Advice for personal project - Mechanical CPR Compression Device - Page 1
Forum section: electronics / beginners

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 02:32:28 am
content: Hello everyone,This is my first post on this forum and I am glad I found it as it's evident how many brilliant minds there are on this page.After going through an EMT course, I came up with the idea and design for a new mechanical cpr device especially after seeing how the already marketed devices are very, very expensive and also large.I have brainstormed a whole lot over the course of the past two months and have a small team of fellow UCLA undergrads who are engineering majors. I am pre-med and have found myself stepping into a territory where I have no idea what I am doing when it comes to the engineering front.I can provide more info if need be, but to cut to the chase, I want to know if linear actuator technology is a good start for a project like this, also would anyone have an idea on making the device able to push 2 inches deep into the chest consistently on people with different weights/muscle mass. Could a linear encoder do that? All this device needs to do is push and pull but keep stroke length consistent over all trialsAny and all advice is appreciated and if anyone is up to it to be an advisor for my team I would be happy to give equity in the product if everything goes to plan obviously.

author: ataradov
author_rank: Super Contributor
timestamp: October 25, 2022, 02:53:34 am
content: The reason existing devices are expensive is certifications and liability protection. By the time your student contraption is allowed to be near live humans without being sued out of existence, it would cost a lot too.There are different types of actuators, but sure, some of them would compress your into pulp, not just push 2 inches. And yes, position sensing is also very much possible.

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 03:21:29 am
content: Thank you for the honest reply.Do you think it's possible to manipulate an already-built actuator to do this or would it take a much more lengthy process(ex. starting from scratch)? Evidently, I have a lot of homework I still need to do, but I was hoping for some hints with the knowledge you have so I could gain some form of progress.

author: freda
author_rank: Regular Contributor
timestamp: October 25, 2022, 03:29:43 am
content: mechanical cpr ? surely anywhere that could host such a machine would better have available adefibrillator ? ( + oxygen )so i have doubts of such a machine. But anyway you say such a machine would be large,CPR in real takes alot of manual effort, its short of breaking rib bones actually, its not just meretaps on the chest.So any such machine is going to be large and the f/b variables very messy.Newtons 3rd law, if there's a force into the patient theres an opposing force, with emt thats basically the weight (know how to adjust) of the human applying the cpr.

author: ataradov
author_rank: Super Contributor
timestamp: October 25, 2022, 03:38:27 am
content: I did a quick search. It looks like those systems cost anywhere between $8K and $30K. This is very cheap for specialty device like this. I would not bother going though designing a new one.Looking at teardowns of LUCAS 3, it seems to use a regular DC motor + some mechanics to translate rotation into linear movement. It is possible to do something like this with off the shelf stuff, but I grantee it would not be as compact.And I don't really see what is so big about exiting units. I expected them to be much bigger. I really see no way to make them significantly smaller.Also based on what I see they are designed more to maintain consistent compressions while patient is transferred to the hospital. In all their demo videos initial help and compressions are provided by the EMT.Lucas 3 service manual has complete block diagram. All of this is possible to prototype with stuff from Amazon, but it won't be anywhere close to this size.There are a ton of internal pictures in the service manual. It is actually refreshing to see a service manual that provides real information on how to service the device.Mechanically it is very well designed. I'm not sure what you can improve there without sacrificing quality. Electronics seems to be a bit ad hoc, but this is very typical for equipment like this and you won't gain much by integrating it all.

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 05:53:06 am
content: It isn't cheap enough because smaller ambulance companies can't afford them and the larger companies can only buy a couple. I believe something like this should be in every school and in every ambulance as consistent quality compressions are important when saving a life. I take into account your point about liability/certifications however I plan on finding more affordable parts/manufacturing, and making this non-profit. Also with my experience in doing CPR, it is one hell of a tiring thing. Based on some professors I have talked to it is possible to make it smaller but there definitely is a long way ahead and I am ready for it. Thank you for taking the time to write me because your comments allowed me to think about the device even more thoroughly than before. Also, I sent you an email, whenever you have a chance if you could take a look at it.

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 06:11:47 am
content: it actually breaks the rib bones almost every time

author: jonpaul
author_rank: Super Contributor
timestamp: October 25, 2022, 06:49:56 am
content: medical and emergency organization and staff are required by law and regulations to use only FDA and other approved devices if a patient is touched.No health care person can use a DIY or non approved device even if mechanical.Our surgical illuminators in 1980s.1990s required 1 yr and 500k$ just for paperwork and approvals.Later bought by Welch AllynJon

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 07:12:34 am
content: yes i understand this, i have to build it though before i can get any kind of medical licensure.And wow, that's a lot of money/time even though I understand that it is expected especially when making devices that have to do with whether a person lives or dies, probably going to have to take a loan for something like that but I will have to cross that bridge when I get there haha

author: jonpaul
author_rank: Super Contributor
timestamp: October 25, 2022, 07:35:18 am
content: Suggest contact lawyer for liability and insurance firm for liability insurance.Jon

author: radiolistener
author_rank: Super Contributor
timestamp: October 25, 2022, 08:12:48 am
content: just think what happens if your device kill some patient. Just because you didn't take into account some details... Are you still think this is a good idea to experimenting with DIY amateur crafts in a medical devices area?

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 07:41:00 pm
content: if they need cpr they are already dead before the device would be in use, and my project would have to go through medical approval for it to ever be used in that setting. Please answer electrical/mechanical engineering questions rather than tell me about medicine we're on THIS forum for a reason

author: ataradov
author_rank: Super Contributor
timestamp: October 25, 2022, 07:50:49 pm
content: The issue here is the idea that you can make it much cheaper after all the certifications and approvals are done.Technically this device is pretty simple. The whole complexity comes from the approvals. This includes complexity of the safety measures and interlocks you need to add for it to get the approvals. And this is not an engineering issue, you need to know all those things before you start engineering work. Or you may end up doing it all over again.As far as engineering goes - their service manual literally described the design in details. Copying is trivial, but I'm not sure what you are going to gain here. If you say you can do it small, then tell us why do you think that? I personally don't see a way to make it much smaller.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 25, 2022, 07:52:24 pm
content: Quote from: underratedbot56 on October 25, 2022, 07:41:00 pmEmphatically wrong.I have been called upon to do real CPR twice in my life. In neither case was even a "crash cart" on hand immediately. One just has to do it. By the time the cart arrived, you are pretty tired. I can see a potential but limited use, but (electro) cardioversion was also available.

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 07:58:29 pm
content: you are wrong lol.I'm a damn EMT haha the patient must be pulseless and apneic to initiate CPR so clinically dead. I said it as a joke but the point is still valid. I have done real CPR myself as well and I know this isn't a product for people to have on hand. Its for schools and ambulance companies, especially smaller ambulance companies who cannot afford the existing CPR devices

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 08:02:04 pm
content: Well there actually are a few ways to make it smaller, and one of those ways is a second design where instead of having a mechanical head punching at the middle of the chest, it could be a seatbelt material and constricts the chest with downward force(kind of like a snake) which actually allows for a thinner, shorter design. Also patents for the lucas are very very lenghty, they patented almost everything about the device.

author: sokoloff
author_rank: Super Contributor
timestamp: October 25, 2022, 08:02:39 pm
content: I would tend to design towards a cam lobe actuator, given that you want a constant 2" compression stroke. Give yourself a cam with a 2" lobe off the base circle, a linear ram with a light spring return, and probably a roller on the machine end. Then, turn the cam with whatever motor tech you want and you'll get repeatable compressions with no risk of over-compression.Disclaimer: I'm just a non-practicing Mechanical Engineer and a gear-head.

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 08:03:45 pm
content: I will look into this!! Thank you!

author: jpanhalt
author_rank: Super Contributor
timestamp: October 25, 2022, 08:05:05 pm
content: Some EMT...Ohio code for death:QuoteNote the word "irreversible." I'm sure you are quite skilled, but I totally doubt your ability to bring the dead back to life.

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 08:06:47 pm
content: Maybe I already have, cowboy

author: ataradov
author_rank: Super Contributor
timestamp: October 25, 2022, 08:11:00 pm
content: Quote from: underratedbot56 on October 25, 2022, 08:02:04 pmAll this will do is move the motor and gearbox some place else, I'm assuming in the back support plate. And you would still need to have some sort of plunger, since belt would just tighten around the person and not actually apply targeted pressure.EDIT: This is essentially what you are describinghttps://www.schiller.ch/en-hu/products/easy-pulse-p49You can move the box to the back, but I see no point in doing that, especially given that it will interfere with a lot of stuff.Quote from: underratedbot56 on October 25, 2022, 08:02:04 pmThere are a lot of devices on the market and they all seem to use about the same principle. You would have to read those patents and avoid specifics. The general idea is pretty obvious.

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 08:17:39 pm
content: I would love to show you the sketches and you can tell me what you think!

author: ataradov
author_rank: Super Contributor
timestamp: October 25, 2022, 08:20:28 pm
content: Quote from: underratedbot56 on October 25, 2022, 08:17:39 pmYes sure. If you don't want to share them publicly, I replied to your email.

author: underratedbot56
author_rank: Contributor
timestamp: October 25, 2022, 08:24:06 pm
content: I will take a look as soon as I get the chance and I will send them over. Also one thing I wanted to tell you about the lucas and I have spoken to health professionals in the past and they do not like the device because it constantly causes very serious hematomas, so the constriction design will minimize risks of severely damaging organs.

author: ataradov
author_rank: Super Contributor
timestamp: October 25, 2022, 08:28:46 pm
content: Would not broken ribs make hematomas insignificant by comparison?If there is an actual science that shows that general constrictions are effective, then yes. But with constrictions you also need to keep in mind the sliding motion. Regular seat belts cause quite a bit of damage in case of an accident. CPR device would not impact nearly as much energy, but some sliding is unavoidable.

author: radiolistener
author_rank: Super Contributor
timestamp: October 26, 2022, 02:20:00 pm
content: Quote from: underratedbot56 on October 25, 2022, 07:41:00 pmthey are NOT dead, they still alive, but needs proper medical help, otherwise they can die.Certification means that you're used proper development life-cycle for a medical device with proper testing and logging, it needs all required records and it also requires mandatory staff learning and periodic examination with external audit. It needs to allow proper investigation of the root of cause in case of patient death or when patient will get injured or become disabled...You're needs to have tracking system to keep all records related to the device, accept and solve all issues and implement fixes for entire device life-time.If you didn't used proper development life-cycle, you will not be able to get certification for your device. All this cost money, and this is why medical devices are expensive.

author: AndyC_772
author_rank: Super Contributor
timestamp: October 26, 2022, 02:58:22 pm
content: They are as a rule - but they're notallhugely expensive to buy.I'm a member of a sports club. Last year we installed an AED machine (defibrillator) on the outside of the clubhouse; these machines cost hundreds of pounds, not hundreds of thousands, and they're designed to deliver an electric shock to the heart.I don't doubt that the machine was expensive to develop and certify, but clearly, somehow, itispossible to develop machines like this, and sell them for use by the general public, not just trained emergency medical personnel.We should be thankful for this. They save lives.With that in mind, I don't think we should be so quick to dismiss theideaof a life saving device, just because of the cost of approvals. As engineers, we should encourage ideas that might work, not dissuade people from ever trying.

author: jonpaul
author_rank: Super Contributor
timestamp: October 26, 2022, 03:36:23 pm
content: OP plan for fail safe detection and emergency stop, eg actuator/motor runs too long and cracks ribs, uncontrolled motion due toSensor failureSW/FW errorsCPU failsFailed Connectorsetc?j

author: underratedbot56
author_rank: Contributor
timestamp: October 27, 2022, 02:13:56 am
content: Thank you I will remember this

author: underratedbot56
author_rank: Contributor
timestamp: October 27, 2022, 02:15:39 am
content: Andy I love your message, thank you for pointing this out

author: golden_labels
author_rank: Super Contributor
timestamp: October 27, 2022, 02:41:24 am
content: Others have mentioned certification and the need for the device to not hurt the patient. What may not be clear is that this work both directions. The malfunction can be damaging the body, but may as well provide insufficient compression. You must guard against both.On top of certifications, the unit price includes costs of variance. Usually insurance, unless your organization is big and rich enough to swallow the hit. And that can go into hundred thousand dollars per single serious malfunction.I do not want to discourage you. I believe others don’t have the intention too. But to fight a problem effectively, one has to understand it first. Be aware what you are facing.