Please explain the difference in these 2 results?

Hi,
Can someone explain to me the difference between "Pressure 95th centile" and "Median Pressure"?
My last results were 7.6 cm and 5.8 cm respectively. Thanks!

The median pressure is the half way point - half the time you were at or above this number, half the time you were at or below this number.

The 95 percentile is a mark where 95 % of the time (in other words most of this time) you were at or below this number. If for example your data was measuring 8 hours, then of those 480 minutes, you spent 456 min (7 hours 36 min) at or below that pressure. The other 24 minutes you spent at or above that pressure.

Country4ever wrote:Can someone explain to me the difference between "Pressure 95th centile" and "Median Pressure"?

95th Percentile Pressure is the pressure at or below which you spent 95% of your sleeping time for the night.

Median Pressure is (more or less) the average pressure over the entire night.

You need to look at a graphical representation of pressure against time to understand when your pressure was at any particular point between the set minumim pressure and the set maximum pressure on your S8.

The instantaneous pressure at any point in time will depend on a number of factors, including how well your airway is passing air to your lungs, mask leak rates, etc etc.

The pressure values themselves don't mean much until combined with the AHI and leak rate values.

Cheers,

Bill

Thanks Jules!
From those numbers can I deduce which CPAP pressure to put myself at? It seems like I'll either be too high some of the time, or too low. This is just a test. If it doesn't work, I'll go back to APAP.
It just doesn't seem right to make myself breath more deeply half the time, if I don't need it. But if I pay attention to that, then I won't breath deep enough the rest of the time.

[quote="Country4ever"]Thanks Jules!
From those numbers can I deduce which CPAP pressure to put myself at? It seems like I'll either be too high some of the time, or too low. This is just a test. If it doesn't work, I'll go back to APAP.
It just doesn't seem right to make myself breath more deeply half the time, if I don't need it. But if I pay attention to that, then I won't breath deep enough the rest of the time.

Thanks Bill and Jules.

The 95th percentile is the value for which 95% of all measured values are equal to or less than. Because the machine takes measurements at equal intervals of time, the 95th percnetile also means that you spent 95% of your time on the machine at or below that value.

The median is defined similarly except that it is the 50th percentile ... half the values measure are above and the other half are below.

Country4ever wrote:It just doesn't seem right to make myself breath more deeply half the time, if I don't need it. But if I pay attention to that, then I won't breath deep enough the rest of the time.

Jules gave a great explanation. Good teacher!

One small clarification in what you wrote, Country4ever. I don't think more pressure makes a person "breathe more deeply." More pressure is simply that...more pressure.

Sometimes high pressure might cause some people to hold their breath at times against the pressure, but I don't think it's likely to cause them to breathe more deeply.

The usual benefits of not using more pressure than needed to keep the airway open at any given time are less chance of mask leaks and less chance or aerophagia.

Some people get more comfortable, less mask-leaky treatment using autopap to find the varying pressures needed throughout the night.

Others get better treatment (and are more comfortable) using one steady pressure throughout the night, even if the pressure is more than actually needed most of the time.

That's one of the beauties of an autopap. Can be used either way..whichever way suits a person better. As an autopap varying the pressure. Or as a cpap delivering one pressure.

billbolton wrote: Median Pressure is (more or less) the average pressure over the entire night.

hmm - more or less - nice statistical idea there -

mean is average - mode is most common - median is half way point ----

ever taught General Education Statistics?

ever even take it?

jules wrote:hmm - more or less - nice statistical idea there

If the OP understood statistical ideas they wouldn't have needed to ask the question.

Ever studied human communication?

jules wrote:

billbolton wrote: Median Pressure is (more or less) the average pressure over the entire night.

hmm - more or less - nice statistical idea there -

mean is average - mode is most common - median is half way point ----

ever taught General Education Statistics?

ever even take it?

Actually, the median IS more or less the average. An average is defined as a measure of central tendency and although the arithmetic mean is generally inferred, it can also refer to other measures such as the median as well as many types of means such as the artithmtic, geometric, harmonic, quadratic, generalized, truncated, trimmed, interquartile, and a host of others.

Without further qualifications, the median defined as the ”half way point” can be more misleading than just calling it the average. The median is more accurately defined as the 50th percentile or the middle value of a sorted set of numerical values.

I have never taught General Education Statistics but I have taken a couple of grad courses in quantitative methods and taught statistical concepts in undergrad science labs. Also use statistics in my profession on a weekly basis although I would never consider myself to be an “expert” in either statistics or mathematics. Oh yea, and I sleep with my PAP machie every night.

billbolton wrote:
If the OP understood statistical ideas they wouldn't have needed to ask the question.

Ever studied human communication?

Bill makes a good point on this.


EDIT: Forgot to mention another interesting fact about median and mean. For a perfect Guassian (normal or bell-curve) distribution, the median and the arithmetic mean have the exact same value

jules wrote:

billbolton wrote: Median Pressure is (more or less) the average pressure over the entire night.

hmm - more or less - nice statistical idea there -

mean is average - mode is most common - median is half way point ----

ever taught General Education Statistics?

ever even take it?

Ever get your machine tweaked properly so you aren't so crabby?

.... and before you ask, yes I am having a heck of a time getting mine tweaked.

Anonymous wrote:

jules wrote:

billbolton wrote: Median Pressure is (more or less) the average pressure over the entire night.

hmm - more or less - nice statistical idea there -

mean is average - mode is most common - median is half way point ----

ever taught General Education Statistics?

ever even take it?

Ever get your machine tweaked properly so you aren't so crabby?

.... and before you ask, yes I am having a heck of a time getting mine tweaked.

And statistically, you're probably in the 95th percentile of PAP users.

(good luck getting it tweaked.....hope it improves YOUR disposition, too)

Den