First OSCAR data

[lars_the_bear]

Hi folks

FIrst, happy Christmas to anybody who's reading this on Christmas morning

As some of you may know, I've been recommended CPAP by a cardiologist because of frequent PVCs (palpitations) that started about six months ago. I've had two sleep studies with conflicting results, and it's not clear whether I have sleep apnoea or not. I don't have any other symptoms except the PVCs, and after six months of extensive tests, I've been told that I'm in perfect health. However, I have unexplained low oxygen saturation, not only whilst I'm asleep, but particularly when I am. And the PVCs, of course.

Anyway, I finally manged to get through a whole night with the mask on, and I'm posting the first data from OSCAR that I think is trustworthy.

Although I have medical background (decades ago), I have no expertise in sleep disorders at all. I have only the vaguest idea what these graphs show.

However, I note that the pressure was always above the minimum of 5cm set on the machine, and peaked at about 12cm. I don't think the machine increased the pressure to compensate for leakage, so I guess there must be some other reason for it to increase the pressure.

Although I couldn't fit it in the screenshot, the pressure peaks are all accompanied by huge increases in respiration rate -- as high as 30/min in places. My respiration rate doesn't increase that much even when I'm running, so I don't know if that's normal during sleep.

So -- does this look like a typical picture of sleep apnoea? When the report says AHI=0.66, does that mean it was that low with the help of the machine, or what it would have been without the machine?

Thanks for any suggestions.

Best wishes
Lars

[rick blaine]

Hello again, lars,

anybody who's reading this on Christmas morning

Do bear in mind that this forum is based in the US, and the majority of users live in America, and thus are at least five hours behind.

I'm not (five hours behind). I'm out in Gloucestershire.

And the first thing I notice – even without the resps-per-minute – is that you are hyper-ventilating. For a male of 5' 8" (1.72m), I'd expect a mean tidal volume of 400 to 440 cc, and a minute volume of 6 litres. Your mean tv is 520, and your mean minute vent is 8.63 litres.

For a healthy male of (age) 30 to (age) 60 and of average fitness, I'd expect minute resps of 12 to 15. And I note that you say (in another thread you started) that you are fit, run, and do exercise. And yet here, your resps are 16-20 while sleeping.

Is there any reason that you or your doctors know of why you might be hyperventilating?

As you may know – given that you mention a background in medical education – in the NHS early warning system, if you have a pulse of 90+ and resps of 20+ and a temp of 38+, they'd be looking for either overt or covert infection.

Hyperventilation that isn't appropriate to context can lead to cardiac symptoms – which, again, you mention in another thread.

As to your question:

does that mean it was that low with the help of the machine, or what it would have been without the machine?

the sensors in the machine record what happens 'with the help of' the machine. You could, in theory, set the machine to minimum 4cm and maximum 4 cm – which is as close as you can get to 'no machine' at all. But there have been patients whose AHI has been reduced by 4 cm (see Pugsy for details). So to be absolutely sure, you would need yet another sleep study. Perhaps the full, 16-channels, over-night-stay-in-the-sleep-lab version this time.

That is hard to get on the NHS, and not every NHS hospital has a sleep lab, so you'd need to be referred 'out of area'. There are a couple of sleep labs in the private sector and in London. Cost about £1700, and need a doctor to refer.

Having said that, my hunch is: you do not have sleep apnea.

[lars_the_bear]

For a healthy male of (age) 30 to (age) 60 and of average fitness, I'd expect minute resps of 12 to 15. And I note that you say (in another thread you started) that you are fit, run, and do exercise. And yet here, your resps are 16-20 while sleeping.

Is there any reason that you or your doctors know of why you might be hyperventilating?

Thanks, and: nope -- and it's particularly the case at night. Since I had Covid my respiratory rate has increased when awake -- from 10-12 to 16-20; but it's always (for years) been > 16 when asleep. I know this because I have one of those watches that measures that kind of thing. My average heart rate is 60-65 both awake and asleep; but except when I'm exercising it holds relatively constant when I'm awake. But when I'm asleep it varies wildly, between 40-100.

All the things that can be measured in heart and lung function have been measured, and are at least as good as predicted -- usually better than predicted (for my age and height). I'm thicker in the middle that I'd like to be, but I still run or cycle every day, as I have for over forty years.

If I don't have sleep apneoa, what is the explanation for the machine increasing the pressure?

Best wishes
Lars.

[rick blaine]

The machine looks at the air flow in a moving four-minute window.

Based on what it 'sees' – and the algorithms it has been programmed with – it either changes the pressure up, changes the pressure down, or does nothing. When it does change, it is usually with one step of 1.5 cm at a time.

In addition to outright obstructions (apneas) or partial obstructions (hypopneas), the algorithms scan for:

– flow disturbances;
– the pattern of breathing generalised from other patients which indicates 'respiratory-effort-related arousal' (the machine itself does not directly measure CNS arousal);
– two kinds of snoring, and
– absence of breathing even though the airway is clear – which some machines test for with a rapid puff (this clear airway thing is sometimes called a 'central' (apnea) – I think because the assumption is 'no signal from the CNS is reaching the breathing muscles').

And one or two of these is rarely sufficient – there has to be 'enough' of these disturbances – either of solo type or in combination – to 'go over threshold'.

Thus, you can have a change in pressure without it following an apnea.

I can show you charts that show my machine chasing a patch of snoring that goes from 10 cm right up to 19cm in six steps – but with no apnea recorded (in that segment). Rather because the machine 'thinks' snoring is bad and is just a step away from apnea.

What else might be going on with you is what a full, 16-channel, over-night sleep-study shows.

You know already that a full, 16-channel, over-night sleep-study is rare in the UK. In the US there are plenty stand-alone facilities which doctors can send their patients to – the first night for the evaluation and diagnosis. The second night for the tailoring of the machine to the individual.

American medicine calls this second night 'doing a titration' or just 'a titration'.

[lars_the_bear]

What else might be going on with you is what a full, 16-channel, over-night sleep-study shows.

Yeah. To be honest, although such a study would be expensive, I'd pay up in a heartbeat if I was confident it would identify the real problem. But after seeing six different doctors and having study after study, I'm not hugely confident that it will help :/

Best wishes
Lars.

[Pugsy]

Good Morning and Merry Christmas.

I have an idea about the respiration rate...
first I don't see a 30 rate...the max was just not quite 25 but I have a potential explanation for the higher than usual rate..more on that in a minute.

Also I would NOT get all excited about the tidal volume numbers either. They actually aren't all that different from mine and I am an old woman (69) who has to stretch things to make it to 4 ft 11 inches. I always see a LOT of variation on the tidal volume numbers but the median is probably the most important number. If it is sort of in line with what we would expect then I don't worry.

These are my numbers from a fairly recent night
Tidal Volume
0.00
320.00
540.00
1180.00

As for respiration rate....I need to see a zoomed in section of the flow rate where the rate is high.
Go here and watch the videos as it explains how to zoom in on sections.
http://freecpapadvice.com/sleepyhead-free-software

I need to see each breath up close...maybe a 2 minute segment where it is showing the higher rate.
Scroll down to the respiration rate and put your mouse cursor over the highest peak on the graph and then zoom in on that peak in the graph. This will change the flow rate as well...so we can see each breath up close but we don't want too close.

I also need a regular screen shot of the detailed data report and this time include the Flow Limitation graph and omit the tidal volume graph.
And see if you can sneak the snore graph in there as well. You can resize the graphs if needed to get them included in the image but not so tiny they are useless.
You should be able to get
Events
Flow rate
Pressure (not mask pressure)
Leak
flow limitations
snores
in one image and decent size graph blocks

[Pugsy]

Regarding the question as to whether or not we an infer from the data the machine gives whether someone has obstructive sleep apnea or not. Sometimes we can get a fairly definitive answer but sometimes not.
In the auto adjusting algorithm the machine can and will respond to flow limitations and snores (as well as OAs and hyponeas that happen withing a certain time frame) so while FLs and snores are potential indicators of OSA...they don't always add up to OSA.

Your pressure changes....if you didn't have known issues with breathing during the day (the low O2 while awake) I would be inclined to infer that the pressure changes you see are some sort of OSA response.
At best, at this point anyway, we can infer that there is some sort of sleep disordered breathing going on which doesn't surprise me since we know that with your low O2 reports while awake there is something going on with your awake breathing and I wouldn't be surprised for that problem to be present while asleep. Could this higher pressure you see point to OSA....it's possible but it is also possible that the machine is just responding to the air flow/breathing that the machine deems needs fixing because there is some sort of breathing issue going on that is also present while awake.

Your pressure changes...fairly significant the last half of the night and that is when we normally have more REM stage sleep which also happens to be when OSA can be markedly worse and cause a need for higher pressures. This is quite common.
My own OSA is markedly worse in REM....in non REM the AHI was about 12 but in REM it was 53...documented in a sleep lab study BTW. This is why sleep studies that measure sleep stages are critically important for some people and why I was trying to figure out if your home studies measured sleep stages or not.
Sleeping position also can worsen OSA just like REM stage....Not everyone of course but common enough to always think about it. And of course some people will/can only have a significant OSA result when both are present...REM and supine sleeping.

Lots of variables are potentially in play which is why an in lab sleep study is sometimes needed so that a much more clear picture of what is going on can be available.

Tell me about your available overnight recording pulse oximeters....what kind do you have?
Are they compatible with OSCAR?

[lars_the_bear]

Also I would NOT get all excited about the tidal volume numbers either. They actually aren't all that different from mine and I am an old woman (69) who has to stretch things to make it to 4 ft 11 inches. I always see a LOT of variation on the tidal volume numbers but the median is probably the most important number.

Thanks. I would guess that the median tidal volume is about 500 ml. In some places, though, the combination of tidal volume and high RR seems to give a minute ventilation of > 20 l/min. I guess that's nowhere near as high as it is when I'm running, and I have no idea how accurately the CPAP machine actually measures it.

As an aside: I dream exercise. I don't know how often I do, because I don't always remember. But when I do dream exercise and I wake up, I wake up panting, as if I had really been exercising.

I am attaching some screenshots showing zoomed-in sections of the RR graph and flow. In one of them, there really does seem to be a reduced flow, of perhaps 15-20 seconds, and that's marked as "OA" by the machinery. The others are (too me) less clear. It seems to me that in places I have really odd patterns in flow -- but again, I'm not sure what is normal here.

Incidentally, I don't see much on the "snore" graph, at least with the standard scale. I'm not sure if the scale can be changed; but I'm reliably informed that I don't snore, so I don't know how significant that trace is.

Incidentally, that you (and others) for the advice. I'm getting better attention here than from people who I'm paying for it :/

Best wishes
Lars.

[lars_the_bear]

Sorry -- this image did not attach to my last. I will try again.

[lars_the_bear]

Tell me about your available overnight recording pulse oximeters....what kind do you have? Are they compatible with OSCAR?

I've ordered one that is. So far, the only detailed information I have about my overnight Sp02 is from the two sleep studies I had. I do have a recording meter, but it needs a proprietary printer --which I don't have -- to show anything useful.

Best wishes
Lars.

[dataq1]

Lars, look for a private message to you on this board

[Pugsy]

The machine thinks you are snoring for some reason or other...it's very low level though and the snore graph along with the flow limitation graph activity explains some of the pressure increases you see.
The machine doesn't rely on the wife's hearing.

Primary driving factors for your pressure increases are the minor snores and the flow limitations.
It's simply the auto adjusting algorithm at work.
Remember the machine is designed to address what it perceives as some sort of airway issue.
Flow limitations and snores are considered early warning signs of an impending airway collapse so it tries to prevent that collapse from ever happening. The whole idea is prevention of the collapse and not fixing during or after the fact.

You can manually count the respirations...and they aren't near 30.
You don't have the red line at 0 mark on the respiration showing up (it can be added) to help visualize the line between inhale and exhale but I think what is happening with the times where the machine is showing the higher respiration rate is a known normal artifact where the machine is "hearing" the heart echo and interpreting it as a respiration because it crosses the 0.0 line. Kind of hard to see on your first image because it is a 1 minute segment and not 2 minute segment.
Zoomed in a little to close.

Anyway...it's called a ballistocardiographic artifact and quite common and usually amounts to the respiration rate being doubled.
Freaks some people out especially when it has doubled their normal 25 rate to 50 respiration rate.
Lot of discussion and examples...start reading
https://www.cpaptalk.com/search.php?key ... diographic

It is usually seen as a teeny tiny little blip in the flow rate breath right at the 0.0 line on the flow rate.
To make it easier to see you can add the red line by right clicking the mouse on the words "flow rate" on the left side of the graph and choosing "dotted lines" and putting a check mark in the "zero" box.

redline.PNG (13.7 KiB) Viewed 15004 times

So you can look for that teeny tiny blip or you can manually count the respirations and get the real respiration rate...either way you ignore it.

I do not know if a PVC popping up will cause this effect or not and we have no way of knowing if the times where your RR is higher also encompasses a PVC. It might...though...and it might account for the increase in perceived RR if there is no cardioballistic artifact present which usually accounts for the doubled pulse rate.

[dataq1]

Hi Lars,
Another element to think about (and hopefully dismiss).
In consideration of your COVID-19 experience (twice, if I understand), did you have a pulmonary function test (PFT) performed? (One thing that would be useful to know is if COVID-19) damaged your lungs in any way

[lars_the_bear]

I do not know if a PVC popping up will cause this effect or not and we have no way of knowing if the times where your RR is higher also encompasses a PVC. It might...though...and it might account for the increase in perceived RR if there is no cardioballistic artifact present which usually accounts for the doubled pulse rate.

Thanks. I think it's entirely plausible that ballistocardiagraphic events account for the odd RR measurement. I think what makes my PVCs so nasty is that they are so early in the cardiac cycle. So there's a long pause (a couple of seconds) after the PVC, followed by a real chest-thumping beat. These delayed beats are certainly enough to disrupt my ordinary breathing when I'm awake. It never occurred to me that they would affect the RR calculation in the CPAP machine but, to be honest, I did not even know I could zoom in and check until you told me

I wonder if this effect could also have affected my recent sleep study? The "PAT" method (which I don't understand) that the equipment uses to detect awakenings is claimed not to be affected by heart rhythm, but the only research studies I've found to support that assertion were funded by the equipment manufacturer. That's always a red flag, to my mind.

There are in my graphs what look like a few genuine periods of low or absent flow, some of which are marked as apnoeas and some, presumably, which are too short to be counted. There are also many periods where there are cyclic reductions in the depth and rate of my respiration which I think are probably not cardiac artefacts (see attached) -- but this might be completely typical, for all I know.

To be honest, I'm not sure what to make of all this. There does appear to be some disorderly breathing -- even allowing for the cardiac artefacts -- but there doesn't seem to be clear evidence of OSA, or any ordinary type of sleep apnoea. Is that how it looks to you as well?

Best wishes
Lars.

[lars_the_bear]

In consideration of your COVID-19 experience (twice, if I understand), did you have a pulmonary function test (PFT) performed? (One thing that would be useful to know is if COVID-19) damaged your lungs in any way

Hi. Thanks. I had a full lung function work-up after my second Covid (about three months ago), and it was completely normal. Because the problems I have are mostly during sleep -- or at least when lying down -- I insisted on all the tests being done with me laying down. I haven't made any friends in the hospital

Best wishes
Lars.