloading from the SD card to your computer there will be days on ResScan that still have this detailed data so the data file doesn't match the data file on your SD card because the file recorded on it has had this data removed. When you choose to overwrite you are replacing the file that has detailed data with the file that only has compliance and summary data.

Open ResScan and go back to the last time you chose to overwrite data, then go back and open the day eight days before that and try to look at the flow chart - it should be gone. To see what data you have for which days, just look at the icon to the left of the date - it stacks icons that symbolize the different types of data stored.

The card read error/reformat prompt is a common and usually indicates incomplete data (card taken out while being written to) or card corruption (computer put files on card or changed something). Macs are notorious for sneaking stuff onto SD cards unannounced as well as the newest incarnations of Windows. To avoid problems, power down your PAP before removing the SD card and write protect it before putting it in the card reader for download. CPAPs are very touchy about those SD cards because they are guarding against any possible corruption of compliance reporting for insurance purposes.


Just before posting this is saw that Paula had already gave the answer to this, but I'm posting anyway because I spent to much time typing with my thumb on my phone to just delete it.

[SuperSleeper]

Just before posting this is saw that Paula had already gave the answer to this, but I'm posting anyway because I spent to much time typing with my thumb on my phone to just delete it.

Been there, done that.