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jskinner wrote:

janp wrote:Sorry James ... but I read a paper to the contrary.

There is a relationship between the two because if an apnea is bad enough it may cause a desaturation event. However believing that they are somehow interchangeable values is not correct. The only time that they will be exactly the same is if every breathing event caused a desaturation. That would be unlikely. They are measuring to different variables.

James ...

Your are correct ... there is a relationship between the two.

Maybe my statement of interchangeability was too strong, but the study that I referenced does state that the two numbers (while different measurements) show correlation.

From the study:

CONCLUSIONS

Agreement was high between the desaturation index and both the apnea-hypopnea index and the respiratory disturbance index in adults with suspected obstructive sleep apnea syndrome in Mexico City.

However, I don't believe that I said that they were exactly the same.

I understand that they are measuring different values ... but they found that the study showed that there was a high agreement in the two numbers.


Jeff ...

Proving a relationship does NOT prove interchangeability.

The study didn't say that it was a "relationship" ... it said there was an "agreement". The implication being that the desaturation index could be used as a reference in relation to the AHI.

Add to that the fact that home oximeters may underestimate the severity of significant dips in O2 or miss them completely.

That's very possible and I suspect depends on whether the oximeter is a $150 unit or a $450 unit and maybe even where it was manufactured.


Look guys, what I had been trying to point out (maybe not as articulate as I should have been) was that in looking at an oximetry report, you can get a feel as to what the AHI is by the O2 DeSaturation Index.

Nothing more complicated than that. That's what I took away from the study I referenced.

Jan

Re: if oximeter shows no desat, mach show AHI,which to believe?

Believe the machine. AHI is important.

Some events that distrub your sleep happen without detectable desats, so a pulse-ox won't tell you diddly about those. But the machine will.

More info is better than less. Sure. But be suspicious of info from any oximeter that is less than PSG quality.

jeff

jnk wrote:But be suspicious of info from any oximeter that is less than PSG quality.
jeff

Aw Shoot, Jeff!! Now why'd you go and say That!! Seriously! I was just researching some of the mid-range (low-range?) oximeters for less than $150...that I maybe could afford....
Do you have information you could share about why we should be suspicious?

plr66 wrote:

jnk wrote:But be suspicious of info from any oximeter that is less than PSG quality.
jeff

Aw Shoot, Jeff!! Now why'd you go and say That!! Seriously! I was just researching some of the mid-range (low-range?) oximeters for less than $150...that I maybe could afford....
Do you have information you could share about why we should be suspicious?

Sorry! I think oximeters are great. I would encourage everyone with moderate-to-severe OSA to get one. I didn't mean suspicious in the sense of thinking they are "wrong" or "unreliable." I just mean that no one should have a false sense of security that there couldn't possibly be anything wrong with their therapy because their pulse-ox is saying everything is fine. As long as everyone understands that the info they get may not be as good as the info from their PSG, I say buy one and use it in good health.

The one I use only records averages for each minute, but the newer ones from China, less than $200, are much more sensitive and have got good reviews on this board.

I seem to recall ozij posting a link to a great study on oximeters. But I can't find it.

Edit: Found it! http://www.chestjournal.org/content/120/2/625.full

janp wrote:Maybe my statement of interchangeability was too strong, but the study that I referenced does state that the two numbers (while different measurements) show correlation.

Correlation yes, interchangeability no.

The correlation is as follows: The number of SpO2 desat events will be less than or equal to the AHI value (baring any other medical condition causing desats)

janp wrote:Look guys, what I had been trying to point out (maybe not as articulate as I should have been) was that in looking at an oximetry report, you can get a feel as to what the AHI is by the O2 DeSaturation Index. Nothing more complicated than that. That's what I took away from the study I referenced.
Jan

I disagree. I have looked at my own AHI charts for almost 3 years and own a recording oximeter. I don't believe for a minute that desaturation index can give you a good feeling for your AHI. For example if your AHI is made up of mostly hypopneas, you'll never see those as desats...

My SPO2 7500 purchased in May records every second, if you tell it to -- and shows desats fo 4% -- my ODI is usually much higher than my AHI -- my desats are almost all in the 4% range -- and they get reported and counted.

O.

If I were buying right now, this deal looks pretty amazing to me:

http://www.semedicalsupply.com/cms-50d_plus.htm

jskinner wrote:

janp wrote:Maybe my statement of interchangeability was too strong, but the study that I referenced does state that the two numbers (while different measurements) show correlation.

Correlation yes, interchangeability no.

The correlation is as follows: The number of SpO2 desat events will be less than or equal to the AHI value (baring any other medical condition causing desats)

janp wrote:Look guys, what I had been trying to point out (maybe not as articulate as I should have been) was that in looking at an oximetry report, you can get a feel as to what the AHI is by the O2 DeSaturation Index. Nothing more complicated than that. That's what I took away from the study I referenced.
Jan

I disagree. I have looked at my own AHI charts for almost 3 years and own a recording oximeter. I don't believe for a minute that desaturation index can give you a good feeling for your AHI. For example if your AHI is made up of mostly hypopneas, you'll never see those as desats...

James ...

No disrespect ... but what your telling me (if I understand correctly) is that the study that I referenced (done in Mexico City) and is titled "Agreement Between Oxygen Desaturation Index and Apnea-Hypopnea Index in Adults With Suspected Obstructive Sleep Apnea at an Altitude of 2240 m" has no relevance.

I can't go back as far as you in comparing oximeter and EP data, I only started using the SP7500 a few months ago and CPAP therapy a year ago (I'm still in a learning mode). However (not in all cases), I can look at the data from the oximeter and say "Uh Oh" ... the number is not good and have it correlated by my EP data.

Jan

janp wrote:Sorry James ... but I read a paper to the contrary.

It indicated that the O2 DeSaturation Index could be used in lieu of an AHI reading ... it was close enough that the doctor could use it as an approximate AHI indicator. Sorry that I can't reference it. I read it quite a while ago (along with many other articles) while researching oximeters...

"Results" and "Conclusions" at ... http://www.sciencedirect.com/science?_o ... 4e16276e99

Actually, I'm not all that surprised that there was a correlation between ODI and AHI, and even RDI. The study was done in Mexico City at altitude, effectively dropping everybody's pO2 by about 35 mmHg:



and plopping them right on the edge of the Oxygen-Hemoglobin Dissociation curve, making them highly susceptible to even minor changes.

Have them do that trick in the flatlands.

Muffy

jnk wrote:If I were buying right now, this deal looks pretty amazing to me:

http://www.semedicalsupply.com/cms-50d_plus.htm

I think it looks like the only differences between this one and the $140 CMS 50E are the alarms and rechargeable Li batteries in the latter model. Seems like you could use rechargeable AAA batts in the less expensive 50D ? Anyone have any recent experience with the 50D to give a review?

Thanks for the link, Jeff.

plr66 wrote:

jnk wrote:If I were buying right now, this deal looks pretty amazing to me:

http://www.semedicalsupply.com/cms-50d_plus.htm

I think it looks like the only differences between this one and the $140 CMS 50E are the alarms and rechargeable Li batteries in the latter model. Seems like you could use rechargeable AAA batts in the less expensive 50D ? Anyone have any recent experience with the 50D to give a review?

Thanks for the link, Jeff.

My pleasure. That's where I got my older pulse-ox.

I assume you saw this discussion from a while back:

viewtopic.php?f=1&t=42129&p=374427&hilit=50d#p370596

Muffy wrote:Have them do that trick in the flatlands.

Excellent point.

janp wrote:The study didn't say that it was a "relationship" ... it said there was an "agreement".

Where I'm from, relationship doesn't imply agreement, but agreement implies a relationship. Then again, it's all relative, and agreeing to disagree is still agreement of a sort, at least among my more disagreeable relatives.

Muffy,

Actually, I'm not all that surprised that there was a correlation between ODI and AHI, and even RDI. The study was done in Mexico City at altitude, effectively dropping everybody's pO2 by about 35 mmHg:

That's really interesting to me. I live at 1250 meters above sea level.

I keep trying to convince the sleep doctors that the sleep test and titration was far from "real life" conditions. That the altitude should make a difference in how my therapy is perceived/handled.

The testing was done a 152 meters and of course under very controlled conditions. Nothing like at home ... in bed

Do you have access to the calculator ... or was the charting a copy from a website?

Jan

janp wrote:was the charting a copy from a website?

http://www.altitude.org/calculators/oxy ... ulator.htm

janp wrote:No disrespect ... but what your telling me (if I understand correctly) is that the study that I referenced (done in Mexico City) and is titled "Agreement Between Oxygen Desaturation Index and Apnea-Hypopnea Index in Adults With Suspected Obstructive Sleep Apnea at an Altitude of 2240 m" has no relevance.

Jan,

I never refereed that study or said it was irrelevant. There is a _correlation_ between desats and AHI, of course. My problem was with suggesting that they where interchangeable values, which they are not. They are measuring two different things: One is breathing events and the other is oxygen level in the blood. Yes one may lead to the other bit its not necessary.

I'm not really interested in debating this issue any longer. We clearly simply disagree

jskinner wrote: We clearly simply disagree

Oops. I feel a song coming on . . .

https://www.youtube.com/watch?v=p8_FOQ7-P30