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Build Your Own ECG
Posted by
michael
on Fri May 23, 2003 09:03 PM
from the home-health-care-made-easy dept.
from the home-health-care-made-easy dept.
Jason writes "I finally finished documenting my $4 home made electrocardiograph (heart monitor). If anyone is interested or wants to build one for themselves, please come by and take a look. Makes me wonder why medical care costs so much. :)"
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Please Come By... (Score:5, Funny)
...please come by and take a look.
Translation:
Please slashdot me and don't even peek... :-)
Re:Please Come By... (Score:3, Insightful)
Re:Please Come By... (Score:5, Informative)
http://saintaardvarkthecarpeted.com [saintaardv...rpeted.com]
Parent
Gnome Toolbar Applet (Score:5, Funny)
Call me back (Score:5, Funny)
Oh, the irony! (Score:5, Funny)
Ahhh! (Score:5, Funny)
I finally finished documenting my $4 home made electrocardiograph (heart monitor).
From the website:
Here you will find information how how to build one with less than $10 in parts.
Lies damned lies!
Re:Ahhh! (Score:5, Funny)
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It seems a bit cheap doesn't it? (Score:5, Funny)
I learned my lesson with the $4 dentistry set, and even worse, the $4 electroshock therapy machine.
I STILL can't quite get my hair to stop standing on end. I can't even wear hats - hair pokes through like skewers through butter (which, incidentally, is one of the only things I can eat now thanks to the dentistry set).
I thank the lord I didn't invest in the $4 eye-surgery kit.
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Re:Ahhh! (Score:5, Informative)
Perhaps the biggest problem with ECG systems is noise filtering. Adaptive filtering has failed miserably; you'd think the engineers designing the systems would implement Bass and Treble-style filters for healthcare providers to use, but condescention has gotten the better of them. Noise makes interpreting an ECG sometimes impossible, yet no such filters. This presents a problem for me on a weekly basis - it is sometimes impossible to interpret the rhythm, because the filters aren't working properly. If they'd only let me adjust the lowpass and highpass cutoff's, I would feel SOOOO much better. And if they'd give me a Savitsky-Golay filter, I'd have a wet-dream....here's hoping.
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Slashdotted Already? (Score:4, Funny)
- clear -
Beep beep...beep beep...beep beep
-Mr. Fusion
Heart Monitor hooked to Web server. (Score:3, Funny)
My wife the nurse said ... (Score:5, Interesting)
Re:My wife the nurse said ... (Score:5, Interesting)
Its possible to automate alot of this stuff. However, its not as simple as it first sounds. I have used alot of ECG's with automatic interpretation, and they mostly get it right nowadays. About 95% of the time. Which isn't really good enough yet to risk your life on.
I think that you will find that eradicating the last few percent of errors will get harder and harder, and who is going to back (and assume liability for) any errors if not trained people - be they medical staff or highly skilled nurses?
I think that by the time that we can have automated diagnosticians, there will be alot of other things in our lives that are far less comples going automatic. Like cars that drive themselves and software computer programmers. But wait, I hear you say, nobody is anywhere near replacing programmers with software - but you think you are going to replace cardiologists?)
Just my 2c worth.
Michael
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Re:My wife the nurse said ... (Score:3, Insightful)
Re:My wife the nurse said ... (Score:4, Informative)
Unfortunately, the *best* in the market can only interpret QRS complexes. ECG techs still have to go into the system by hand, and label the PR, QRS, QT, and RR intervals. This is still quite an active area of research.
And for the record, they're nowhere NEAR 95% accurate. 70% would sound more accurate. And I would know, having been an ECG tech at a the local teaching hospital. The hospital spent $110,000 on the system and we were so unhappy with it that the engineering team came down from Massachusetts.
The rub? They're using a statistically-based FFT program, and their sample set is ~250 AHA ECG recordings. Humans who are good at ECG interpretation need to expose their neuro-fuzzy brains to at least 2,000 ECG's in order to know what they're doing. And they wondered why we were having problems.
When the head engineer got up to speak, he made an interesting comment. He said that when he was a student at MIT, a physician from Beth-Israel Deaconess Hospital came to the engineering department and asked if they could analyze ECG signals. They looked at them, and seeing their simplicity, said of course. Thirty years later, he's still working on the problem.
You'd think he would have tried something other than the FFT by now, but he hasn't. So much for thinking outside of the box.
--V--
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Re:My wife the nurse said ... (Score:5, Funny)
But wait, I hear you say, nobody is anywhere near replacing programmers with software - but you think you are going to replace cardiologists?)
Yeah, first we'd have to program a computer to be arrogant and have a God complex...
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Re:My wife the nurse said ... (Score:5, Informative)
Where computer-automated reading of ECG is much more effective is in the automated defib units that you might find in airplanes, malls, ambulances, etc. The computer is good enough to know if a jolt of electricity would be helpful in correcting the problem.
Of course, the expense and the value of ECG is in the physician interpretation. Likewise, an aspirin in the hospital will cost you dollars instead of cents due to administration costs, nursing costs, insurance, etc.
What has really helped ECGs is fax machines and now the internet. If a health care professional has a question regarding a waveform, they can get it to someone who can give an accurate reading. Soon, if not already, physicians will be able to see the ECG live (and in living color) of patients on planes...
And quit dogging the editors for posting this... We need more tech-related medicine news. It warms this geek MD's heart.
Davak
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Your wife is correct (Score:5, Insightful)
NEVER trust a physician who allows his ECG machine to interpret your tracing... run for the door... I'm quite serious about that. If the guy doesn't have the expertise to read your tracing himself, don't trust your cardiovascular health to him.
I've sent people home with ECGs that read ****ACUTE MI***** in large, upper-case font on the top, because the machine was totally, completely wrong. The only thing it's sometimes useful for is in reading QT intervals, and occasionally rate (though the machine can be easily fooled on this one as well).
Have a doc read it, preferably a cardiologist. Of course, if you don't want to pay a guy like that for his expertise you don't have to... but you get what you pay for.
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Re:Your wife is correct (Score:5, Insightful)
I'm obviously not qualified to comment on your clinical diagnosis, but this statement worries me. My expectation as an engineer (but not one of medical devices) is not to replace the professional operating the device, but to supplement him or her in a useful way. That is, if I designed the ECG you use, I would like that 99% of the time it agrees with you, and the 1% of the time that it doesn't you take it so seriously that you consult a panel of specialists. That's my idea of a working man-machine system.
If you regularly ignore its conclusions, then it's better not even having the feature. The one time in a thousand that you're wrong and it's right, you'll ignore it anyway. There's something broken in the system here, in my uninformed opinion.
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Re:Your wife is correct (Score:5, Informative)
Perhaps I should expand on my initial comments. A previous poster pointed out that the first thing you are taught in medical school is to ignore the machine read... that's true, and medical students are still taught that way (I teach in an academic setting, and I teach my students the same thing).
As I understand the machine's algorithms (if somebody who programs these things wants to correct me, please do), they interpret the waveforms based on an ideal model, and attempt to interpret current-of-injury patterns, based on deviation from an expected baseline.
Many situations make the machine read useless (and to be fair, extraordinarily difficult)... any patient in a paced rhythmn (pacemaker, single or dual chamber), the machine will default, and not give a read. An excellent call for the engineer that designed the machine... reading injury on some paced rhythms can be very sticky, even for an experienced clinician. Some of these machines regularly read "digitalis effect".. a difficult call, particularly in a suspected ischemic or strain-induced ST depression. A noisy baseline (in a patient who's shaking, for instance)will often throw off the machine. Many patients who have known cardiac disease have EKGs that are difficult to interpret, and injury that can only be discovered based on comparison to a previous EKG.
What I'd like to see is a program that compares old EKGs to new ones, and automatically gives you a change summary (in addition to the tracings themselves, naturally). I could see that being very useful, particularly if it uses the previous EKG tracings to redefine "normal" for itself. That might help the over-sensitivity problem. Many people are walking around with tracings that are nowhere near the classic "normal," but are normal for THEM. What I'm saying is that I'd like to see a program with a dynamic "normal;" one it can redefine on the fly.
It's not to say that I don't read the machine's interpretation... I do, but I subordinate it to my own clinical interpretation. To be fair, I have the luxury of knowing the history... something the machine may never know, and as any physician will tell you, history makes the diagnosis 80% of the time; the tests are simply to confirm what you suspected all along.
Maybe if you frame it like that, EKG machine reads don't really need to be perfect... they are, after all, just an adjunct... A human still makes the decisions.
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A warning to experimenters (Score:5, Informative)
Normally, the skin resistance is high enough to make the current flow negligible; however, when the pads are on, the resistance in the path is very low, and you could seriously injure or kill yourself if even a small amount of circuit flows 'back' through the electrodes.
Professional ECG machines usually have a lot of protection circuitry on their front ends (the instrumentation amplifiers) as well as between the amplifier and the ADC/output circuits to prevent this from happening. This is obviously even more critical in line- (i.e. 110V or 220V-) operated devices.
Re:A warning to experimenters (Score:5, Informative)
One of the reasons EKG systems (and I've used a fair handful) are expensive is that they go to extreme measures to insure that under no conditions will excessive current flow through the electrodes. (Ever wonder why hospital-grade power plugs are rated explosion-proof?)
I cannot comment on the original posting's circuit because it is slashdotted but I'm racking my brains trying to figure out how less than $10 can create a safe circuit
Also, keep in mind that just because a circuit is battery powered does not make it safe once you attach the output to an instrument (computer, oscilloscope, DAC, etc.) which is plugged in to the wall.
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Re:A warning to experimenters (Score:4, Interesting)
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Re:A warning to experimenters (Score:5, Informative)
Use Ethernet transformers for isolation. They're rated for a coupla kV. The FDA probably wouldn't certify them, but I wouldn't be very afraid of them.
For power, use a 555 timer to drive one of the transformers. On the other side, rectify the current with a diode, filter it with a big cap.
To get the signal across the gap, use another 555 to turn the EKG voltage into frequency, and send the frequency across using the transformer. Feed it into the line input of the computer, do FM demodulation in software. Alternatively you can use a frequency-to-voltage converter (74HC-whatever PLL). Sound cards are terrible near DC, though, so doing the FM thing would give you the best signal.
Total cost would easily be less than $10. Even with medical-grade everything, you could probably make a production version for under $30 (in large quantities).
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EXACTLY! MOD UP PARENT, PLEASE! (Score:5, Informative)
Kids, DO NOT TRY THIS AT HOME.
Real medical gear has full galvanic isolation - that means there is NO current path that goes from the patient's body to the equipment - the signals pass through either an isolation transformer, an optocoupler, or a capacitive coupling. That way, any ground leakage in the equipment won't fry the user.
It takes about
When you put the gel on, you reduce the resistance to a few hundred ohms. Now you need only a volt.
Normal consumer equipment can have "leakage currents" - places current shouldn't be flowing but is. You hook your home-brew circuit up to the printer port on your PC, and maybe you are OK. Then one day, while screwing around with it, a cap starts to fizzle in your power supply, or maybe you reach up to adjust your monitor, or maybe you put your foot on the ventilation register. Then you get to start (posthumously) on the 6 o'clock news.
At a MINIMUM, you should power the circuit with a nine volt battery, and communicate with the PC via an opto-isolated RS-232 link.
Even better, splurge and get the real medical isolation amplifier modules. Yes, they will cost a bit more than US$4, but then, if that is all the value you place on your life....
On second thought - go for it! And make sure you clip the ground lead off your computer's power cord while you are at it. And do it in the bathtub - that will help shield the fnord rays out.
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Re:A warning to experimenters (Score:4, Informative)
While planning this I asked my father, an electronics hobbyist for the past 50+ years, about building such a circuit and he said that the main hobbyist electronics rags such as Radio Electronics and Popular Electronics (which melded a few years ago into Poptronics and then recently folded) refused to publish any EKG schematics because of the possibility of someone electrocuting themselves.
While any electronic circuit you build will put you at some finite risk, you rarely only probe these circuits when they're powered (usually just for debugging). However, heart monitors are deliberately designed to provide an electrical connection not only across your body but across the organ most susceptible to electrocution (ie, heart fibrillations).
So definitely be very careful, especially if you connect to a line-powered oscilloscope or other equipment.
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Cost (Score:3, Funny)
Um I'm assuming it has something to do with this odd word called 'reliability'....
Why the cost? (Score:5, Insightful)
I'm suprised nobody's said it already.... (Score:3, Funny)
Medical equipment. (Score:5, Insightful)
Being disabled (SMA type 2, A type of MD, Donate to MDA!) I deal with medical equipment a lot, less then some in more critical situations, but more then your average user.
It's outrageous the markup medical tag gives to an item, one of the most outlandish of them that I saw was a flag, a metal mounting bracket, fyberglass rod, and cheap neon flag. You know the kind, sold in the walmart bike department for a measly 3$
Do you know how much they wanted at a medical store? No you dont.... 18$
So the price of "medical" is 15$ on top of 3$ It's insane.
You can buy an Ok car for the price of an electric wheelchair. And that's just for what's on the low end.
How exactly are people who can't walk suppossed to affoard this shit? Sure it's possible, and often times picked up by the government (thank god)
And if you're not covered, forget footing this bill your self, unless you've got cash to burn. And it's not like the freedom of mobility is important or any thing. Just one of life's liberties some people take for granted.
"I wish I could sit all day"
Fuck you buddy
Grrr, can you tell I'm bitter?
And then theres red tape. I've been using this same wheelchair for several years now, it needs replaced. But fighting for them is a nightmare. So much paper work.
Re:Medical equipment. (Score:3, Interesting)
This is because most doctors specialize in diseases of the rich.
+1, Tom Lehrer. ;-)
Gotta be certified (Score:5, Informative)
Damn near everything used in a hospital has to be certified to be used for medical purposes. People's lives are at stake, and you have to be sure that your device operates within tolerances, doesn't crash, doesn't electrocute people, etc. It costs money to think of every possible problem and design a device around that. Also, as other people have said, the people that run these things are some of the most educated people in the world. Try to start a hospital with your $4 device and let me know how it goes.
DANGER Will Robinson (Score:4, Insightful)
Places like UL/CSA say that voltages under 40V or so are safe. But if you apply it to electrodes pasted to your chest, the unsafe voltage is WAY lower than 40V.
If you build a simple ECG and connect it to a computer, that computer had better be battery-powered. If not, then you might get a nasty surprise (waking up in the afterlife of your choice.)
...you get what you pay for (Score:5, Interesting)
Higher-quality ECGs systems don't use generic op-amps, they use special devices called instrumentation amplifiers that are able to reject common-mode signals at the inputs really well. Turns out then when you place electrodes on the skin, the skin between the electrodes acts like a crude battery (we're full of electrolyte after all!) and you get a large, shifting potential difference between the two electrodes that can drown out the millivolt-range ECG signal.
Oh and by the way, the electrodes and wires will make great radio antennas (esp for 60 hz noise)! Check out the AD624AD instrumentation amp from Analog Devices.
Polygraph (Score:4, Interesting)
The ECG measurement is a key piece of the standard polygraph. One of these can be combined with a galvanometer (easy), a skin thermometer (easy), and possibly a respiratory rate measurement (harder: standard technique is to wrap the chest with a stress-sensitive band and build a circuit similar to the ECG one) for a lie detector that should be great fun at parties.
Malpractice (Score:5, Insightful)
Not to say that's the only factor... but that's one of them.
Re:Malpractice (Score:3, Insightful)
Being a physician and having a friend who received a multi-million dollar settlement, I think I have a unique view of this.
The problem started when MD's somehow got placed on a pedestal many years ago. People feel that doctors should know all the answers... well, we don't. There is still a lot of art in medicine... experience, knowledge, skill--all of these things are important.
Doctors that practice _wrong_ medicine
It's dead Jim (Score:5, Funny)
Eeep...eep...eep..eeeeeeeeeeee
time of death 927PM CST.
Damnit jim I'm a doctor not a webserver admin..
Why It Costs So Much (Score:5, Informative)
There are several reasons healthcare is so expensive.
1. Litigation. Does the phrase "malpractice insurance crisis" ring a bell?
2. A side effect of (1.) is something called "CYA medicine". Ever receive a chest CT because your heartburn just might be a pulmonary embolism? It happened to me just recently.
3. Failed accountability. This one takes a bit more explaining. Ever bother to look at your bill? Of course not. Why? Because chances are, the insurance company pays it. Aha! You say. What if I'm not insured? Well then, many people who aren't insured "spend down" and go on Medicaid. Once more, nobody looks at what Medicaid is being billed, except for the hardworking beurocrats (cough)bull***(cough). Only the very narrow slice of the population that is "self paying" actually looks at a bill (more on thatlater) You would think that insurance companies would be on guard for their bottom line, but corporate inefficiency is often no better than government inefficiency.
4. Complex and inefficient billing. Health care is one of the few businesses where you receive service at a single location, yet billing goes from subconractors directly to insurance companies or patients. Worse yet, billing from some contractors takes weeks, or even months. Yuck! Imagine if every business worked like this. Imagine getting your car fixed, and you get bills from the mechanic, the parts department, and the oil supplier spread out over 2 months. It's not just inconvenient. It actually hinders your ability to make financial plans because you don't know what's coming. And why don't you know what's coming? That leads us to...
5. ...Secrecy. That's right. Secrecy. Try to call up a hospital and ask them for their price list. Chances are, you'll get the same answer I got: "That's on a computer and it's confidential". I was transferred to a manager who had her phone on voicemail. In retrospect, I should have known I was in trouble when the phone tree had "press 2 if you're an attorney". This is probably one of the biggest reasons healthcare costs too much. Sure, there are several hospitals within driving distance, but if I think I am going to need an exam that is likely to involve half an hour with a doctor, some medication, and an x-ray... I have no idea who charges the least for an x-ray, or what the hourly billing rate is for a doctor, or what the average examining time is for diagnosing a condtion. We have more accountability at the garage than we do at the hospital (Chilton's guides, posted labor rates, etc).This alone is probably the single biggest factor driving up healthcare costs. Lack of pricing information makes comparison impossible, resulting in a virtual monopoly even though there are multiple companies. So, what did I do? I gave up and paid a price that I could not verify as accurate because I knew that the only way to get the price list was to make a federal case out of it, and spend 100 times more in legal fees than my bill was.
6. Vested interests. You can call me a conspiracy theorist if you like, but I think various interests want the price of healthcare to skyrocket so that they can use that as an excuse to socialize it. The corporations actually secretly like the idea of socialized medecine, because then they get to become government agencies. If you are a corporate sleazeball, the next step up is to become a government sleazeball; the perks are just that much better. You can just hear them salivating.
Want to fix healthcare? Fine. Require providers to give one bill in a timely manner--no pass-throughs to subcontractors. Require providers to post price-lists online if they have a website, or to make price-lists available to the local libraries. Require employers who insure their employees to provider high deductable insurance. There should be no claims or forms until annual out-of-pocket costs exceed 10% of your annual pay. Place a cap punitive damages, as many have suggested.
um, $$$ because it can kill you (Score:5, Informative)
Well, issues of "medical care" and "medical equipment" costs being two rather separate things(one of the biggest costs in medical care is liability insurance, probably followed by administrative overhead)...
...it might be because the expensive REAL version won't kill you when there's a lightning strike nearby, or when someone touches the case after building up a static charge, or something shorts out in the computer half...the list goes on. It only takes a few microamps to stop your heart- it's all in the path the current takes. Having those nice electrodes in the right places, making great electrical conduct with your skin...well, umm...you should get the picture.
Medical equipment is designed to be 'bulletproof' in almost every way- there's a standard, for example, for medical-rated Edison plugs and sockets.(Edison plug = US electrical plug). It's VERY heavy duty, makes really good contact, has excellent stress relief on the cord, etc...because something VERY important might be using it, like an artificial heart pump in an operating room, or a dosage machine for an IV, or a ventilator. The REAL version also can't crash or stop working- so, for example, if it has a computer, the instruction code, the chips...everything is heavily tested. Jokes aside, the Pentium math dividing bug is a perfect example of why you can't just use "anything" for medical equipment. What if that bug caused the heart monitor to display the wrong heart beat rate? Electronics used for medical equipment get a LOT more testing- lives are at stake. Same idea behind the MIL specs, although with MILSPEC stuff, the idea is more that the military really abuses the crap out of stuff ON TOP of similar concerns as medical stuff.
All of the above are why you often see these days disclaimers from chip makers that say "this device is not certified for use in life support equipment" and such. The statement often extends to industrial automation- "situations where malfunction may result in injury or death", stuff like that. Ie, "don't use this where if it screws up, it dumps 10 tons of molten steel on a bunch of steel workers' heads."
Beeeeeeee..... (Score:3, Funny)
That's the sound of yet another web server flatlining.
BTW the only lame thing around here is your bloody "lameness" filters! How in hell else can I simulate a flatline in text without using repetition?
Mirror (Score:3, Informative)
If you can, please mirror my mirror. I'm sure a large number of slashdot readers have servers available they can put to good use.
A better version can be made (Score:4, Informative)
Medical Costs (Score:4, Interesting)
Although I will agree that medical costs are high, it's not due to the costs of the parts used to build ECG machines. Geez!
You would trust your diagnosis to a $4 machine built by some hobbyist on the weekend? I sure as well wouldn't. But even if the parts for a real ECG cost $400, it still doesn't demonstrate why you can't buy one for $400. So let me explain why it costs so much more: the price of ECGs has nothing to do with the price of its parts. Price is subject to the buyer's and seller's wants. If the price is too low the seller won't sell. If it's too high the buyer won't buy. If you've just spent two years developing a new ECG machine involving the work of a couple dozen engineers, testers, clinicians and marketroids, and hammered it out in clinical trials, fenced with the FDA, and met all the spurious checkboxes of the bureaucracies, you want some return on your investement. If you manage to sell only 50,000 then $400 a pop isn't going to cut it! (do the math) On the other hand, if you're a hospital with an increasingly shrinking budget and overseen by a hospital board composed of well-meaning but ignorant politicians, then $40,000 isn't going to cut it either. So a price is eventually reached that is mutually acceptable. It's going to be a lot higher than the price *you* would have paid, but you're not a hospital.
Why don't you get any input into the price? After all, you're the patient, and thus indirectly the buyer. The reason is that you have absolved yourself of any buyer responsibilities by foisting them off on an insurance company. If everyone who had an ECG reading had to pay for them out of their own pockets, you damn well better believe the price will come down! One reason medical prices are high because people (you, your employer, etc) don't shop for medical prices, they shop for monthly payments to an insurance company instead.
But ignore what I just said. I'll tell you what the real price of ECGs is. Free. Zero dollars and zero cents. You see, when a company like Siemens, Philips or GE makes a sale to a hospital, they throw in the ECG (and lightbulbs) for free. I may still cost those companies $500 in parts and $5,000,000 in R&D, but they'll make it up on the MRI, CAT, and US. And of course, on the service plans.
If you DO try this at home.... (Score:4, Funny)
Re:Visual Basic? (Score:3, Funny)
What are you going to tell me next, people buy Windows? ahahaha
Re:Visual Basic? (Score:5, Funny)
parts list:
* one surplus patient cable with sensor and plug ($4 on ebay)
instructions:
* Plug the sensor into a strip chart recordor or heart monitor you might have lying around the house. For instance I found and old Hewlett-Packard model 78534C EKG and dual-channel pressure monitor.
You're done! It's THAT EASY! And just FOUR BUCKS!
Tune in next week when I tell you how to build your own x-ray machine for the cost of some X-ray film (you might need to find some medical equipment you might have laying around the house to complete the project).
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Re:Visual Basic? (Score:4, Insightful)
He gives you the compiled software, as well as the source, so you don't need VB to make your own. Guess you could still complain that he didn't give you a computer though, if you just want to cry about something.
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Doctors are NOT trained like engineers (Score:4, Interesting)
Real engineers are thorough thinkers. That is the most fundamental skill one is supposed to learn in engineering. Engineers should think about what the real root cause of the problem is and every possible answer to the problem. While cost is a consideration, an engineer will tell it like it is and tell you that you have to choose between something that works and something that costs what you want it to cost.
Doctors, on the other hand...well, I've gone to doctors telling them that I can't sleep and the first thing they do is want to pump me full of Xanax. They never asked me if there was something wrong going on personally in my life, or if I'm consuming too much caffeine or MSG, or anything. Just wanted to prescribe crap and get me out of their office. Fortunately, I told the doctor I wasn't taking Xanax and promptly found another doctor who sorted it out (too much caffeine). These are the same idiots who prescribe Ritalin to kids who won't behave in class because their parents are too busy stuffing them full of sodas.
But that's my point. As an engineer, it's my job both to identify the root cause of the problem and investigate the most feasible solution. I will never sign off on an engineering document if I feel someone will be in danger, including my reputation. Piss-poor engineers (and, unfortunately, your average doctor) will let it go through. So please, don't make that comparison, because it's patently ridiculous.
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