Your CPAP machine quietly records data every single night. So why do so few people ever look at it? I'm Jo Ng, a Registered Polysomnographic Technologist (RPSGT) in Singapore, and I've used CPAP myself since 2015. In this guide, I show you how to access and read your therapy data, what the key numbers mean, and exactly when to bring them to your provider.
Let me be clear about the goal first. Reading your data helps you spot problems early, like leaks or unsettled breathing. However, understanding a number is not the same as changing your therapy. Therefore, treat this as data literacy, with your provider making any clinical adjustments.
How do you access your CPAP data?
Most CPAP machines store your data on an SD card, and some also offer Wi-Fi or Bluetooth. You can view summaries in the manufacturer's own app. However, for deeper detail, two free tools stand out: OSCAR, formerly known as Sleepyhead, and SleepHQ. Both let you see your night in far more detail than a basic app does.
The process is simple. You remove the SD card, load it into the software, and your nights appear as charts. From there, you can zoom into a single breath or scan a whole week. Consequently, patterns that a summary screen hides become obvious. You'll find step-by-step setup guides for each tool on YouTube, so I won't repeat them here.
The key numbers to know
Three readings carry most of the weight: AHI, leaks, and your pressure percentile. AHI counts breathing events per hour, so lower generally means calmer sleep. Leak readings show how much air escapes your mask. Your pressure percentile, shown as P95 or P90, reveals the pressure your machine mostly worked at through the night.
Each number tells a different part of the story. For example, a low AHI with high leaks suggests the therapy is working but your mask isn't sealing. Meanwhile, a P95 sitting right at your maximum hints your pressure may be capping out. Notably, you read these together, not in isolation, to understand the full night.
What your leak chart is telling you
Your leak chart is one of the most useful things to read, because leaks quietly wreck therapy. A flat, low line means a good seal. A gradually rising line usually points to mouth leaks. A sudden jump from zero to maximum usually points to mask leaks. Therefore, the shape of the line tells you where the air is escaping.
| Leak chart pattern | Likely cause | Sensible next step |
|---|---|---|
| Flat, low line | Good seal | Nothing needed |
| Gradually rising | Mouth leak | Discuss options like a chin strap with your provider |
| Sudden zero-to-max | Mask leak | Try different mask sizes or a different mask type |
These fixes are mechanical, so they're safe to explore yourself. For a deeper walkthrough of leaks and dryness, see my guide on how to troubleshoot CPAP leaks and dry mouth. Importantly, changing your mask never means changing your pressure on your own.
Reading your breath shapes
If you zoom into your breath-by-breath chart, the shape of each breath matters. Healthy breaths look rounded on top. When the tops flatten out, it can suggest your airway isn't opening fully, which points to flow limitation. Therefore, repeated flattening is a useful signal, even when your headline AHI looks acceptable.
Here's the crucial part, though. Flattened breaths may indicate you need a pressure review, but that's a decision for your provider, not a dial you turn yourself. So record what you see and raise it with them. For context on how settings get changed clinically, see my guide on how CPAP pressure settings are adjusted.
What you can fix yourself, and what your provider should change
This distinction keeps you safe, so read it carefully. You can safely adjust mechanical things: mask fit, mask type, cushion size, humidity, and tubing setup. However, you should never change your pressure settings on your own. Pressure is effectively a prescription, and the wrong move carries real risk, so it belongs with your provider.
The reason is simple physiology. Lowering pressure too far can let your apnoeas return, while pushing it too high can trigger central apnoea. Consequently, a number that "looks off" is a prompt to report, not to experiment. In short, you handle the hardware, and your provider handles the prescription.
OSCAR vs SleepHQ: which should you use?
Both tools read the same SD-card data, so the choice comes down to preference. OSCAR runs on your computer and gives detailed, granular charts. SleepHQ runs in the cloud, syncs easily, and makes sharing your data with others straightforward. Therefore, many people use OSCAR for deep analysis and SleepHQ for convenient sharing.
| Tool | Where it runs | Best for |
|---|---|---|
| OSCAR | Desktop software | Detailed, offline analysis of each night |
| SleepHQ | Cloud / web | Easy syncing and sharing your data |
Either way, the software is just a window onto your night. The value comes from what you do with what you see. So pick whichever feels easier, then focus on spotting leaks and unsettled breathing rather than chasing every tiny fluctuation.
Signs your therapy is actually working
Good data should match how you feel. On the screen, look for a low AHI, low and flat leaks, and steady breathing. In daily life, look for clearer mornings, more daytime energy, and lifting brain fog. Therefore, the best confirmation combines both: the numbers settle, and you genuinely feel more rested.
Some people also notice unexpected wins. For example, previous dizziness, vertigo, or reflux can ease once therapy is well settled. An AHI under 5 is generally considered well-controlled, although your provider sets the right target for you. For the full picture of progress, see my guide on how to succeed with CPAP therapy.
When to bring your data to your provider
Bring your data in whenever the numbers and your symptoms disagree. For instance, raise it if your AHI stays high, if leaks won't settle after mask changes, or if you still feel exhausted despite good-looking charts. Additionally, share repeated flow limitation or a P95 stuck at your maximum. These are exactly the patterns a provider should review.
A good provider welcomes your data and uses it to optimise your therapy over time. If yours never reviews or adjusts anything, it's fair to seek one who will. If you'd like a second opinion on your readings, reach out via our contact page or message us on WhatsApp. You can also explore machines that surface data clearly in our catalogue.
Common mistakes when reading your data
A few habits trip people up when they first read CPAP data, so watch for them. Notably, reacting to one bad night, chasing a perfect score, or trusting numbers over how you feel all cause needless worry. Worst of all, some people adjust their own pressure. Therefore, avoid these traps to keep your reading useful and safe.
- Reacting to a single night instead of looking at trends over a week.
- Chasing an AHI of zero, which isn't the goal; a low, stable AHI is.
- Ignoring how you feel and trusting the charts alone.
- Adjusting your own pressure rather than reporting patterns to your provider.
Frequently asked questions
How do I see my CPAP data?
Most machines store data on an SD card, and some offer Wi-Fi or Bluetooth too. You can view summaries in the manufacturer's app. For deeper detail, load the SD card into free software like OSCAR or SleepHQ. From there, you can view each night as charts and zoom into individual breaths and leaks.
What is the difference between OSCAR and SleepHQ?
Both read the same SD-card data, so it's mostly preference. OSCAR is desktop software offering detailed, offline charts. SleepHQ runs in the cloud, syncs easily, and makes sharing your data simple. Therefore, many people use OSCAR for deep analysis and SleepHQ for convenient sharing. Either tool helps you spot leaks and unsettled breathing.
What is a good AHI on CPAP?
An AHI under 5 is generally considered well-controlled on therapy. However, your provider sets the right target for your situation, since the full picture matters more than one number. Read your AHI alongside your leaks, your breathing shapes, and how rested you feel. If your AHI stays high, raise it with your provider.
What does a high leak reading mean?
A high leak reading means air is escaping, which weakens your therapy. A gradually rising leak line usually points to mouth leaks, while a sudden zero-to-maximum jump usually points to mask leaks. Therefore, address mouth leaks by discussing options like a chin strap, and address mask leaks by trying different sizes or mask types.
Should I change my pressure if my data looks off?
No. Your pressure is effectively a prescription, so you should never change it on your own. Lowering it too far can let apnoeas return, while raising it too high can trigger central apnoea. Instead, record what you see in your data and bring it to your provider, who can review and adjust it safely.
What does P95 or P90 pressure mean?
P95 or P90 shows the pressure your machine mostly stayed at or below during the night. It tells you how hard the machine worked to keep your airway open. If your P95 sits right at your maximum, your pressure may be capping out. Therefore, share that pattern with your provider for review.
