B.L.O.O.D.Y. L.E.G.

Meet the BLOODY LEG, the Blood Leaking Obscenely Overengeneered Do-it-Yourself Lower Extremity Graft!

It’s a microcontroller-powered device for simulation maniquin legs. It leaks blood, controlled per bluetooth. The blood does not just flow, it pulsates! You can even set the pulse frequency and volume of blood per pulse. And it shows the battery state of both the remote control and the reciever in the leg. They connect on power-up, and if the two loose connection, the flow shuts down after a moment. Pretty cool, ey?

About ten years ago, I made a simpler version with the innards of a tiny toy RC car and a metronome. Every beep of the metronome would trigger a signal of a certain lenght, which could be set by a potentiometer.

The signal was picked up by the reciever, which opened an solenoid valve from an old dishwasher. One side of the valve was connected to a pressure reservoir made with a syringe and a steel spring.

The other side went to the amputated end of the leg, where the foot was missing. Every beep would release a drop or a squirt of blood, depending on the setting of the potentiometer.

The leg itself is made of fibreglass resin casting tape (3M Scotchcast), coated with colored construction silicone.

But while it worked OK, this system had some drawbacks, too. You had to be really close with the remote control (about 1m), you had to recharge the reciever every 5 minutes, and you never knew when the two 9V batteries powering the solenoid would run out. So I desinged a new system, with a LCD screen and a bluetooth connection. Powered by a microcontroller. Welcome to the digital age!

Take a look at this video on youtube to see how it works.

Remote control with LCD on the left, watertight reciever with small 5V solenoid on the right. The reciever box fits into the old leg, as it has the same dimensions as the old box.

LCD showing the connection status, charging state of remote control (A) and reciever (B). The blood flow ist set on 60 bpm with 30% volume and is currently off. The black switch turns everything on and off, the membrane arrow buttons control the settings, the middle round button turns the flow on or off.

The reciever electronics are very compact and fit into a watertight housing, together with a 9V battery. Instead of installing this in a leg, one could also use it on other maniquin body parts or even on a standardized patient. Instead of the syringe/spring pressure reservoir, one could also use a pressure infusion bag.

For both elements I desinged a custom PCB to solder everything together in a very compact manner. See this making-of video for a timelapse of the soldering process.

Please let me know if you are interested in making your own BLOODY LEG. I will write down some instructions for you and send you the arduino code, the scematics and the gerber files for the PCB. IMPORTANT: If you life in Switzerland, I could send you a pair of blank PCBs (I have some left). Just let me know in the comments. For all other countries: Sadly, the Swiss Post is so expensive, that you will be better off ordering the PCBs directly from a manufacturer…

DIY-Connector for ShockLink

At my shop, we recently bought the ShockLink training system from Laerdal. It is basically a cable to put between your live defibrillator and manikin, with a built-in ECG-generator and energy dissipator. As with all Laerdal products, it comes equipped with a defibrillation electrode plug for Phillips-brand defibrillators. It’s a great product and really easy to use, even without a manikin. You can simulate defibrillating a bag of potatoes if you like.

The problem is: At my hospital, we only have Zoll R-Series defibrillators, which use different plugs. So we need to use an adapter to connect ShockLink to our machines.

If we want to use the Zoll CPR-Sensor, as we do in real life, we even need TWO adapters. One to break out the CPR-sensor from the electrode contacts, and one to connect those with the ShockLink cable. This has two significant drawbacks.

First, cost, as the adapters are over 100 $ each. If you are the unlucky owner of a Corpuls defibrillator, the adapter is even priced at an insane 424 $!!!

And second, ergonomics. Instead of one cable from defibrillator to electrodes, you get a bunch of them, with y-pieces and an unwieldy adapter in the middle. Instead of ACLS-skills, you need a bachelor degree in advanced cable management, as you can clearly see in this Laerdal video.

So, long story short, I designed a more practical and cheaper solution: A 3D-printed connector to put on a Zoll OneStep CPR electrode plug. You can find the stl-file at Thingiverse. You will also need two small banana-plugs like these, a soldering iron and some glue.

Parts A, B and C after printing

Banana plugs

Solder the cable to the plugs, secure with screw. If you don’t know which cable goes where, you should probably not be doing this!

When you have both cables in, glue the base plate on. Only of course you have forgotten to thread it on the wires before soldering in the first place, so you will have to desolder the whole mess and do it again 😉

Voilà!

The finished adapter is the black box between the grey Zoll plug and the green band on the top left. I would have liked to shorten the thick black cable to the ShockLink box, but this seems to act as the resistor (gets warm after shock). So I won’t touch it, just coiled it up a bit.

Disclaimer: Build this at your own risk! I will not take any responsability if you electrocute yourself, your manikin, your students or your cat!

I desingned this using the Revopoint Mini 3D-Scanner on the original plug and constructing the adapter in CAD around it. Thankfully, the original plug was white and not shiny, which are about the only circumstances this rotten scanner actually works as advertised…

Revopoint Mini with Philips-style plug on the turntable.