"please keep me updated about oximeters "
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Is AHI a good measurement unit?
There are (only) 3 things there is international consensus about when we talk Sleep Apnea.
1. AHI (Apnea Hypopneas events > 10 seconds per hour)
2. SaO2 Desaturations.
3. The full PSG study as the "Gold Standard".
Furthermore, there is international consensus on an AHI scale of severity:
Mild SA = AHI between 5 and 15
Moderate SA = AHI between 15 and 30
Severe SA = AHI > 30
Of course I agree that AHI is a good measuring unit to detect SA. But as with previous measurement of Nocturnal pulse oximetry, I believe that this unit has several shortcomings.
After this measurement unit was introduced, we have got a lot of new knowledge, e.g. about UARS. Most of PSG studies cannot measure this.
Even when we discuss the severity of SA, I am not sure this unit is good. For example, a person with severe SA can have very little or no desaturations, and conversely, a person with very mild SA can have strong desaturations. Corresponding with symptoms. I have also seen new studies that indicate that even AHI <5 can bring severe sleep problems.
I therefore think it is pointless to talk about the severity associated with AHI. I don’t know who and how this scale has been decided, but it is certainly comfortable among some doctors because they can use it for the preparation of guidelines and I have even seen that this scale is used in a simple decision table to determine the severity and the treatment of SA (or maybe the lack of treatment).
IMO There is too much focus on the AHI as the sole determinant of the severity of SA, from Sleep centers, Public health care systems and maybe especially Insurance companies.
I think that we need to look more at the whole person, and all of the symptoms until we have a better measuring unit.
Let me hear your opinion.
Henning
1. AHI (Apnea Hypopneas events > 10 seconds per hour)
2. SaO2 Desaturations.
3. The full PSG study as the "Gold Standard".
Furthermore, there is international consensus on an AHI scale of severity:
Mild SA = AHI between 5 and 15
Moderate SA = AHI between 15 and 30
Severe SA = AHI > 30
Of course I agree that AHI is a good measuring unit to detect SA. But as with previous measurement of Nocturnal pulse oximetry, I believe that this unit has several shortcomings.
After this measurement unit was introduced, we have got a lot of new knowledge, e.g. about UARS. Most of PSG studies cannot measure this.
Even when we discuss the severity of SA, I am not sure this unit is good. For example, a person with severe SA can have very little or no desaturations, and conversely, a person with very mild SA can have strong desaturations. Corresponding with symptoms. I have also seen new studies that indicate that even AHI <5 can bring severe sleep problems.
I therefore think it is pointless to talk about the severity associated with AHI. I don’t know who and how this scale has been decided, but it is certainly comfortable among some doctors because they can use it for the preparation of guidelines and I have even seen that this scale is used in a simple decision table to determine the severity and the treatment of SA (or maybe the lack of treatment).
IMO There is too much focus on the AHI as the sole determinant of the severity of SA, from Sleep centers, Public health care systems and maybe especially Insurance companies.
I think that we need to look more at the whole person, and all of the symptoms until we have a better measuring unit.
Let me hear your opinion.
Henning
Views: 3490
Replies to This Discussion
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Permalink Reply by Dave on
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For me the following question is relevant:
Assuming we are talking about common obstructive sleep apnea (OSA) and that is the only condition a patient has, Is it possible to have a high Apnea Index (we are talking apneas not hyponeas) and normal Oxygen Levels? Assuming we were in ideal world and there was no costs/bureaucracy to claim such devices, should all of us straight away OSA patients have oximeters?
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Permalink Reply by Daniel on
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Apneas are defined as having a duration of ten seconds or more. If your apneas only last ten seconds, it is possible to see apneas without a large drop in oxygen level. However, if your apneas last 30 seconds, you can be pretty sure there will be a significant O2 drop.
O2 levels are also a fuzzy scale. Some doctors get concerned when O2 levels drop below 93%. Others are only concerned if it drops below 90%. If your O2 level drops from 99% to 95%, it will be scored as a significant drop, even if your average O2 level is 94%.
I think it is ridiculous to consider dispensing oximeters as part of a CPAP setup. Oximetry with CPAP at home may have a role in an overnight test to be sure the device is effective, but if you feel better using CPAP, such a test is probably unneccessary. Please don't get obsessed with statistics! Focus on how you feel during your waking hours.
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Permalink Reply by sleepycarol on
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Sorry but I have to disagree with you Daniel. If a patient wants to track their O2 levels they should be allowed to do so. Granted not all patients are proactive -- but in my opinion this should be an option that is available if the patient desires it.
As far as being obsessed with statistics, it is my life, I like being in the know and do not like "flying" blind. Would you tell a diabetic that their numbers were unimportant? To focus on how they felt? Don't think so as there are serious consequences if they do not monitor their levels.
I do not check my numbers daily or even weekly. I typically check my numbers with Encore Pro about once a month. I can then tweak my therapy if needed. I know for myself I would much rather keep track of my therapy as I NEVER want to go back to feeling like I did prior to treatment. Patients have died in their sleep -- did sleep apnea cause it? I don't think at times they really know -- and I do not intend to become a statistic.
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Permalink Reply by Henning on
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As Judy wrote, we must all keep in mind that OSAS are NOT the only sleep disturbances that can be detected by a full PSG (polysomnography), so I think this discussion only is about uncomplicated OSAS. But I also think, that most SA sufferers only have uncomplicated OSAS, but you can’t know this without a full PSG.
Daniel wrote: (taken out of the context)
- It's my understanding the AHI scale was defined at Stanford, and they are the first to acknowledge that the scale does not adequately address the severity of the symptoms of sleep apnea.
However, I also remind them that ultimately, it isn't about the numbers. It's about how you feel when you wake up in the morning.
Then Dr. Colin E. Sullivan (from the article linked above by Ed) is right when he gave these statements:
“The apnea-hypopnea index (AHI) is useless for measuring the severity of sleep-disordered breathing (SDB).”
“The management of SDB should hinge on the history, physical examination, and clinical judgment.”
“Probably the best indicator of SDB, however, is simply the response to continuous positive airway pressure (CPAP) treatment. “It really is a no-brainer,” Dr. Sullivan remarked, pointing out that CPAP administration is especially easy with the newer devices that automatically set the appropriate amount of positive pressure.”
But then I have to ask, why is AHI used to decide if we need treatment? Is it because of Insurance companies and Health Care Systems, or is it only because we don’t have anything better?
Some people might be denied treatment because of a useless number.
Daniel wrote:
Therefore, the "Hypopneas" as measured by a data-collecting CPAP use a definition of hypopnea that has little to do with the variable measures used in sleep labs. Each brand uses a different definition of hypopnea. I have a patient who has both a BiPAP Auto and a VPAP Auto. He uses them with fixed pressures, but the HI on the ResMed device is much higher. At best, the hypopneas readings from your CPAP are only a rough estimate.
It is also my experience that ResMed devices are more sensitive to detect Hypopneas. I have spoken with ResMed a couple of times about this, and the answer was that I should NOT think of the Hypopneas, because my machine takes care of them, even if they increase the number. (I have a ResMed S8 Autoset Spirit). In my own experience it is only AI who is important for me. But this is with AUTO CPAP.
Henning
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Henning wrote:
But then I have to ask, why is AHI used to decide if we need treatment? Is it because of Insurance companies and Health Care Systems, or is it only because we don’t have anything better?
I believe it is the former. Insurance companies like to have a quantifiable system where they can say that if your AHI is below 15, there isn't medical necessity for CPAP and therefore won't pay the claim.
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I have found that the difference in the definition of hypopneas can vary a great deal.
For the highest score: Airflow limitation at 30% and above and desaturations at least at 3%.
For the lowest score: Airflow limitation at 70% and above and desaturations at least at 4%.
The latter is defined by some insurers in the US.
Here in the country we use the following definition: Airflow limitation at 50% or more and desaturations at least at 3%.
So this alone, will lead to large differences in AHI.
In my own case, my first sleep study was showing an AHI just at the borderline at 15. If there have been used another (and lower score) definition I would probably not have been qualified for treatment with CPAP.
Since I now know how big benefit I have with my CPAP treatment, it's discouraging to think on how many are being denied treatment because of a coincidence.
Henning
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In cases where AHI is less than 15, Medicare has specified certain instances wherein beneficiaries may still qualify. The provider must have documentation on file from the prescribing physician stating one or more of the following:
- Excessive Daytime Sleepiness
- Impaired Cognition
- Insomnia
- Mood Disorders
- Hypertension
- Ischemic Heart Disease
- History of Stroke
Most private insurance companies also adhere to these guidellines, although it can be an arduous appeal process to get approved. It's pretty easy for a doctor to qualify any low AHI patient under the Excessive Daytime Sleepiness or Insomnia conditions, if they truly want to get a CPAP.
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Permalink Reply by RichM on
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So If I read this right my AHI is has a 30 day avg of 68.1 that means I must have very severe sleep SA right?
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You need to clarify. By mentioning a 30-day average, I assume that you are reading information from the display on a Respironics CPAP/Auto or BiPAP. If the display says your AHI is 68.1 while using your device, it means either: a) You have very severe sleep apnea even with PAP therapy, or B) Something is very amiss with your pressure settings, mask fit, or the device itself. My gut says B, and if that's the case, you should head to your provider immediately to figure out what's going on.
If your AHI was 68.1 for your diagnostic sleep study, than you do indeed have very severe sleep apnea. Basically, your breathing is disturbing your sleep more than once a minute. If you think you're severe, at SomniHealth, I have a patient whose AHI was 145 events per hour! After two weeks with her CPAP, her AHI registered 6 on her device. More important than that was the vitality I could see in her. She gave me a big hug and told me that I had given her life back to her. For two year's now, she's been SomniHealth's "Poster Girl"
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Hi Daniel,
I learned something new here.
I spoke with my sleep specialist today in another context, and he told me that it is the same here in the country. I assume when you are talking about “the prescribing physician” that you are talking about what I call “my sleep specialist” and not my primary doctor?
BTW. I was also told that our system has reduced the borderline for CPAP treatment to AHI=10.
Henning
Daniel Levy said:In cases where AHI is less than 15, Medicare has specified certain instances wherein beneficiaries may still qualify. The provider must have documentation on file from the prescribing physician stating one or more of the following:
- Excessive Daytime Sleepiness - Impaired Cognition - Insomnia - Mood Disorders - Hypertension
- Ischemic Heart Disease
- History of Stroke
Most private insurance companies also adhere to these guidellines, although it can be an arduous appeal process to get approved. It's pretty easy for a doctor to qualify any low AHI patient under the Excessive Daytime Sleepiness or Insomnia conditions, if they truly want to get a CPAP.
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It's easiest for us to get additional documentation from the doctor who referred the patient to SomniHealth. 99% of the time, that's the doctor who signed the prescription for the device. It isn't required to be the same doctor, though. The documentation can come from the primary care physician as well. In some cases, the PCP (primary care physician) receives the results and recommendations from the sleep lab's supervising physician, and then the PCP writes the Rx. In most cases, the lab's supervising MD writes the Rx.
Confusing? You bet! That's why I like to position SomniHealth as the patient's "sleep advocate," helping to steer them through the maze of doctors and faciilities than can be dreadfully disconnected.
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I can see there is a difference here. In Denmark, it is only the sleep specialist who can deal with CPAP treatment. The primary doctor has rarely any knowledge about this. And as mentioned in another diskussion, we have no DME's.
But what is missing in our system is a "project leader" (maybe a good DME) who can guide the patient and especially if there are some problems to deal with. I have otherwise just read your website, and am very positive about your approach.
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