REMstar A-Flex 90% Display?

PMG · Post by **PMG** » Sat Mar 15, 2008 9:53 am

What exactly does the 90% number mean?

Thank you,
Patty

lking · Post by **lking** » Sat Mar 15, 2008 9:57 am

The 90% number is the pressure you were at for 90% of the time during that session used.

Wulfman · Post by **Wulfman** » Sat Mar 15, 2008 11:34 am

Nooooo......the 90% pressure means that you were at that pressure or below for 90% of the night.

Den

ozij · Post by **ozij** » Sat Mar 15, 2008 11:46 am

Well, no, not really. [Edit: Oooops. Den beat me to the "no"....]

It is the pressure at which or below which you spent 90% of your night. The 90th percentile - if the terminology is familiar to you.

Suppose your pressure is 8-12
Theoretically, you can spend 70% of your time at the bottom of the range, at a pressure of 8 , 10% at a pressure of 9, (that's 80% of the time) another 10% at 11 (that's 90% of the night) and another 10% at 12. You need a pressure of 11 or less for 90% of the night.

At 8 - 12 your average, will be: 8*.7 (pressure times part of the night spent in it) + 9*.1 +11*.1 + 12*.1 = 5.6 + .9 +1.1 +1.2= 8.8. It's meaningless, because you would need higher pressure for 30% of the night.

Now, suppose you move the bottom pressure to 9. Your 90% pressure will not change, it will still be 11. But your average will change dramatically: it will now be (9-8)*.7 higher, i.e. 8.8 + 0.7 which come out to 9.5 - but you'll still be spending 30% of the time needing more than that.

Which is why when prescribing pressure, the labs and machines report the percentile.
O.