Oxygen Desturation Index -- we need help -- Muffy et al. ?

[ozij]

Muffy, et al. as you well know, the recent year has more and more forum members using oximeters.

I turned to one since my 'cycle states' in the SilverLining report are at times abysmal --and the way I feel - while not abysmal is sometimes pretty so-so, and I wanted to know what was going on.

Little did I know how complicated this would turn out...

Some oximeters (all?) give an ODI -- the SPO2 7500 is (rigidly, can't be changed) based on 4% drop in saturation.

Now:

Does a drop in saturation, from 98 to 94, unaccompanied by a change in pulse rate mean anything? Does any 4 point drop above 90% unaccompanied etc. mean anything? What about 98 to 92? When does duration become relevant?

When is a change in pulse rate accompanied by a desaturation considered significant?

How stable should the saturation line look?

What about percentage of time spent a various saturation rates -- are there any agreed definitions of that? The reports can be so very granular -- how do we read them?

I was told the at my altitude (about 800ms), a waking saturation of 95% is an expected default, and fine. Is that so? Does that effect the interpretation I should give the numbers on the SPO2 report?

Edited to add: Should a baseline be measured without cpap (if yes, for how long)?

Thanks,
O.

[Hawthorne]

Ozij - I can't answer your questions but I am certainly glad you posted them! Thanks!

I have an oximeter as well and was wondering about the questions you articulated. I just didn't know what I wanted to ask or how to word it!

I'll be following this thread!!

[jnk]

This study involving diagnosing nursing-home patients does little to address directly your very good questions, which I too would like answers to, but I found it interesting:

http://biomed.gerontologyjournals.org/c ... l/60/1/104

[jinroh]

I am also a new oximeter user and have the same questions as OP.

[jnk]

Link-post bump.

http://www.sleepreviewmag.com/issues/ar ... -04_10.asp

[mars]

Hi All

Ozij has quite rightly started a new thread on this, which I hope will result in some answers.

My original thread was about clusters -
viewtopic/t45111/posting.php?mode=edit&f=1&p=403611
and then I digressed with oximeters, and never solved the cluster question.

However, Ozij has pulled up many other relevant oximeter questions, which hopefully can be answered.

My original oximeter question, which I will add to the above questions - was

Quote - My other thought is ------- what if I say that a cluster is when one AH event occurs before I have recovered from the previous Ah event. Now comes the oximeter digression; but as I never go below 90% SpO2 on my machine, then it may be that clusters are not that important, unless desaturation from 97% to 90% is significant. Now let me make this clear - I am talking about clusters where desaturation under 90% does not, I repeat not, happen.

So my secondary question is--------------is a drop in SpO2 from 97% to 90% of significance. I gather that the sleep labs do not think so, nor do the makers of oximeter machines. - End Quote

It looks like a lot of exploring of the web is in order.

As a good introduction to oximeter use I found the following link useful -

http://www.lancastergeneral.org/content ... _27211.htm

I am thinking that the best of the next generation of cpap machines will include an oximeter as standard.

Now - hopefully - someone has some answers out there.

cheers

Mars

[Muffy]

So I guess this topic will focus on a comparison of absolute desaturation (a drop below a predefined threshold, often 90%) and relative desaturation (a drop from the baseline value using a pre-defined value, usually 4% when talking about sleep). A relative desaturation will/should also have a minimum duration.

This should be a very informative and exciting discussion! Let me just do a couple of things for Variable Breathing and the effect of desvenlafaxine on sleep.

(Desvenlafaxine, touted as "The New Effexor", is claimed to be relatively specific in that it's the active metabolite vs something that needs to be processed and potentially leaving "unprocessed" problematic components lying around. I would think that the study groups took a bunch of normal people to determine Side Effect%, but a better question might be what happens when you give this stuff to a baseline "bad sleeper".)

Muffy

[elg5cats]

So I guess this topic will focus on a comparison of absolute desaturation (a drop below a predefined threshold, often 90%) and relative desaturation (a drop from the baseline value using a pre-defined value, usually 4% when talking about sleep). A relative desaturation will/should also have a minimum duration. This should be a very informative and exciting discussion! Muffy

On Sunday I did an online MD consult about pulse ox and asthma when my asthma symptoms were approaching a need for a ER visit. The online MD response to my pulse ox question of what's the definitive 02 sats support an ER visit. The follow was her response. If you are breathing fairly comfortably, a pulse ox reading of greater than or equal to 92% is acceptable. In adult asthmatics, a drop in pulse ox is a very late sign- meaning if it is below 90% the situation is quite severe. (This is different than the physiology in kids, where the pulse ox is more variable and often can drop down during asthma flares).
For me, this response sort of opened pandora's box with regards to understanding pulse ox data and sleep apnea. I have no idea if this information is relative, but left it me with questions. So, Muffy and others, I too think this can be a very interesting discussion.

elg5cats

[jnk]

Sounds complicated:

http://www.chestjournal.org/content/ear ... 7.full.pdf

. . . We analyzed 28 oxyhemoglobin indices. . . . The oxyhemoglobin desaturation indices (ODI) include three components, a certain threshold, baseline parameter and lasting time parameter: ODI(n)_(baseline parameter)_(lasting time parameter). The ODI calculated the amount of oxyhemoglobin desaturation below a certain threshold, when n equaled 3, it meant a 3%, and 4 meant a 4% decline from the baseline. The three different baseline definitions were a mean of all-night oxygen (A); a mean of the first 3 min of overnight oxygen recording (3M); and a mean of the top 20% of oxyhemoglobin saturation values over the 1 min preceding the scanned oxyhemoglobin value (1M20P). The definition of lasting time parameters was that the oxyhemoglobin desaturation had to continue for more than a certain criterion period. We tested three different lasting time parameters, including 1 sec (1), 3 sec (3) and 5 sec (5) . Finally, the ODI was the total oxyhemoglobin desaturation counts divided by the total recording time (hour). The four time domain indices were minimal or mean nocturnal oxyhemoglobin saturation (SpO2_min; SpO2_mean), cumulative time spent below 90% or 80% (CT90, CT80), threshold and fall index in SpO2 to [less than or equal to] 90% (DI90), and the Delta index. The Delta index measured the average of absolute differences of oxyhemoglobin saturation between successive 12 s intervals. . . . PSG is the gold standard for a definitive diagnosis of OSAHS.

[Muffy]

Does a drop in saturation, from 98 to 94, unaccompanied by a change in pulse rate mean anything?

Does any 4 point drop above 90% unaccompanied etc. mean anything?

What about 98 to 92?

When does duration become relevant?

When is a change in pulse rate accompanied by a desaturation considered significant?

How stable should the saturation line look?

What about percentage of time spent a various saturation rates -- are there any agreed definitions of that?

The reports can be so very granular -- how do we read them?

I was told the at my altitude (about 800ms), a waking saturation of 95% is an expected default, and fine. Is that so?

Does that effect the interpretation I should give the numbers on the SPO2 report?

Should a baseline be measured without cpap?

If yes, for how long?

Sounds complicated

It does only until one realizes that most, if not all of the documentation that people are going to present in this discussion will relate to the use of oximetry for diagnosis of SBD (ambient pressure, or no CPAP), yet the question that's really on the table is "What is the value of oximetry in routine monitoring of xPAP therapy?", to which I would reply "almost none".

Chances are that people reading this are on some sort of pressure therapy, may have already engaged in a certain amount of "dial wingin'" and arrived at some effective or near-effective pressure. Going out on a limb, I would further propose that if they're surfing cpap forums, they are continuing to have symptoms. After fixing the easy stuff, and once the Leak Obsession has passed ("Omigod! My predicted leak is 35, and I have a 38! It's the APOCALYPSE!!) and if they continue to have symptoms, then they may think that pressure therapy is ineffective, needs more precise monitoring and start buying more junk.

Desaturations, however, are relatively easy to fix, so for the majority of patients, there really won't be any. Exceptions to this would include uncontrolled central SDB (especially CompSAS) and baseline drops, which would suggest another disease entity. So, back to our story, if persistent EDS is the problem, I think the next step would be to look at sleep itself.

Overall, while routine monitoring of oximetry during xPAP therapy may be highly sensitive, I believe that it would not be very specific, which is what's really needed for day-to-day monitoring. If poor sleep is the underlying issue, then artifact contamination could result in chasing sleep disruption with pressure therapy.

There are three components of SBD that create problems: desaturations, intrathoracic pressure swings and sleep fragmentation. Isolating sub-components can take everything out of context, but with the proviso that the Ozij Grocery List is an academic micro-analysis, my answers are: no, no, still no, when it's <90%, when it's not artifact, perfectly, yes, you get somebody with an experienced eye, yes, no, that's the whole point of diagnostic NPSG, and all sleep states (including wake) and body positions.

Muffy

[ozij]

Does a drop in saturation, from 98 to 94, unaccompanied by a change in pulse rate mean anything?

no

Does any 4 point drop above 90% unaccompanied etc. mean anything?

no,

What about 98 to 92?
still no, , , ,

When does duration become relevant?

when it's <90%,

When is a change in pulse rate accompanied by a desaturation considered significant?

when it's not artifact,

How stable should the saturation line look?
perfectly,

What about percentage of time spent a various saturation rates -- are there any agreed definitions of that?
yes

The reports can be so very granular -- how do we read them?
you get somebody with an experienced eye

Thanks for the info.

O.

I was told the at my altitude (about 800ms), a waking saturation of 95% is an expected default, and fine. Is that so?

Yes

Does that effect the interpretation I should give the numbers on the SPO2 report?
no,

Should a baseline be measured without cpap?

that's the whole point of diagnostic NPSG and all sleep states (including wake) and body positions.

[jnk]

Speaking strictly for myself (and even I don't agree with me half the time), I bought my pulse-ox mostly to see with my own eyes that I was staying above 90% all night. That is why I didn't worry about high resolution or catching brief dips and movement artifact and the like. I was using an auto that was staying at a lower pressure than my titrated pressures (wingin' its own dials) to treat very severe OSA, and I felt I needed to be sure all those hypopneas showing up in ResScan weren't desaturating me, without going in for a third sleep study to check efficacy, although that would have been ideal.

I no longer suffer from EDS, but I hang around out of thankfulness for the help I got here and in order to support the good work being done by the likes of ozij and Muffy and because TV seems trite and pointless compared to the edifying entertainment being served up in these threads.

Thanks both for the questions and for the answers.

jeff

ps- As a side note, my primary doc at the time had me stay in his clinic overnight hooked up to a pulse ox to try to screen me for OSA years before I got sent for a sleep study. That doc saw no reason to send me for an NPSG at that time. I lost a few good years of my life to that decision. He should have sent me for a sleep study back then instead of trying to run his own one-signal imitation sleep lab. I have forgiven him, but not the idea.

[NotMuffy]

Hi there! I'm new here and know absolutely nothing about anything, but in re: a lack of pulse rate response with desaturation being a benign event, what if the patient is in beta-blockade, atrial fibrillation or has unpredictable autonomic response in REM, wouldn't a desaturation then be potentially significant?

TIA for your response.

NotMuffy

[jinroh]

yet the question that's really on the table is "What is the value of oximetry in routine monitoring of xPAP therapy?", to which I would reply "almost none".

I think it depends. For my case, I only started xPAP 3 weeks ago. Without getting an oximeter, I would have no idea that every night my SpO2 level drop below 85%, twice or more. So at least now I know I still have problem, even with BiPAP on 18/14.
Will contact my sleep doc.

[Muffy]

yet the question that's really on the table is "What is the value of oximetry in routine monitoring of xPAP therapy?", to which I would reply "almost none".

I think it depends. For my case, I only started xPAP 3 weeks ago. Without getting an oximeter, I would have no idea that every night my SpO2 level drop below 85%, twice or more. So at least now I know I still have problem, even with BiPAP on 18/14.

Keep in mind that

Exceptions to this would include uncontrolled central SDB (especially CompSAS)...

and I see where

The sleep doc wrote such in polysomnograph report: "The patient seemed to be best at CPAP/BiPAP pressure of 18 inspiration/14 expiration, with a backup rate of 12 .... If BiPAP ineffective, adaptive servo-ventilation is also an option for treatment of complex sleep apnea"

in

viewtopic/p404229/viewtopic.php?f=1&t=4 ... 86#p401386

Muffy