Flow Limitation Diagnosis / Treatment Help

Hi -

Background:
* I've been on CPAP for 5 years for a diagnosis of moderate OSA. I've used it consistently but I never feel refreshed in the morning. My AHI is fairly low and almost zero for obstructive events. My AHI usually ranged from 5-10 and was dominated by CAs. A took a deeper dive about 8 months ago after discovering OSCAR and have evaluated these CAs, which are almost always in the 2nd half of the night, to be arousal-based CAs or sleep/wake transition CAs. I've ruled out treatment-emergent sleep apnea.
* My subjective sleep quality is almost always very poor. My sleep is extremely fragmented (as per my garmin watch and past sleep studies).
* I've come to the conclusion that my CPAP treatment does effectively treat my obstructive sleep apnea (which was almost all hypopneas in my sleep study) but that my sleep quality hasn't improved because of the sleep fragmentation, and that fragmentation is due to a high number of arousals due to flow limitations. CPAP with EPR of 3 helped round out the top but didn't help enough - and didn't improve my subjective sleep quality
* I've had a few sleep studies in the past 5 years but UARS wasn't identified. A sleep study a few years ago yielded an AHI of 8.7 and RDI of 21.
* I had 3D CBCT imaging done a few years ago and it revealed a very narrow airway bottleneck of 68mm2.
* I'm a couple days into a bipap (aircurve 11 Vauto) and hoping I can find settings that improve my sleep quality.
* I thought I'd start conservatively with EPAP of 8, PS of 3, and IPAP of 11. I then moved to EPAP of 9, PS of 3, and IPAP of 12. Still feel really bad in the morning and my flow graph still looks bad.

Questions:
1) The rounded tops of my respiration don't look horrible to me. I think my issue is that the inhalation of my respiration for 50%+ of the night pauses (goes horizontal) halfway up for 0.3 to 1 second and then resumes going up. I think this pause, which goes undetected with Resmed's FL metric, is the result of persistent flow limitation that is leading to arousals - some of which are minor and some of which lead to CAs - but all of which fragment my sleep. I'm looking for feedback on whether or not this is a real issue - for whatever reason, I can't find FL examples that look like mine.
2) If the answer is yes that's an issue, then what should I do settings-wise? I'm going to try EPAP of 9, PS of 4, and IPAP of 13 tonight, and change trigger from Med to High. I'm hoping more of pressure boost, and early on in the inhalation, will help with this.

I've attached a 2 min zoom-in on my respiration in 1st half and 2nd half of night. Any help would be really appreciated.

gregbe2000 wrote: ↑

Thu May 15, 2025 4:14 pm

Questions:
1) The rounded tops of my respiration don't look horrible to me. I think my issue is that the inhalation of my respiration for 50%+ of the night pauses (goes horizontal) halfway up for 0.3 to 1 second and then resumes going up. I think this pause, which goes undetected with Resmed's FL metric, is the result of persistent flow limitation that is leading to arousals - some of which are minor and some of which lead to CAs - but all of which fragment my sleep. I'm looking for feedback on whether or not this is a real issue - for whatever reason, I can't find FL examples that look like mine.

You are misreading the flow rate graph. Here's a marked up version of a small snippet of your data:



You are inhaling when the flow rate curve is above the red line: Positive air flow means air is moving into your lungs.

You are exhaling when the flow rate curve is below the red line: Negative air flow means air is moving out of your lungs.

It is quite common and normal for there to be a small (up to 1 second) pause at the end of an exhalation before the next inhalation starts. That is the horizontal flat part halfway between the bottoms and tops of the bumps in the flow rate curve. It's NORMAL. That pause is not "undetected" with Resmed's flow limitation detection algorithm because it is NORMAL. And those pauses between the end of your exhalations and the start of your inhalations are NOT leading to arousals or CAs or any other thing fragmenting your sleep---they're just a normal part of the way your body transitions between the end of the exhalation and the beginning of the next inhalation.

2) If the answer is yes that's an issue, then what should I do settings-wise?

It's NOT an issue. So don't change your settings because you see breathing patterns that look like these do.

I'm going to try EPAP of 9, PS of 4, and IPAP of 13 tonight, and change trigger from Med to High. I'm hoping more of pressure boost, and early on in the inhalation, will help with this.

Don't do this. You don't have a problem that needs to be addressed by changing the settings, particularly since it seems like you do not yet fully understand the data you are looking at.

If (and it's a big IF) you are experiencing enough arousals during the night for it to be affecting the quality of your sleep, you need to first look at what's going on around the events that the machine is in fact scoring. The fact that your machine is scoring some CAs during the night is an argument against raising the pressure: Too much pressure can cause CAs in some people. You don't have enough CAs (yet) to pose a serious problem, but it is worth looking at those CAs and seeing how many of them are post arousal CAs that indicate you're not sleeping well, but the sleep problem is not necessarily respiratory related vs how many of the CAs might be real.

Thank you for your response! I didn't notice there was a response until just now. I really appreciate it. Yes, I understand now that the this is a normal transition from exhaling to inhaling - I just couldn't find other flow rate data that was as exaggerated as mine seems to be at times. I do get a lot of CAs on some nights, normally in 2nd half. Almost all, if not all of them, can be attributed to an arousal first as I can see a spike in respiration prior to the CA - these typically cluster, I assume due to some amount of high loop gain breathing instability. I can get a lot of these sleep/wake transition CAs and I'm not sure of the underlying reason. I was hoping if I fixed the flow limitation issue that I'd see improvement, but that's not the case yet. I'm getting pretty depressed, as I've discovered by video'ing my sleep that I also have a fair amount of time with PLMS - I verified with video and it correlates to a distinctive look in my flow rate chart (periodic blips of higher amplitude flow maybe due to breathing deeper on every movement). My movements involve my shoulder/upper arm and trunk - not so much as I can tell with my legs. I have no pain or tightness, without the video I would have never guessed this was going on. PLMS did register with my last sleep study with an index of 14.5 but very few arousals based on this so my doctor didn't really consider it relevant. It didn't register at all in previous sleep studies. I've noticed the length of the PLMS episodes being highly variable night to night - so one sleep study could hide or exaggerate the issue. I attached a pic of this below. When I go back to my historic cpap data going back 5 years I almost always have portions of the night that look like this. I assume this has always been fragmenting my sleep. I'm not sure what the remedy here is - I don't want to take drugs that could worsen this over time. I do the baseline stuff already - I exercise daily, good sleep hygiene, etc. If there's an advice out there for this then I'd really appreciate it. I've sifted through some of the threads with this - and I'll try experimenting the Mg supplements to start, but in most of the threads there is pain involved, not for me. My pain is being exhausted every day.

similar case here. my UARS is caused by a large tongue and it's hard to treat to satisfaction.

Please try napping in prone position and see if flow limiations disappears. My suggestion is to avoid sleeping on your back at all costs.

musculus wrote: ↑

Tue May 27, 2025 6:10 am

Please try napping in prone position and see if flow limiations disappears.

What flow limitations are you talking about?

Yes, I think sleeping in prone position helps, but it's not comfortable to me and I can't stay there. Sleeping on back produces the worse results, I wear a vest with a ball on the back to prevent it. I sleep on my side 95% of the night.

I think my UARS is taken care of while on my side and using a bipap. My flow chart seems ok for flow limitatinos, but crappy due to a ton of sleep/wake transitions causing CAs and PLMS.

gregbe2000 wrote: ↑

Wed May 28, 2025 10:45 am

Yes, I think sleeping in prone position helps, but it's not comfortable to me and I can't stay there. Sleeping on back produces the worse results, I wear a vest with a ball on the back to prevent it. I sleep on my side 95% of the night.

I think my UARS is taken care of while on my side and using a bipap. My flow chart seems ok for flow limitatinos, but crappy due to a ton of sleep/wake transitions causing CAs and PLMS.

Since you can do a lot of side sleep then probably worthwhile to try a low constant pressure setting such as fixed 9 cm with epr =1or 2. Maybe that will reduce the CAs. And can you look at the flow chart just before the clusters of CA and see what kind of flow pattern causes the arousal and open airway CAs?

I'm on a bipap and trying an EPAP of 7cm and IPAP of 10 cm. That seems to take care of the flow limitations but I have about an hour of PLMS movements (so I assume bad sleep) in the 1st half of the night and a lot of sleep/wake transition CA clusters in the 2nd half. I think I have an arousal that kicks off these CA clusters but I don't know from what (it's a movement on the video but not sure what causes the movement) and I must have high loop gain as I get waxing and waning and repeated CAs for long periods (it's not CSR, but looks like it could be) afterwards. I'm not sure if I can mitigate the CA clusters and loop gain by minimizing pressure and pressure changes - but that's what I'll try. I'll move down to 6cm EPAP and 9cm IPAP tonight to see if this still keeps the flow restrictions in check. Chatgtp recommended changing rise time to a longer stable rise time to have a more gradual pressure change on the inhalation - but I haven't gone there yet.