ResMed AirSense 11 SD Card Data Explained

The ResMed AirSense 11 records detailed therapy data on its SD card every night, including breath-by-breath airflow, pressure delivered, leak rate, respiratory rate, tidal volume, snore index, flow limitation, and every apnea or hypopnea event with exact timestamps. The myAir app shows a daily score and, since October 2026, a Nightly Timeline of key events. The SD card contains far more detail, and reading it lets you see when events happened, what triggered them, and whether your therapy is genuinely working or just looks good on the score.

What Your AirSense 11 Records

The ResMed AirSense 11 is one of the most data-rich CPAP machines available. Every night, it records:

Breath-by-breath airflow at 25 samples per second
Mask pressure: what pressure is actually being delivered
Therapy pressure: what the machine is targeting
Leak rate: how well your mask is sealing
Respiratory rate: breaths per minute
Tidal volume: air volume per breath
Minute ventilation: total air moved per minute
Snore index: detected snoring events
Flow limitation: subtle airway narrowing
Every respiratory event: obstructive apneas, central apneas, hypopneas, and RERAs with exact timestamps and durations
SpO2 and pulse (if an oximeter is connected)

All of this data is stored on the machine's SD card in a medical data format called EDF (European Data Format).

What the myAir Score Leaves Out

ResMed's myAir app turns your night into a single "score" out of 100 based on:

Usage hours (did you wear it?)
Mask seal (was your leak acceptable?)
Events per hour (your AHI)
Mask on/off (how many times you removed it?)

That score hides important nuances. You can get a "perfect" 100 with an AHI of 4.9, which sits right at the edge of the under-5 mark the AASM associates with well-controlled therapy. Since October 2026, myAir's Nightly Timeline shows Air11 users when key events happened and when the mask went on and off. ResMed has not published which event types it labels, and it does not describe graphs of how your pressure varied or how leak affected your therapy.

The detailed data on your SD card tells a much more complete story.

How to Access Your SD Card Data

Step 1: Take the Card Out

On the AirSense 11, the card sits behind the SD card cover on the side of the machine. ResMed's user guide says the light there "is blue when data is written to the SD card", and "Do not remove the SD card from the device when the SD light is flashing, because data is being written to the card." So do it in the morning, after therapy has stopped:

Check that the SD light is not flashing
Push the card in to release it, as ResMed's guide describes, and pull it out

ResMed's guide also says to remove the card only when your care provider asks you to, and that the card "should not be used for any other purpose as it may corrupt therapy data stored on the card". CPAP Clarity only reads the card and never writes to it. Do not delete, rename or reformat anything on it.

Step 2: Read the Card

Insert the SD card into your computer using:

A built-in SD card reader (many laptops have one)
A USB SD card reader (available for a few dollars)

Your computer should mount it like a regular drive. A phone works too, with a card reader that plugs into it (Safari on iOS 18.4 or later, Chrome 132 or later on Android).

Step 3: Understand the File Structure

Your SD card contains:

SD Card Root/
├── STR.edf          ← Daily summary database
├── Identification.json
├── DATALOG/
│   ├── 20260327/    ← One folder per date
│   │   ├── ..._BRP.edf  ← Breath data (high-res flow)
│   │   ├── ..._PLD.edf  ← Periodic data (pressure, leak, etc.)
│   │   ├── ..._EVE.edf  ← Respiratory events
│   │   ├── ..._CSL.edf  ← Cheyne-Stokes data
│   │   └── ..._SA2.edf  ← Oximetry data (if connected)
│   └── 20260328/
│       └── ...
└── SETTINGS/

Each night may have multiple session files if you removed the mask during the night (bathroom breaks, for example).

Step 4: Analyze the Data

The EDF files are binary. You can't open them in a text editor. You need an analysis tool:

CPAP Clarity reads these files directly in your web browser, with nothing uploaded. Choose the whole card, not the DATALOG folder inside it, so your settings come along too. Open your card in CPAP Clarity.

When you are done, put the card back the same day so the machine keeps writing to it. The short version of these steps, and what the AirSense 11 can show you without the card, is on our page on seeing your AirSense 11 data. Other ResMed machines read the same way: the AirSense 10, the AirCurve 11 VAuto, the AirCurve 11 ASV and the S9.

Key AirSense 11 Data Points to Watch

Pressure Behavior

The AirSense 11 in AutoSet mode adjusts pressure throughout the night. Watching the pressure curve tells you:

Flat, low pressure: The machine is not raising pressure much through the night.
Gradually increasing pressure: The machine is responding to increasing events (common as you enter deeper sleep stages).
Frequent large swings: May indicate the machine is "chasing" events caused by leak or positional changes.
Pressure near maximum: Discuss with your provider whether your maximum pressure setting needs adjustment.

EPR (Expiratory Pressure Relief)

The AirSense 11 supports EPR levels 1-3, which reduces pressure when you breathe out for comfort. Your data shows the actual EPR pressure delivered. If you're seeing flow limitation events, discuss your EPR setting with your provider.

The STR.edf Summary File

This is a hidden gem. It contains a daily summary of every metric going back up to a year. It includes AHI, leak percentiles, pressure percentiles, respiratory rate, tidal volume, and all machine settings for every day. This is where trend analysis gets powerful.

AirSense 11 Settings Your Data Reveals

On the AirSense 11 in the US and Canada, myAir's Therapy Control lets you view and adjust comfort settings like EPR and ramp. The SD card shows what the machine actually did with your settings all night. Three are worth checking on every import:

AutoSet vs. fixed CPAP mode. AutoSet is the default on most AirSense 11 prescriptions. The data shows whether the machine is genuinely adjusting (which is what AutoSet is for) or sitting near the minimum pressure most of the night (which can mean either your airway is stable or your prescribed range is set too low). The single most useful pressure number here is the 95th-percentile (P95) pressure, the level your machine spent most of the night at or below. For a deeper look at how pressure should behave through the night, see our CPAP pressure settings guide.

EPR level and mode. EPR (Expiratory Pressure Relief) drops the pressure during exhale by 1, 2, or 3 cmH2O. Your data shows the actual EPR pressure delivered breath by breath, so you can confirm the prescribed setting is what is reaching you. EPR Full Time is the most common setup; EPR Ramp Only turns the relief off after the ramp period ends.

Response setting (Soft / Standard). AutoSet has a responsiveness setting that controls how quickly the machine raises pressure when it detects an event. Standard is the default; Soft responds more slowly. You will not see "Response" as a labeled channel in the data, but you can infer it from how aggressively the pressure climbs after a cluster of events.

Common Patterns Your AirSense 11 Data Will Show

Once you can see the breath-by-breath chart, certain patterns repeat across nights:

REM-clustered events. Your throat muscles relax more during REM sleep, so apneas and hypopneas tend to bunch into ~90-minute cycles. APAP handles this automatically; fixed CPAP users sometimes see clusters that the single prescribed pressure was not titrated against.

Position-dependent events. Apneas often cluster when you roll onto your back. If you correlate the event timeline with your sleeping position (a journal entry or an Apple Watch / Oura overlay), you can see whether positional therapy alone might reduce your AHI.

Leak signatures. Mouth leaks at higher pressures look like a steady high-leak baseline that lasts hours. Mask-shift leaks look like brief leak spikes when you change position. Telling the two apart matters: the first is a mask-type or chin strap question; the second is a fit-and-headgear question. Our leak fix guide walks through both.

Central apnea cluster after starting CPAP. If your data shows a sudden rise in central apneas (CA) after a prescription change, that is the signature of treatment-emergent central sleep apnea. Worth mentioning to your provider.

AirSense 11 Supply Replacement: Let the Data Tell You When

The Medicare and ResMed replacement schedules are calendar-based ceilings, not personalized signals. Your data tells you when each consumable is actually starting to fail.

Filters affect motor noise + airflow restriction. A clogged filter shows up as gradually rising machine noise (subjective) and on AutoSet machines as wider pressure variability (the machine works harder to deliver the same prescribed pressure). ResMed's AirSense 11 user guide says to replace the filter every six months, and more often if it has holes or is blocked by dirt or dust, so check it sooner if you live somewhere dusty or have pets.

Water chamber affects humidity output + biofilm risk. Mineral buildup that does not dissolve with a vinegar soak is the signal. ResMed recommends every 6 months on the AirSense 11 HumidAir chamber; tap-water users typically need to replace sooner.

AirSense 11 supplies for data-driven replacement

Monthly Filter

AirSense 11 Disposable Filter (30-pack)

Disposable air filters for the AirSense 11. ResMed's AirSense 11 guide says to use only ResMed parts, the air inlet filter included, and to replace it every six months.

Humidifier Replacement

ResMed HumidAir 11 Standard Tub

ResMed's AirSense 11 guide names the HumidAir 11 Standard and Cleanable tubs as the only water tubs used with the AirSense 11, and gives the standard tub a 6-month design life; replace it sooner if mineral buildup will not dissolve with a vinegar soak.

For the full cross-machine supply timeline, see our CPAP supply replacement schedule.

If You Also Have an AirSense 10 Card

An AirSense 10 card holds largely the same data as an AirSense 11 card (its own walkthrough is the AirSense 10 data guide), with a few file differences:

Feature	AirSense 10	AirSense 11
Signal naming	"Mask Pres", "Leak"	"MaskPress.2s", "Leak.2s"
Connectivity	SD card + cellular	SD card + Bluetooth + cellular
Oximetry file	SAD.edf	SA2.edf
EPR options	Same	Same
Data resolution	Same	Same

The therapy data itself is comparable. Which machine to choose is a different question, answered in AirSense 10 vs 11. And if your data shows pressure maxing out or events persisting at high pressure, the question may not be which generation but which machine class: AirSense 11 vs AirCurve 11 covers when a bilevel makes sense.

Making the Most of Your Data

Check weekly, not daily. Night-to-night variation is normal. Weekly trends matter more.
Look at leak first. Most "bad nights" trace back to mask seal issues.
Track after changes. Changed your mask, pillow, or settings? Compare data before and after.
Bring data to appointments. Your sleep doctor will appreciate detailed reports instead of "I think I'm sleeping better."
Don't obsess. Data should inform, not stress you. An AHI of 3 vs. 2 isn't clinically meaningful; see what a good AHI looks like for the bands and what they mean.

For a deeper walkthrough of what each metric means, see how to read your CPAP data. Ready to get started? Our CPAP Clarity guide shows you how to go from SD card to insights in 60 seconds.

See what CPAP Clarity shows for AirSense 11 users →

Frequently Asked Questions

Does the AirSense 11 record more data than myAir shows? Yes, by a large margin. The myAir app shows a daily score, your usage hours, your AHI, leak status, and mask on/off events, and its Nightly Timeline shows when key events happened. The SD card carries the underlying breath-by-breath airflow + pressure + leak + flow-limitation + every event with timestamps + a full year of daily summaries in the STR.edf file. Reading the SD card is the way to see every event with its exact time, what was happening around it, and how your therapy varied through the night.

Where is the SD card slot on the AirSense 11? Behind the machine's SD card cover, whose light is blue while data is being written. ResMed's guide says not to remove the card while the SD light is flashing, and to push the card in to release it.

Can I read AirSense 11 data on my phone instead of a computer? Yes. Safari on iOS 18.4 or later and Chrome 132 or later on Android both support folder picking from an SD card reader plugged into the phone. See our phone import guide for the step-by-step.

What file format does the AirSense 11 use? EDF (European Data Format), a standard medical-data format. The files are binary, not readable in a text editor. CPAP Clarity parses them directly in your browser; OSCAR (a free desktop app) also reads them.

What is in the STR.edf file? A daily summary database covering up to a year of past nights. Each row has AHI, leak percentiles, pressure percentiles, respiratory rate, tidal volume, and the machine settings active that day. This is where trend analysis gets powerful; one bad night is rarely the story.

How often should I import my AirSense 11 data? Weekly is enough for trend awareness; nightly is overkill for most users. Night-to-night variation in AHI is normal. Import after any change (new mask, new pillow, new pressure setting) so you can compare before and after, and import before every sleep doctor appointment.

Primary Sources

Patil SP, Ayappa IA, Caples SM, Kimoff RJ, Patel SR, Harrod CG. Treatment of Adult Obstructive Sleep Apnea with Positive Airway Pressure: An American Academy of Sleep Medicine Clinical Practice Guideline. J Clin Sleep Med. 2019 Feb 15;15(2):335-343. The current AASM guideline on when CPAP, APAP, and BiPAP are appropriate for adults with OSA. PubMed 30736887 (opens in new tab)
National Heart, Lung, and Blood Institute. CPAP (NHLBI patient education page). Plain-language overview of how CPAP works and the common side effects to expect. nhlbi.nih.gov CPAP (opens in new tab)