ResMed S9 Data: AHI, Events & Flow

The ResMed S9 is an older machine, part of the System 9 range that came before the AirSense. If you still run an S9 AutoSet or S9 Elite, you may have assumed its data was locked away or too old to read. It is not. The S9 saves a surprising amount of detail to its SD card, including a high resolution recording of your breathing, and CPAP Clarity can read it right in your browser.

Here is the honest picture: what the S9 records, what CPAP Clarity shows you from its card today, and how to make sense of your nightly numbers.

The short answer

The S9 writes both a daily summary and detailed nightly files to its SD card. The card holds your nightly AHI, the individual breathing events the machine scored, a breath-by-breath flow trace, and your pressure and leak figures. That is far more than a usage log. It is close to what the newer AirSense machines record, just from an older generation of hardware.

CPAP Clarity reads that card directly on your own device and shows you your nights. Nothing is uploaded to a server. Your AHI, your events, your flow trace, and your pressure and leak all come through in full.

What the S9 records

Take the SD card out of your S9 and it holds, for each night:

AHI, your apnea hypopnea index, the number of breathing events per hour, computed from the events the S9 scored
Scored events, each apnea and hypopnea the S9 detected, with its type and the time it happened
A flow trace, a high resolution breath-by-breath recording of your airflow through the night
Pressure, the therapy pressure the machine delivered, recorded across the night
Leak, how much air escaped around your mask, recorded across the night
Usage, how long you wore the mask that night

These are the machine's own measurements. The AHI and the events are what the S9 scored, and the flow trace is the same detailed recording a clinician's software would read from the card.

What CPAP Clarity shows you

Drop your whole SD card folder into CPAP Clarity and you will see a real night:

Your AHI for the night, with the standard severity context
Your events, broken down by type and placed on a timeline, so you can see when across the night they clustered
A flow trace you can scroll and zoom, so you can look at the breathing around a single event
Your pressure and leak across the night, plotted as trend charts, with the 95th percentile called out as your headline numbers
Your usage, feeding the same therapy score, trends, and compliance view as any other ResMed machine

The pressure and leak trend charts plot both values across the night, next to the breath-by-breath flow trace, so you can watch how your pressure moved and see when your leak climbed. For a walkthrough of that flow trace, see our guide on how to read your flow rate graph.

How to import your S9 data

You will need the SD card from the machine and a way to read it on your computer or phone.

Power down the S9 and remove the SD card from the slot on the side.
Put the card into your computer, or a card reader on your phone.
Open CPAP Clarity and drag the whole card folder onto the import area. On a phone, choose the folder when prompted.
Wait a moment while your nights are read, then review your data.

Always select the entire card folder, not a single file. The S9 keeps your daily summary and your detailed nightly files in separate places on the card, and CPAP Clarity needs the whole folder to show a complete picture.

For a quick overview of what the S9 import shows, see the ResMed S9 device page.

How to read your S9 numbers

Your nightly numbers are most useful as a trend, not a single night. A good way to think about each one:

AHI is the headline. The AASM defines 5 or more events per hour as sleep apnea, so it is a diagnostic threshold rather than a verdict on how your night went. Watch whether your nightly value is steady or creeping up, and confirm your own target with your doctor.
Events tell you the shape of the night. A cluster of events early on reads differently from events spread evenly, and the flow trace lets you look at the breathing around them yourself.
Pressure is what your machine actually delivered. On an auto machine it moves night to night as your airway needs change. A sudden jump can hint at congestion, a new sleeping position, or a mask issue.
Leak is about mask fit. A high 95th percentile leak means a lot of air escaped, which can let events slip through even when pressure looks fine. If your leak is consistently high, a mask refit is usually the first thing to try.
Usage is the simplest and often the most important. Consistent nightly use is what gets you the most out of your therapy.

If your numbers raise questions, the right next step is a conversation with the clinician who prescribed your machine, with your CPAP Clarity summary in hand. For more on what your headline number means, our guide to what AHI is goes deeper.

Frequently Asked Questions

Does CPAP Clarity work with the older ResMed S9?

Yes. The S9 is part of ResMed's System 9 range, and CPAP Clarity reads its SD card directly in your browser. You get your nightly AHI, your scored events with a timeline, a breath-by-breath flow trace, and your pressure and leak, with nothing uploaded to a server.

Which S9 models are supported?

The detailed S9 models: S9 AutoSet, S9 Elite, S9 AutoSet for Her, and the S9 VPAP family. The S9 Escape and Escape Auto are simpler machines that save only a daily summary, so they show usage and a nightly figure rather than a flow trace.

Can I see my events, not just my AHI?

Yes. CPAP Clarity shows each event the S9 scored, broken down by type and placed on a timeline, alongside the breath-by-breath flow trace, so you can look at the breathing around any event yourself.

Can I see my pressure and leak across the night?

Yes. CPAP Clarity plots your pressure and your leak as trend charts across the night, right next to the breath-by-breath flow trace, and calls out the 95th-percentile pressure and leak as your headline numbers. All of it is read from the SD card in your browser.

Is my ResMed S9 data private in CPAP Clarity?

Yes. All reading and analysis of your card happens on your own device, in your browser. Your therapy data is never uploaded to any server.

The bottom line

The S9 is an older machine, but it is far from a dead end. Its SD card holds your nightly AHI, your scored events, a breath-by-breath flow trace, and your pressure and leak, and CPAP Clarity reads all of it in your browser, pressure and leak trends included. If you have an S9 gathering dust with a card full of nights, you can finally look at your own data. Import your card and take a look.