Flow Limitations ??

[TangledHose]

I am using a F&P Auto and have been looking at my AHI numbers from the screen on the machine - - they look excelent at an average of around 1.2 with a low of 0.7 which makes me very happy. Recently I decided to get the InfoSmart software so I could look into more detail, and one thing that comes up are lots of "Flow Limitations" and now that I am looking beyond simply AHI numbers the flow limitations are concerning me a bit - - as an example on the night of March 10th my data shows:

AHI = 0.8

Total Flow Limitations = 24
Flow Limitation/hr: 3

Since my AHI numbers are good should I stop fretting over the Flow Limitations or should I be concerned?

APAP presures are set at low of 8 and high of 12; my 90th percentile pressure is 9.5 and only hit 12 for 4 minutes during the night.

I am going to try and imbed my data sheet:

[Pugsy]

How are you sleeping or feeling?

[TangledHose]

well, I am not 20 years old anymore !!

But I feel pretty good about the sleep quality, and I feel like I get more REM sleep than before......I just never knew much about the "Flow Limitations" and am not sure how important they are considering that my AHI numbers are good. The Flow Limitations are a bit new to me so I don't know what "normal" is when it comes to that measurement.

[Otter]

Maybe someone more familiar with how F&P scores FL will have more insight. I really don't know much about those machines, but for what it's worth,

"Flow limitation" usually means the tops of your waveform are somewhat rounded off. This may indicate that your airway isn't fully open. You can breathe, but the flow is more limited near the end of the breath than it would normally be, hence the name for the event. As you can see, your machine sees the limitation and raises the pressure to keep your airway open. If the volume you were breathing went down too far, the machine would score either apnea or hypopnea. Hence, FL really isn't a problem as far as O2 goes. The only problem would be if it's waking you up or kicking you out of REM or deep sleep.

If you feel good, I wouldn't worry about it. If you think this is disturbing your sleep, though, you might try raising your pressure above where most of the FL occurs and see if that helps. if you do make changes, be sure to pay attention for a week or so. You're not going to kill yourself, but it is possible to make things worse, and you'd want to catch that sooner rather than later.

[Otter]

Say, is "SenseAwake" simply F&Ps euphemism for central apnea?

[Pugsy]

Say, is "SenseAwake" simply F&Ps euphemism for central apnea?

No.
SenseAwake is a feature where the machine is supposed to sense that you are awake and reduce pressure to make it more comfortable instead of exhaling against a hurricane.

Flow limitations are minor reductions in air flow through the airway that don't meet criteria for the main event categories..due to either amount of reduction or duration. Could be a tiny reduction for maybe 3 seconds or maybe a little more for a little longer. There has to be a certain amount of minimum reduction for at least 10 seconds to meet criteria for the regularly flagged apnea events.

They will vary as with everything else and 3 per hour if you are feeling decent and sleeping well are not usually considered worth worrying about.

[Otter]

SenseAwake is a feature where the machine is supposed to sense that you are awake and reduce pressure to make it more comfortable instead of exhaling against a hurricane.

Sounds like ramp 2.0. I wonder if it would be better to turn that off. There's no obvious problem in the data, but is the pressure actually bothersome? I use higher pressures than Tangled, and I sometimes don't realize I have the mask on until I've been awake for a bit.

[Pugsy]

Sounds like ramp 2.0. I wonder if it would be better to turn that off. There's no obvious problem in the data, but is the pressure actually bothersome? I use higher pressures than Tangled, and I sometimes don't realize I have the mask on until I've been awake for a bit.

I don't know. I have never used a F & P machine so I have no idea how low it goes. I wouldn't think it could go any lower than the minimum for the machine though. Personally, I thought it was a bunch of hype and fluff similar to Respironics promoting CFlex or their Mask Resistance thing as the greatest thing since sliced bread. Marketing ploy but hey, it may feel great and help someone out. On the other hand if it is indeed accurate it might point to potential problems with frequent awakenings that aren't remembered because the software flags them. If someone has a high number of SenseAwake events then it could point to severely fragmented sleep since we don't always remember those little mini awakenings.

[TangledHose]

yeah as Pugsy said SenseAwake is just an algorithm that senses from your breathing pattern that you are in an awake state so it lowers pressure in order to make it easier to get back to sleep; it doesn't seem to ever go below the minimum pressure set in the auto settings. I have always been a restless sleeper and change positions a lot, so I actually kinda like the sense awake feature, but for grins maybe I'll turn it off and see if it makes much difference to me.

So I kinda get from the above replies that the flow limitations don't really go far enough to meet the criteria of an Apnea or Hypopnea event either due to small duration or not enough obstruction - - so like mini events - - I guess I won't pay a lot of attention to them - - it was just new data for me since I didn't see that information until I loaded the software and saw all the data in detail. I did raise my max pressure to 12.5 for the last two nights, but I looked at the data for those last two nights and found that the auto machine never even got to 12 over those last two nights.

I'll try and get back to you about the difference with the SenseAwake system turned off - - I suspect I probably may not really notice, but I'll play with it non the less.

Thanks for the good feedback!!

[Otter]

If it doesn't go below the minimum then I guess it's okay, maybe even useful. This would be preferable for people who don't like the way ResMed machines stay high for a good while after increasing the pressure.

I wonder how good the machine is at detecting waking states. Sometimes it's pretty obvious, but other times REM and wake are so close even we can't tell which we're in.

[TangledHose]

I just moved from the Icon Premo which didn't have Auto or SensAwake to this Icon Auto -- have used it for a week now and I started using it with the SenseAwake feature on and it seems to work well. I think I am actually falling asleep more quickly than when I did not have this feature, but I will play with it and try the same settings with the SenseAwake off and report back to let you know if I can tell a difference.

One byproduct of the SenseAwake data is it gives me a clue to how long I am awake and how long I am asleep while on the machine; as an example from the data above it shows that I was using the machine for a little over 7 hours and the SenseAwake was activated for one hour, so that would imply that out of the seven hours on the machine I was acctually in a sleep state for six of those seven hours - - that is assuming it is accurate

At any rate I did find some information on the SenseAwake system that I am reprinting here if you are curious about how it works:

"WHAT IS SENSAWAKETM?

SensAwake is a technology that is integrated into our Icon Auto. SensAwake uses flow to continuously monitor patients’ breathing patterns. What it does is it senses the change from breathing patterns associated with sleep to those associated with awake states. Once it detects a transition from sleep to awake it promptly reduces that pressure delivered to the patient.

WHY WAS SENSAWAKETM DEVELOPED?

Patients on CPAP therapy commonly arouse from sleep and experience periods of wakefulness. Pressure delivery can impact a patient’s ability to get back to sleep; comfort during this time is critical. Since pressure is not required while patients are awake, we developed a technology that could sense the patient transition from sleep to wake. Once this was developed, the next logical step would be to reduce the pressure to the lowest, most comfortable level for the patient to help them get back to sleep. Once they get back to sleep, the pressure treatment profile will return to the auto algorithm to determine the appropriate pressure delivery for the patient at that time".

ISN’T THERE A RISK THAT LOWERING THE PRESSURE WILL INDUCE MORE EVENTS?

SensAwakeTM technology works in conjunction with our Auto CPAP algorithm. In fact, the auto algorithm is the dominant algorithm. So, if SensAwakeTM begins to lower pressure delivery and the patient returns to sleep and begins to have sleep disordered breathing events, the auto algorithm will immediately take over and treat any events.

[Otter]

One byproduct of the SenseAwake data is it gives me a clue to how long I am awake and how long I am asleep while on the machine; as an example from the data above it shows that I was using the machine for a little over 7 hours and the SenseAwake was activated for one hour, so that would imply that out of the seven hours on the machine I was acctually in a sleep state for six of those seven hours - - that is assuming it is accurate

I make similar guesses based on my respiratory rate and tidal volume data. It's not prefect, but once I got my Zeo, I was able to confirm that what I thought I was seeing was usually correct (not that the Zeo is 100% accurate either). I think you could probably come up with an algorithm based on CPAP data that did a passable job for most people. If it's good enough to tell REM from wake, it could easily tell REM from other phases of sleep, so you could have wake, REM, and other sleep as categories. It will never replace PSG, of course, but it could be useful.