Heart Rate Variability - Anyone looked into this?

[lowT]

Great. My appointment with the sleep doc is nearly here (two more days). I had to wait 3 weeks so in the meantime I became curious about things. It will be interesting to see what he says (in-lab versus at home test). The in-lab test is very expensive so I am concerned about that, but I may just have to bit the bullet.

It looks like any additional equipment might be a moot point if you have normal SpO2 levels, since you are saying an EEG would be required at that point. FYI, here is the data from last night with the newly received CMS50I instead of the CMS50D+. The SpO2 levels seems to generally be lower on average, but I am not sure it makes a difference. In theory, the CMS50I is more accurate, but I have no way to determine how accurate this individual unit is.

Side note: Should be from 2AM to 10AM instead of 2PM to 10PM.

[DocWils]

I don't see anything terribly alarming here - the thin spikes are most likely noise than anything else - you would have to expand on the spike itself to be sure, but if the spike is say less than a few seconds once expanded, it is noise in all likelihood. Your sO2 levels are never dropping below 92 with three exceptions that all correspond to sleep state changes and your PI is insignificant - we don't use it unless there is a clinical reason (trauma, illness, anaesthesia, etc) as in healthy people it is all over the place and gives insignificant results, although in your case I would venture to say you want to try measuring with another finger - perhaps your third finger (you have four fingers, not five - the other is a thumb) - it is thinner and you get a better refill on it so the PI will be a bit more steady and more prone to matching up with the sO2 traces. PI is not a really more accurate method to monitor sO2 levels in healthy people, it is a non-invasive way to monitor certain problems that would otherwise require invasive techniques and for people with circulatory problems, for anaesthesiologists, transplant verification, or for infants. You can safely ignore it unless your doc says you have a circulatory problem.

This would indeed indicate you want to look at other problems besides apnoea, although that COULD be a problem, just one that is not obvious from this chart. Unless they have a take home eeg kit (we don't have any in our hospital, only Holters for cardiac work and basic sleep apnoea monitoring, which does not include eeg), you are most likely to need a night at the lab - stay awake as much as you can the day before, get sleep deprived and avoid caffeine, sugar and salts, and you should nod off all right. Also do a nice bit of exercise before coming to the lab for the night - it will help you to get to sleep better. I also suggest you use my trick - imagine in excruciating detail a trip to Mars, which takes two years in a small confined space of never ending monotony, and that will put you under out of sheer boredom in any strange bed.

No, I would not bother to waste money on more gear, it won't help you at this point. I have a ton of gear at home, but as a physician, I am required to have all that stuff in case of emergency, and honestly, I use it more on myself than anyone else, and even then, I don't think it was worth the cost. And even on myself I only use it to spot check certain health problems that I have, even though it actually isn't necessary to, but all docs are hypochondriacs and all docs ignore their real health problems. Hazard of the trade. And I have yet to meet one that is a real health nut. We are our own worst advertising for our advice.

[lowT]

Sounds great! My big concern is that I would waste $1,000 on a sleep study...but I guess there is not other way. Oh well.

I will try the 50I on the third finger tonight and see how it goes.

FYI, here is the difference between them. I have 2 clip style (different brands) and the 50I has rubber holder. The 2 clip ons seem to give the same readings, while the rubber holder is usually about 2-3% lower.

[DocWils]

On the exact same finger?

They sit differently, btw, and so don't read from the same spot on the same finger - the sensor is sensitive to calluses, finger thickness, fat, nail thickness, etc, so you won't get identical readings - the 3% difference is insignificant. The biggest difference with the second model is actually it doesn't need tape to hold it in place for overnight use (to avoid noise when moving around) but it gets hotter over hours of use. One is not more accurate than the other. We use the first type in hospitals, and a finger cover like the second type (no wrist piece, it plugs into the bed-side monitor) for long term care and monitoring, because of comfort, not accuracy.

[lowT]

Yeah, I am not sweatin it. I didn't sleep that great last night (too many things swimming in my head I think), but here are the results for curiosity sake. The posted strip chart is from the 50I on the third finger (right hand). I also used the 50D+ on the index finger (left hand) and started a recording at exactly the same time. I overlayed the results in Excel (not posted) and the pulse was pretty close, while the SpO2 was consistently about 2% higher for the 50D+ than the 50I (but the trends were the same). I can post them if you want, but I think it is just excess data really. Anyway, nothing really significant...just thought I would post it.

[DocWils]

You won't get the same readings from two different fingers, no matter what, so that doesn't work as a comparison - what I am curious about are the spikes in the bpm - are they arousals or just noise? Do you toss and turn a lot? More or less, if you get the same spikes in the same places on both devices, that pretty much eliminates noise as a factor, but I wonder in your case if it is arousal or just tossing and turning.

[lowT]

I wouldn't say I toss and turn a "lot", but I do usually wake and shift positions about 3 times a night. Usually turn from one side to the other. If I start sleeping on my back, I will shift to the side after a couple hours usually.

As far as the spikes go, I had assumed they were just "noise" or a more probably an "error" in the reading. Having looked at raw data, it seems to confirm this. After a few additional experiments, the 50I reports 255 for a "finger out" and the 50D+ reports 0 for a "finger out". From the raw data from the overnight results, I got these values for the spikes. You can't see this because I clipped the scale at 65bpm though. I must have shifted or got out of bed to urinate, etc. Also, it would seem nearly impossible for the pulse to increase that quickly, especially without noticing it. Also, I looked and one of the spikes went from 52 to 255 in just a single second, remained at 255 for 15 seconds, then back to 50 in a single second. This seems like an obvious "finger out".

[DocWils]

Yep, those were either finger out errors or noise.

[lowT]

Met with the sleep doctor. His comments were:

- At home test would not be appropriate. He suggested an overnight lab test followed by more testing the next day.
- My prior history is that I have had a hard time making it through day (and always need a nap in the afternoon) since I was 20 (40 now). Therefore, it may be a bigger problem than just low testosterone and warrants the lab test.
- He didn't think I had sleep apnea, but may have narcolepsy or related sleep disorder (currently sleep about 11 hours a day). Again, the lab test would be needed to identify this.
- Suggested I have a brain scan to eliminate any potential for other causes, which seems like a good idea. I did have one about 15 years (while I still had sleep problems) and it was OK.

Anyway, I think what I am going to do is have a brain scan. After that, I am going to try testosterone treatment since that *may* improve the fatigue/sleep issue. If that still doesn't work, then I will the sleep study (pretty expensive for the 2 day deal - $1500 or so out of pocket).

- Also, he said in my case, a sleep disorder would be treated by medication and not a CPAP. Uggh....I hate meds and don't want to be on any. I guess I just need more testing.

[DocWils]

Correct on all counts- you need to be hooked up to an EEG to get a good diagnosis on this. I would do the sleep test before the Testosterone treatment, because Testosterone may be a blind alley, or worse, mask the real problem. Nothing in your readings pointed to apnoea events, so I seriously thing you need to look at your thyroid, your brain and other possible explanations. Good luck.