Key Takeaways
Every night your CPAP machine is in use, it's quietly recording a small mountain of data: how many breathing events you had, how much air leaked around your mask, what pressure your machine actually delivered, and how long you wore it. Most modern machines display a nightly summary right on the screen, and companion apps like ResMed's myAir turn that data into simple daily scores.
And yet the most common way people interact with this information is... not at all. They wear the machine, hear it hiss, and wait for a three- or six-month follow-up appointment to find out if it's actually working. That's a long time to fly blind on a therapy you're using every single night.
The good news: you don't need a sleep medicine degree to read your own reports. Two numbers do most of the heavy lifting — AHI and leak rate — and once you know what they mean, checking your own data becomes a five-minute habit instead of a mystery.
AHI stands for Apnea-Hypopnea Index — the average number of apneas (complete pauses in breathing) and hypopneas (partial reductions in airflow) you experience per hour of sleep. Your machine calculates it by counting every event that lasts 10 seconds or longer and dividing the total by your estimated sleep time.
Here's the scale most sleep clinicians use to interpret it:
| AHI SCORE | SEVERITY |
| Under 5 | Normal |
| 5-15 | Mild sleep apnea |
| 15-30 | Moderate sleep apnea |
| 30+ | Severe sleep apnea |
The goal of CPAP therapy is straightforward: get your nightly AHI under 5. If your machine is doing its job, your "on-CPAP" AHI should look dramatically different from your original diagnostic number. Someone diagnosed at 40 or 50 events per hour might see that number fall to 2 or 3 on a well-fitted, well-tuned setup.
A few things worth knowing before you start reading too much into a single night's number:
Leak rate measures how much air is escaping around your mask, reported in liters per minute (L/min). Every mask is designed with a small "intentional" exhaust leak built into the vent — that's normal and accounted for. What your machine is actually flagging is the unintentional leak: air sneaking out from a poor seal, a shifted mask, or an open mouth.
The commonly cited threshold is around 24 L/min or lower for a well-sealed mask, though the exact cutoff varies slightly by manufacturer. Once leak rates climb well beyond that — into the 50–70 L/min range on some machines — the device can start struggling to accurately sense your breathing at all, which means your AHI reading for that night becomes unreliable too.
This is the part people miss: a high leak rate doesn't just mean a leaky mask — it can quietly make your AHI look better than it actually is, because the machine loses its ability to detect events accurately during major leak periods. If your leak rate and your AHI are both elevated on the same nights, the leak is very likely the root cause, not a separate issue.
Common causes of a rising leak rate:
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AHI and leak rate are more useful when you look at them together rather than in isolation. Use the guide below to understand what different combinations may mean and when it may be worth troubleshooting your mask or discussing your results with your sleep clinician.
AHI <5 • ResMed unintentional leak ≤24 L/min
These AHI and leak numbers are generally reassuring.
What to do:
AHI <5 • ResMed unintentional leak >24 L/min
A large leak may make the device-reported AHI less reliable and may interfere with effective therapy.
What to do:
AHI ≥5 • ResMed unintentional leak ≤24 L/min
Your device is still detecting an elevated number of breathing events even though leak appears to be within range.
What to do:
AHI ≥5 • ResMed unintentional leak >24 L/min
High leak can make device-reported AHI less reliable, so both the leak and the elevated event rate deserve attention.
What to do:
AHI (device-reported): The average number of apneas and hypopneas per hour as estimated by your CPAP device.
Leak (unintentional): Air escaping beyond the mask's normal intentional vent flow—for example, around the mask or through the mouth when using a nasal interface.
This information is for educational purposes and is not a substitute for professional medical advice. Treatment goals vary by individual.
If you're on a fixed-pressure CPAP, your pressure setting is a single number your provider chose, and there's not much to interpret — it either matches what was prescribed or it doesn't.
If you're on an auto-adjusting machine (APAP), the pressure moves within a prescribed range throughout the night, and your report will show a 95th percentile pressure — the level your machine stayed at or below for 95% of the night. Sleep specialists treat this as the "effective" pressure, since it filters out brief spikes caused by a swallow or a position change.
A rough way to read it:
You have a few options, depending on how deep you want to go:
Press the info button on your machine each morning. Most display last night's AHI, usage hours, and often leak rate. Good for a quick daily gut-check.
ResMed AirSense machines pair with myAir; Transcend travel machines pair with MySleepDash. There are others too. These translate raw data into simple daily scores and trend graphs — the easiest option for most people.
If you want the full picture — event-by-event breakdowns, synchronized AHI/leak/pressure/flow charts — free tools like OSCAR can read your machine's SD card data directly. This is more than most people need, but it's the closest you can get to what your sleep doctor actually sees.
A simple weekly routine covers most of what matters: check that your AHI is trending under 5, your leak rate is staying well below the 24 L/min range, your 95th percentile pressure is stable, and your usage hours are above 4 per night. When one of these drifts, the others often move with it — which is exactly why they're worth checking together, not in isolation.
Reading your own data isn't about replacing your sleep medicine provider — it's about knowing when a call is actually necessary instead of waiting for a scheduled follow-up that might be months away. Reach out if you notice:
You don't have to wait for a quarterly appointment to know whether your CPAP therapy is actually working. Your machine is already generating the answer every single night — you just have to look. An AHI under 5, a leak rate under roughly 24 L/min, and a stable pressure trend are the three numbers that tell you almost everything you need to know, and checking them takes less time than it took to read this sentence twice.
This content is for informational purposes only and is not a substitute for professional medical advice. Always discuss changes to your therapy or pressure settings with your sleep medicine provider before adjusting anything yourself.
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