OSCAR CPAP Software

Most CPAP users meet their sleep data through a small app on their phone. ResMed customers get MyAir. Philips users get DreamMapper. Each morning, the app shows a usage time, a leak indicator, a single number for breathing events, and some kind of score if the night went well. For a lot of people, that’s enough. For others, it’s nowhere near enough.

The alternative most often pointed to in CPAP forums is OSCAR, short for Open Source CPAP Analysis Reporter. It is a free desktop program, maintained by volunteers, that reads the SD card from a CPAP machine and renders every breath as a chart. The same data the manufacturer’s app summarizes into a smiley face, OSCAR lays out in graphs you can zoom into second by second.

What follows is a layperson’s overview of what OSCAR is, where it came from, what it actually shows, which machines it supports, and the honest limits of pulling raw data off a CPAP. I have been on a ResMed AirSense 10 for more than a decade. My background is in computer science, not medicine. Anything in here that touches on therapy decisions belongs in a conversation with your sleep specialist, not in a forum thread.

A fork with an Australian backstory

OSCAR did not start as OSCAR. It began as SleepyHead, written by Mark Watkins, an Australian software developer who had sleep apnea himself and wanted to see his own data. He released the program under an open source license and developed it through several major versions before stepping away from the project. A small group of contributors picked up the code, renamed it OSCAR, and have continued releasing updates ever since. The Apnea Board forum, a long running community for CPAP users, hosts the official downloads at sleepfiles.com/OSCAR. The current release is version 1.7.1, with builds for Windows, Mac (both Intel and Apple Silicon), Linux, Chromebook, and Raspberry Pi OS.

Two details about that history are worth keeping in mind. First, OSCAR is volunteer maintained, not a commercial product. There is no support phone number, no salesperson, no upgrade pressure. There is also no marketing budget, which is part of why the patient apps that ship with each machine can leave OSCAR out of their conversations entirely. Second, the project is open source, which means anyone can read the code that interprets your data. For people from a software background, that is a meaningful trust signal. For most users, it mainly means the program will keep running for free.

What OSCAR shows that the manufacturer apps don’t

The gap between MyAir and OSCAR is not subtle. MyAir gives a single AHI number for the night. OSCAR breaks the same number into its parts: obstructive apneas, central apneas, hypopneas, and, on supported machines, flow limitations. MyAir reports a leak indicator that compresses an entire night into a category. OSCAR plots the leak rate as a continuous line, so a five-minute leak spike at three in the morning shows up clearly even when the average for the night looks fine.

That difference matters because two nights with the same AHI can be very different nights. A score of four made up almost entirely of hypopneas suggests one kind of problem. A score of four made up of central apneas after a stretch of normal breathing suggests something else. The total is identical. The story behind it is not. OSCAR shows the story.

The other thing OSCAR adds is the flow rate graph: a wave that moves up for inhalation and down for exhalation, drawn for every breath of the night. Most people do not need to read this graph in detail, and most people should not try. But when something specific seems off, being able to scroll into a single five minute window and see the actual shape of the breathing is the difference between guessing and looking. For a deeper walkthrough of what each of these metrics means in everyday terms, my piece on how to interpret CPAP data covers AHI, leak rate, and usage hours in plain language. The Sleep Foundation’s overview of AHI is also a useful general reference for what the score actually represents and where it falls short.

Which machines work with it

OSCAR is built around two main families: ResMed and Philips Respironics. Within those families, the coverage is broad. Most ResMed AirSense 10 and AirCurve 10 models are fully supported, including the Card to Cloud variants that lack a cellular modem. The newer ResMed AirSense 11 has been supported since version 1.3.0, released in late 2021, so the older claim that the AirSense 11 only works in a limited way is no longer accurate. Philips Respironics machines from the System One and DreamStation generations are supported as well, including the DreamStation 2 lineup. Fisher and Paykel SleepStyle is supported, as is the older Icon, although the Icon does not record a flow rate signal so its waveform views are limited.

Some smaller manufacturers are also covered. DeVilbiss machines including the IntelliPAP and the BLUE (DV6) work with OSCAR, although Drive Medical announced it was leaving the CPAP business in late 2021, so those machines are increasingly hard to find new. The Apnea Board wiki maintains a current supported machines list and is the right place to check before you assume a particular model will import correctly.

A practical caveat for AirSense 11 owners: the machine ships without an SD card because ResMed expects you to use the cellular link to MyAir. You can buy an SD card separately, format it as FAT32 (32 GB or smaller), and slot it in. The machine will start writing detailed data, and OSCAR will read it the same way it reads AirSense 10 cards. There is one wrinkle worth knowing about. If you insert a 64 GB card in exFAT format, the AirSense 11 may reformat it. Stick to 32 GB or under, formatted as FAT32, and you sidestep the problem. For people considering the upgrade, my ResMed AirSense 11 review goes into more detail on the machine itself.

A few machines do not work with OSCAR, mostly older or budget oriented models that only record summary data and never write detailed efficacy information. The Apnea Board wiki flags these specifically and recommends avoiding them if data is important to you.

Getting OSCAR onto your computer

The download lives at sleepfiles.com/OSCAR, the page maintained by the Apnea Board volunteers. Pick the build for your operating system, install it the way you would any desktop application, and launch it. There is no account, no email signup, no tier of features locked behind a paywall. The first time it opens, OSCAR asks you to set up a profile, which lives locally on your computer. None of your data leaves your machine.

Reading the SD card requires a card reader. Many laptops still have built in SD slots; on machines that do not, a USB SD card reader costs a few dollars. Pull the card from the side of your CPAP, slide it into the reader, and OSCAR’s import tool walks you through pointing it at the right folder.

The first import can take a while if you have years of data on the card. ResMed machines store roughly a year of detailed data and several years of summary data on a 4 GB card, and OSCAR reads all of it. After the first import, subsequent imports are much faster because OSCAR only adds the new sessions.

What people actually look at

Inside OSCAR, the daily view is where most people spend their time. It shows the date, a few summary statistics across the top, and below that a stack of graphs: events flagged during the night, pressure, leak rate, flow rate, snore, respiration rate, tidal volume, minute ventilation. Any of them can be hidden, dragged into a different order, or zoomed in on with a click and drag.

A few things tend to catch a new user’s eye. The leak rate graph is one. ResMed’s leak number on MyAir is averaged in a way that hides short, severe leaks. In OSCAR, those leaks show as spikes you can match to a specific time of night. People who routinely wake with dry mouth often discover the leaks are happening on their side, late in the night, when the mask seal shifts. My guide to CPAP mask leaks goes deeper into the causes and what helps.

The event types are the other revelation. A night with an AHI of three sounds fine. A night with an AHI of three made up entirely of central apneas is a different conversation, and one worth bringing to a sleep specialist. OSCAR labels each event by type so the breakdown is clear without any extra effort. For background on what AHI actually measures and how the categories differ, my explainer on the apnea hypopnea index covers it.

For users on auto-adjusting machines, the pressure trace is the third thing worth looking at. It shows where the machine moved up to address events and where it settled back down. Patterns can emerge: a slow ramp upward in the small hours, repeated bumps after a meal heavy night, plateaus that suggest the machine wanted more headroom than its current ceiling allowed. None of this is a substitute for a sleep doctor’s read, but it is grist for the conversation.

The community angle

A surprising amount of OSCAR’s value, in practice, is social. Apnea Board, the r/CPAP and r/SleepApnea subreddits, and various Discord communities are full of people sharing OSCAR screenshots and trading interpretations. The unwritten norm is that you post a chart, describe what you are seeing, and ask. People with experience reply with what they would look at next. Sometimes those replies catch things a rushed clinical follow up might miss. Sometimes they overstate the importance of a single bad night. The signal is real, but it is not a substitute for medical advice, and the better forum members are the first to say so.

OSCAR exports the daily and overview pages as PDFs, which makes the social workflow possible. The same PDF is the right format to bring to a sleep specialist appointment. Specialists who work with CPAP patients increasingly recognize OSCAR reports and can read them at a glance. Some are wary of patients arriving with their own data and theories. Others welcome it. Asking a prospective specialist whether they are comfortable with patient supplied data is a fair question to put before the first appointment.

Honest caveats

There are real reasons to slow down before treating OSCAR as the answer to a stalled therapy.

The first is that raw data invites overinterpretation. A single night with a higher AHI is usually weather, sinus pressure, alcohol, sleep position, or a bad seal. It is not a crisis. People who check OSCAR every morning and adjust their thinking based on each night tend to drive themselves a little crazy. Reviewing weekly is plenty, and looking for patterns across two or three weeks is more useful than reading any single night closely.

The second is that some of OSCAR’s most interesting graphs require interpretation a layperson is not equipped to do. Flow limitation curves, for instance, can suggest upper airway resistance that the machine is not fully addressing, but reading them well takes practice. Confusing OSCAR’s central apnea label for true central sleep apnea, or assuming a leak spike is a mask problem when it is actually a mouth leak, is easy. The Apnea Board wiki has a long reference called OSCAR The Guide that is the best free starting point for learning to read the views without jumping to conclusions.

The third is the simplest. Changing pressure settings yourself, without a sleep specialist’s input, is not what OSCAR is for. The clinical menu on most ResMed and Philips machines can be unlocked, and many users in the forums change their own settings. That is their decision, made with the risks and tradeoffs that come with it. For most patients, the right use of OSCAR is to see what is happening, not to override the clinician’s plan. Bring the data to the appointment. Let the specialist adjust the machine.

Where it fits

OSCAR is not for everyone. People who feel rested, who use their CPAP every night, and whose MyAir scores are consistently high probably do not need it. The smiley face is doing its job. People who feel like the smiley face is lying, who wake tired, who suspect something is happening at night that the app is not telling them, or who simply want to understand what their machine is doing, are the audience the program was written for. The price of admission is a free download, an SD card reader, and an evening of getting comfortable with the interface.

For someone with a software background and a long history with the same ResMed machine, OSCAR is the kind of tool that exists because someone in the patient community decided the manufacturer’s view of their own sleep data was not enough. That fact, on its own, is a useful piece of information about what patient apps are designed to do, and about what they are designed not to do.

⚠️ MEDICAL DISCLAIMER This blog provides general information only and is not a substitute for professional medical advice, diagnosis, or treatment. Sleep apnea is a serious condition, and CPAP equipment should be used under proper medical supervision. Always consult your doctor or sleep specialist before starting, stopping, or changing any therapy. I share personal experiences as a CPAP user, not as a medical professional. Individual results vary. For medical guidance, please consult a qualified clinician or the American Academy of Sleep Medicine (aasm.org).