Reading the detail

95th percentile pressure

On an auto-adjusting machine, pressure changes all night, so no single number describes it perfectly. The 95th percentile is the closest thing: the level your machine stayed at or below for 95 percent of the night. On fixed CPAP it is simply your set pressure, which is why the figure only becomes interesting on APAP.

The numbers that matter

Meaning: pressure not exceeded for 95 percent of the night
Versus average: average is dragged down by long low-pressure stretches
Versus maximum: maximum can reflect a single brief peak
Common clinical use: the starting point when converting APAP to fixed CPAP

Why not the average or the maximum

The average is pulled down by the long calm stretches when you needed very little. It describes a typical moment, not the pressure that dealt with your problems. The maximum has the opposite fault: one three-second spike sets it for the whole night.

The 95th percentile ignores both distortions. It answers the practical question, which is what pressure was genuinely needed to keep the airway open through nearly all of the night.

How to read it over time

A 95th percentile that creeps up over months, with the same range and the same mode, means your airway is asking for more. Weight, alcohol, nasal congestion and ageing tissue all do this. It is a slow signal, so it only shows up if you keep your history.

It also tells you whether your range is set sensibly. Sitting right at the top of your range every night means the machine is being capped, and there may be pressure it wanted to deliver and could not.

What it is used for clinically

When a prescriber moves someone from APAP to a fixed pressure, the 95th percentile from a representative period is the usual starting point. That is the number that covered you, so it is the sensible candidate for a constant.

It is a starting point and not a conclusion. The decision still depends on your events, your leak and your comfort, which is why this belongs in a consultation rather than in a self-adjustment.

Common questions

My 95th percentile is at the top of my range, is that a problem?

It suggests the machine may be constrained by the ceiling rather than by your airway. It is a good thing to raise with your prescriber, who can judge whether widening the range is appropriate.

Why does my 95th percentile change from night to night?

Because what your airway needs changes: position, alcohol, congestion, sleep stage distribution. Night-to-night movement is normal. A sustained drift across weeks is the part worth noticing.

See these numbers on your own nights

Your ResMed SD card is read in your browser, and only the nights you choose to save go to your account, hosted in the European Union. Accounts are not open yet: leave your email to be among the first to get access.

Request my access

All terms