Need Help - What's Causing Atypical Flow Rate Shapes

Had one of my better nights with an AHI of 0.69 and minimal leaks. In keeping with this, the majority of flow rate shapes were normal, however, there were two periods with atypical flow rate shapes, which are posted below.

Seeking suggestions on possible causes to account for these.

Unless you're not feeling well rested or otherwise not well, alert, etc, given your AHIs, I wonder why you're concerned about the flow rates.

ElusiveSleep, I can't offer authoritative help, but can say I share your low AHI that is accompanied by two flow rate patterns that raise questions. You have a co-puzzler who is looking into the same matters.

My guesses are these, having seen lots of either or both of your flow rate patterns in my FR every night. First, howevever, the point Julie raises about your low AHI is good, backed up as it by her most important question about how restful your sleep is. My AHI is good, but as much as my sleep has improved, as I feel and low AHI confirms, I suspect it could be much better if I could discover how to reduce my airway's low level restrictions that, in my case, cause many wakeful unaware-arousals as are indicated in some combination of two or more concurrent motions, FR, FL, mini-leak, pulse rate and SpO2-changes and recovery breaths. We often see those with low AHI asking why their sleep is not as restful as they, like me, think it should be.

That first FR of yours:

More than 90% of the many scattered instances of your two-horn pattern (I see in every sleep session) are preceded by always-present but greater irregularities in the immediately preceding crest(s) of the inhale curve. Most often the very next inhalation after a "two-horn" will have a flow limit begin and it will continue for various time periods. In my case I see one to maybe two two-horn maxima in one or a few successive inhalations--not long strings of nearly identical forms like yours. My FR has few if any smooth-curve "caps" at the maximum rate of flow for the sleep session. All said, my opinion is I have significant inspiration/inhale limited breathing, IFL, which may or may not rise, from time to time, to an AASM-defined and scoreable level for RERA or UARS although my AHI is often 0.0. In your instance you have large numbers of successive two-horn breaths that are accompanied by either zero machine-noted FL or a very low level FL'

A pattern some have called some form of a "Norwegian sigh" strikes me as a variant of the second horn. Milliseconds after the inhalation FR has passed the maximum and the rate of inhale has just started to slow(just before its normal sharp drop toward zero and the max exhale flow) rate there is a second sharp rise in the inhale flow rate. That second sharp burst of inhalation produces tall (needle like) positive and negative spikes in the FR curve's inhale-exhale amplitude. I once saw these as puzzling but innocuous. Zooming in on them (mine anyway), I've come to see them as having the same purpose as makes it necessary to clear throat (of phlegm?, whatever) when we speak. Immediately after the "sigh", usually within the next inhale, a short FL often occurs, but not as regularly as a FL will follow your two-horn pattern. I think my "sighs" at about 6-10-minute intervals is an airway clearing defense and that it sometimes clears moveable obstructions well enough and sometimes does not, as it either triggers or doesn't prevent an immediate FL.

If I have another sleep study, I will ask for a Pes, miserable as it sounds, unless I become convinced a measurement by some form of nasal cannula is sufficient. It is my rough recollections (of a Brazilian research team's finding, I think) that experimental control Normals are those who have less than 30% of sleep time with a certain indicated but still significant level of negative esophageal pressure, the Pes being the diagnostic tool for evaluating IFL.

That second FR of yours:

When I see stretches of that I puzzle over whether that is an instance of lip-leak flapping or of palatal prolapse. Visually, the areas beween the zero-flow-rate axis and the inhale and exhale segments of the breath cycle curve usually seem to be about equal. The airway being open and then being snap-slammed shut is common to both kinds, lip leaking and PP. Looking at this and the concurrent leakage rate usually leaves me unable to decide which it is (assuming it is one or the other). In my instances of it--10-50 continuous minutes for the sleep session, mostly in right-side sleep and in the later a part of the sleep session after a pee break--I haven't noticed the pattern being accompanied by any particular change in other sleep or circulatory metrics.

I hope someone will enlighten us. IMO it would be good to have a sticky thread on flow limited breathing. I've been studying my case recently with the benefit of OSCAR zooming features, a Vauto, a CMS50I oximeter and a X2-2 accelerometer (position and motion sensor). My mental model is curenntly and roughly this: an airway "pipe" or passageway, possibly with fixed or moveable and/or growing and shrinking swellings or caving walls, possibly with fixed or moving flagging flaps, probably viscous substances that can move toward pinch-points, possibly with a wave crest. One or more of these impediment factors are present and change the crest of the inhale FR curve maximum in various ways that may or may not make breathing more difficult.

ASB

I can't offer an analysis in the detail that ASB has, but I do concur that the top chart shows flow-limited breathing. Not all FLs are picked up by the ResMed algorithms, and the markers often come right after a detected FL. In case you're interested, I think the little variance around the 0 line between breaths is your heart beat. This is called the cardioballistic effect, or cardiogenic oscillation. It's nothing to worry about in the slightest.

If you are sleeping well and feel refreshed during the day, there's no reason to worry about FLs. If you don't sleep well and don't feel refreshed, that's another story. I am using a ResMed VAuto Aircurve machine to address FLs and the problems they caused for me. This machine provides more EPR/pressure support, which cuts down on FLs. With a low AHI, however, it's impossible to get insurance coverage for a bi-level machine like mine; I bought mine (lightly used) from forum member LSAT.

I agree that the second chart shows exhalation through the mouth. You might want to try taping your lips closed, at least just to see whether that resolves the issue. Somnifix makes strips that adhere well but are very gentle on the skin.

Second chart, "palatal prolapse", not mouth breathing.

Here is a Thread discussing these wave forms and palatal prolapse.

viewtopic/t171982/Mystery-solved-ever-h ... ticle.html

JPB