Hypopnea Index Help

I guess I don't have a very good understanding of what the hypopnea index measures and how to get the number down.

I know the definition describes reduced airflow, but is this like holding your breath?

My AI is usually pretty low, but it ranges from about .5 - 3.0, but my HI can range from 2.0 - 10.0 for a AHI of between 4.8 - 18. Seems like this is still on the high side because the AHI is rarely below 8.

I have been compliant now for 2 weeks and assume that some adjustments will need to be made to my S8 (set to Auto 6 - 16).

I don't plan to start changing my pressure settings myself (yet), but what changes should I expect my doctor to prescribe to get the HI down. Is it raising the lower pressure?

My machine has never gone above 12.2 during the night.

Your equipment shows you have an S8 Elite, which isn't an auto machine. But since you say your setting is 6-16, I'm assuming you have the S8 Vantage.

Does your data show the pressure at which the hypopneas occur? That would give you an indication of what you might want to try next.

Do you know what your titrated pressure was? I would suggest raising the low end of your range to maybe 1 cm lower than your titrated pressure and lowering the high end of your range to 14 (since you report 12.2 has been your highest usage.)

Changing the pressure is simple and straight-forward. There's no need to wait for a doctor or DME to do it when you can do it yourself in less than 1 minute. It's as easy as raising or lowering the temperature on a thermostat.

A hypopnea is kind of like a baby apnea. If your pressure range is narrowed, there will be a better chance of nipping those in the bud.

Your right about the equipment in my profile. The devices are listed alphabetically and there was no S8 Vantage in the list. After looking a little more, I found a listing for Resmed S8 Vantage.

There was no determination on pressure during sleep study. That is why my pressure range is pretty broad right now. I have been on the machine a little over 60 hours, so I should be able to start narrowing down the range.

Resmed machines use the A-10 algorythm called Autoset, therefor they don't detect and respond to hypoapneas.

Resmed machines only respond to (from Resmed website):

AutoSet® Technology

The amount of pressure required for effective CPAP therapy varies according to sleep stage, sleep position, and other factors. Insufficient pressure results in ineffective therapy while too much pressure can lead to discomfort, non-compliance, and pressure-related side effects.

ResMed’s AutoSet SpiritTM is an automatic titration system for the treatment of obstructive sleep apnea (OSA). AutoSet devices adjust pressure on a breath-by-breath basis to suit patient needs as they vary throughout the night. As a result, the patient receives the minimum pressure required for effective therapy. The lower pressures may improve patient comfort, reduce pressure-related side effects, and lead to increased patient compliance.

The AutoSet algorithm responds to three key respiratory parameters:

* Inspiratory flow limitation
* Snore
* Apnea

Additionally, AutoSet devices maintain pressure by compensating for mask leak.

Referenced link:
http://www.resmed.com/portal/site/ResMe ... &vgnPNum=1

to lower your AHI index, you need to increase the bottom pressure from 6cm to 7 or even 8cm (if you can tolerate it).

Resmed machines treat hypoapneas as flow limitations. Think of these flow limitations as the beginning or making of a hypoapnea. The only difference between a flow limitation and a hypoapnea is the amount of collapse or decrease in air flow and its duration (time).

So a hypoapnea would be more severe and last longer than a flow limitation. A apnea would be even more severe with complete blockage (vs. partial blockage). There was an analogy once from a fireman, it was like stepping on a firehose, if you step on the firehose and collapse it one quarter of the way, you have a flow limitation, if you continue to half way you have a hypoapnea, if you continue to collapse it until the water stops you have an apnea.

So it goes in severity similar to the following:

flow limitation->hypoapnea->apnea.

In reality it normally goes:
flow limitation->hypoapnea->snore->apnea.

Snores typically take place on inhale right before a apnea event, this can usually be seen on reports, but snores don't usually result in that great of collapse of the airway nor do they cause decrease to oxygen levels (because they are so short). But since snores are generally a precurser to an apnea event, most machines try and eliminate them which can prevent the follow-on apena run.

From this, you can see that if the Resmed machines respond to flow limitation and snore, they can prevent the hypoapnea and also the following apnea as they are classified.

Anonymous wrote:Resmed machines use the A-10 algorythm called Autoset, therefor they don't detect and respond to hypoapneas.

Guest, that statement is not quite correct. The machine detects and responds to flow limitations. A hypopnea cannot exist without a flow limitation.

Anonymous wrote:

Anonymous wrote:Resmed machines use the A-10 algorythm called Autoset, therefor they don't detect and respond to hypoapneas.

Guest, that statement is not quite correct. The machine detects and responds to flow limitations. A hypopnea cannot exist without a flow limitation.

The machine doesn't know if the flow limitation is a just that, or a hypopnea. It is capable of detecting and responding to flow limitations. Since it is detecting and responding to flow limitations, and hypopneas do not exist without flow limitations, it is obviously detecting and responding to hypopneas as well.

I suggest you do not fool with your pressure unlessw you have data to go by.

Raising pressure is no guarantee that it will reduce HI. It might have the opposite result.

Look at an AHI/Pressure chart from MyEncore and you will see HI & AI broken out so you can see how each responds to different pressures.

Tom

roztom wrote:I suggest you do not fool with your pressure unlessw you have data to go by.

He does have data. See the first post on the thread.

Even if he didn't have data, "fooling" with his pressure is a great way to determine what gives him the best night's sleep.

Let me divert a little from the previous information - all of which you will need to understand as you continue to use CPAP therapy.

I too had problems with getting my AHI down to what I felt was an acceptable level and it bounced from 15 one night to 7 another back up to 11 and down again. I couldn't get it stable or as low as I would like. Then I switched masks. I was using a FF and a nasal mask then switched to a nasal pillow (Aura). I use a relatively high pressure range with my APAP from 10 to 15 cm H2O and I found that with the Aura (and using the rubber bands to assist in maintaining a good fit) my leakage rate went down significantly and so did my AHI. There are now times when I have an AHI of less than one - although not too often - and most often it averages 5 or less. I attribute that to changing masks and getting a better fit and lower leakage. Less air leakage the better the therapy is working - at least for me.

Anyway, it is just a thought and it worked for me. Of course getting the right mask is often difficult thru trial and error and somewhat costly. And you will discover that not everyone will prefer the same mask.

Wish you luck,

Guest wrote:Even if he didn't have data, "fooling" with his pressure is a great way to determine what gives him the best night's sleep.

While it's probably better to have as much info as possible, fiddling with the pressure -- with no software data to go by -- is how these test subjects were able to titrate themselves quite well at home. And with just a simple CPAP machine, not even an autopap:

Can Patients with Obstructive Sleep Apnea Titrate Their Own Continuous Positive Airway Pressure? Published: American Journal of Respiratory and Critical Care Medicine Vol 167. pp. 716-722, (2003)

Autopap and software could make finding one's ideal pressure(s) a lot easier, but that study showed it can be done with the most basic equipment.