How to make ECG pads & conductive gel

It's easy to find a bedside monitor in a hospital in the developing world, but it's harder to find one in use. Western hospitals replace their electrocardiogram machines every few years and donate their used equipment. The second-hand machines work fine, with one glaring exception: They don't come with pads. The pads are disposable and often in short supply in impoverished regions.

The solution is to make ECG pads (link to E4C's how-to) from easy-to-find materials such as snap buttons and bottle caps. Robert Malkin and students at Duke University invented the trick, and our friends at Engineering World Health travel the world and demonstrate that making ECG pads and conductive gel is fun for the whole family. The materials required are bottle caps (read: beer and soft drinks) and the conductive gel is a gooey mess that kids enjoy. Incidentally, the gel is two ingredients and some changed proportions shy of homemade Playdough (another Instructable), which may also also go over well in the pediatric ward. 

Electrocardiogram (ECG, sometimes EKG for the German name) machines measure the heart rate and rhythm and indirectly assess the blood flow to the heart. They monitor electrical activity through the pads stuck to the patients' skin.

Here's how to make the the pads, and see the last step for directions for use.

Step 1: Materials

Pad materials:

1. Bottle caps
2. Nickel-plated brass sewing snap buttons, size 3
3. Flathead screwdriver
4. Utility knife (boxcutter, X-Acto or another sharp-bladed, small knife)
5. Pot, water and a stove
6. Optional: tweezers/forceps

Comments

[DouglasG1]

Could you use cotton for the pads?

[rick.leasure]

Step 3, "1. Cut an “X” in the center of the lining to make a hole, no larger than 1cm on each line." Typo: this should read "...no longer than 1mm on each line." I'm sure everyone else read it correctly, though.

[mokcarthy]

When I was learning to do ECGs as a medical student, a little over 20 years ago in Melbourne Australia, our ECG machines used washable suction cups as electrodes. Actually, I see they are still made - http://www.diytrade.com/china/4/products/7681402/Multifunction_Suction_ECG_electrodes.html
I bet a lot of these have been thrown out, when they might have gone with the ecg machines to better homes.

If you cook the flour water mix, you'll need a lot less flour to get the same texture.

Great work!

Jennifer

[agis68]

creative idea now the issue where to get some pads is well ended!!!

[marc.cryan]

Hello - This is a very nice solution and well documented. I had not thought about medical equipment from this perspective.

It sound like donated equipment needs to be "de-Americanized" for use without disposables.

I could also see where there maybe safety and proprietary features that are useful in the developed would, but would present a significant barrier to use elsewhere.

Is there ever an opportunity to modify the equipment before it is shipped off?

I also wanted to add that if you have disposable diapers, you can make electrode gel from the water absorbing crystals by removing them from the diaper and adding salt and water. One diaper will make a cup or so of gel. It is like ultrasound gel.

A disposable diaper with salt and water should work as an ES ground pad as well.

Of course, that is if you have disposable diapers.

I like the 'play-dough' solution better.

[J-Ri]

Do you use new diapers, or can you cheat and use one that already has salt and water added to it? :)

[Engineering for Change]

Yuck...

[Engineering for Change]

Huh, hadn't thought of diaper crystals. Interesting, thanks!

[k24tea]

This is absolutely brilliant, and a much needed alternative to massive use of disposable supplies. Thank you for sharing this excellent idea.

Do you think the pads and conductive gel will work well for use with a wearable TENS unit for pain management? I could try making the pads bigger like mine, which are some sort of black conductive rubbery stuff, about 40 mm across. But the best gel I've been able to buy is usually only good for a few hours before it dries out and needs to be re-applied to the pads, and new skin tape.

A long time ago I tried some self-stick conductive pads coated with a thick conductive gel made with (I think) agar. They were marketed for people with sensitive skin. They worked well, since I have trouble with the glue on skin tapes, and they lasted for several days of application, removal, and re-application, but they were disposable and quite expensive. Any ideas on how to make your pads & gel self-stick? It could radically reduce the need for all the tape needed to keep the pads in place, especially if the gel doesn't dry out too fast without needing tape around the pads.

I'm delighted to see this excellent and important contribution on Instructables! Thank you!

[Engineering for Change]

Haven't heard of DIY self-stick pads, yet, but we'd be interested to see it if someone has an idea. Thanks!

[SolidRaven]

Nice method. A few hints on ECG pad usage though since I can imagine a few people here using these in their own experiments.

After cleaning be sure to dry the skin. Ironic as it might be; Don't use wipes with alcohol at all since it may cause excessive drying of the skin. And go over the skin once or twice with a fine abrasive, just be sure it's clean and doesn't cause any skin damage. Fine sandpaper generally does well. All of the above is essentially what makes those "ECG Prep Pads" so special (and expensive). Especially the latter step might seem weird, but it reduces the skin contact resistance significantly.

Also be sure to not leave the wire hanging if the person the pad is applied to is able to move. Movement causes a lot of noise. Attach the wire to the skin with some extra tape.

[Engineering for Change]

Great, thanks. These tips are a nice complement to the Instructable. We'll pass them on to our friends at EWH.

[sniffydogs]

Cornstarch might work instead of flour. It's a very interesting Instructable. Thank-you for teaching me something.

[iwish]

I have used a thin layer of (liquid) honey very successfully, and find that it lasts for quite a while.

[CEVMarauder]

Is Borax 'slime' conductive? That might make a better gel than flour, although I can see how flour would be easier to get ahold of in the developing world.

[yardleydobon]

Sometimes the soft drinks have a look under the cap contest where you can peel away the liner by hand. That'd make collecting the liners much easier.

There is also an abundance of scratched prepaid phone cards that are discarded in Africa everyday. Do you think they would make a suitable substrate?

[Engineering for Change]

Good tips. We'll suggest the phone card idea to EWH to see if they can use it. Those cards are all over the place, right?

[LaserBazooka]

Have you considered using rolled up condoms in lieu of the plastic liner in the bottle caps? They are significantly larger but they may serve equally well and avoid the need to boil the caps which could be a bit of an undertaking in certain parts of the world. Just a thought.

Great post! 

[Engineering for Change]

Interesting idea, thanks. We'll pass it on to the researchers at EWH.

[oldbike]

I have never had reason to comment on this site, although I enjoy many of the instructables. This one tops them all. This could truly be life saving. Thank you, from the rest of the world.

[Engineering for Change]

Thank you, so good of you to say. We'll pass your kind words on to our friends at Engineering World Health, too, to spread the love.

[fjordcarver]

Great work!! I can't wait to try this out.

[mash4077]

you could save the world with this you need to tell someone!

[Engineering for Change]

Thanks, we're trying! We have this project as a solution in our Solutions Library: https://www.engineeringforchange.org/solution/library/view/detail/Health/S00058

And Engineering World Health is also trying to spread the word through training courses it offers in developing countries.

[TekoMuto]

now... can these be used to detec nerves, and pulses and stuff like that?

[Engineering for Change]

They're part of ECG machines, which can detect electrical potential on the skin to measure heart rates and, indirectly, blood flow to the heart. New applications might require new machines that they link to. Thanks for your interest!

[MaryT8M]

THANK YOU