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Re: AutoAdjust LT question

Posted by Perry on July 29, 2002 at 17:03:38:

In Reply to: AutoAdjust LT question posted by Peter on July 29, 2002 at 04:30:32:

I will try to clear up the confusion.

First: There is no accepted medical definition of hypopneas. So from a sense - the AutoAdjust LT responds to all hypopneas.

On the other hand, a lot of people want to see a comparison to how they are doing now compared to before (ie: how many 50% 10 second "Hypopneas" do they have now....). The AutoAdjust LT cannot tell you that.

What it does is allow you to change the definition of Apnea (highly not recommended) and Hypopnea (changing this works for the vast majority of people who are not being treated correctly by the default settings of 50% flow reduction for 10 seconds).

However, once you change the definition (perhaps to 50% for 8 seconds, or 40% for 10 seconds, or 70% for 15 seconds, etc) -- your changed definition is what the machine counts, records, and responds to. Thus, people who make their "hypopnea" settings more aggresive typically see a lot more "hypopneas" than before. As several have mentioned, many people can almost eliminate their Apneas (one reason for leaving the Apnea definintion alone - so you can see how changing the hypopnea definition affected apneas). You can also decreas event if you change the definition to less aggressive.

But, they can no longer see how many "old definition hypopneas" they had at night. Hence why some people talk of two differnt kinds of Hypopnea events with the AutoAdjust LT (and that it doesn't show one of them).

I would like to clarify an additional point. Many AutoCPAP's do indeed respond to central events. The AutoAdjust LT's detection routine is only about 85% effective compared to a sleep lab. Some machines make no attempt to differentiate at all (418A, and AutoSet T) and respond to any apnea that occurs in its response pressure range (10 cm H20 for the AutoSet T). The 418P dectection routine is only about 60% effective. So if you have the right kind of central event at the right pressuere - almost all AutoCPAPs will respond.

Hope this helps.

Perry

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