Central Detection Driving Me Nuts!!

[Reznik]

While DeVilbiss dismisses pulse and FOT detection, the methods have been researched and verified in scientific studies as accurate methods of determining open or obstructed airway. I remain uncertain what method DeVilbiss is using.
https://www.atsjournals.org/doi/full/10.....5.9902085
https://www.atsjournals.org/doi/full/10.....3.2006168
https://erj.ersjournals.com/content/17/3/456

There is a lot more out there, and most find the technique valid.

I may have missed it, but I couldn't find that any of the articles you cited had "verified [that FOT is an] accurate method[] of determining open or obstructed airway" as you state in your post.

The first article you cited involved only 14 patients who did an overnight study, and found that FOT was only accurate when done in conjunction with breathing waveform analysis.  That seems to suggest that FOT is not accurate without the waveform analysis.  Devilbiss and F&P are both using breathing waveform analysis, without FOT, to do central apnea detection.  At best, this article casts doubt on the validity of FOT.  And combined with the fact that waveform analysis alone can produce valid result, it supports the idea that FOT may be inferior.  The sample size of 14 who slept the entire night is obviously inadequate.

The second article you cited says nothing about the accuracy of FOT in differentiating obstructive v. central.  It says only that FOT resulted in lower apnea indexes.  That doesn't surprise me.  FOT disrupts sleep.  That's how it reduces the AHI.  You could also disrupt sleep apnea by yelling in patient's ears or by shaking them to partially awaken them (that's how my wife used to do it).  As I stated in a prior post, that's the problem with FOT.  It disrupts sleep.  The fact that it happens to reduce AHI doesn't change that fact.

The third article you cited involved 9 patients.  It only found that a simplified method of FOT produced the same results as a more complex method of FOT.  It doesn't appear to have made an effort to determine whether either FOT method produced accurate results.  And, again, a sample size of 9 is inadequate to reach any valid scientific conclusions.

If you have an article that shows that FOT produces accurate results that has an adequate sample size, I'd love to see it.

[AlanE]

...FOT disrupts sleep.  That's how it reduces the AHI.  ... 

Can you cite the source for this?

[Reznik]

...FOT disrupts sleep.  That's how it reduces the AHI.  ... 

Can you cite the source for this?

That's my own theory.  

I've cited several pieces of evidence to support my theory in this thread, including my own personal experience and the fact that studies of machines using FOT consistently produce lower AHI scores than machines that don't use FOT.  Others have also come forward with similar experiences to mine, i.e., they have better sleep when using machines that don't deliver FOT.  

There are two ways to lower AHI.  You can either open the airway (which is what CPAP is supposed to do) or disrupt sleep (which is what apneas, snoring, and sleep partners do).  Since studies using FOTs show lower AHI scores without increasing pressure, my theory is that they are disrupting the sleep of the users.  I can also say without hesitation that I sleep much better and have more refreshing sleep when using machines that don't deliver FOT pulses, and several other apneaboard users have given similar reports here and in other threads.

Unfortunately, ResMed has made it very difficult for us to test my theory.  Their lab machines don't deliver FOT pulses, and so your sleep lab did not test you to see if FOT disrupts your brainwaves during sleep before sending you home with a machine that delivers FOT pulses.  Also, you either have a machine that uses FOT or you don't, and with one exception (the AirCurve 10 VAUTO), ResMed has made it impossible for the user or a clinician to turn FOT on or off.  

If you're getting an AHI above 0 and your machine delivers FOTs, the only way for you to find out if you'd get better sleep without FOT pulses is to buy a second machine that doesn't deliver them at all.  If you fail on CPAP, your doctor will eventually elevate you to a machine like the AirCurve 10 ST or ASV, and neither of them deliver FOTs either.

I suspect that there are more people who are impacted, but they don't know it because their sleep is better with the machine than it was without the machine.  These people likely have no idea that they could be getting even better, deeper sleep if their machine didn't pulse them throughout the night.

[AlanE]

A machine does not deliver FOT pulses for no reason. More likely it is the CA, OA, or HA, that caused the machine to activate FOT, that is disrupting sleep and not FOT itself since if you had an obstruction with a machine with no FOT capabilities, you (most likely) would still experience disrupted sleep.

[Reznik]

A machine does not deliver FOT pulses for no reason. More likely it is the CA, OA, or HA, that caused the machine to activate FOT, that is disrupting sleep and not FOT itself since if you had an obstruction with a machine with no FOT capabilities, you (most likely) would still experience disrupted sleep.

The evidence is pretty strong that the contrary is true.  I've already explained why twice, in this thread. 

When I use a machine that does not deliver FOT pulses, but otherwise with the same settings, my AHI is higher, but I awake feeling more refreshed.  When I use a machine that does deliver FOT pulses, my AHI is much lower, but I awake feeling awful.  The FOT pulses are what are waking me up, and disrupting my sleep.  Without them, I get better and deeper sleep, my AHI is higher, and I feel better in the morning.  If the apneas were disrupting my sleep, the opposite would be happening:  I'd feel better in the morning on days when I use the machine with FOT because my AHI is lower.


And the second of three studies listed by someone else in a prior post seems to support the view that FOT pulses, by themselves, reduce AHI.  Since the pulses involve very low pressure, they're not doing so by splinting the airway.  They're very likely reducing AHI by impacting sleep architecture.

[isuckatsleeping]

Just adding my personal experience here as well, although I'm pretty sure I have done so already in this thread. I too am very sensitive to FOT pulses. They often wake me up when falling back to sleep, and my body naturally stops breathing as I enter a sleep stage. The FOTs wake me up out of that initial sleep phase. I haven't yet been able to purchase a machine that does not have FOT, so I can't say that I sleep better without a FOT machine. But, I can very confidently say that FOT has a negative effect on my sleep.

[Reznik]

Just adding my personal experience here as well, although I'm pretty sure I have done so already in this thread. I too am very sensitive to FOT pulses. They often wake me up when falling back to sleep, and my body naturally stops breathing as I enter a sleep stage. The FOTs wake me up out of that initial sleep phase. I haven't yet been able to purchase a machine that does not have FOT, so I can't say that I sleep better without a FOT machine. But, I can very confidently say that FOT has a negative effect on my sleep.

FYI- Resmed machines do not deliver FOT pulses during timed ramp.  So, if you set the Ramp to 45 minutes, you should be able to get to sleep before the FOT pulses start. 

Note my use of the word "timed."  Auto Ramp on ResMed machines does deliver pulses.

[isuckatsleeping]

Just adding my personal experience here as well, although I'm pretty sure I have done so already in this thread. I too am very sensitive to FOT pulses. They often wake me up when falling back to sleep, and my body naturally stops breathing as I enter a sleep stage. The FOTs wake me up out of that initial sleep phase. I haven't yet been able to purchase a machine that does not have FOT, so I can't say that I sleep better without a FOT machine. But, I can very confidently say that FOT has a negative effect on my sleep.

FYI- Resmed machines do not deliver FOT pulses during timed ramp.  So, if you set the Ramp to 45 minutes, you should be able to get to sleep before the FOT pulses start. 

Note my use of the word "timed."  Auto Ramp on ResMed machines does deliver pulses.

Ah, yeah, now that I'm thinking about this again. That's exactly what I did. Increased timed ramp to 30 minutes. I wish I could shut FOT off completely though. Resmed should give us the ability to at least shut off the function when using the fixed pressure in CPAP mode, where the difference between OA & CA makes no difference to the machine.

[AlanE]

I would rather have a FOT pulse wake me up or arouse me enough that the cause is corrected than to continue and allow my O2 to plummet further. Everything you are writing is your experience and that's fine but it would not necessarily be true for everyone using a machine with FOT. I guess when it comes to xPAP machines w/FOT algorithms, you are more sensitive than me. I'll take a machine with FOT over one without and never bat an eyelash. Wish you lots of luck on your crusade and many nights of deep sleep. Also, thanks for the information on ResMed FOT.

[Reznik]

The pulses start at 3 seconds into a breathing cessation, well before an apnea, which requires 10 seconds.  It affects you all night long, even if your AHI would have been under 5, and thus would never have impacted oxygen saturation.

That means that FOTs could wake you up 5 times an hour, even though your O2 saturation would never go below normal.  And if you have breathing cessations that are more than 3 seconds and less than 10, it could disrupt your sleep all night long and never improve your oxygen saturation.

I've already explained why the studies support my theory.  I'm not the only one who finds that FOTs impact AHI.  The studies show the same result with larger populations.  There's only two ways that can happen:  Either the FOTs are splinting the airway, which seems very unlikely given their size, or they're disrupting sleep architecture.  Since the whole point of CPAP is to STOP the disruption of sleep architecture, FOTs may very well be counterproductive - even if the user doesn't actually notice them.