ResMed AirSense 11 Data: What Your SD Card Holds (and myAir Hides)

Your ResMed AirSense 11 is quietly recording far more about your sleep than the myAir app ever shows you. Every night, the machine writes breath-by-breath detail to the small SD card tucked into its side — leak rates, flow limitation, the type of each event, and the exact pressure it delivered. The myAir app distills all of that into a single daily number. This guide walks through what's actually on the card, why it matters, and how to read the full picture.

What the AirSense 11 records on the SD card

The myAir score is a summary. The SD card is the source data. While the app shows you a friendly 0–100 number, the card stores a rich, time-stamped record of how you actually breathed all night.

Here's what the AirSense 11 captures on the card:

• Flow rate — the breath-by-breath airflow waveform, the most detailed signal the machine produces. It's the raw material behind every event the machine flags.
• Leak rate — how much air escaped past your mask (ResMed reports excess leak, more on that below).
• Respiratory rate — breaths per minute.
• Tidal volume — the volume of air per breath.
• Snore — a vibration-derived snore signal.
• Flow limitation — a subtle measure of partially obstructed breathing that often precedes full events.
• Timestamped events — each obstructive apnea, central (clear-airway) apnea, hypopnea, and RERA, with the exact second it occurred.
• Delivered pressure — the actual pressure the machine used moment to moment, not just your prescribed setting.

That last cluster — leak, flow limitation, and event types — is exactly what myAir leaves out, and it's what turns "my score was 82" into "I had a cluster of central events at 3 a.m. while my leak was high." For a plain-English tour of what each number means, see How to Read Your CPAP Data.

EDF format and session capacity

The AirSense 11 writes its data in EDF (European Data Format), an open, industry-standard format originally designed for medical signals like EEG and EKG recordings. Because EDF is open and documented — not a proprietary, encrypted blob — independent tools can read it. (This is a meaningful contrast with the Philips DreamStation 2, whose SD-card data is encrypted and unreadable by most third-party software.)

The card has a finite memory footprint, and it's shared across ResMed's AirSense and AirCurve 10 and 11 lines:

In practice, that means the machine keeps about a month of full breath-by-breath detail and about a year of summary statistics. Once the detailed buffer fills, the oldest waveforms roll off — so if you want to preserve the granular data, pull it off the card periodically rather than letting it overwrite. This is one reason a cloud archive of your history matters, especially if you ever switch CPAP brands and want to keep your data history.

myAir vs the SD card — the detail gap

myAir is genuinely useful for staying motivated and confirming you used the machine. But it's important to understand what it is — and isn't.

myAir gives you a myAir score: a 0–100 number weighted heavily toward usage hours, with smaller contributions from mask seal, events per hour, and how often you take the mask on and off. ResMed has never published the exact formula. Because usage dominates, the score can look excellent even when the underlying therapy isn't optimal — it's possible to see a score near 100 while your residual AHI sits just under 5.

Here's the gap, side by side:

The event-type omission is the big one. The myAir score treats all events as one lump, but obstructive and central apneas mean very different things. CPAP is designed to splint the airway open and reliably treats obstructive events, but it does not directly correct the unstable breathing drive behind central (clear-airway) events. A rise in central events on CPAP can signal treatment-emergent central sleep apnea (TECSA) — see what 'clear airway' (CA) events mean and our deeper look at central apneas showing up on CPAP. myAir can't tell you which kind you're having; the SD card can.

The leak omission matters just as much, and it's a trust issue. Large leaks invalidate or under-report your AHI — when air is escaping past the mask, the machine can miss events it would otherwise catch, so a "good" AHI during a high-leak night may not be trustworthy. ResMed's threshold is 24 L/min of excess leak at the 95th percentile. (Note that ResMed reports excess leak — the leak beyond expected intentional venting — while Philips reports total leak, so the two brands' numbers aren't directly comparable.) myAir reduces all of this to a seal star; the card shows you the real curve. Learn more in CPAP Leak Rate: What's Acceptable.

A standing reminder for any of these numbers: single-night readings are noise. Trends over weeks are what matter — see why your AHI changes night to night.

Where the SD slot is (side of the AirSense 11)

The SD card lives in a slot on the side of the AirSense 11, near the back of the unit. It's a standard SD card, already inserted from the factory.

To remove it:

1. Make sure the machine is not actively running a session (it's fine when idle).
2. Find the slot on the side of the device.
3. Gently push the card in until it clicks, then release — it will pop out slightly (it's a spring-loaded push-push slot, so don't pull it straight out cold).
4. Pull the card the rest of the way and insert it into your computer's card reader (or a USB SD adapter).

When you're done, slide it back in and push until it clicks to seat it. The machine needs the card in place to keep recording detailed data — if it's missing, you'll typically only get summary data. For a brand-by-brand walkthrough, see How to Download CPAP Data from Your SD Card.

The Card-to-Cloud variant (no cellular/myAir)

Not every AirSense 11 has a cellular modem. ResMed ships a Card-to-Cloud variant that has no cellular connection and no myAir app integration. These are common in regions or supply situations where the cellular model isn't available, and they're sometimes provided through specific distribution channels.

If you have a Card-to-Cloud machine, the SD card isn't just more detail than myAir — it's your only record. There's no app, no automatic upload, and no remote view for your provider. Everything depends on physically reading the card. (The AirSense 10 has the same split between cellular and Card-to-Cloud units; we cover it in the AirSense 10 data guide.)

The practical takeaway: whether you have a cellular or Card-to-Cloud AirSense 11, the SD card is the complete record. The cellular model just adds a thin app layer on top.

How to read the full data

Once the card is in your computer, you need software that understands EDF. A few options:

• OSCAR — a free, open-source desktop program that reads ResMed EDF data in depth. It's powerful and well-respected, but it requires a desktop install, does no automatic scoring, and doesn't run on Chromebooks. See the OSCAR CPAP Software Guide.
• SleepHQ — a cloud tool, ResMed-leaning, with a paid Pro tier for the full feature set.
• AirwayLab — browser-based but ResMed-only.
• SomniCharts — reads your AirSense 11 SD card and shows everything myAir hides — leak, flow limitation, event types, and pressure — in plain language, with no desktop install. It works in your browser, automatically interprets the data through its SomniDoc assistant, and supports more than just ResMed: it imports ResMed, Philips Respironics (including the encrypted DreamStation 2), and Löwenstein prisma data. If you're comparing tools, our OSCAR vs SleepHQ vs SomniCharts support matrix lays out which tool reads which machine.

Whichever tool you choose, here's what to actually look at once the data loads:

1. Residual AHI — your events per hour on therapy. A residual AHI below 5 events per hour is the widely used benchmark for effective CPAP; the AASM defines an "optimal" titration as reducing AHI to fewer than 5. Some clinicians aim lower (e.g., under 1–2) when comfortably achievable, but there's no formal guideline setting "below 2" as a target — goals are individualized with your provider. See What Is a Good AHI on CPAP?.
2. Event types — is your AHI mostly obstructive, or are central events climbing? This changes the conversation entirely. Do not raise your own pressure to chase central events — higher pressure doesn't fix them and can sometimes provoke them. Bring a rising central count to your clinician.
3. Leak rate — was leak above the 24 L/min excess-leak threshold? If so, treat that night's AHI with suspicion and look at mask fit. See CPAP mask leaks and mouth leak.
4. Flow limitation — this often explains why you might still feel tired on CPAP despite good numbers. It's the hidden metric beyond AHI.
5. 95th-percentile and median pressure — what the machine actually needed most of the night, which is more informative than the prescribed range. See 95th-percentile vs median pressure.
6. Trends over weeks — line up several nights, not one, before drawing conclusions.

One important framing for device-reported numbers: the AHI your AirSense 11 calculates is an estimate. It differs from a lab-scored AHI because the machine has no EEG and can't detect cortical arousals. The AASM's recommended hypopnea rule (Rule 1A) counts a 3% oxygen desaturation or an arousal; the older CMS-aligned rule (1B) requires a 4% desaturation. Your machine can't see arousals at all, so it estimates differently than a sleep lab would. That doesn't make the data useless — it makes it a starting point for an informed conversation with your provider.

FAQ

Does the AirSense 11 record data without an internet or cellular connection? Yes. All detailed recording happens locally on the SD card. The cellular modem (on non–Card-to-Cloud models) only uploads a summary to myAir; it isn't required for the machine to capture the full breath-by-breath data.

What format is AirSense 11 data in? EDF (European Data Format), an open, industry-standard medical signal format. Because it's open and unencrypted, third-party tools like OSCAR and SomniCharts can read it directly.

How many nights does the SD card hold? Roughly 30 nights of detailed waveform data plus around 365 nights of summary statistics. The detailed buffer is the one that fills first, so pull the card periodically if you want to preserve granular history.

Why does myAir show a high score when my AHI isn't great? The myAir score is weighted heavily toward usage hours and mask seal. Because usage dominates, you can score near 100 even with a residual AHI just under 5. The SD card shows the underlying detail — including event types and leak — that the score smooths over.

Can I use the AirSense 11 SD card to adjust my pressure myself? The data is excellent for understanding your therapy and having an informed conversation with your provider. Adjusting prescribed pressure is a clinical decision — see what the data can and can't tell you about pressure.

For the broader landscape of machines and how to read each one, return to our CPAP Machines & Devices hub.