A Question about Pressure

I would like to understand how to read the pressure graph on the daily Sleepyhead report. First of all, there's a red line and a green line, and since the red line's higher, I guess that indicates the max. pressure and the green is the lower pressure--right?? They seem to mirror each other, though, which is confusing.

Why on some nights does this graph have regular ups and downs that look like spikey teeth, and other nights there's a flat line--sometimes for 15 minutes and sometimes for an hour? And what's that giant spike like a mountain in the middle?

My machine's on autopap, currently with a min. pressure of 8.5 because I decided that if my 90% pressure was 8.5, it made sense to put it there. Before that, I'd been having lots of awakenings and when I looked at the pressure graph, it appeared that most of them happened at a pressure of under 8.5. However, last night my 90% pressure was 9.80. I'm wondering if, as you raise the minimum pressure, does that increase the 90% pressure for some reason? My sleep pattern isn't the greatest. I still wake up 3-4 times a night, but I feel pretty good most of the time and my AHI is rarely higher than .2.

Does everyone continuously tinker with pressure to try and fine-tune their machines?

Jeanne Ellen wrote:I would like to understand how to read the pressure graph on the daily Sleepyhead report. First of all, there's a red line and a green line, and since the red line's higher, I guess that indicates the max. pressure and the green is the lower pressure--right?? They seem to mirror each other, though, which is confusing.

Why on some nights does this graph have regular ups and downs that look like spikey teeth, and other nights there's a flat line--sometimes for 15 minutes and sometimes for an hour? And what's that giant spike like a mountain in the middle?

My machine's on autopap, currently with a min. pressure of 8.5 because I decided that if my 90% pressure was 8.5, it made sense to put it there. Before that, I'd been having lots of awakenings and when I looked at the pressure graph, it appeared that most of them happened at a pressure of under 8.5. However, last night my 90% pressure was 9.80. I'm wondering if, as you raise the minimum pressure, does that increase the 90% pressure for some reason? My sleep pattern isn't the greatest. I still wake up 3-4 times a night, but I feel pretty good most of the time and my AHI is rarely higher than .2.

Does everyone continuously tinker with pressure to try and fine-tune their machines?

In many cases......"yes".
The main breathing characteristics that cause an APAP to raise pressures are Flow Limitations and/or Snores. If the pressure increases don't "squash" them, then the pressures are still going to increase. The theory is that those items precede Hypopneas and Apneas and the algorithms are programmed that way. For some people they do and for some they don't. You need to review and analyze your reports to see what's happening. Are the pressure increases (changes) beneficial or are they just bouncing around all night based on a few snores or flow limitations. Some of us don't have many apneas or that are preceded by those events and the pressure changes can disturb our sleep. Therefore, using a single/straight pressure setting works best. On the other hand, many do just fine with changing pressures. It's something each user needs to experiment with to see what method works best.


Den

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If you see 2 pressure lines on a Respironics APAP pressure graph then one is inhale and one is exhale and they are likely different because you are using some sort of exhale relief...Flex of some sort at some setting. Not a big deal and normal.

The spikey things you see are just test pressure probes and the machine doing small increases to test things out. Normal function and it varies depending on what the machine senses is going on and does it or doesn't it need to do the test pressure probes.
They look faster than they are really happening. Actually it is a very slow increase and a very slow decrease and very smooth.

The 90% pressure numbers...yes they can increase as the minimum pressure is increased. It's part of the law of numbers thing and partly because 90% numbers can vary a lot anyway. They aren't averages...90% numbers by definition are just a number where the person was AT OR BELOW for 90% of the night. The "or below" part of the definition is often overlooked or forgotten. They can also vary because we don't sleep the same each night and pressure needs change each night so we expect them to vary and often considerably.
So your reasoning for setting the machine minimum to the 90% pressure because "it seems to want to stay there anyway" is a bit flawed. You didn't know about the "or below" part of the definitioin. You may or may not even need that much pressure though 8.5 is relatively low and probably isn't harming anything.

Did you know that it is normal to wake up after a REM cycle? Often we simply go back to sleep but sometimes we don't go right back to sleep and we are awake long enough to form a memory. Also we can sometimes just wake up for any unknown reason.
People tend to think that it's abnormal to wake up but it's actually normal and to turn the lights out and go to sleep and not remember waking up until we get up is actually the unusual thing to do. So 3 or 4 remembered awakenings doesn't necessarily mean anything bad is going on if they are brief and we go right back to sleep.

If your are feeling good, getting enough good sleep (don't stay awake very long with those awakenings) so that you feel decent during the day and your AHI is nice and low...I wouldn't worry about a handful of wake ups. Now if you have trouble getting back to sleep and the awake time is prolonged then we have a different discussion.
It's extremely rare that I don't remember a handful of awakenings...like 4 to 6 and sometimes even more because I have other issues like pain that can cause me to wake up. For me to not have any remembered awakenings would be extremely unusual. Some of mine are probably after a REM cycle..some are probably pain related and unfortunately I usually have a few that might be cat related.

Jeanne Ellen wrote:And what's that giant spike like a mountain in the middle?

Not sure what you are meaning here but it sounds like a period of time where the pressure went up and stayed up for some reason.
Maybe you were on your back or maybe you were in REM sleep...with either it is common to need more pressure. My OSA is worse in REM and I often see some times where the pressure goes up quite a bit and stays up for a while.

Here's a report I have handy.
The first part at around 1:00....those little spikey things are the test pressure probes in action. They can show up at any time...even at the top of a significant increase in pressure that is a bit prolonged.
You can see one of them at about 2:00 right in the middle of that prolonged increase. There is also a substantial increase (mountain) at 2:30 and again between 4 and 4:30 and shorter increases after that.
This person I suspect those increases are REM sleep related. They sort of fit the pattern of when we would expect to see REM sleep happen.
First REM is usually around 90 minutes after sleep onset and then it comes on more frequently as the night goes on with the greatest amount of REM occurring in those wee hours of the morning.
This person might have even been on their back during part of this. There is a little bit of snoring going on which might be triggering some of the pressure increases because snores is one of the things this machine will try to kill because a snore is a warning sign that the airway is trying to collapse.
Sometimes it goes on to collapse and sometimes it's just a little snore that is easily resolved.
At around 4:00 there is also a little cluster of OA events...and some snores so the snores grew up and the airway went on to collapse enough to earn an OA flag.

Oh...the leak line...it's normal for it to vary a bit as the pressure varies because that top leak line includes the vent rate and the vent rate will increase as the pressure increases so we expect to see some movement on the leak line.
The bottom leak line is an approximation of the excess only leak. It's close but not 100% accurate because the author of SH was having trouble figuring out the needed coding to figure excess only leak because the machine didn't make it clear because of the fact that in auto mode large leak territory varies quite a bit with the pressure varying. So I don't worry too much about the bottom leak line. Instead I look at the Events graph and if there are no flags in the LL line (large leak) then it doesn't really matter what that bottom leak line does.

When I first started using my CPAP device, I experimented with the pressure settings because I didn't feel I was getting the results I should have with the amount of effort wearing the equipment required. When my clinician saw that I was "experimenting" with the pressure, she told me that I was tampering with my Doctors prescription and that I shouldn't.

What are your feelings on this? I think if I do it again I'm just going to call my Dr and tell him what I'm doing.

Sandbag wrote:When I first started using my CPAP device, I experimented with the pressure settings because I didn't feel I was getting the results I should have with the amount of effort wearing the equipment required. When my clinician saw that I was "experimenting" with the pressure, she told me that I was tampering with my Doctors prescription and that I shouldn't.

What are your feelings on this? I think if I do it again I'm just going to call my Dr and tell him what I'm doing.

It all depends on what your prescribed pressure was, what you changed it to and if your results were better than before. Along with that, were you monitoring your therapy with software? If a person is just changing settings without monitoring their therapy, that's called " dial wingin' ".
Another factor is how the doctor feels about the user taking control of their own therapy. For most users, they get better results after they take control of their own therapy. But, again, that involves using software and getting an understanding of WHY they are making changes.
In reality, you're not "tampering" with your doctor's prescription........it's YOUR prescription and YOUR therapy.

Anyway, keep at it, take control of YOUR therapy and become as knowledgeable as YOU can, as fast as YOU can.
And, feel free to ask questions on the forum.


Den

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Sandbag wrote:When I first started using my CPAP device, I experimented with the pressure settings because I didn't feel I was getting the results I should have with the amount of effort wearing the equipment required. When my clinician saw that I was "experimenting" with the pressure, she told me that I was tampering with my Doctors prescription and that I shouldn't.

What are your feelings on this? I think if I do it again I'm just going to call my Dr and tell him what I'm doing.

Some thoughts:

Your physician/clinician should understand why you feel the need to 'experiment', and also agree to monitor and to continue advising you when you do so. You won't generate good will from others if they feel they are merely an impediment to what you want to do with your treatment. IOW, if you won't follow genuine advice, don't ask for it in the first place.

In case that sounded a bit harsh or blunt, these people have a lot of time and experience on their hands unless they're fresh out of school. They would know that the best results don't come from samples of "1", or even two nights, but from consistency and longer periods until a trend is noticed. If the trend is generally favourable, they'll consider leaving the settings where they are and take another look in a couple of weeks. If the results are not salutary, they'll adjust as seems right and continue to monitor....BUt not for one or two nights before they draw conclusions again. Try something for a week....at least...to establish reliable data (this is important). If a week's worth of data says you need more pressure, they'll advise you accordingly. Or, if you are treating yourself, and find the clinician to be wrong for some reason, again...try a new setting for at least a week to see if things level out at a more therapeutic advantage for you.

Thanks for the good advice.

Thank you, Pugsy, once again, for your excellent advice. It's always reassuring to hear from you that I'm normal--or at least not too abnormal. The only thing you didn't explain is the flat line, like in your example, about 3 AM. What does that mean? Is it a period of shallow breathing, and if so, why does the machine wait so long (like an hour sometimes for me) to ramp the pressure up? Is that normal too? In my case, last night I had all my Rera events during the flat line periods, when my pressure was the lowest, about 8.5.

Sandbag wrote:When I first started using my CPAP device, I experimented with the pressure settings because I didn't feel I was getting the results I should have with the amount of effort wearing the equipment required. When my clinician saw that I was "experimenting" with the pressure, she told me that I was tampering with my Doctors prescription and that I shouldn't.

What are your feelings on this? I think if I do it again I'm just going to call my Dr and tell him what I'm doing.

Some people are control freaks, that doesn't mean that they know best.
Also, she CAN'T fiddle with it, by law... however, you can.

Jeanne Ellen wrote: The only thing you didn't explain is the flat line, like in your example, about 3 AM. What does that mean? Is it a period of shallow breathing, and if so, why does the machine wait so long (like an hour sometimes for me) to ramp the pressure up? Is that normal too? In my case, last night I had all my Rera events during the flat line periods, when my pressure was the lowest, about 8.5.

The flat line just means the machine didn't sense anything that it needed or wanted to respond to. The pressure flat line has nothing to do with shallow breathing. Pressure line and breathing line are two different things.
To see shallow breathing (or any breathing) we would maybe have to zoom way in on the flow rate graph. I will post a zoomed in flow rate example at the bottom of this post so you can see it. It's not shallow breathing but instead an example of an apnea event so you can see the difference.

Here's the deal with how I understand the Respironics algorithm works..when you see the flat lines and the machine not doing the test pressure probes it's when our sleep maybe isn't so smooth and the machine doesn't sense the need to really make much of a chance and it doesn't want to do the test pressure probes just in case they might disrupt something. When you see the test pressure probes and not much else then you are most likely sleeping soundly. Seems kinda backwards to me but that's supposedly what they do. Sleep soundly and you get the test pressure probes and not so soundly and it sits by and twiddles its thumbs until something really knocks it in the head to cause it to do something.

RERAs....are not apnea events and the machine doesn't respond to them. The machine responds to flow limitations, snores, OAs and hyponeas.
RERAs are just times where the breathing pattern is similar to what the breathing pattern is when a person experiences an arousal.
Arousals can come from anything...doesn't necessarily have to be apnea/airway related.
So when we see RERAs flagged about all we know is that the breathing pattern matches arousal breathing pattern associated with respiratory related arousals (and it has to last so long and I forget how long) and so you may have not been sleeping so great at that time. So think of RERAs as a symptom of not so sound sleep...but now what is causing the not so sound sleep..dunno...supposedly related to the air flow.
The machine is thinking your breathing is like the breathing seen when people have a respiratory related arousal.

I would need to see your graphs to see if you are having enough RERAs along with maybe one or more of the usual triggers (snores, FLs, etc) to see if they are numerous enough to warrant concern. A few here or there all by themselves that we don't remember being awake...probably not a big deal.
If we see a lot of them and we are knowing we are waking often and sleeping poorly then I would at least try to reduce the numbers with a little more pressure because that's about all we can do.
So again like so much of the other stuff with cpap data...how we feel and sleep plays a big factor and not just the numbers of what we might see.

Here's a nice example of normal asleep breathing with a couple of apnea events happening. You have to zoom way in to see the flow rate.
I wouldn't call this "shallow" breathing. I don't have any good examples of maybe shallow breathing. Shallow breathing itself doesn't mean airway restriction. Just means a person doesn't take big breaths and it may or may not be a problem. It's when the airway gets restricted and the flow reduces because of the airway tissues collapsing that we have the apnea situation. With just plain shallow breathing the airway is still open but the person just doesn't take deep breaths. It's not because they can't though (because of the airway tissues) it's just because they don't.