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LEARN · 6 MIN READ
What is P95 pressure on a CPAP?
P95 pressure is the pressure your CPAP machine stayed at or below for 95 percent of the night. It is the standard way to summarise what an auto-adjusting machine actually did, because it shows where the pressure needed to be when the machine was working hardest without being skewed by a few seconds at the maximum.
Why one number is not enough
On a fixed-pressure CPAP, describing the night's pressure is trivial: it was 10 all night. On an auto machine the pressure moves constantly, up when the machine detects flow limitation or events, down when breathing settles. Across seven hours it might spend time anywhere between the minimum and maximum you set.
To summarise that into something you can look at each morning, the machine records a handful of statistics from the pressure trace. The three you will see are the median, the 95th percentile and the maximum. Each answers a different question.
Median, P95 and maximum
Median is the middle value. Half the night was above it, half below. It tells you where the machine spent its typical minute. On many nights the median sits close to your minimum pressure, because most sleep is uneventful.
Maximum is the single highest reading. It is often meaningless on its own: a brief spike when you rolled over, pulled the mask askew or had a cluster of events for two minutes at 4 a.m. One spike defines the maximum but says little about the night.
P95, the 95th percentile, is the value that 95 percent of the night was at or below. Put another way, only the top 5 percent of the night, about 20 minutes in a 7-hour sleep, was higher. It captures "how much pressure did I need when I needed the most" while ignoring the briefest spikes.
P95 is the one clinicians look at, the one ResMed highlights in its own reports, and the one Apnealytics puts on your dashboard.
| Statistic | What it tells you | Weakness |
|---|---|---|
| Median | Typical pressure | Hides the hard parts of the night |
| P95 | Pressure during the demanding 95% | Still a summary; no timing |
| Maximum | Worst moment | Dominated by brief spikes |
What a P95 reading can tell you
Reading P95 against your set range is where it becomes useful. A few patterns:
P95 at or near the maximum, night after night. The machine was pressed against its ceiling for a meaningful part of the night. It may have wanted to go higher. Whether raising the maximum is right depends on your AHI, leak and event types, and is a clinician decision. See CPAP pressure settings explained.
P95 well below the maximum with a good AHI. Your range is comfortable. The ceiling is not constraining the machine and there is probably no reason to touch it.
P95 close to the median. A calm night. Pressure barely moved, which usually means little flow limitation and few events.
P95 far above the median. The machine spent most of the night low and then had to climb hard for a stretch. Common causes are a REM period, a spell of back sleeping, or a run of events after a position change. Worth looking at the trace if you have Pro.
P95 that jumps on specific nights. Alcohol, congestion, a new pillow. Correlate with your trigger journal.
P95 and leak
As pressure rises, mask seal gets harder. Many people have a pressure above which their mask starts to leak. If your pressure P95 and your leak P95 climb together, the mask is probably the first thing to address, because high leak also causes the machine to hold pressure up or mark events as unclassified. See CPAP leak rate explained.
P95 and central events
For some people, higher pressure provokes central apneas. If your P95 has risen and your event composition shows a growing central share, that is a pattern your clinician will want to see. See central vs obstructive apnea on CPAP.
Why P95 is used for leak too
The same logic applies to leak. A single moment of 80 L/min when you took the mask off to drink water does not describe your seal. The leak P95 does: the level you were under for 95 percent of the night. On a ResMed card, leak is summarised the same way as pressure, with median, P95 and maximum, and Apnealytics shows leak P95 as the headline leak figure for the same reasons.
Where P95 comes from on your SD card
ResMed machines write a nightly summary to the SD card that includes pressure median, P95 and maximum along with the configured minimum and maximum, EPR level and mode. These are the values Apnealytics reads during SD card import and shows on the dashboard without any further processing. On Pro, the high-resolution pressure trace is also parsed, so you can see the moments that made up that P95.
How Apnealytics shows P95 pressure
The pressure insights feature is built around P95. On the dashboard, the pressure tile reads P95 against your set range with EPR beside it.
In Trends, P95 is a line drawn inside the shaded band of your minimum and maximum over 30, 90 or 365 nights. When the band changes because your settings changed, the "What changed?" panel marks the date. Period-over-period comparison shows the mean P95 before and after.
On Pro, the breath-by-breath viewer shows the pressure trace for any night with a crosshair, so you can find the stretch that produced your P95 and look at the airflow beside it: flow limitation, events, leak, or just REM.
A word of caution
P95 is a summary of what your machine did inside limits you or your clinician set. It is not a recommendation for a new setting, and Apnealytics never presents it as one. A high P95 is a reason to bring your data to a conversation, not a reason to change the number on the machine.
Questions people ask
What does P95 mean on a CPAP machine?
P95 is the 95th percentile. For pressure, it is the level your machine stayed at or below for 95 percent of the night; only the highest 5 percent of the night was above it. It is used because it shows how much pressure you needed during the demanding parts of the night without being distorted by a brief spike to the maximum.
What is a good P95 pressure?
There is no universal good value; it depends on your prescription. The useful comparison is against your own set range. A P95 well below your maximum with a controlled AHI suggests a comfortable range. A P95 pressed against the maximum night after night suggests the machine may want more room, which is a conversation for your clinician.
Why is my P95 pressure always at my maximum?
Because the machine spent at least 5 percent of the night, roughly 20 minutes or more, at the ceiling. It may have wanted to go higher and was limited by your settings. It can also reflect leak, which makes the machine hold pressure, or events it was chasing. Review AHI, leak and event types alongside it before discussing with your clinician.
What is the difference between median and P95 pressure?
Median is the pressure you were at for the typical minute of the night; half the night was above it, half below. P95 is the pressure 95 percent of the night was at or below. A median near your minimum with a P95 much higher means the machine was mostly low and climbed hard for a stretch, often during REM or a run of events.
Is P95 pressure the same as my prescribed pressure?
No. Your prescription is the setting: a fixed pressure or a minimum and maximum range. P95 is a measurement of what the machine actually delivered within that range. On a fixed-pressure machine the two will match. On an auto machine P95 shows where the algorithm needed to go, which is often well below the maximum you set.
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