Your CPAP SD Card: What Data It Stores and How to Use It

Your SD Card Is a Sleep Data Goldmine

Every night, your ResMed AirSense 10 or AirSense 11 records a detailed log of your entire therapy session to the SD card inside the machine. This data goes far beyond what myAir shows you. While myAir gives you a simplified score and a few summary numbers, your SD card contains second-by-second waveform data, detailed event logs, pressure curves, leak rate charts, and machine configuration files.

If you have never looked at your SD card data, you are seeing roughly 5% of what your machine actually records. The other 95% is sitting on that tiny card, waiting to be read.

What Files Are on the Card

When you remove the SD card from your CPAP and plug it into a computer or phone, you will see a folder structure. Here is what the key files and folders contain:

DATALOG Folder

This is where the detailed session data lives. Inside DATALOG, you will find subfolders organized by date, and within each subfolder, EDF (European Data Format) files that contain time-series waveform data recorded during your sleep session.

These EDF files include:

• Mask pressure (the actual pressure at the mask, recorded every 2 seconds on AirSense 11, or at 25Hz on AirSense 10 detailed data)
• Therapy pressure (the pressure the machine is targeting)
• Leak rate (unintentional leak, recorded continuously)
• Tidal volume (the volume of air in each breath)
• Respiratory rate (breaths per minute)
• Minute ventilation (total air volume per minute)
• Flow rate waveform (on AirSense 10 with detailed data enabled, the actual breath-by-breath airflow signal)

This is the data that lets tools like CPAP Clarity draw detailed charts of your entire night, showing you exactly when events happened, how your pressure changed, and when leak occurred.

STR.edf (Summary Time Record)

This single file contains a compressed summary of every therapy session the machine has recorded, going back months or even years. Each row represents one session and includes:

• Session date and duration
• AHI and event counts (obstructive, central, hypopnea)
• Average and 95th percentile leak rate
• Average and 95th percentile pressure
• Usage hours

STR.edf is what allows data tools to show your long-term trends without needing to parse every individual session file. It is the fastest way to see how your therapy has changed over weeks and months.

Identification.json

This file contains your machine's identity: model number, serial number, firmware version, and device type. It is how analysis tools know whether you have an AirSense 10 or AirSense 11, which matters because the two models use different data formats and signal labels.

SETTINGS Folder

Inside this folder, CurrentSettings.json contains your machine's current configuration:

• Therapy mode (CPAP, APAP, or other modes set by your provider)
• Pressure range (minimum and maximum pressure for APAP, or fixed pressure for CPAP)
• EPR level (Expiratory Pressure Relief setting, 0 to 3)
• Ramp settings (starting pressure and ramp duration)
• Mask type (full face, nasal, or nasal pillow, as configured in the machine)
• Humidity level and climate control settings
• Smart features (auto-start, auto-stop, response settings)

This is the same information your sleep physician or equipment provider configures when they set up your machine. Being able to see it helps you understand exactly how your machine is configured, which is useful context when reviewing your data or talking to your provider.

How to Remove and Reinsert the SD Card

ResMed AirSense 11

The SD card slot is behind the water chamber on the left side of the machine (when facing the front). To access it:

1. Unplug the machine from power.
2. Remove the water chamber by pressing the release button and sliding it out.
3. The SD card slot is now visible. Press the card gently inward to release it (push-to-eject mechanism).
4. Pull the card out.

To reinsert, slide the card back in with the label facing up until it clicks into place. Replace the water chamber. Done.

ResMed AirSense 10

The SD card slot is on the right side of the machine behind a small flip-open door. Press the card gently inward to release it. Reinsertion is the same: slide it in with the label facing up until it clicks.

Important: Always power off the machine before removing the SD card. Removing it while the machine is running or recording can corrupt the current session file.

Why SD Card Data Is Richer Than myAir

myAir is ResMed's mobile app for reviewing your therapy. It connects to your machine via Bluetooth and shows you a daily score from 0 to 100, along with basic summary numbers. It is a good starting point, but it intentionally simplifies your data.

Here is what myAir shows vs. what your SD card contains:

Data Point	myAir	SD Card
AHI	Daily total	Hourly breakdown + event types
Events	Total count	Individual events with timestamps
Leak rate	Summary (high/low)	Continuous chart, second by second
Pressure	Not shown	Full pressure curve, all night
Mask pressure	Not shown	Actual pressure at the mask
Respiratory rate	Not shown	Continuous, all night
Tidal volume	Not shown	Continuous, all night
Session history	30 days on phone	Months to years on card
Flow waveform	Not shown	Available on AS10 (detailed mode)

The SD card data lets you answer questions myAir simply cannot: When did my events happen? Were they clustered in the first hour or the last? Did leak cause my AHI spike? What was my pressure doing when I had that cluster of events at 3am? Did my EPR setting change anything about my event pattern?

For a deeper comparison of what myAir hides, see our article on going beyond myAir.

Tools That Read Your SD Card

Several tools can read and visualize your CPAP SD card data:

CPAP Clarity

CPAP Clarity is a free, browser-based tool that reads your SD card data entirely on your device. No upload, no account, no cloud storage. Your health data never leaves your browser. It shows detailed charts, event breakdowns, leak analysis, therapy scoring, and generates PDF reports you can share with your doctor.

CPAP Clarity supports both AirSense 10 and AirSense 11 SD cards. You drag and drop your SD card folder into the browser, and within seconds you have a full dashboard with insights and trends. For a step-by-step walkthrough, see our guide on how to use CPAP Clarity.

OSCAR

OSCAR (Open Source CPAP Analysis Reporter) is a free desktop application for Windows, Mac, and Linux. It provides extremely detailed charts and statistics, including flow rate waveforms on supported machines. OSCAR is powerful but has a steeper learning curve. It requires installation and runs as a native application.

myAir

ResMed's own app reads a limited subset of SD card data via Bluetooth (not the card itself). As noted above, it simplifies the data into a daily score and summary. For many users, myAir is the starting point that leads them to seek more detailed tools.

What You Need to Read the Card

Your SD card is a standard micro-SD card. To read it on a computer or phone, you need:

For a computer (USB): A micro-SD card reader (opens in new tab) that plugs into a USB port. These are inexpensive (typically $8 to $15 as of March 2026) and widely available. Many laptops have built-in SD card slots, though you may need a micro-to-full-size SD adapter (usually included with the reader or the SD card itself).

For a phone or tablet: A USB-C micro-SD card reader (opens in new tab) that plugs directly into your phone's charging port. This works with most modern Android phones and iPhones (iPhone 15 and later with USB-C). For older iPhones with Lightning ports, you will need a Lightning-compatible reader. See our detailed guide on importing CPAP data on your phone for step-by-step instructions.

Replacement SD cards: If your SD card is damaged, lost, or full, any standard micro-SD card will work. A 16GB or 32GB micro-SD card (opens in new tab) is more than sufficient. CPAP data files are small, typically a few megabytes per night. A 32GB card can hold years of data.

How Much Data Fits on the Card

CPAP data is compact. A typical night generates 2 to 5 MB of data on an AirSense 11, or 5 to 15 MB on an AirSense 10 with detailed recording enabled. The stock 8GB card that comes with most ResMed machines can hold approximately 1 to 3 years of nightly data, depending on your settings.

If your card does fill up, the machine overwrites the oldest data to make room for new sessions. You will not lose the ability to record. But if you want to preserve historical data, periodically copy the contents of the card to your computer before it fills up.

Should You Leave the Card in the Machine?

Yes. The SD card should stay in the machine during normal use. The machine writes to it every night automatically. You only need to remove it when you want to view the data on a computer or phone.

Some users worry about removing and reinserting the card frequently. The card and slot are designed for this. Micro-SD cards have no moving parts and are rated for thousands of insertion cycles. Just make sure the machine is powered off when you remove or insert the card.

If you use CPAP Clarity on your phone, the workflow is: power off the machine, remove the card, plug it into your phone with a card reader, import the data, then put the card back in the machine. The whole process takes about 60 seconds.

When to Talk to Your Provider

The data on your SD card is the same data your sleep physician uses to evaluate your therapy. Bringing a summary to your appointments can make conversations more productive. CPAP Clarity generates a PDF report that you can download and share with your doctor, including AHI trends, event breakdowns, and leak analysis.

Consult your sleep physician if your data shows:

• AHI consistently above 5. Your pressure settings may need adjustment by your provider.
• A sudden change in your event pattern. A jump in central apneas or a sustained increase in AHI could signal something worth investigating.
• High leak rates that you cannot resolve. Persistent leak affects therapy delivery and may require a mask change or pressure review.
• Data that does not match how you feel. If your numbers look good but you are still exhausted, there may be factors beyond what CPAP treats. Your physician can evaluate further.

The Bottom Line

Your CPAP SD card contains a detailed, night-by-night record of your therapy that is far more comprehensive than what myAir shows. You need nothing more than an inexpensive card reader and a free tool like CPAP Clarity to unlock all of it. The data is already being recorded every night. All you have to do is look at it.

Analyze your CPAP data free with CPAP Clarity →