When there are more critical patients than ventilators to keep them alive, doctors need to take hard decisions on which patient gets to live on the ventilator and which patient will need to die. It’s hard to believe, but this is exactly what happens in hospitals in crisis situations.
Back in 2006, two doctors demonstrated that by using T-tubes and adapters, a ventilator circuit could be divided such that four simulated patients could share a single ventilator in emergency circumstances. This remained a simulation till 2017 when there was a mass shooting in Las Vegas. A doctor used this technique to keep patients alive till more ventilators could arrive.
A group of four anesthesiologists have taken this concept further and have designed a splitter which can be printed on a 3D printer. They have published the design on their web site. Before going any further I would like list the disclaimer on their web site:
Use at your own risk, and if loss of life is otherwise inevitable!
This is important to understand because a ventilator is designed to manage the breathing of a single person only. So this should be used only when a doctor needs to take a life and death decision and if he is confident that using a splitter will save a second life but not put the first life in danger.
There are two parts to this – the splitter and the flow limiters. The flow limiters are basically end caps that fit onto the limbs of the splitter. Each flow limiter has a hole of a specific size. This is important because you need to regulate the flow of air to each patient depending on the capacity of their lungs. For example, if you want a ventilator to serve a healthy young man and a frail old woman, you can’t simply send the same amount of air to both their lungs. Doing that would cause more problems that it solves. You need to use the appropriate size flow limiter to regulate the amount of air going to each patient.
The picture above shows a splitter with a set of flow limiters printed on a Figure 4 Standalone 3D printer using the MED-AMB 10 material. This material is perfect for this particular application because it is capable of meeting the ISO 10993-5 & 10993-10 standards for biocompatibility (cytotoxicity, sensitization and irritation). More importantly, with a Heat Deflection Temperature (HDT) of 119 degrees Centigrade, it can be sterilized in an autoclave machine. You can also use the Figure 4 PRO-BLK 10 material. Although it is capable of meeting the above mentioned ISO standards, it can’t be sterilized in an autoclave machine. You will need to use another method of sterilization.
If you want to print a large number of these splitters, or any similar medical device for that matter, another option is to use a SLS 3D printer using a bio-compatible material. In the case of 3D Systems, we offer the ProX SLS 6100 with Duraform PA 12, a material can meet the ISO standards as well as be sterilized in an autoclave. Using the full build volume you can print around 200 splitters in a day.
Shree Rapid Technologies, our partner based in Mumbai, has already started using their Figure 4 and SLS 3D printers in their Customer Innovation Center to print these splitters and flow limiters among other COVID-19 related applications.
Here, I would like to repeat something I mentioned in my previous blog post titled “First, Do No Harm“:
We need to realize that if a hospital is using a 3D printed part instead of a part made using a traditional method in a certified facility using a certified process, it means that they are desperate to do something to keep a very sick patient alive. They have obviously run out of their regular supplies or venturi valves for ventilators or face marks and shields and now the doctors need to take some very critical life and death decisions.
Thankfully, at the moment in India the number of COVID-19 cases hasn’t hit unmanageable levels and I hope it stays that way. But in case our hospitals face similar situations like those in Italy and Spain, then we want to be ready with solutions that have been tested.
For now I’m generating awareness that such emergency solutions exist and can be deployed relatively quickly in India. Please share this with whoever you think needs to know.