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Re: Re: Re: Re: AutoAdjust LT question

Posted by Perry on July 29, 2002 at 17:23:31:

In Reply to: Re: Re: Re: AutoAdjust LT question posted by BeardedMan on July 29, 2002 at 10:21:21:

Central Apnea: Stopage of breathing muscle function (your diaphram stops contracting) for 10 seconds, and not occuring during sleep transition.

In the US the legal definintion requires the measurment of muscle effort - hence those upper and lower chest straps you wear during a sleep study. This also explains why the AutoCPAP software cannot call them centrals in the US - even when the technique they are using is 100% certain that it is a central. As an example the 418P detects heart beat "artifacts" from the small pressure/flow pluses created by your pulse in your lungs at a time of no breathing flow (the advantages of pneumotachs). This event only occurs during an "open throat" central apnea - thus anything called by the 418P is actaully a central event if it does not occur during sleep transition. The downside is that on average only 60% of central apneas are "open throat" centrals, and the machine cannot see the heart beat "artifacts" when your thoat is closed (or mostly closed). Thus if you typically have "closed throat" centrals - the 418P will complete miss them and clasify them as obstructive apneas.

Sleep transition events occur when your brain is going through a "muddled" stage while you fall asleap (visable on the EKG). Non-obstructive breath stoppage events are common while your brain is in this "muddled" stage. Sleep labs do not score these as Centrals, but AutoCPAPs will see these as some form of apnea, and will sort the event as best it can. It is not uncommon for a person to have a couple of these a night. So if you see a few "central type events" or other apnea at night - you may only be seeing the sleep transition events that the machine caught.

There are three machines that make an attempt to resolve the central event issue: AutoAdjust LT - with an effectiveness of 85% when scored against sleel lab scored centrals. 418P with its 60% on average of "open throat" centrals. The Remstar Auto, who's effectiveness is unknown and has not been formally tested.

Each of these three technique is completely different than the others.

I actually know how each of those machines makes it call. But some of what I have been told was provided under the guize of proprietary information (the 418P's is published). Hence why I do not further describe how they work.

I hope this helps.

Perry

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