ResMed AirCurve 10 & 11 (VAuto, ST, ASV): Reading Bilevel Data

Bilevel and adaptive machines are the most data-rich devices ResMed makes — and ironically the worst served by the apps most people use to read them. If you have an AirCurve 10 or AirCurve 11, your SD card holds two pressure values, breath-by-breath flow, and (on ASV models) a moving target your machine is actively chasing all night. This guide explains what each AirCurve mode records, how that data is stored, and why a tool built for single-pressure CPAP leaves most of your night invisible.

For background on how AirCurve fits alongside ResMed's straight-CPAP lineup, see APAP vs CPAP vs BiPAP: machine modes and the data each produces and the broader CPAP Machines & Devices hub.

The AirCurve family (VAuto, ST, ASV, CS)

"AirCurve" is ResMed's bilevel line. Bilevel — often called BiPAP or BiLevel — means the machine delivers two pressures instead of one: a higher pressure when you breathe in (IPAP) and a lower pressure when you breathe out (EPAP). The gap between them, called pressure support, is what makes inhaling easier and is the defining feature of the whole family.

The AirCurve 10 and the newer AirCurve 11 ship in several modes, and the mode matters more than the model number because it determines what gets recorded:

ASV in particular is clinician-directed therapy, prescribed specifically for central or Cheyne-Stokes breathing rather than ordinary obstructive apnea. You don't choose it off a shelf; it's set up and titrated by your sleep physician. If you want to understand the breathing patterns behind these modes, see central vs obstructive apnea and periodic breathing and Cheyne-Stokes on your CPAP chart.

What bilevel data records — IPAP, EPAP, pressure support

A standard CPAP logs one pressure. A bilevel machine logs the full pressure picture, which is what makes AirCurve data uniquely informative:

• IPAP — inspiratory positive airway pressure, the higher pressure delivered as you breathe in.
• EPAP — expiratory positive airway pressure, the lower pressure that splints the airway open as you breathe out (this is the part that prevents obstructive collapse).
• Pressure support (PS) — IPAP minus EPAP. This single number tells you how much "boost" each breath received.
• Breath-by-breath flow — the same high-resolution flow rate waveform ResMed CPAPs record, showing the shape of every breath.

Because the AirCurve separates inhale and exhale pressure, you can see things a single-pressure chart can't. On a VAuto, for example, EPAP may auto-titrate upward across the night to chase obstructive events while pressure support stays fixed — so watching EPAP and the event types together tells you whether the machine is keeping the airway open. The flow rate trace remains the richest signal of all; learning to read it (how to read the CPAP flow rate waveform) reveals flow limitation that never shows up in your AHI.

One thing that carries over from straight CPAP: leak still governs whether your numbers are trustworthy. ResMed reports excess leak (leak above the expected vented amount), with a commonly cited concern threshold around 24 L/min at the 95th percentile. Large leak can cause the machine to under-detect events and report an artificially low AHI, so a "great" night with high leak is not actually a great night. See CPAP leak rate: what's acceptable.

ASV's extra data — target ventilation and servo response

ASV models record everything above and then add a layer no other home device does. ASV stands for adaptive servo-ventilation: the machine continuously measures your breathing, calculates a target ventilation (a moving baseline of how much air you should be moving, typically based on a rolling average of your recent minute ventilation), and then varies pressure support breath-by-breath to keep you near that target.

That means ASV data includes:

• Target ventilation — the goal the machine is steering toward, which itself drifts as your breathing changes.
• Servo response — the moment-to-moment pressure-support adjustments the machine makes to hit the target. When your breathing fades (the trough of a Cheyne-Stokes cycle), the machine pushes more support; when you over-breathe, it backs off.

Reading ASV data well means watching the relationship between your actual ventilation, the target, and the servo's response — not just a single AHI number. A residual central event on ASV, or a target the machine struggles to maintain, is clinically meaningful information for your provider, especially since ASV is used for Cheyne-Stokes respiration and its heart connection. This is also why central events deserve careful, clinician-led interpretation: CPAP and bilevel splint the airway open and reliably treat obstructive apneas, but they don't directly correct the unstable breathing drive behind central (clear-airway) events — which is exactly the gap ASV's servo logic is built to address. More on that distinction in central apneas showing up on CPAP (treatment-emergent CSA).

SD/EDF storage and session capacity

The good news for AirCurve owners: the storage format is the same one ResMed has used for years, so getting the data out is straightforward. AirCurve machines write to a standard SD card, storing detailed therapy data in EDF (European Data Format) files — the same open, well-documented format used by the AirSense family, and the same session capacity as those CPAP models.

Practically, that means:

• You pop the SD card into a reader and the raw EDF files are right there — no proprietary cloud round-trip required to access full-detail data.
• The card holds the same span of detailed nightly data as an AirSense, so you get high-resolution waveforms going back the same amount of time, with summary data going back further.
• The files include the extra bilevel and ASV channels described above, not just summary statistics.

If you're new to extracting the card, the mechanics mirror the AirSense process exactly — see how to download CPAP data from your SD card and the AirSense 11 SD card data and AirSense 10 data guides, which apply to the AirCurve hardware too.

One caution: as with all CPAP analysis, a single night is mostly noise. EPAP swings, pressure support spikes, and the odd central event on ASV are far more meaningful as trends over weeks than as one bad-looking chart. Read your data the way a clinician does — over time.

Why bilevel users are underserved by consumer tools

Here's the frustration AirCurve owners discover quickly: the consumer apps and even some third-party tools were designed around single-pressure CPAP, so they flatten or ignore the very data that makes bilevel worth analyzing.

• myAir (ResMed's own app) gives you a 0–100 score weighted heavily toward usage hours. It shows no event-type breakdown, no leak or flow-limitation detail, and certainly no IPAP/EPAP split or ASV target ventilation. The scoring formula has never been published, and a night can score 100 even at an AHI just under 5. For a bilevel user, myAir is essentially a usage tracker. See how to read your myAir score.
• OSCAR (the free desktop standard) does read AirCurve EDF data including the bilevel channels, which makes it genuinely useful — but it's desktop-only, won't run on a Chromebook, does no auto-scoring or plain-language interpretation, and has a learning curve. See the OSCAR CPAP software guide.
• SleepHQ is cloud-based and ResMed-leaning, with a paid Pro tier for the deeper features.

So a VAuto or ASV user is often stuck choosing between an app that hides their best data (myAir) and a powerful tool that shows everything but explains nothing (OSCAR).

This is exactly the gap SomniCharts is built to close. It imports ResMed (including AirCurve VAuto, ST, and ASV), Philips Respironics (including the encrypted DreamStation 2), and Löwenstein prisma data, then reads your pressure-support detail — IPAP, EPAP, the PS gap, and ASV's target ventilation and servo response — and explains it in plain language automatically, in the browser, with no desktop install. For machines whose richest data most apps throw away, having SomniDoc surface and translate it is the difference between a usage score and an actual understanding of your night. Compare options in SomniCharts vs SleepHQ and the OSCAR vs SleepHQ vs SomniCharts support matrix.

Whatever tool you use, the goal is the same: turn that uniquely rich bilevel data into an informed conversation with your sleep clinician — not a reason to change settings on your own. The treatment goal for adults on PAP therapy is generally a residual AHI below 5 events per hour (many clinicians aim lower when it's comfortably achievable, though targets are individualized), and on ASV in particular, what your servo response and central-event trend are doing matters as much as the headline number. Bring the trend; let your provider set the dial.