Apnea Forum Posting

Posted by Perry on September 15, 2000 at 09:01:24:

In Reply to: UARS, flow transducer and ResMed Auto pap posted by kev on September 12, 2000 at 18:28:09:

The machine in question with the features you mention is the Goodnight 418P (the 418A is a simpler machine).

This machine does not have a unique capability in the respect of being able to trigger off of low flow events; just a differnt approach (which I somewhat like).

Here is how the 418P is set up. The machine triggers off of Snore, "Flow Limitations", Hypopneas, and Apneas. In all cases the machine is looking for several events in a time period before triggering a pressure increase of 0.3 cmH20 (this counting is to prevent false triggers from rolling over, being jabbed by spouse, etc: even the AutoSet T now uses it at presures over 10).

The machine definition of Apneas, Hypopneas, and "Flow limitation" is fixed. Interestingly, I aM told that they define a "hypopnea" as 60% reduction for 10s instead of the medical standard of 50% for 10s.

A "Flow Limitation" is just a lower flow/time setting (and the tech rep could not easily find what that setting was). My guess is that it is probably in the range of 30% to 40% - but that is only my guess.

Hence the Detection routine triggers off of snores, a lower flow reduction than a formal medical hypopnea, a slightly stronger than medical hypopnea, and finally triggers off of an Apnea (and usually these events happen in that order).

Personally I like the feature as it provides a lower trigger point for flow problems while still giving a data set for stronger hypopneas (although I wish they would have stuck with the medical defined hypopnea of 50% for 10s to provide a valid comparison of AHI)

The data from the software is substaintial and long. I have a 19 page printout in hand which I got from Mallinckrodt. Some of the information is interesting and I can see the use of it; some of it is baffling to me (it seems that they included every possible form of output that any Dr asked for).

The Silverlining softare captures some detailed 12 hour data which includes typical daily event summaris, however, these daily summaries are not stored and then get mushed into a general period calculation (so you must download daily if you want to see if your indexes are getting better as you change things and fix mask problems). The data does not include a standard AHI calculation, instead provides independent index calculations for each trigger feature.

The 418P and software does have some interesting real time data capture features which could aid in understanding problem situations.

Also, the machine tracks probable central apneas which they call "open airway apnea" on the spec sheet but appears as "Apneas with Carciad Oscillations" on the printout (there is a "long" time where there is no breath and the machine is seeing your heartbeat from the pulse vibrations induced in your lungs - yes the sensors are that accurate). Note that the software is over $1000.

Interesting machine and if I can find one to use for a few days or a week I will try one (with the software).

As I said the lower flow trigger feature in not unique. The AutoAdjust LT allows you to adjust the definition of both Hypopnea and Apnea settings to accomplish much the same thing. Hypopnea setting can be adjusted down to 30% flow reduction for 6s up to up to a flow reduction of 70% for 150s.

Thus the AutoAdjust LT will also sense and trigger off of "flow limitiations" if you set it thus (with a 2 stage "flow" trigger process vs the 418P 3 stage "flow" trigger). The downside is that it will count these events as "hypopneas" and they will be sumarized and included in the AHI calculation; thus, you cannot compare AHI's to other machines if you adjust your definitions away from the medically defined settings. I will caution people that while this setting feature allows you to fine tune your machine to you - that you can really mess up your machine response with the wrong settings (too sensitive - rarely respond at all: In my opinion both data and knowledge is required here).

The AutoAdjust LT also tracks probably central apneas - they call them "Mixed" on the output.

Hope this helps and answers your question.

Perry

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