You can get a cheap manometer from a lot of the online places. It will get a fairly accurate reading. An electronic one is kinda overkill unless you were in the repair business or just extremely obsessive compulsive.
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07-30-2015, 11:34 PM
(This post was last modified: 07-30-2015, 11:54 PM by under pressure.)
Each manufacture uses their own proprietary Auto algorithm in their machines, therefore you'll never get the exact same data or pressure settings from one manufacturers' machine to another, some of them have some pretty significant differences in terms of how they react to flow limitations, snores, and Apneas.
I've owned and used four different auto machines from four different companies, they all have some differences in how they work, how they report events, and how they respond to events. You mention the Z1 Auto - one big draw back with the data it reports is there is absolutely no breakdown as to what your AHI number break down is, are the events Obstructive, Central, or Hypopnes? No way to know for sure. Of the four Autos I use the Z1 is by far the most "Suspect" in its data and its response to events.
I have a manometer and have tested the pressure from the Z1, it's pretty darn close, I had the machine set for 12 cm and the manometer reported 11.8 so it's within the accuracy range specified by HDM. But the machine responds differently to my events and never gets up to the pressures that my Resmed machines get to, I think this happens because the Resmed Algorithm is much more sensitive to Flow Limitations and as a result it increases pressure several cm higher than any of my other Auto machines. I have an F&P Auto Icon, it gets to pressures above what the Z1 gets to, but never reaches the pressures that the Resmeds get to. My Transcend Auto seems to be pretty close in pressure responses to the F&P Auto and the Z1 has the smallest pressure responses.
As a result of each machine operating somewhat differently I find that I end up setting each one up slightly differently so that I get the pressures I want from each machine. I know from previous experience that I want the machines to at least give me a 90% pressure of 13 cm so I set the lower pressure a little higher on the Z1 than I do with the Resmeds, so it boils down to a little trial and error setting up each different brand of machine to get the pressures from them that you want based on your previous experience. I actually have to limit how high the Resmeds will go because they tend to raise the pressure more than I am comfortable with, so I set the upper pressure so the machine will top out where I want it. All the others I can leave the upper limit wide open at 20 because they'll never go much past 13 or 14, but I have to set the lower limit a bit higher on the F&P, the Transcend, and the Z1 than I do on the Resmeds to get them to a higher minimum pressure than the Auto Algorithms would want them to go.
So just set each machine up to get the pressures that you feel that you need based on your previous experience.
As a side note I have heard from folks that used the older Resmed S8 Auto and then later switched to the S9 Auto or the newer Airsense machine and are surprised how different they are in their pressure responses. Resmed made some major changes to their Auto Algorithm when they came out with the S9 Autosense. So those people that moved up from the S8 noticed fairly significant differences, most being that the S9 would tend to go to higher pressures than the S8 would if the upper limit was set to allow higher pressures. I think another big difference between the S8 and the S9 is that when they came out with the S9 they had developed the FOT technique so that the S9 could differentiate between an Obstructive Apnea and a Central Apnea, so the S8 would not respond to Apnea events above a pressure of 10 cm, it would only respond to Flow Limitations and Snores above 10 cm the thinking being that they didn't want to have pressure increases in response to Apneas alone above 10 cm in case they might be Central events in which case raising the pressure would not correct a Central Apnea, and might even induce more Centrals. They solved this issue with the S9 machines because they could now distinguish between Obstructive Apneas and Centrals, therefore their Auto Algorithm changed substantially between the S8 and the S9. The Airsense stayed with basically the same Auto Algorithm as the S9 except for the development of the "For Her" Algorithm, but that's a story for another time ;+)
Nice post, very interesting.
if you can't decide then you don't have enough data.
I think to further clarify my post for the original poster in terms of what to do in this case.
I would use your Resmed S9 as your baseline machine, it gives you the best, and most complete picture of what's going on with your therapy when you sleep. I would consider your S9 as the best proxy based on the extensive data it provides for you.
When you use a different machine, especially in the case of the Z1 Auto (suspect data) set the Z1 up so it will give you the same pressures that you get from your S9 despite what the Z1 data might say. Don't go the other way around where you set up the S9 based on data you get from the Z1.
I think most people would agree here that the information and treatment pressures that you get from your S9 are the most realistic and the best source of information for your therapy, so use your S9 as the "Master Machine" that you would want to mimic with your Z1 travel unit.
That's not surprising. I wouldn't worry about it unless it's causing you problems.
The S9 does a lot of looking at subtle things like restricted airflow, not just apneas.
Remember, you can always set the max pressure yourself and see what the results look like.
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If it's midnight and a DME tells you it's dark outside, go and check it yourself.