Most CPAP and BiPAP machines record a lot more than whether you wore the mask. Every night, your device is quietly logging dozens of data points — breathing patterns, pressure changes, mask seal, and more. The trouble is, most of that data never leaves the machine unless you go looking for it.
This guide walks through how to get your data off the machine, what the main numbers actually mean, and how to use that information to have a more productive conversation with your sleep specialist.
Note
This article is for informational purposes only. It does not constitute medical advice, diagnosis, or treatment recommendations. Always discuss your therapy data and any changes to your treatment with a qualified clinician.
What Does Your CPAP Machine Actually Record?
Modern CPAP and BiPAP machines record data at two levels: summary statistics (what most apps show you) and full night flow data (what reveals the complete picture).
Summary data — recorded every night:
Usage hours
How long you wore the device.
AHI (Apnoea-Hypopnoea Index)
The number of apnoeas and hypopnoeas per hour.
Leak rate
How much air is escaping around your mask.
Pressure
The pressure your machine delivered (average, 95th percentile, or fixed, depending on your device mode).
Full flow data — recorded on SD card or internal memory:
Breath-by-breath flow waveforms
The actual shape of each breath.
Flow limitation
A subtler signal than AHI, showing partial airway narrowing that restricts airflow without fully triggering an event.
RERAs (Respiratory Effort-Related Arousals)
Effort-induced arousals that fragment sleep without meeting the threshold for a scored event.
Snore index
Detected snoring, which can co-occur with residual upper-airway resistance.
The summary AHI on your machine's screen or companion app is useful, but it's often incomplete. A low AHI doesn't always mean your therapy is well optimised — flow limitation and RERAs can persist even when the headline number looks fine. Full flow data is where the detail lives.
How to Export Your Data
The method varies by manufacturer. In all cases, your data is stored on a standard SD card or via USB — no account or cloud service is required to access it.
ResMed (AirSense 10, AirSense 11, S9 series)
ResMed machines store detailed flow data on a standard SD card (older machines) or internal memory accessible via SD slot.
.edf and other data files holding your full-resolution flow data.ResMed's myAir app shows you a nightly summary score, but does not give access to raw flow data. For the full picture, the SD card is the route.
Supported by: OSCAR, AirwayLab, and other open tools.
Philips Respironics (DreamStation, DreamStation 2, System One)
Philips machines use an SD card on older DreamStation and System One units.
.001 Encore data files (System One) or Encore Pro format files (DreamStation).Note: The DreamStation 2 stores data internally and currently has limited third-party compatibility. Check the OSCAR compatibility list for up-to-date support status.
The DreamMapper app provides summary data but does not expose raw flow waveforms.
Fisher & Paykel (ICON, SleepStyle, F&P series)
Fisher & Paykel machines generally use an SD card or USB export.
A general note on data formats
Raw CPAP data comes in proprietary formats that differ by manufacturer and device generation. Tools like OSCAR and AirwayLab handle the parsing — you just point the tool at the folder on your SD card.
What the Numbers Mean
Once you have your data open in an analysis tool, here's how to read the main signals:
AHI
Your machine's headline number. It counts complete airway obstructions (apnoeas) and partial obstructions with a drop in airflow (hypopnoeas), expressed per hour of sleep. A lower AHI generally indicates fewer scored breathing interruptions. However, scoring thresholds and event detection logic vary between devices — so a machine-scored AHI and a lab-scored AHI can differ.
Leak rate
Expressed in litres per minute. Most devices have a built-in intentional vent leak to allow CO₂ to escape — this is normal. What to watch for is unintentionalleak: a sustained elevation above your device's leak baseline. Elevated leak can reduce therapy effectiveness and is often fixable with mask fit adjustments.
Flow limitation
Shown as a value between 0 and 1, or as a time-series graph. It represents how “flattened” the top of each breath is. A rounded breath peak indicates unobstructed flow; a flat-topped peak suggests partial upper-airway narrowing. This signal may help you understand whether residual obstruction is present even when AHI is low.
RERAs
Effort-induced arousals — the airway doesn't completely close, but increased respiratory effort causes a brief awakening or lightening of sleep. They contribute to sleep fragmentation without necessarily being counted in AHI. Not all machines report RERAs directly; it depends on the device and algorithm.
Pressure
If you're on APAP (auto-adjusting), your nightly pressure graph shows how the machine responded to detected events. Consistent high-pressure clustering at certain times of night can suggest positional obstruction or other patterns worth discussing with your clinician.
Exploring Your Data with AirwayLab
AirwayLab is an open-source tool for visualising and exploring PAP therapy data. It runs entirely in your browser — your data never leaves your device, which matters when you're dealing with sensitive health information.
Load your SD card data directly and explore:
Nightly trend charts
AHI, leak, pressure, and usage across nights and weeks.
Full-resolution flow waveforms
Breath-by-breath waveform view for any night.
Flow limitation and RERA trends
Track these secondary signals over time.
Side-by-side comparison
Compare nights and weeks to spot patterns.
The source code is published under GPL-3.0, so the analysis is verifiable — you can see exactly how events are being scored. AirwayLab is free and always will be for core analysis features. A premium tier is available for those who want to support continued development.
AirwayLab is designed to complement, not replace, tools like OSCAR. Many users use both — OSCAR for deep clinical-format reporting, AirwayLab for day-to-day visual exploration. They read the same underlying data.
Having a Better Conversation with Your Clinician
Your data is most useful when you bring it into a clinical conversation. A few practical approaches:
Export a trend report before your appointment.
Most analysis tools can export a PDF summary covering the past 30–90 days. Bring this to your follow-up — it gives your specialist context faster than relying on device remote-monitoring summaries alone.
Note specific nights that felt different.
If you woke up feeling unrefreshed, pull up that night's data and look at pressure and leak graphs. Targeted observations are often more useful than averages.
Ask about flow limitation and RERAs, not just AHI.
If your AHI is “controlled” but you still feel tired, your clinician may want to look at these secondary signals. Having the data makes that conversation concrete.
Be specific about mask issues.
If your leak data shows spikes at consistent times, that's useful clinical information — it might indicate movement during the night that breaks the seal.
Always frame observations from home analysis tools as things to discuss, not conclusions. Your clinician has your full history and clinical context that a visualisation tool doesn't replicate.
Summary
Your CPAP machine is generating detailed data every night. Getting it off the device is straightforward — an SD card and a free tool is all it takes. Understanding what AHI, leak rate, flow limitation, and RERAs may tell you about your breathing patterns can help you engage more meaningfully with your therapy and your care team.
Tools like AirwayLab and OSCAR exist to make your data accessible — in your browser, on your terms, with open and verifiable analysis.
Medical disclaimer
AirwayLab is not a medical device. The analysis provided is informational and educational. Always discuss your results with your sleep physician or clinician. AirwayLab does not diagnose, treat, or provide clinical recommendations.
Related reading
How to Read Your CPAP Data — a full guide to CPAP metrics beyond AHI.
Understanding Flow Limitation — what flow limitation is, how the Glasgow Index scores it, and how to detect it.
Why Your AHI Is Lying to You — the evidence that AHI misses the majority of breathing problems.
Your PAP Data Belongs to You — who can see your sleep data and how to keep control of it.
AirwayLab vs OSCAR — how AirwayLab and OSCAR complement each other.
Explore your data free — load your SD card into AirwayLab
Drag your SD card folder into AirwayLab and see your breathing patterns scored and visualised in seconds. Free, open source, and your data never leaves your browser.