Treating the most serious cases of COVID-19 calls for the use of ventilators. We’ve all heard this, and also that there is a shortage of these devices. But there is not one single type of ventilator, and that type of machine is not the only option when it comes to assisted breathing being used in treatment. Information is power and having better grasp on this topic will help us all better understand the situation.
We recently wrote about a Facebook group focused on open source ventilators and other technology that could assist in the COVID-19 pandemic. There was an outpouring of support, and while the community is great when it comes to building things, it’s clear we all need more information about the problems doctors are currently dealing with, and how existing equipment was designed to address them.
It’s a long and complicated topic, though, so go get what’s left of your quarantine snacks and let’s dig in.
Continue reading “Ventilators 101: What They Do And How They Work”
Watching the hardware community respond to the global pandemic is a fascinating process, because of the breadth of projects being considered, and also because of the differing experiences and perspectives being brought to the table. Components most of us might have been unaware of are appearing, such as the CPAP blower used by [Jcl5m1] in his ventilator design.
He starts with a very necessary disclaimer against trusting a random person on the Internet on the subject of medical equipment design, and since it must be possible to do damage with an inappropriate ventilator we can only echo that. But as a CPAP user he’s familiar with their operation and parts, and he’s taken the centrifugal blower from one of them and paired it with a speed controller and an Arduino to provide an adjustable pressure.
What we take away from this is not in any way a ventilator that’s ready to be hooked up to sick patients, but an interesting look at ventilators in general, CPAP components, and the possibility that this project and others like it might eventually form the basis of something more useful if they attract the attention of people with more experience in the field. We’ve already seen 3D-printing used to make valves for a respirator at a hospital in Italy.
Continuous Positive Airway Pressure machines are a common treatment tool for sleep apnea and other respiratory issues. A common problem with their use is that the mask becomes dislodged during sleep, and thus fails to provide airway pressure to the patient. [Bin Sun] decided to take a stab at solving this problem.
The project consists of an Arduino fitted with a MPXV7002DP pressure sensor. The sensor is used to monitor the pressure in the CPAP pipes. If the pressure varies regularly, it is likely the system is working. If however, the pressure remains at a roughly constant level, that suggests the mask is no longer properly fitted to the wearer, or that there is another problem. In this event, the device sounds a buzzer to wake the wearer, alerting them to check the equipment.
It’s a simple solution to the problem, and something we’re surprised isn’t built into most CPAP machines from the factory. It’s important to be careful before modifying any medical equipment, though we see plenty of hackers taking the plunge to innovate in this area.
Of all the parts on your average desktop 3D printer, the nozzle itself is arguably where the real magic happens. Above the nozzle, plastic is being heated to the precise temperature required to get it flowing smoothly. Immediately below the nozzle there’s a fan blowing to get the plastic cooled back down again. This carefully balanced arrangement of heating and cooling is the secret that makes high quality fused deposition modeling (FDM) printing possible.
But as it turns out, getting the plastic hot ends up being easier than cooling it back down again. The harsh reality is that most of the fans small enough to hang on the side of a 3D printer nozzle are pretty weak. They lack the power to push the volume of air necessary to get the plastic cooled down fast enough. But with his latest project, [Mark Rehorst] hopes to change that. Rather than using some anemic little fan that would be better suited blowing on the heatsink of a Raspberry Pi, he’s using a hacked CPAP machine to deliver some serious airflow.
The brilliance of using a CPAP machine for this hack is two-fold. For one, the machine uses a powerful centrifugal fan rather than the wimpy axial “muffin” fans we usually see on 3D printers. Second, the CPAP pushes air down a lightweight and flexible hose, which means the device itself doesn’t have to be physically mounted to the printer head. All you need is manifold around the printer’s nozzle that connects up to the CPAP hose. This “remote” fan setup means the print head is lighter, which translates (potentially) into higher speed and acceleration.
[Mark] was able to connect the fan MOSFET on his printer’s SmoothieBoard controller up to the brushless motor driver from the CPAP motor, which lets the printer control this monster new fan. As far as the software is concerned, nothing has changed.
He hasn’t come up with a manifold design that’s really optimized yet, but initial tests look promising. But even without a highly optimized outlet for the air, this setup is already superior to the traditional part cooler designs since it’s got more power and gets the fan motor off of the print head.
Getting your 3D printed parts to cool down is serious business, and it’s only going to get harder as printers get faster. We wouldn’t be surprised if fan setups like this start becoming more common on higher-end printers.
CPAP (Continuous Positive Airway Pressure) machines can be life-changing for people with sleep apnea. [Scott Clandinin] benefits from his CPAP machine and devised a way to improve his quality of life even further with a non-destructive modification to monitor his machine’s humidifier.
With a CPAP machine, all air the wearer breathes is air that has gone through the machine. [Scott]’s CPAP machine has a small water reservoir which is heated to humidify the air before it goes to the wearer. However, depending on conditions the water reservoir may run dry during use, leading to the user waking up dried out and uncomfortable.
To solve this in a non-invasive way that required no modifications to the machine itself, [Scott] created a two-part device. The first part is a platform upon which the CPAP machine rests. A load cell interfaced to an HX711 Load Cell Amplifier allows an Arduino Nano to measure the mass of the CPAP machine plus the integrated water reservoir. By taking regular measurements, the Arduino can detect when the reservoir is about to run dry and sound an alarm. Getting one’s sleep interrupted by an alarm isn’t a pleasant way to wake up, but it’s much more pleasant than waking up dried out and uncomfortable from breathing hot, dry air for a while.
The second part of the device is a simple button interfaced to a hanger for the mask itself. While the mask is hung up, the system is idle. When the mask is removed from the hook, the system takes measurements and goes to work. This makes activation hassle-free, not to mention also avoids spurious alarms while the user removes and fills the water reservoir.
Non-invasive modifications to medical or other health-related devices is common, and a perfect example of nondestructive interfacing is the Eyedriveomatic which won the 2015 Hackaday Prize. Also, the HX711 Load Cell Amplifier has an Arduino library that was used in this bathroom scale refurb project.
Preterm infants frequently require ventilator support while they’re in the neonatal ICU, and this is usually done with a CPAP machine. The machine to infant interface is called a nasal cannula, a bit of plastic that connects an infant’s nose to the machine. Because there aren’t that many sizes of nasal cannula available, and preemies come in all sizes, there are inevitable problems. Ill-fitting nasal cannula can reduce the effectiveness of a CPAP, and can even cause significant damage to an infant’s septum.
For his Hackaday Prize entry, [Ben] is tackling this problem head on. He’s working on creating individualized nasal cannula for newborns using 3D modeling and printing, allowing nasal cannula of all shapes and sizes to be created in a matter of hours.
To create these customized cannula, [Ben] is 3D scanning an infant mannequin head to gather enough data to import it into a Processing sketch. A custom cannula is then created and printed with flexible 3D printer filament. In theory, it should work, apart from the considerations involved in building a medical device.
As for why custom plastic tubes matter, [Ben] works at the only NICU in Western Australia. Even though he only sees 8-10 CPAP ‘pressure injuries’ in his unit each year, these kids are extremely fragile and some parents have expressed a desire for something that isn’t as uncomfortable for their newborn than the off-the-shelf solution. Customizing these cannula from a quick 3D scan is a great way to do that, and a perfect example of the Hackaday Prize theme of ‘build something that matters.’