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Interpreting Pulse Oximetry Data

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  • Interpreting Pulse Oximetry Data

    Hello forum,

    Not sure if I should be in the "introductions" forum. I did post on here before, 7 years ago:

    but I haven't really made any progress since then. I have the exact same problems, to this day.

    I had a sleep study carried out by Papworth Hospital in 2013. I had a first test which they called "borderline" and a second test which gave a negative result.

    In 2015 I had a heart attack (aged 45!). One stent fitted successfully, and I recovered quickly. Within about 6 weeks I was back to normal. The problem for me is that "normal" isn't very good.

    I had another sleep study carried out here in London about 6 months ago and was told that the results were normal, average spO2 during the night of 95%.

    I wonder if I might share a couple of photos on here. They're printouts from the "SPO2 monitor" software which came with a pulse oximeter that I bought recently (which can store and transmit data).

    The first one is about an hour's data from yesterday afternoon. I felt crushingly tired, quite suddenly, and slept fitfully for about an hour. This happens often for me. When I woke up, my upper body was quivering although it stopped quickly. I felt terrible - like I wasn't getting enough breath. My breathing seemed "lazy" - quite slow and shallow. No noticeable impediment to breathing, just that my body didn't seem to want to do it. Had a choking sensation - head/adam's apple/stomach. Felt confused & disorientated. Looking at the two graphs, it's noticeable to me that my pulse and spO2 seem to be a little bit unstable. I seem to remember being told by Papworth that this had been a feature of the "borderline" test I had back in 2013.

    The second one is from last night, about 1am to 2:30am. Seems noticeable that for the first half of the period, my spO2 and pulse were *much* more stable. Then around 1:40am they started to fluctuate (much like they had during the afternoon nap), dropping below 90% quite a number of times. and also rebounding up to close to 100% within a very short period. After about 45 minutes of this I woke up.

    Waking every hour or two during the night is very common for me.

    Today I feel tired, groggy, grumpy, disorientated, lethargic. As I do most days.

    If I lie down flat on my back while awake, this "lazy breathing" I described is often there. And then suddenly I can feel a jolt inside and I'll take some deeper breaths. It doesn't feel right to me.

    If anyone reading this posting has any experience of interpreting this sort of data and is able to offer any comments or advice, I'd be very grateful. My health is very poor. No doctor seems to be able to find anything wrong with me - all my blood test results are normal, nice BP numbers (110/70 ish), on paper everything looks good. But I'm so exhausted than I'm unable to work, or sometimes even to get out of bed. Occasionally the symptoms ease and I'm able to climb mountains, go on long bike rides, dig the garden, socialise, etc. but this is fairly uncommon, sadly. Sleep apnoea would do a very good job of explaining all my symptoms, but there's no positive diagnosis to be had, it seems.

    Grateful for any advice...

    Attached Files
    Last edited by bigalxyz; 28th August 2017, 12:11.

  • #2
    Hi Alex, sorry this is a very late response but it might still be relevant - and may help others, also. I'd missed this as it wasn't in one of my watched forums - so I've moved it to a more appropriate one.

    Analysing oximetry data is not straightforward; it takes a lot of training and experience to understand what the data shows. On top of that, it is not always reliable when it comes to Obstructive Sleep Apnoea.

    The theory behind them is simple; with OSA, you stop breathing, and when you stop breathing, the oxygen levels in your blood drops.

    However - not everyone with OSA experiences these drops, and there are also numerous other factors that can affect blood oxygen levels during sleep. So they're not 100% accurate when taken in isolation, but give a pretty good indication.

    Without the statistics and ability to zoom in at particular points on the graphs you provided would make it nigh impossible for a professional to be able to draw accurate conclusions from; let alone laymen like you and I (with all due respect ).

    It is for reasons such as this that we don't sell oximeters ourselves; the data is not always accurate, and without knowing exactly what the data is showing it can cause more confusion than they solve. We therefore leave this to the experts.

    What you might want to consider instead, if you've not already since your post, is a more detailed in-home sleep test - with equipment far more accurate than simply oximetry and is analysed by a sleep professional. You may find this provides a far more conclusive result one way or the other with regards to your sleep; certainly more so than a simply oximeter would provide. Generally speaking, if the detailed study says you have it, then you have it, and if it says you don't, then you don't. Whereas with oximetry, there's a notable percentage where the results may give the wrong outcome.

    We do also do oximetry sleep tests ourselves, but for the reasons I mentioned above we don't recommend them unless OSA is an open-and-shut case, where confirmation is a formality. For people in your situation, where OSA is a strong possibility but far from the only possible cause, the more detailed study is far more suitable. For example, what you described about your afternoon sleep (upper body quivering, body seemingly reluctant to breathe) are not typical symptoms of OSA and there may be something else at play, but oximetry doesn't provides enough data to draw such conclusions from.
    Tom @ Intus

    You can now follow Intus on Twitter!


    • #3
      Hi Alex,
      What Tom says is exactly correct.
      Pulse Oximetry cannot be taken in isolation with ANY condition; be it cardiac, respiratory or trauma.
      I spent over 30 years in front line health care and can tell you that only a sleep clinic or home sleep data recording ( usually overnight) provided by your hospital consultant can determine whether or not you have Obstructive Sleep Apnoea (OSA).

      Firstly, you would go to your GP if you suspect you have sleep apnoea and discuss your symptoms with him or her. There are symptoms that are often treated as other things first, such as depression. So, don't be afraid to ask for a referral to a sleep disorder clinic.

      What is helpful is if you have a partner or friend that has witnessed episodes of apparent stopped breathing to go along with you and add their witnessing of your apnoea.

      ​​​​​​From the data recording they dermine your level, number of events and length of events, of apnoea (period of interrupted breathing).
      The kit you would likely be given is:
      * 3 Cardiac monitoring leads. This only records your heart rate and cannot determine heart problems in isolation either.
      *Chest expansion measure (elasticated chest band)
      *Pulse Oximeter

      I can tell you that even though I was skinny I still had sleep apnea and had to ask for a referral.

      I have been on CPAP for five years and it has literally changed my life.

      Sure, I had to get used to sleeping connected to a machine by a pipe. But, I would NEVER be without it.