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Oximeter Alarm - What SPO2 Level for Safety?

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tiredofbeingtired +0 points · over 3 years ago Original Poster

I have been diagnosed with mild to moderate sleep apnea. I bought a pulse oximeter with an alarm as a measure of insurance/safety to wake me up if my SPO2 ever gets dangerously low.

I used the oximeter with alarm last night. Set the alarm at SPO2 level of 88% - it went off shortly after drifting off to sleep and saw the level was at 86%. Terrifying. I set the alarm at a lower level of 74 because I figured - what if I'm just going to get woken up every 20 minutes and not sleep a wink tonight? It took me a while to get back to sleep but the alarm never went off. I would wake periodically and check the oximeter, but it always showed something around 95. I don't know what the actual lowest SPO2 level was as I haven't had time to plug in the data and look at it.

Anybody know what a good alarm safety level is that I should be setting? I want to wake myself to prevent any catastrophic/emergency situations, but not prevent me from ever sleeping during the night. I have not been prescribed CPAP, only a dental appliance.

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wiredgeorge +0 points · over 3 years ago Sleep Enthusiast

I have a Pulse Oxymeter that looks like a wrist watch and records. I use it periodically to ensure my blood-oxygen levels are where they should be. Values under 90 are considered low. I will say that if you move around any, it disrupts the accuracy of the recording. It is hard to sit on the couch and watch TV (for me at least) without readings being disrupted and the most accurate are when I am perfectly still (as when asleep). If you move around at all and set the alarm, it will likely go off. I have never set the alarm and only focus on results after I am asleep. I am not sure being roused for alarms is productive for these reasons. Does your Pulse Oxymeter record? If so, look at the results in the AM after the machine has stopped recording and see if there are significant drops. If there are, these will either correlate to you AHI or you may need supplemental O2 but the alarms are likely generated by moving around would be my guess.

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tiredofbeingtired +0 points · over 3 years ago Original Poster

Thanks, wiredgeorge. Do you think it is life threatening that mine is going down to 86 when asleep? The oximeter is pretty secure - it doesn't seem to fluctuate even if I move around a lot, as I did wear it while watching TV to see where I am at (usually somewhere between 97-94). Is there an absolute minimum level I should be setting the alarm at to prevent life threatening situations? Understand you are (probably) not a doctor, but any anecdotal advice would be great.

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wiredgeorge +0 points · over 3 years ago Sleep Enthusiast

Low blood oxygen has a negative effect over time. Mine dipped into the low 70s numerous times during my sleep study. It had probably been doing this for years. I can say with absolute assurance that it didn't kill me as I am still kicking but I am also sure I was a lot smarter at 18 years old than I am today. Heck, at the early age, I knew everything as well. I doubt 86 is dangerous but prolonged 86 may start to have an effect. Lack of O2 to the brain and heart and other organs is the issue so try and correlate these sags in O2 saturation with your AHI. If you can, then that is the culprit but if not, time to talk with the doc if you are concerned. I am not sure what type Pulse Oxymeter you own but mine does produce bogus results if I move AT ALL and not just SPO2 but pulse readings.

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jnk +0 points · over 3 years ago

If you are desaturating at all, that indicates (1) that your dental appliance is not working and (2) that you need to be on CPAP.

A pulse-ox has some diagnostic value when used in conjunction with other data, but is has *zero *value for treatment purposes. Even when CPAP pressures are not sufficiently optimized to allow for good sleep, the pressures can still be efficiently preventing desaturations. In other words, during a titration, as a tech raises pressure(s), the saturation usually gets fixed at a lower pressure than what is required to fix sleep disturbance. So even if you weren't desaturating at all, that would not prove you were getting good sleep. On the other hand, a PAP machine with full efficacy data could give you data that would be of some use in discerning whether your sleep-breathing problem was being fully treated.

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sleeptech +1 point · over 3 years ago Sleep Enthusiast

You say "during a titration, as a tech raises pressure(s), the saturation usually gets fixed at a lower pressure than what is required to fix sleep disturbance"

In most cases this is incorrect. I am a tech who raises pressure during a titration and usually oxygen saturation is not fully stabilised at a lower pressure than is required to fix sleep disturbances. While this can be true occasionally, it is far more common that the pressure at which oxygen saturation is fully stabilised is the best one to fix sleep disturbance.

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jnk +1 point · over 3 years ago

Sorry, sleeptech. My wording was sloppy. I was referring to sustained desaturation, where a patient dips low and stays there for longer periods of time. That gets fixed at a lower PAP treatment pressure than what it takes to fix sleep. You don't stop titrating once the several-minute long desaturations are fixed, for example. I am NOT referring to the transient desats that lab equipment reports to indicate an event. Those events are often too quick or subtle for home-use oximeters to effectively detect and report anyway.

In other words, my point was that when a tech gets sustained saturation up out of the cellar and into the 90s, his work is not done yet, obviously. He still has to fix sleep. But yes, I agree wholeheartedly that fixing sleep requires using the continued monitoring of transient desats (and brain activity) with lab equipment for successfully establishing the best pressure for treating sleep.

The reason I mentioned it is that some patients truly believe that if their home pulse-ox isn't reporting sustained desats, that proves their sleep is fine or that their machine is perfectly adjusted. They forget that a good titration is about more than just preventing seriously-low and long desaturations that their home equipment records and reports.

Overnight pulse-ox alone to monitor desaturation can prove someone has a breathing problem during sleep. However, alone, it cannot be used to exclude the possibility of sleep-breathing troubles, since it is possible for breathing to disturb sleep without that showing up on recordings by a home pulse-ox.

Or as the experts put it:

"Nocturnal (overnight) pulse-oximetry is not recommended for the definitive diagnosis of OSAS, or to exclude the presence of OSAS." -- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3869111/

And as the nerd experts put it, discussing the false-negatives during OSA screening with oximetry alone:

"The false-negative and indeterminate groups were misclassified by oximetry because of a failure to demonstrate significant falls in saturation (as defined by the protocol). This may in large part be explained by their less severe disease, as evidenced by fewer and shorter apneas than in those patients correctly identified as positive for sleep apnea." -- http://journal.chestnet.org/article/S0012-3692(16)32780-5/fulltext

Bottom line is, as the Harvard dudes say:

"Some people with OSA have little reduction in blood oxygen levels." -- http://healthysleep.med.harvard.edu/sleep-apnea/diagnosing-osa/testing

Again, I apologize for my unclear wording. I appreciate your correction and welcome that opportunity to clarify. Feel free to point out anything wrong with this post, too. You do good work here.

Thanks.

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tiredofbeingtired +0 points · over 3 years ago Original Poster

you're right - I will push for CPAP. But until I receive CPAP, I will need to find some gage + alarm to at least mitigate possible life threatening situations.

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jnk +1 point · over 3 years ago

In the meantime, if I were in your position, until I was on CPAP, I would not eat or drink anything but water within 3 hrs of bed. (Apneas tend to pull the contents of your stomach up into the airway.) I would prop up the head of my bed to sleep at an incline with my head higher than the rest of me. I would keep my sinuses clear with corticosteroid nose spray, possibly short-term decongestants (although there is some risk of rebound sinus issues with decongestant sprays). I would take nothing to get to sleep that has a sedating effect. I would keep using my dental appliance at all times when asleep. I would consider Provent (needs an Rx) or the anti-snore version of it (which doesn't need an Rx) to create a slight bit of back pressure for my airway. I would rig up a way that makes it impossible (not just uncomfortable) for me to sleep on my back. None of those things would I consider to be treatments, but I might consider them risk-lowerers, of a sort.

I am not a big fan of pulse-ox alarms (as you may have noticed :-) ), since they are not all that dependable as an alarm in the home setting. In a hospital setting, someone listens and gets notified of the alarm. It is too easy for someone at home whose nervous system is already ignoring things (in the form of OSA) to stay unconscious during an alarm, especially in a life-threatening situation. For that reason, I would hesitate to even suggest a number to you. That said, I get what you are trying to do, I respect it, and I hope you choose a number you are comfortable with. Perhaps the greatest value in your having that oximeter is having something objective to prove to your medical team that the dental appliance ain't even comin' CLOSE to cutting it for you.

Again, if it were me, until I was on CPAP a few days, I would recognize that I was impaired for driving or doing anything that might harm myself or others. Sleepy people have accidents. That is likely where any person's highest risk is of injury or death. By likely, I can't mean likely for you since I don't know you or your medical history. But statistically across the population, that is where the likelihood of serious harm is. I don't mean to be scary about it, just frank, in view of your expressed concerns.

I am glad you are taking it seriously. Don't consider the dental appliance wasted money. It may come in handy for you and is likely helping you a little even now. You just didn't happen to be among the 50% of people who get the 50% reduction in AHI, or at least you are not benefitting from it sufficiently for it to be something workable alone for you. That isn't your dentist's fault. They have no way of knowing who will benefit by how much and who won't at all. I still have my dental appliance and have used it from time to time when my PAP data indicated I was opening my mouth during therapy. I used it to retrain me to keep my mouth shut using nasal pillows for PAP. It has proven very valuable to me in that way.

Insist on full-efficacy data for your machine, not just compliance data. The payers care about compliance. You care about having leak and AHI numbers to get your treatment as effective as possible. CPAPs and APAPs are the same insurance code in the US, so don't let any DME force on you a machine without full, full-time efficacy data. Sometimes DMEs are tempted to do that, since they get the same amount of money either way, and the cheaper the machine they give you the more money they make.

Volunteer to fill in for last-minute cancellations on testing in order to shorten wait time, if testing is something your doc/payers require before you get your life-saving machine.

Be vocal, though cooperative, with your medical team. Give them the same details you posted here. Feel free to give them printouts of what I have said in order for them to agree with or disagree with my statements. They have extra letters in front of and after their names that I don't have, and what they have to say should carry more weight than what I or anyone else says here. But also be vocal on the forums for help from fellow patients in making your therapy work.

Also, don't forget the disclaimer at the bottom of every page here, which says, in part:

"The information provided on this site is not intended nor recommended as a substitute for advice from a health care professional who has evaluated you."

I point that out because I am tiptoeing a line here with how specific I am being in my attempts to be helpful to you. My heart goes out to you, since I read a lot of myself and my past experiences in the words you have typed on this forum.

-jeff

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jnk +0 points · over 3 years ago

Not to beat a dead horse, but even most docs can't agree how to figure out the meaning of overnight oximetry results in isolation:

[Physicians] expressed negative opinions on the utility of overnight oximetry on a number of levels. First, there was concern that test interpretation was unduly subjective and not properly validated or standardized. “The problem with this test is that it's available but I don't think we know what to do with it. Each one of us has their own thing about it (the test). So its utility is very poor.” Second, many participants expressed doubt that the test added any value to a history and physical examination or affected decision making. “It almost never obviates the need to do a polysomnography”. “If I was really worried that a patient had obstructive sleep apnea I wouldn't go fishing with this test.” -- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2734414/

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