RE: Heart Rate Variability - Anyone looked into this?
I haven't heard of one, but that doesn't mean one doesn't exist. There was a headband for a while that took a primitive EEG, I forget the name, some members here had them and liked them very much, but the company went out of business. It more or less could show your state of sleep/arousal, I don't know if could track down to the various forms of REM and NREM sleep. In a pinch, a recording pulse-ox is method to make a first rough assessment if someone suffers from clinical level sleep apnoea in the sense that it will show desaturations of sO2 levels, which is a primary part of sleep apnoea, however it is not enough for final diagnostic, partly because knowing that one has desaturations does not indicate how and why the desaturations take place, and therefore a proper treatment solution cannot be determined. Certain wrist band pulse-ox devices now come with a cannula to monitor respiration levels and flow rates, so come even closer to a home polysomnograph, and there are hand held cardiac monitors that can take recordings of up to six hours, enough for a night's sleep, but they only follow one lead, so you would have to choose your electrode placement wisely (V3 or V4 would be my first choice - nice, clear, juicy P and T waves, clear recovery phases and an easily recognisable QRS complex, which is easier for amateurs to interpret). Please note the pule recordings on a pulse-ox are not enough to do any clear heart diagnostic, as they only record the beat and not the electrical activity of the heart. At most it can indicate a fast or slow beat or a skipped beat, but they give no indication as to what exactly is happening in the heart at all. As such, it is far easier to determine state of sleep from an EKG than a pulse-ox, and of course, an EEG will tell you pretty much exactly where you are, within reason.
But all this gear together costs more money than a sleep test, especially a hospital guided home test. And you get the experts to interpret it then, to boot. Far better choice, even if you are not certain you have sleep apnoea, as it can at least clearly eliminate one avenue of enquiry and give some nice indication as to other things (for instance, part of a sleep test is wearing a portable EKG device called a Holter device so you get nice, clear 3D indication as to the state of the heart's health for a good six or seven hours worth of recording, which is nice, as it gives plenty of time for anomalies to show up) so my advice is to get thee to thy physician and get the process going.
As for using the pulse-ox to tell if you hit REM sleep, it takes a practised eye to make anything of that at all - sleep medicine was still in early stages when I was in med school, back when dinosaurs ruled the earth, and we used to, more or less for a lark, try out different methods of seeing what stage of sleep the patient was in, so we got very practised in "black-box" methods. Younger doctors never got that practice, I am afraid - technology had by then advanced and taken over (and became more accurate) but if we were stranded on a desert island, I would have a better change at doing my job than a lot of the young whipper-snappers today. Most of the kids today would not know how to make a cat-gut suture at all (no, you don't' need cats for it - a bit of a mis-nomer, I am afraid, but cows or sheep are a must). So most docs today will tell you that you can't do it with a pulse-ox, which is true, but what they mean is you can't get better than a decent guess with a pulse-ox, which is more to the point. I don't think it is a useful avenue to pursue in, for instance, developing a "state of sleep" indicator that has any clinical value.
(This post was last modified: 07-20-2015 05:53 PM by DocWils.)