Need Data Graphs Explained....

[Randyp1234]

So I've installed ReScan and SleepyHead and am now comfortable zooming in and out and looking at the various graphs. For us noobs are there any tutorials explaining what these graphs are showing us?

Randy

[sol]

So I've installed ReScan and SleepyHead and am now comfortable zooming in and out and looking at the various graphs. For us noobs are there any tutorials explaining what these graphs are showing us?

Randy

http://www.cpaplibrary.com/software.html
http://montfordhouse.com/cpap/resscan_tutorial/

[Pugsy]

Mostly it is just a matter of understanding the terminology and how it all relates.
If you are looking for something you can plug your numbers into in hopes of comparing your numbers to "normals" then there really isn't that kind of tutorial available. We sort of learn as we go and if you have a specific question we post them along with any reports and ask for specific answers as to what so and so might mean.

ResMed users need to understand that the machine reports excess leak so any leak is unwanted but the machine can compensate very well for leaks up to around 24 L/min. Above that amount of leak then ResMed says that therapy and data scoring can be impacted. Short lived spikes of leak above 24 L/min will happen from time to time and unless someone spends a lot of time at or above that 24 L/min line therapy won't be hugely impacted. Now if leaks wake you up..different story since anything that disturbs sleep (even if small leaks) would be unwanted.

AHI we like to see below 5 and some people say that they feel even more better with half that amount.

Was there something specific you didn't understand or was wondering about?

[Randyp1234]

Let me try and voice what I'm wondering by posting some screen shots. Some I think I know but want to be sure.



The flow rate. What exactly are the squiggly lines telling me? I'm assuming something to do with the air flow as I inhale and exhale (or don't). But what is what?



Mask pressure. Is this the pressure being pushed to the mask by the machine or the actual pressure measured at the mask? And why the flat areas the coincide with the centrals? More on the central thing later.

What is the Tidal Volume and Minute Vent?

Centrals - As I recall most of these recorded centrals are when I was awake (or maybe they woke me up?). Am I correct in remembering that things like rolling over and such disrupt our breathing enough that the machine cores a central?

I'm sure I'll have more but it's time to get dinner on the grill.

Thanks!!!

Randy

[robysue]

Let me try and voice what I'm wondering by posting some screen shots. Some I think I know but want to be sure.



The flow rate. What exactly are the squiggly lines telling me? I'm assuming something to do with the air flow as I inhale and exhale (or don't). But what is what?

Each "double hump" is a breath. The part of the breath above the "0" line is when you are inhaling. The part of the breath below the "0" line is when you are exhaling. The "O" line is the line that cuts the humps in half.

Notice those flat areas with the flag marked "CA" on them? The areas are flat because the machine could detect no airflow into/out of your lungs. Because they went on long enough, they are flagged as apneas. Because they met the machine's criteria for detecting an "clear (open) airway", they are marked "CA---Clear airway Apneas". The machine's manufacturer presumes that most CAs are likely "central apneas. In other words, the machine and the engineers who designed its CA detection algorithm believe that your airway was not collapsed when these particular apneas occurred.

Obstructive apneas (ones where your airway is collapsed) are marked with flags that say OA on them.

Periods of shallow breathing that meet the machine's definition of "hypopnea" are marked by flags with H's on them.

Mask pressure. Is this the pressure being pushed to the mask by the machine or the actual pressure measured at the mask? And why the flat areas the coincide with the centrals? More on the central thing later.

Since there's not a pressure gauge inside the mask, the machine is measuring the pressure through some kind of algorithm that determines a good approximation of the pressure at the mask. The Mask Pressure curve for a Resmed machine shows the EPR algorithm in action---that's why it goes up and down in time with your breaths as shown on the Flow curve.

And why does the pressure stay at the bottom EXHALE pressure level when you're in the middle of a Central Apnea? I really don't know. All I can assume is that somehow the machine is designed that way. I had thought that EPR was suspended when events were being detected and that the pressure was then held constant at the prescribed level, which is the pressure level at the tops of the peaks on the mask pressure graph. Perhaps someone who has some hands on knowledge of the Resmed EPR algorithm can comment on this.

What is the Tidal Volume and Minute Vent

I believe Tidal Volume is the volume of air you inhale with each breath. Minute Ventilation is the total amount of air you inhale per minute. The units for the Tidal Volume graph are in mL, and the units for the Minute Ventilation graph are in L/min (Liters per minute).

In normal sleep breathing, the respiration rate is pretty constant AND each breath is pretty much identical; hence in normal sleep breathing, the Minute Ventilation number measured in mL per minute would be pretty close to (# of breaths per minute) * (Average tidal volume for one breath). But because Minute Ventilation is measured in L/min and there are 1000 ml in one L, the Minute Ventilation reported by SH will be pretty close to

• Minute Ventilation in L/min = ( (# of breaths per minute) * (Average tidal volume for one breath) )/1000

Hence the Tidal Volume and Minute Ventilation graphs usually look pretty similar to each other except for the vertical scale.

Centrals - As I recall most of these recorded centrals are when I was awake (or maybe they woke me up?). Am I correct in remembering that things like rolling over and such disrupt our breathing enough that the machine cores a central?

Yes, wakeful breathing can lead the machine to score events that would not have been scored on a PSG. And some of these events can indeed be centrals that show up when you are transitioning to/from sleep or when you are rolling over in bed.

[Randyp1234]

Thanks so much RobySue!!! I suspect a good portion of the CA's and therefore most of the reported AHI each night is when I'm awake because the mask gets out of whack or one of the cats, or whatever, wakes me up.





Randy

[Pugsy]

Randy I have nights where my Central index is like yours and nights where I don't have any centrals. Since an hourly index of 1 to 4 centrals isn't really a big deal unless we see large numbers every hour and every night I just mentally toss that Central index out the AHI window and concentrate on the OA and Hyponea index to evaluate my nightly data.

I figure that the centrals..well some might be real, some might be tossing and turning, some might be sleep transition or even awake. We have limited scoring ability by the machines for centrals and the machine doesn't do anything except sit there and twiddle its thumbs about centrals...these minor numbers aren't really enough to worry over. I suspect mine are toss and turn events with occasional sleep transition during the nights when I have more pain than usual and wake more often.

Different story for people who have Central index over 5..every hour, every night, all week long. They need to talk to their doctor.

[Randyp1234]

According to SleepyHead my 17 day average is AHI=4.11 CA=2.63 OA=1.11 UA=.01 H=.42

I'm kind of getting fond of SleepyHead over ResScan. Thanks JediMark.

Randy

[idamtnboy]

Thanks so much RobySue!!! I suspect a good portion of the CA's and therefore most of the reported AHI each night is when I'm awake because the mask gets out of whack or one of the cats, or whatever, wakes me up.

Take a look at the flow graph for a period when you know you were awake. I'll bet the graph is a whole lot rougher in shape than the one you posted, at least mine is. I can tell instantly when looking at my graph which portions reflect sleep and which are awake times. The CAs in the graph you posted were not wakeful times I don't believe. They look pretty much like mine when I definitely slept right through them.

[JeffL]

Thanks so much RobySue!!! I suspect a good portion of the CA's and therefore most of the reported AHI each night is when I'm awake because the mask gets out of whack or one of the cats, or whatever, wakes me up.





Randy

How to you get that pie chart?

[robysue]

How to you get that pie chart?

In SH, go to Preferences (it's under the File menu)

Once the Preferences panel pops up, select the General tab.

Once you are in the General tab, make sure that the box labeled Enable Graph Snapshots is CHECKED

Click OK and restart SH. Once you restart SH, the pie charts should show up.

NOTE: JediMark has said this feature is unstable on older computers. It's also unstable on computers with nonstandard video cards. For example, on my Eee PC, turning this feature on creates a bunch of problems that don't happen when it's off. On my mac, on the other hand, there seems to be no problem with turning this feature on.

[JeffL]

TNX, I thought it was a ResScan chart. I can see it now with SH. Looks like it's only a daily chart. Maybe Mark will make it work over a range of dates someday.

[archangle]

When looking at the events, make note of how long they last. An apnea that lasts for 15 seconds is not nearly as harmful as one that lasts 120 seconds, even though they are scored the same in terms of AHI. Also, some events will not be 0% airflow for the whole time.

The fuzz on the pressure graphs at the low pressure during your CA events is interesting. I presume that's the Forced Oscillation Technique (FOT) ResMed uses to determine if it's obstructive or not.

[Grand-PAP]

*

[Pugsy]

What software are you using to produce those graphs (Flow Rate and Mask Pressure)?

I have ResScan and SleepyHead and my graphs are NO WHERE near the quality of these.

Those are SleepyHead graphs and zoomed in to small detail.
Go to the events tab....then pick obstructive events from that list....then you should see all the obstructive events with the times that each happened....click on one of those events at a specified time and watch the graphs on the right change to zoom in on that one event.