What is Average 90% CPAP Pressure?

Am I correct that "Average 90% CPAP Pressure" is the pressure that you are at for 90% or less of the night?

That would mean you could have been at that pressure for anywhere from 89% to 1% of the night? I don't get it?

Yes that is correct. Because the machine samples at equal time intervals, time can substitute observations which is what the statisitcs is based on.

So you could have spen 1% at that 90% value or you could have spent 89% at that same value ... in any case, only 10% of the time (or observed data samples) were above that 90% value.

90% value is bsically the same as what is known in statistics as the 90th percentile ... 90% of the observed values are at or below that number and 10% of the observed values are above that number. The "average" 90% is basically the average of several nights of 90% values ... or an average of all of the 90th percentiles for each night.

OK, now I can see the value of the data, you spend 10% of the time over the 90% pressure.