Sudden burst of CA's because left arm was out of bed!

[BigWing]

I wonder if anyone can explain this brief weird set of occurrences. 

2 nights ago I was woken at 6:04am by an arousal, and felt the need to switch from my right side to my left side. I confirmed this for my records with 5 quick sniffs followed by 4 more (easily seen on a Flow Rate chart).

Just 70 seconds later I was awoken (not from real sleep, I suspect) by an oximeter vibration because my SpO2 had dropped to 89%. I was on my left side with my left wrist (the one with the oximeter on) hanging slightly off the bed and my right arm was across it. I lifted my right arm off it and then lifted my left wrist in the air, and the vibration stopped and SpO2 immediately jumped to 98%!

I thought this odd so, after about 3 minutes, I deliberately put my left wrist back hanging off the bed. That didn't seem to cause a vibration (though it looks like O2 did drop a lot). After mulling that over for another few minutes, I put my left wrist back hanging off the bed and laid my right arm across it. In less than a minute, the oximeter vibrated again!

I repeated this again and got the same result - and decided it was time to get up.

When I got all the data from the CPAP and the oximeter and SomnoPose into Oscar (see attached chart showing the most relevant clips), I realised the situation was even more complex than I thought. During this 20 minute episode, the ResMed 10 said I had NONE CA's (something I don't often get actually). I suspect none of these were real, especially as I was mostly awake during this time.

So is the oximeter really telling the truth about my body being short of oxygen, or is it just responding erroneously to a slightly cut-off blood supply to that hand?

[BigWing]

Sorry - when I wrote "NONE CA's" I obviously meant "NINE CA's"!

While I'm here, here is an expanded view of the first CA.

[G. Szabo]

My observation is that the oxygen figures depend on how tight the sensor fits on my finger. I tried different fingers and different positions.
I suspect your finger swelled/shinked when you changed your arm position. Hence, the sensor's distance from your skin changed, delivering erroneous figures.

[BigWing]

My observation is that the oxygen figures depend on how tight the sensor fits on my finger. I tried different fingers and different positions.
I suspect your finger swelled/shinked when you changed your arm position. Hence, the sensor's distance from your skin changed, delivering erroneous figures.

That was my first thought, until I also saw the weird CPAP data at exactly the same time.

[G. Szabo]

See the similar experience of joeblough  who wrote " see this also - i record my position with SomnoPose and whenever i turn, of course there is an associated arousal. in turn i see central apneas on the CPAP right after the position change, and a drop in O2 sat - a series of drops of decreasing amplitude."
Here: https://www.apneaboard.com/forums/Thread-Symptoms-Mysterious-Arousals?action=newpost

[CPAPfriend]

Pure speculation from me, but seems like the right arm may be limiting the blood flow of the left. The pressure could be compressing the tissues and limiting flow beneath the surface too, not just the blood vessels near the skin.

[BigWing]

Pure speculation from me, but seems like the right arm may be limiting the blood flow of the left. The pressure could be compressing the tissues and limiting flow beneath the surface too, not just the blood vessels near the skin.

That was one of my first thoughts - ignoring the CA's for now, could reduced blood flow to the oximeter finger affect its reading?

So I laid down on the sofa with my arms in the same weird position and watched the oximeter data. I also had my wife squeeze my left forearm with even more pressure than my right arm laying on it would create.

I did not get any data to support the theory.

[SarcasticDave94]

I would agree with the theory about lying on your left causing a restriction of left arm blood flow.

Also in known times of being awake, the events can't be Sleep Apnea, but might be sleep wake junk (SWJ), as in a confusion in breath control due to that in/out sleep transition.

[BigWing]

I would agree with the theory about lying on your left causing a restriction of left arm blood flow.

I'd try switching the oximeter to my right wrist, but I don't think it's a valid experiment unless I can get more examples of the problem on my left first.

Also in known times of being awake, the events can't be Sleep Apnea, but might be sleep wake junk (SWJ), as in a confusion in breath control due to that in/out sleep transition.

I understand that, but the difficulty I am having is knowing what to consider "being awake". Is it simply "not asleep"? i.e. which pot do we throw the transition into?

I've seen it said (by "Pugsy") that to be considered asleep (and thus be unable to discount marked events) you need to see the Flow Rate waveform:
  (a) change from typical awake pseudo-sinusoidal to the well-known long tail-off of exhalation
 AND
  (b) have an amplitude that has become consistent

That second restriction seems unreasonable to me, as I do have long periods where the amplitude is rock-steady but for some other periods it bounces up and down a lot (is that REM sleep, perhaps?).

I've noticed for the latter — for me anyway — that the inspiration amplitude is actually fairly consistent. It's the expiration amplitude which is varying. I wonder if that should tell me something?

[Jay51]

This is something I wrote down that Red posted before on the validity of oximeters.  The best finger to use is the right middle finger (for right handed people).  2nd best is the right thumb.  Right little finger would be less accurate than both the right middle finger and right thumb.  Also, the left middle finger is supposedly the worst for measurement, as it will give the least accurate reading.  Just some thoughts.  Changing the digit that the sensor is oncould significantly change the results.  Also, the position on the specific digit could change the reporting.