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input requested, need for low cost arousal sensors? - BB63 - 08-08-2020
Greetings all,
Thanks to many on the forum, my apnea related issues are greatly diminished. It's clear that apnea and related issues ARE NOT responsible for my perception of extremely poor sleep and feeling like crap all day long.
I need to investigate other issues, and next on my hit list is arousal(s). We (in the forum) don't evaluate them often, though the professional sleep study people realize how devastating they can be in reaching and staying in deep sleep. The body heals itself during sleep and without proper sleep, we as people are far less functional and less healthy than many realize.
I need to know if I am suffering from arousals. The best arousal detector (gold standard) is strategically placed EEG sensors. However, I think the output from a very inexpensive accelerometer might serve just as well. I have discovered just how cheap they are and I am making progress towards building and designing proper hardware and firmware to do the job. For my purposes, a standalone datalogging accelerometer might be adequate (without integrating it into OSCAR). However, I am curious whether there is sufficient interest among the forum members for me to design a more complete and user friendly version that integrates seamlessly into OSCAR which would utilize OSCARs ability and flexibility to display data in a user configurable way.
This would (for now) be a 3 axis accelerometer with firmware to compute movement of limbs and give positional data as we sleep. The cost could be as low as $50 for the datalogger and the accelerometer combination-though this is preliminary.
I'd like to know whether the forum membership would have interest in evaluating whether they have arousals by sensing arm and or leg movements while they sleep and having OSCAR display the data??
Please COMMENT, whether Yay or Nay, or PM me if you like.
TY and sweet dreams.
AB
RE: input requested, need for low cost arousal sensors? - 2SleepBetta - 08-09-2020
BB63,
At least one other member, Kappa, and I are using accelerometers for our studies and we have posts of some results. I have seen wrist wearable devices by WIT available online for under $40 (and more for 9-axis devices: magnetometer and gyro features). My 3-axis devices were made by Gulf Data Concepts. The GCDC's data loggers can be set to a wide range of sampling rates, dead zone durations and revival indicators, etc. Those are simple, easy to use, and they write to a CSV file. You might want to look at WIT's and GDC's devices. The latter's operators' manuals are online. I use Excel to convert the CSV data to the format OSCAR will import--import as if the emulating data came from a Somnopose device--and OSCAR displays our sleep position and motion graphs integrated with the other sleep graphs. The data conversion is scaled in different ways by Kappa and I, but the Somnopose "Inclination" feature indicates motion for both of us along with "Orientation" that shows our sleep position. I think some members use one or the other of those two Somnopose slots in OSCAR to display SpO2.
Here are tangential details of my similar quest to understand and assess sleep disturbing arousals with the benefit of an accelerometer. This may be helpful, particularly in correlating deformed shapes (a link) of FR curve peaks with FL and motions, as well as in correlating strings of minor irregularities in the patterns with "incoming" FL or FR spikes.
[attachment=25413]
I have two motivations for study of sleep: First, I too and many want to know what I might do to reduce anything that is RERA, or near the RERA threshold. I'd like to reduce the numbers of spikes in the FR curve. I once saw those as benign but now see their enlargements as a kind of throat clearing--successful and unsuccessful about half the time: no FL occurs at the spike or one still does immediately after the spike. (Second, being new to these medically involved topics, the topic and its puzzles fascinate me.)
As I take long looks at series and zooms of FR, FL , deformed FR-curve peaks and (nearly coincident) sleep motions the questions that continually arise are which is cause, which is effect. The presence or absence of what seem to be recovery breaths is strongly suggestive. But against my background of persistently irregular peaks, the sleep motions may be triggered by a move for, say, comfort, not a breathing disorder. One MD, Peretz Lavie, a sleep specialist researcher in Israel, wrote--ages ago in the sleep medicine era, ca 2002--that sleepers move 26 times (as I recall) a night during sleep and my experience is often close to that with motions correlating with FR changes and some FL. As I recall, researchers use the term IFL for inspiratory flow limited breathing.
My VAuto has dramatically reduced FL, after my AirSense AutoSet got me down below AHI 1.0 (from high 50's), so why bother with my low AHI's members are prone to ask. Again, the drive to understand is important, plus I had moderate and then severe untreated OSA for so many years I can't remember how good sleep felt before; clearly sleep is greatly improved, but possibly can be made better with reasonable changes. Further, as with measures that stopped bad lip flutter and (much preferred ) supine sleep--for this nasal pillow using mouthbreather, there are likely to be measures that can be taken reduce the disturbances that are so evident in the FR peaks and FL.
First, try a longer period of eliminating, say, dairy from my diet. But liking it all, ice cream, yogurt, NF milk and cottage chees, I tried eliminating them for just a week and saw no difference. Before a longer trial or other measures, I want to have a good handle on patterns of metrics and generalizations that seem to be emerging. Low levels of phlegm, for example (if tissue is not the problem), may be coating and building constricting waves in my airways, much as wind kicks up water waves and flag waving. Certain patterns and regularities of VAuto-OSCAR FL, continual inhalation peak deformities and throat clearings, if not, actual phelgm removals, suggest wave or flagging motions of some kind in airways.
RE: input requested, need for low cost arousal sensors? - kappa - 08-09-2020
Here's a comparison of use of a 3-axis accelerometer (bottom red graph) vs using a rotational "tuning fork" sensor (top - log, middle raw values) from a 6 minute interval from my sleep (@ 5 samples/sec):
[attachment=25420]
The rotation sensor is much more stable around zero while the normalized accelerometer reading (which should be exactly 1g when stationary) can fluctuate quite a bit at different orientations (due to differences in the different axes I guess). I've seen similar artifacts in 2SB's graphs.
I then use a log calculation to show more detail of small movements. I guess both are usable... but the rotation version is easier to use.
Here's the corresponding flow rates (for completeness):
[attachment=25421]
I think the cheaper WIT Motion device uses regular bluetooth and has significantly shorter battery life. The 9 axis low energy bluetooth version (WT901BLECL) I'm using has over 10 hours battery life.
RE: input requested, need for low cost arousal sensors? - Geer1 - 08-09-2020
As 2SleepBeta and Kappa demonstrated you can determine a lot of this based on flow rates alone. That and a video camera recording and oximeter (the two items plus OSCAR data I use) can allow you to distinguish a lot about sleep quality. Oximeter data is probably the least helpful but it is a good initial test to ensure you aren't having desaturations that could maybe be treated by better pap machine etc. Once you confirm that it is near useless other than in rare cases like noticing slight improvement in SPO2 values like I have recently noticed.
The problem with using accelerometers for arousals is that arousals aren't required for movement to occur nor does movement occur with every arousal. EEG is the only way to accurately diagnose arousals. A video recording will show you movements and a lot more about them rather than an accelerometer will ever tell. Instant accelerometer data that can be incorporated into OSCAR makes for much quicker review though.
I am not sure if 2SleepBeta has seen some of my other posts or is just commenting about dairy intolerance for another reason but the long and short of my experience is explore all avenues especially if you have other symptoms (ibs, nasal congestion, reflux, things like that). My life has changed significantly after doing elimination diets and a couple other changes. I am fairly certain either removing dairy or undergoing antimicrobial treatment is the cause of feeling significantly better. Like so many others my treated ahi was always less than 5 yet I still never felt good and in fact was starting yo feel worse and other non ahi related breathing stats were also getting worse (tidal volume and ventilation).
Food intolerances mess up all sorts of things, fatigue, sleep issues and breathing being commonly affected. Anyone with fatigue and other symptoms should research food intolerance and try elimination diets, removing dairy, wheat/gluten, soy, eggs, nuts etc for a month is a good start. Imo if you have all these types of symptoms it is likely to be something bigger that is the issue, not just a restricted or blocked airway. One week is nowhere near long enough although it can be possible to notice an improvement in that time. My improvements for the most part have been gradual since mid June when I went dairy free and started antimicrobial treatment. Some of my digestive symptoms were remedied fairly quickly though.
In my case I think it was dairy but there are a lot of food intolerances that can cause similar issues so if you think it is a possibility explore them all. Break the elimination diets up into manageable diets. One month is a very short time i the big picture, many of us have already been fighting these issues for many months if not years.
Just to add a disclaimer as mentioned I am not 100% sure the dairy removal is what has caused my improvement . Either it or my antimicrobial treatment did cause improvement for the first time in 1.5 years I have been struggling with these issues though (I think it was likely a combination of both), I have numerous data to prove my health has improved just dont exactly know for certain why. I am still not back to what I would consider normal or feeling great but it has definitely been a move in the right direction.
Good luck and keep searching. It is easy to fall into a rabbit hole (like pap treatment) and chase it for far too long. In short the only thing you could maybe try is a Vauto but I think in a lot of peoples cases the improvement you may find with such a treatment is by treating a symptom and not necessarily the cause.
RE: input requested, need for low cost arousal sensors? - BB63 - 08-09-2020
TY Geer1.
I was fascinated by your message content! I'm curious, do you practice Functional Medicine? I ask for several reasons. First, the elimination diet-it is the first step towards recovery and should be followed up by eating organic foods rather than supermarket/prepared foods-these prepackaged meals are packed with biotoxins, preservatives, dies, and chemicals that the FDA don't even require disclosure on the products label.
Did you dump man made vegetable oil yet? Bread and processed flour? Have you been tested for Leaky Gut or food intolerance (notice I didn't say food allergies). It's clear from reading your post that you recognize the difference, which is also cornerstone of FM.
And, finally, you said 'treatment is by treating a symptom and not necessarily the cause'....which again is fundamental in FM.
Have you gotten off pharmaceuticals that you don't absolutely need? I have dumped 2/3's of the pharmaceuticals that I was previously consuming! Pharmaceuticals are notorious for treating symptoms only-but they have side effects and often destroy the microbiome or worse! In these days of covid, a weakened immune system can cost the patient his life. Dumped sugar (a biggie)?
Just curious whether you practice FM!
=========
I do understand that arousals are best detected by EEG technology and that many arousals don't produce actual (major) physical moment. But detecting RLS and related maladays with an accelerometer would be fairly conclusive evidence of arousals. I became interested in detecting arousals because I always feel like I haven't slept well, even though the sleep data doesn't show major apneas and other types of known sleep disorders. Hence my interest in the accelerometer and getting more conclusive evidence that I do or do not have arousals.
TY for the great info though! I hope you pursue and make improvements to your food intake-food is the best medicine!
AB.
PS:I might build an EEG (single point), though I am currently working on the accelerometer design.
RE: input requested, need for low cost arousal sensors? - Geer1 - 08-09-2020
I am a mechanical engineer and take naturopathic and functional medicine with a grain of salt as some of it appears to have basis but some of it does not. I have seen multiple doctors including a naturopath but he was more interested in things like adrenaline fatigue and wanted me to try taking adrenal extract which I did not agree with at all after researching it. He did arrange the SIBO testing after I brought up that I thought it might be an issue which is ultimately how I got the antimicrobial treatment but if that was part of the reason for improvement I think it was more blind luck and prodding on my side then his knowledge. Overall I am willing to believe a lot but if there is data disproving something then I shy away from it, if it is just something complicated and the science isn't good enough yet (food sensitivity) then I am a lot more willing to try.
I might be one of very few individuals that actually ended up doing elimination diets via a medical doctors recommendation, that being my internist. Then I was put into contact with a dietician who has been the most helpful. Part of this was due to covid, doctors were most interested in getting a sleep study done but it got cancelled and still hasn't been done. As another note IGG or food sensitivity testing as some naturopaths like to call it is complete bunk and has been researched and tested multiple times and proven not to be accurate for these issues. Even my naturopath seemed to understand this and recommended just trying elimination diets and said I could do the testing if I wanted. My dietician says they are useless and that the only test that works for intolerances are elimination diets. They are a bit time consuming and a pain at times but if a person is struggling with health issues then it is a small price to pay.
There is enough science and research to support stuff about food sensitivities/intolerances. Even medical doctors sources like uptodate make note of many of these things although the functional medicine side of things has the most information (due to accepting things that aren't yet fully proven). I also have family members with similar issues (an aunt with gluten sensitivity) and Dietician said she is sure that these are all real things as she sees it all on a daily basis. The problem is that all of this stuff is complicated, it is a mixture of digestive and immune systems, there is no testing for it and therefore mainstream medicine sort of turns a blind eye on it because they don't yet know the science behind it.
As for diets I started out with a low fodmap diet and was primarily eating meats and acceptable vegetables and had heavily cut out sugars and carbs (was doing a mixture with specific carbohydrate diet). I started to feel a bit better but was still up and down. Then I noticed my up and down seemed like it might correlate with lactose free dairy intake (which I was on since lactose is a fodmap), I did a couple quick tests that seemed to support that dairy caused flare ups of my digestive symptoms (constipation, bloating and reflux to the point I had started to take laxatives daily, elevated my bed for reflux and for a while had been on PPIs). It was the up and downs that had also made me wonder about SIBO which fit some of the symptoms and which my cousin suffers with. I got tested and came back borderline positive (either positive or fast transit) and started the antimicrobial supplements (Candibactin AR & BR plus NAC) to treat it at the same time I started going dairy free. That is part of the reason I am not sure which one has helped me.
In 2 months of dairy free/antimicrobial treatment my digestion has improved significantly. I haven't needed to use a laxative in this time, I haven't felt signs of reflux, my chronic cough (probably from reflux) has gone away, my tidal volume and minute ventilation which had been dropping started improving, a wart like thing on my finger that doctors had tried treating for over a year(multiple nitrogen freezes, acid treatment and even an acid with chemotherapy drug) healed on its own. During this time I have lost almost 30 lbs, gotten off almost all of my medications (the only one I still take is Dymista and only on a every few days case compared to the daily/twice daily had been taking it). My cognitive ability has improved and my fatigue levels have dropped substantially. I had been struggling to work 30 hours a week and a day out fishing (my favourite hobby) etc would wipe me out for a day or two. The last few weeks I have been working 50-60 hrs a week and this past weekend I went fishing for 4 12+ hour days in a row. I haven't had this kind of energy/ability in a long time. I still don't feel healed though and it will be curious to see how things change these next couple months as I continue to be dairy free (I am off antimicrobials now so if they were helping with something but didn't solve it then I would expect my symptoms to start to relapse).
Individual spikes or weird shapped breaths in your flow rate are often a sign of arousal. If you look at Kappa's data you can see how almost all his accelerometer data correlates with breathing. The problem and near impossible thing to solve is figuring out which is the actual problem. Is it the breathing, the movement or something else causing both? Only way to figure this out would be with polysomnography quality equipment capable of accurate syncing and without EEG data I think the rest is kind of a waste of time.
My thoughts when it comes to PAP treatment is that if you think breathing is the problem then it can be worthwhile to try Vauto with higher pressure support. If that doesn't solve your symptoms and you don't have obvious AHI/breathing issues then there is likely something else at play you need to figure out. If you think breathing is unlikely the symptom and have numerous other symptoms you are probably right. The hard part is figuring out what it is.
RE: input requested, need for low cost arousal sensors? - BB63 - 08-09-2020
Geer1, your last message left me stunned (in a good way), you've seen what the very limited FM/naturopathic treatment has done for you already.
But, I think you would benefit by doing a more complete plan rather than just the limited plan you have already done. I am an EE, retired at the age of 40 for medical reasons, namely Early Onset Arthritis. I believe your naturopathic doctor was clearly on the right track-but didn't go far enough! You're the final judge on that topic however!
The elimination diet, followed by a more proper food intake lifestyle change is only the beginning. The elimination diet should be no soy (very inflammatory, omega 6 to omege 3 ratio makes it unsuitable for human consumption), no flour/Gluten (especially processed man made flour, which causes Leaky Gut and sleep disorders), minimize carb and sugar intake (except for that which you'll get from naturally occurring and healthy fruits and vegetables), all man made vegetable oils including innocent sounding variants such as canola oil, corn oil, safflower, pecan etc (use Olive or coconut oil instead), eggs and dairy are controversial though, many believe the food that hens and cows are fed is the problem-not the dairy products themselves. After the elimination diet, we switch to a more healthy diet (without the foods in the elimination diet). After the diet, we get you on a prebiotic and probiotics, especially the prebiotics!! Don't get sucked into expensive pills, Potato Starch is a powerful prebiotic and it's cheap...without prebiotics, the probiotics you take are a waste, so you need both! If you don't take both, then just take the prebiotics. Prebiotics fight SIBO by making the microbiome more favorable to 'good bacteria' which crowd out and discourage the bad bacteria (especially yeast species). The bacteria in your microbiome connect directly to every system in your body (especially the brain) through chemical messengers and the microbiome is 2/3 to 3/4 of your immune system! You microbiome and the proper function of the cell's Mitochondria keep the body alive! After sometime on the improved regimen, the food intolerance test is repeated-elimination of chemical additives and other toxins in prepared foods, makes many of the previously detected intolerance(s) will be gone and the improvement in the microbiome function and more proper feed to the cell's Mitochondria also help.
Do elimination and a more proper diet for 1 month, and then look at your body for inflammation signs and you will be a believer!!! Get your basic blood work repeated after 1 month, and your doctor will say 'holy crap, your results are so much better' and he WILL ASK YOU 'what you did to get the improved blood test results'! Those are sweet words, when I heard them from my doctor it FELT SO GOOD!
I joined the forum in 2018, my 'new member intro' post at http://www.apneaboard.com/forums/Thread-New-Member-Intro--21603 might be of interest to you as it contains my history and first impression of Functional Medicine and what it had done for me in such a short trial!
If nothing else, follow Dr. Mark Hyman on youtube, he is for real and is a major player when it comes to FM and gives much information to followers for free. He is actively involved in teaching other doctors who have seen the light regarding FM and want to transition to FM. He also addresses societal issues as they affect our health. He has convinced several big players in the processed food business that they need to change the way they use additives in their products. There are copy cat youtube doctors, but Dr. Mark is the real deal::>
In a nutshell, FM addresses the entire body condition rather than treating a symptom while not recognizing the root cause of the problem is likely not where the symptoms are found!
Hope this helps, although I hope it's not to far off topic for the forum. I'm glad to correspond via email if you like.
AB
PS:At the risk of over doing it, I'd like to discuss just one issue that profoundly effects our sleep, but that conventional doctors and even sleep specialists are totally unaware of! So, let's take a quick look at Leaky Gut and how it destroys sleep and eventually kills us. Leaky Gut is caused by the intake of Gluten and is exacerbated by food additives and other biotoxins that the FDA allows processed food producers to include in our foods. Leaky Gut has been proven and many labs actually test for it these days and the traditional doctors are coming around to some extent.
So, we eat man made processed Gluten, which irritates our gut and causes the nearly perfect seal between our intestine and the rest of the body to become compromised. The actual sealing mechanism in our intestine walls is a spiraling single molecule thick layer of tissue. It is fragile and only recently has been proven by high tech physics instrumentation. The compromised seal in the intestine walls allows very small food particles to leak into the body cavity, normally the digestion process in the intestines would completely dissolve/digest these food particles and they would STAY in the intestines. Once undigested food particles leave the intestine, the body's own immune system recognizes them as invaders and attacks with all its might! Antibodies to food are produced, which the food intolerance test can measure. Your body is ignoring other important functions because it is attacking what it thinks are bacteria invading the body. This attack is like a 10 alarm fire-the body is totally committed to fighting off these invaders and ignores all else. So, how can this negatively effect sleep?
Sleep is a time of healing, especially in the brains blood-brain barrier. But all systems in the body heal during sleep. When there is Leaky Gut, the body's normal cycle of healing, cell renewal, Circadian Rhythm, etc DOES NOT HAPPEN. The body follows Circadian Rhythm, and organs are very active according to the Circadian Rhythm clock-even though we are sleeping. Stress hormones, especially Cortisol, Adrenaline, Insulin and many others disrupt sleep as the body is under attack. C-Reactive Protein (an indicator of inflammation or infection) soars, before I started in FM, my CRP was 90, the normal range is around 1!!! It is currently running around .7! The only 'cure' for this insidious condition is to eat less Gluten/processed flour although the elevated CRP isn't conclusive (by itself) as it can be caused by other factors)!
Basically the body is under attack and it's biology considers fighting off the invasion is more important than sleep!!! So, we have sleep disorders that aren't apparent because the symptom is severely disturbed sleep. Lack of sleep kills us slowly and our society and traditional medicine doctors regard sleep disorders as something that can be fixed or treated with a CPAP!!!
Don't believe you have Leaky Gut? Get the test, check your Cortisol and Adrenaline during the night time hours. Check the CRP. Try to realize that RLS and multiple arousals are a symptom of your body's immune response to blood serum food particles from Leaky Gut!
And, finally, is the CPAP a treatment of a symptom, when the real cause of erratic breathing during sleep lies elsewhere? Again, I hope this helps.
RE: input requested, need for low cost arousal sensors? - kappa - 08-10-2020
(08-09-2020, 06:48 PM)Geer1 Wrote: Individual spikes or weird shapped breaths in your flow rate are often a sign of arousal. If you look at Kappa's data you can see how almost all his accelerometer data correlates with breathing. The problem and near impossible thing to solve is figuring out which is the actual problem. Is it the breathing, the movement or something else causing both? Only way to figure this out would be with polysomnography quality equipment capable of accurate syncing and without EEG data I think the rest is kind of a waste of time.My CPAP and accelerometer data is synced to within 0.5 seconds through the use of simultaneous leg movements and distinctive breathing at the start of the night (then manual adjustment before import in to OSCAR). EEG I also base off the same PC clock. Adding EEG visualisation to OSCAR would help. Here's some EEG (+Spectrogram), movement and flow data. I move from NREM3 in to various levels of arousal and NREM2. The trigger in this case appears to be the leg movements rather than any breathing disturbance (breathing seems regular the for 13 minutes prior).
[attachment=25457]
(08-09-2020, 10:50 PM)BB63 Wrote: And, finally, is the CPAP a treatment of a symptom, when the real cause of erratic breathing during sleep lies elsewhere? Again, I hope this helps.Humans (well, biological life in general) are annoyingly complex and we're all different, so definitely need a good data driven approach here...
RE: input requested, need for low cost arousal sensors? - BB63 - 08-10-2020
TY for the screen capture, it is extremely telling, though I confess I am not absolutely positive what each trace is (ie what it actually depicts). Mainly, I am not quite sure what the inclination trace is. I notice the values in the inclination trace are from zero to 360, so I believe it's positional data...whether the patient is on the back or on the left or right side.
I think the spectrogram is a capture from the EEG, which was analyzed for it's spectral characteristics by Audacity (a cross platform open source audio editing and analysation program). The detected frequencies in the output of the spectrogram strongly correlate to sleep stages. I'd like to have an EEG for my own use someday!
I notice the inclination trace correlates well to flow anomalies, if inclination shows movement detected by the accelerometer, the evidence is strong that an arousal has been detected.
Thanks for sharing the data!!!
I have been studying the companies that you and 2SleepBeta referenced, and their hardware offerings. I'm not sure I would choose either of those vendors, both have problems. But, I am still looking into the hardware offerings and I'll get a more appropriate post to you and 2SleepBeta sometime soon. Relative to the formula's given, I don't quite understand them. Possibly I am trying to over simplify, or maybe I don't know what the raw data format is from the chip they use.
When I first envisioned basic accelerometer datalogging and graphing (for my own use), I thought reading of the 3 dimensional accelerometer outputs depict whether the patient was on their side or on their back. But, I also thought that I could get the magnitude of the acceleration directly from the raw acceleration data by using math to analyze the slope of the line between each datapoint, which would give me the magnitude of the movement without the need for a gyro, barometer and temperature compensation.
With regard to the power consumption (battery life) skyrockets when a gyro is used, the chip uses about 10X more power. When I determined this, I hoped I would be able to achieve positional info and magnitude of the acceleration without having to resort to powering up a gyro, barometer or temperature sensors.
I'm still mulling it over!!!
If anomalies in the flow rate are indicative of arousals, then I am having hundreds of them each night! I attached a few examples iof my zoomed in flow rate from last night. Note that these flow rate inconsistencies DO NOT happen in sync with any apnea related events and that my AHI is very low overall.
More later.
Aloha, AB
RE: input requested, need for low cost arousal sensors? - kappa - 08-10-2020
Hi BB63,
Inclination trace is a measure of movement (because we're using the Somnopose input that's what OSCAR gives us). It's using the rotational sensors only (which don't use much power from what I can see...) and is based on the 100 x the natural log of (1 + sum of the absolute rotation velocities (in degrees/sec)). So 0 deg/s = log(1) = 0, 1.71 deg/s = 100 log(2.71) = 100, 6.39 deg/s = 200, ..., 147.4 deg/s = 500, etc. Details are not really that important, it's just a visualisation. I have some code to count movements and plms and have used 100 (1.71 deg/s) as the threshold for determining movement, which doesn't seem much but seems to correlate with arousals in my case. I have position data as well but didn't include it in this grab (I was on my side).
Regarding the formula for the accelerometer based graph (rather than the rotation sensor one), that was calculating the absolute acceleration (in g), i.e. sqrt(ax^2+ay^2+az^2) and subtracting 1 (i.e. force due to gravity).
The spectrogram is generated from the EEG captured by my Zeo bedside via the serial port output, using visbrain-python/Sleep, using a 2s multitaper visualisation after passing through a 0.5-40Hz bandpass filter (order 8) to remove 50Hz mains power noise...
In my case I have PLMS, probably due to RLS, and suspect the origin of much (but not all) of my sleep disturbance is initiated with the limb movement, rather than the limb movement being a consequence of a respiratory effort related arousal.