Oxygen sat levels

Question???

So many of you have posted that your O2 sat levels are in the 70's, 60's and 50's....

My question is, why did the technicians let it get so low??? When mine began a steady decline they stopped it at 85% and gave me supplemental O2. They said that 85% was too low (although there were apneas and hypopneas where technically your O2 sat drops to 50% or less.)

How or what do they actually measure and record?

How could my lowest sat be 85% on the same test where they documented apneas & hypopneas that by definition must have lower O2 levels?

Confused
- JB

ahujudybear wrote:...(although there were apneas and hypopneas where technically your O2 sat drops to 50% or less.)

How or what do they actually measure and record?

How could my lowest sat be 85% on the same test where they documented apneas & hypopneas that by definition must have lower O2 levels?...

Hey JB,

I am not sure what you mean by this. The way I understand it, Apneas and Hypopneas are when your airway closes or partially closes. The length of time they occur for, lowers the amount of oxygen your body is taking in, and causes the oxygen level in your blood to fall. The more total time spent in apnea/hypopnea, the lower your oxyen level will fall. Apneas and Hypopneas occur independently of what your blood oxygen level is. At least i have never seen a classification of apnea/hypopnea types as related to blood oxygen levels (Of course this may be meaningless since I'm not really an expert, lol). So at some point your brain wakes you to end the event and get you to breathe, causing your blood oxygen to rise.

My oxygen level fell to 79% at times. My test was a home test so noone was observing, thus noone to take any action about the level it hit.

The act of adding oxygen is an interesting one. Given you have to breathe for it to help. Unless of course your low oxygen level was hit during a hypopnea, in which case the extra oxygen rich air probably would raise the oxygen level in your blood, even though you were experiencing limited air flow. It seems waking you would be more effective than adding oxygen, since blood oxygen level is falling because you are not breathing.


Ron

well... Not exactly, Ron.

To begin with, technically a hypopnea is when your breathing pauses and O2 level drops 50%. I had a few of these, a few apneas and a couple of central apneas. Nothing remarkable.

But because of underventilation, my O2 sat was falling. Once it reached 85% they decided to intervene.

Unfortunately the added O2 kept me at an even shallower level of sleep and the report said that i never actually slept afterward (but then why was I dreaming???)

So is the pulse Ox just an average? Then how do they determine that your O2 sat drops 50% (hypopneas)? Especially when they say it only went down to 85%?

- JB (still )

JB you are confusing air flow with blood oxygen levels. A blood oxygen level of say 85% is different than the reduction of air flow caused by a hypopnea.

When people talk about O2 sat levels, they are talking about how saturated your blood is with oxygen.


Ron

-JB,
I think you've got the Hypopnea definition wrong - it's not 50% oxygen, it's 50% breath volume, and as Ron said, the definition has nothing to do with with oxygen saturation.

I've read of people whose desats were very bad (50%) being waked up and give CPAP during the study, and their treatment expedited.

Could it be that in your case, your oxygen desat was constant? In many cases of OSA its an up and down kind of thing - get into apnea oxygen dips, wake up, snore/snort oxygen back to normal, fall asleep, etc.

O.

Apnea can cause sharp desats, but I had obstructive apneas lasting 63 seconds and frequent hypopneas lasting 73 seconds, yet my O2 sats never went below 91. The were originally supposed to do a split study, but the O2 sats didn't go low enough, so I had to go back for titration another time. It turned out that I have severe OSA along with PLMD.

OH!!! It's 50% air flow?? Hmmm.. OK. That answers that part of the question...

But the other part still remains: how do people get such low sat readings? Mine was in a pretty steady decline when they intervened and added the O2. It was up & down, but more down than up. I found out at the hospital before surgery last week that even when I'm awake, when I lie down my sat level drops: 95 to 91 in about 5 minutes.

Don't ALL labs intervene on lower sat levels, or do they really bounce around when you have a lot of apneas? Still, 59% is pretty low!

Thanks for all the info Ron & Ozi! (So, after that little bit of surgery when they took off my mask and I was scarcely breathing, I suppose that could be called one long hypopnea, before they decided to restart the machine because my breathing was so shallow?

Oh! And I learned something from my new pulmonologist: anesthesia paralyzes the diaphragm. Not sure if that's all anesthesias... maybe only the curare-based ones?

- JB

Hello ahujudybear! I hope that I can clear some things up for you.

First of all, The definition of a hypopnea is a drop in airflow of 50% or more for a lab/technician/dr. preset amount of time. The definition of an apnea is the cessation of breathing, also for a predetermined amount of time, correlating with a drop of oxygen saturation of usually 3-4%. This shows the sleep docs, whether or not your body is capable of handling the apneas. Some people, like ITeach, have severe OSA but never meet those guidelines, so the initial scoring by the software doesn't pick it up. Usually, the sleep labs have programs that are smart enough to look at your study and "score", or mark, the things that fall outside those predetermined parameters. The techs look through the study after this and either agree or disagree with what the software scored.

With any disorganized breathing episode, our hearts begin pumping harder, thus requiring more oxygen. Any time we are in an active state, our bodies burn more fuel. Our fuel is oxygen. Without it, our tissues die. When your brain senses that our levels are lower than optimal, usually less than 90% on the pulse oximeter, it triggers our lungs to breath more. Either in the form of breathing faster or deeper or both. When our airways are obstructed or partially obstructed, this can get tricky! The lab techs can put oxygen on us, but if we can't get any in, it won't do us any good. Or if we can only get some of it in, our bodies are still requiring it and it may just get the downward spiral to stop, not necessarily get the numbers to go up. I hope that makes sense.

As for the bouncing around thing, sometimes after you finish one obstructive episode and your oxygen levels start to come back up by breathing again, your body relaxes again and then you obstruct again, making your oxygen levels fall again! Depending on where the oxygen levels were to begin with or how bad an obstructive episode this is, your oxygen level may or may not do worse than the previous one.
The bouncing around thing is how the report can show a 'mean SpO2' during different sleep stages. There are several different machines that can be used to record your SpO2, all of which have their own "formula" by which they determine your level at any given time.

The surgery thing...Depending on what kind of anesthesia they use, different people can react different ways. If you had 'general anesthesia', that usually consists of a sedative to make you drowsy, a pain reliever, and a paralytic so that you can't move. Your pulmonologist was right, it does paralyze your diaphragm. It may have been the case with you that when you got out of surgery, you were still grogy from the sedative, the ventilator doing the breathing for you and/or the pain reliever that your brain hadn't kicked back into breathing mode yet. This happens more times than you think. I had worked in the recovery room for 3 years and saw this more times than I can count! The doctors usually wait another half hour and try again, or they sometimes give a medicine called Narcan to reverse the effects of the pain reliever. Morphine is a common pain reliever that is used in hospitals. Too much of it can knock out a person's drive to breath, usually characterized by shallow breathing. Sometimes you never know how much is too much, until you've given too much! What a wonderful formula huh?!

I really love this forum and I hope that any tidbits of information I give will be helpful to you guys, as your wisdom is helping me, help my patients!

There are a few more things going on with shallow respiration:::

If the CO2 is not completely ejected, it still clings to those things in your lungs where O2/CO2 is exchanged. If they are blocked by CO2, they will not be able to take in the O2. Until your body moves to force a deeper breath, this continues in a downward spiral. (The BiPAP seems to be taking care of this, but I will have another sleep study after recovering from this surgery where they will be doing a running recording of CO2 levels along with the pulse Ox, etc., first without, and then with MY BiPAP machine - and then titrate with my machine.) This is why an acceptable level of O2 is generally regarded as a sign that CO2 is being cleared out, but this is not always the case - especially when there are mechanical/musculoskeletal problems (weak muscles, scoliosis, injured muscles or ribs).

Using a BiPAP handles this problem better than simply administering O2 because the machine keeps air moving through the lungs, whereas simply adding more O2 will signal the body that it has enough O2 and slow down the process, increasing the proportion of CO2. Or at least that is what we are hoping the machine is doing! At least I haven't had any CO2 headaches since I've been using it.

Oh and the shallow breathing thing? That happens every time I take off the mask. .... but my muscles usually kick in after a few minutes. In this case they didn't - and that was after only a half-hour procedure.

But thank you for your thorough explanation.... "guest" (Are you MM?)

- JB

One would think that the greatest harm from sleep apnea comes from depriving one's organs and tissues of oxygen. Essentially, pauses and obstructions to breathing suffocates the entire body as oxygen in the bloodstream becomes scarce.

Many of us attempt to measure effectiveness of xpap therapy using software that accumulates data on apneas/hypopneas, etc.

Aren't these just surrogate indicators? Oxygen Saturation monitors can measure oxygen levels in the bloodstream continuously through the night while we sleep. Shouldn't the Gold Standard measure be oxygen saturation?
Does anyone use such a device?

guest wrote:One would think that the greatest harm from sleep apnea comes from depriving one's organs and tissues of oxygen. Essentially, pauses and obstructions to breathing suffocates the entire body as oxygen in the bloodstream becomes scarce.

Many of us attempt to measure effectiveness of xpap therapy using software that accumulates data on apneas/hypopneas, etc.

Aren't these just surrogate indicators? Oxygen Saturation monitors can measure oxygen levels in the bloodstream continuously through the night while we sleep. Shouldn't the Gold Standard measure be oxygen saturation?
Does anyone use such a device?

Exactly guest. The test my sleep Dr's use to make sure the therapy is going well is to loan me an oxygenation meter that logs my blood oxygen level throughout an entire nights sleep. So far these tests have shown my blood oxygen is staying well within the normal range, even though my AHI averages between 4 and 10 with an average of about 7.

However, while maintaining a healthy blood oxygen level is the critical factor, my AHI remaining a bit high can still affect my quality of sleep. I think this is proven by the fact that I'm still not feeling well rested and energetic after more than 2 months on therapy. So I keep working on trying to reduce it. At least I'm not depriving my body of oxygen any more.

Oxygenation meters are available and have been discussed on this board in the past. I'm not sure it's worth purchasing one, unless your sleep Dr's are not following up with regular oxygenation tests. It seems to me that a periodic check is adequate. For me there is no way I would wear the oxygen sensor on my finger every night anyway.


Ron

Not necessarily, Guest.

You can suffocate from having too much CO2 in your system, even though you have an 85% to 90% O2 sat level. Not exactly sure how it works, but O2 levels are not the only parameter that must be watched. For instance, not reaching a deep level of sleep keeps your body producing urine and gastric acids/enzymes, leading to GERD & acid reflux problems and frequent nocturnal urination.

Children's sleep labs routinely monitor CO2 levels. Adult sleep labs rarely do. Milwaukee just got their first adult CO2 monitor in the pulmonary sleep lab at Froedtert. Unfortunately I won't be able to test it until September (Dr. wants me fully recovered from surgery first.)

CO2 is important, but eventually we all breathe and our bodies exhale built-up CO2. Tissues die when deprived of oxygen, so even when we wake up and breathe more normally, dead brain cells do not, so an Oxygen Saturation Monitor to be assured that oxygen levels are adequate with xpap therapy seems like it may be the best way to measure and assure adequate treatment.

Yes CO is important. COPD patients (usually smokers) cannot be given 100% O2 . It turns off the breathing process. That said , Without O2 you die !

:twis ted:

Not only that, but patients who are on O2 at levels under 5 lpm cannot use a mask because of the CO2 reabsorption. They'll end up in the hospital with CO2 toxicity or, like you said, they could die.