Open-source firmware turns CPAP machines into coronavirus ventilators

The Airbreak firmware is a big step toward transforming the Airsense 10 CPAP machine into a non-invasive ventilator.
Written by Steven Vaughan-Nichols, Senior Contributing Editor

Thanks to the coronavirus pandemic, we are woefully short of ventilators that can give the most gravely ill a chance for life. There are many efforts afoot to build more ventilators. Now, instead of building ventilators, a group of open-source developers has a new idea: Create a firmware update, Airbreak, which can transform common Constant Positive Airway Pressure (CPAP) machines into non-invasive ventilators. 

Their first effort -- a proof of concept -- converts the Airsense 10 CPAP machine, which is a common, inexpensive sleep apnea treatment device, into a ventilator. It does so by simply replacing its existing firmware with updated firmware

With this upgrade, the Airsense could be used as an emergency ventilator until a better, purpose-built ventilator is available. It has the following ventilator features:

  • Adds a Pressure Control Ventilator (PCV) mode that oscillates between high and low pressure at a configurable breathing rate (stock firmware supports only a single pressure, with no breath rate control).
  • Allows maximum pressure to be increased to 30 cm H2O, as required by clinical protocols (stock firmware is limited to 20cm H2O).
  • Allows smooth rapid pressure change rates for respiration rates up to 30 breaths per minute (stock firmware changes pressure at less than 1cm/sec).
  • Unlocks all the vendor modes and tunable configuration parameters, including ST and iVAPS modes present in the firmware.
  • Provides access to all of the sensors (flow, pressure, temperature, tidal volume, minute ventilation, etc).
  • Displays real-time graphs on the screen to show an immediate history of sensor data.

What the firmware is doing is changing a CPAP device into a Bilevel Positive Airway Pressure (BIPAP). These aren't ventilators either, but hospitals -- like New York's Mount Sinai -- have been able to deploy these as ventilators. The reason why this is worth doing is CPAP machines are cheaper and more common than BIPAP devices. The FDA has already approved the use of modified BiPAP devices as ventilators.

Now, CPAP devices with this firmware patch are not drop-in-replacements for ventilators. Far from it. Additional equipment like viral filters and monitoring alarms are also required. As its creators state:

We want to be very clear here: This modified firmware should not be flashed on CPAP machines and used to treat COVID patients immediately. The firmware that we've developed is an effective demonstration of the capability, and while it has been reviewed and validated by expert researchers, biomedical engineers, and clinical pulmonologists, it has not yet been put through FDA [Food and Drug Administration] approval. Additionally, the Mt Sinai's protocols for off-label non-invasive ventilation require additional modifications such as viral filter and remote control before the machines would be ready for clinical use.

The programmers could send its firmware through the FDA approval process themselves, but its developers think "the best route for rolling out these upgrades is to work with the manufacturers to use their resources to validate and distribute these upgrades safely and at scale."

The code has great potential. It would also be easy to deploy. The five million CPAP devices shipped over the last three years have an always-on cellular connection. Thanks to that, these devices can easily be upgraded over-the-air by device manufacturers. With this, hundreds of thousands of CPAP machines could be upgraded overnight. This could easily bring millions of unused or underutilized CPAP machines into hospitals just when we need them. 

Further coding, testing, and evaluation need to be done with FDA approval received before these patched CPAP machines can be deployed. But, the need is urgent, and it's a heck of a lot easier to wirelessly update firmware than it is to build and deploy millions of new hardware ventilators. This project isn't just a good idea -- it's one that deserves close attention from CPAP manufacturers and medical professionals as soon as possible.

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