[Equipment] What do you think of the Resmed FOT? I think it is bad.

[liuzilong]

My machine is Resmed S9 AutoSet. It has a Forced Oscillation Technique (FOT) feature, which is designed to detect whether a breathing stop is caused by central apnea or obstructive apnea. However, I’ve noticed something strange—it tends to trigger when I breathe slowly as I'm falling asleep. This has woken me up on several occasions, which has made me question whether it’s actually helping my sleep or interrupting it.
Here’s my suspicion: The FOT might be acting like a gentle "pat" from a sleeping partner. It doesn’t seem to cause a full awakening, but rather a kind of micro-awakening—just enough to disrupt my sleep cycle. It could be lowering my AHI (Apnea-Hypopnea Index), but at the cost of my overall sleep quality.

For example, in this graph, I don’t breathe for about 20 seconds, which I think is acceptable, and my O2 level will absolutely not experience a significant drop. But the flow rate fluctuates at a 4Hz frequency during this 20 seconds, just like a phone message buzzing for 20 seconds while I’m sleeping, just to determine whether I have a CA or OA. I think this feature is bad for our sleep. What do you think? At the very least, I think ResMed should give us an option to turn it off if I don’t care whether it is OA or CA. I just want to have a good sleep. Maybe some of you don't even feel it during a CPAP therapy, but I think it is bad even if you don't notice it.
To test this, I’m planning a purely subjective experiment next week. I’ll track how I feel during the day based on my energy levels and compare that to how well I sleep (i.e., the amount of time I spend sleeping, which I can measure). I’ll use my brother’s CPAP machine, which doesn’t have FOT, as a comparison to see if the lack of this feature leads to a noticeable improvement in my daytime energy levels.
Has anyone else experienced this issue with FOT? I’d love to hear your thoughts and experiences in the comments.
To anyone who is bothered: This feature will not work during the ramping time, so I set the ramp time to 45 minutes. This allows me to fall asleep. But as I said, I suspect this FOT feature is bad for our sleep.
The original discussion is on the apnea board:
https://www.apneaboard.com/forums/Thread-Central-Detection-Driving-Me-Nuts

[Crimson Nape]

Since turning this option off on a Resmed is not possible, I think the next step is to explore other CPAP brands. Seeing your location, you have a slew of CPAP manufacturers. Some are and some are not available to others on this forum. This can make a recommendation difficult. Not knowing how devices are made available in your area, I would see if any allow a short term rental to see if you like their performance and features before buying.

- Red

[Rickyricardo]

I'm not a physician but I'd think that stopping breathing for 20 seconds at a time could result in a respiration rate of 3 times a minute which is not acceptable, falling asleep or not.

Does this do the same in CPAP mode?

[liuzilong]

This feature is enabled by default in almost all Resmed machine. you can look at any apnea event and zoom in or normalize the wave form. No matter what mode CPAP or APAP. 

20 seconds may sounds intolerable, but the oscillation is introduced if I don't inhale for merely 4 seconds. Many time I am about to fall asleep and the mask starts "vibrating". Exhale, hold your breath for 10s and try to inhale. That's what I experience every day.

[SarcasticDave94]

I myself would find not breathing 20 seconds to be totally unacceptable. The FOT does bother some, some like myself it didn't. What I couldn't accept would be a 45 minute Ramp with no therapy.

To avoid this you'll need to choose another brand than ResMed it seems.