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Build Your Own ECG
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. :)"
Yea, but does it interpret the data. That's one of the big expenses according to her: have the cardiologist examine the data and give his opinion. Since it's all waveform stuff, I wonder how much of that could be automated in the future?
This space for rent.
Congrats on what you've done so far...if you want to take the next step:
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.
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.
I don't know what everyone's one about. I just built one of these. I'm monitoring my heart rate in a window right now and it works gr9'0wrtup
CEE5210S The signal SIGHUP was received.
This is because most doctors specialize in diseases of the rich.
+1, Tom Lehrer. ;-)
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I have always said that if engineering were practiced like medicine is practiced by doctors, people would be dead. Gone due to a bridge or building falling down, or electrocution, or a chemical plant exploding because they rely on what they've seen before rather than what the problem might really be.
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.
Only one volt? You mean with the fancy gel thingy I could kill a person with an innocent little AA cell?
I gotta get me summa dat gel >:)
the high price is due to liability....personally i like the idea of sueing bad doctors but the problem is that the cost is spread out to all doctors good or bad...a good idea would be to create a list of bad doctors that anyone can look at. Like i don't know on the web??? just a crazy idea. Then the insurance companies could focus on them paying more for liability instead of everyone else. Of course no one likes this idea. Instead of going after the bad doctors the industry (insurance and medical) go after the people sueing making laws limiting your right to sue if they fuck up.
We cannot emphasize this enough. By applying electrodes or gel to yourself, you are opening yourself up to "microshock" Current at the correct frequency can STOP YOUR HEART (technical term = ventricular fibrillation) This can happen at shocks as low as 300 mA if applied at exactly the wrong time and place. The risk depends on the frequency of the AC current. And guess what the worst frequency is? 60 Hz ... exactly what is coursing through your household current and appliances ... including the computer that you're looking at right now.
Building an EKG was a simple homework problem in my Biomed Engineering course. My final exam was an EEG (brain electrical activity, not heart electrical activity). We paid a lot of attention to ground isolation and electrical safety. The key was to use a battery and not be hooked up to AC wall current at all.
Unfortunately, the strength of an EEG signal is much less than EKG, and my final exam instrument wasn't working well enough to pick the signal out of the background noise. I got it to work by rubbing the skin off my temples so that the gell pads were on raw flesh (cutting down the resistance). Now that is what I call a "bloody hard" final exam.
Well, chances are if you can visit the site, you already have a computer. It's not like he used it up in order to display the results.
But I understand your point. A hospital wouldn't be able to dedicate the price of a $400 computer and monitor or a $200 pda just for displaying the ecg results.
Oh wait. I guess they wouldn't have to dedicate it if the computer is can handle any of the computing requirements. And they already spend much more than that on the medical industry made ecg machines.
How much is a dedicated ecg machine? I saw on http://www.numed.co.uk/prices.html that pda's with the attachment and the software cost upwards of $1350.
Still, I'd rather have a tricorder.
Makes me wonder why medical care costs so much.
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.
A Government Is a Body of People, Usually Notably Ungoverned
I don't see where your post addresses the inefficiency issue. You spoke more about accuracy and procedure than efficiency.
Most people in this thread are bitching about how expensive medical care is, and we're not blaming you doctors. We're blaming the people who have your hands tied: the lawyers and insurance companies. As an ER doctor, you probably aren't subject to a lot of the abuse that family practice doctors are. You aren't forced to promote the latest fad drug just so you can stay in business. You aren't told by some bureaucrat how much you can charge for your services (or are you?). You probably aren't a puppet to big-pharma, big-insurance, and big-litigation, but maybe you are, we don't know.
You have a great opportunity in this public forum to expose a lot of the crap that we lay-people speculate about. We know lots of things go on behind closed doors that seriously inflate the cost of medical care - like price-fixing among big-pharma, secretive pricing structures, and flat out "pay us $100,000 or you die" extortion of seriously ill people.
In Pennsylvania, even expensive doctors can't afford to say in business because of high malpractice insurance premiums and the fear of being sued. Also, CYA-medicine is rampant (patient: *cough* I think I'm sick, doctor: here, I want you to go in for a full-body MRI, an echocardiogram, a colonoscopy, and a full-body diagnostic) because if a doctor overlooks something or makes even the slightest error, he/she can be sued out of business regardless of whether there were even any negative consequences for the patient.
You'd be doing a much better public service by confirming or denying some of these allegations or at least shedding some light on why medical care has become such a fat bloated pig.
I refuse to go to doctors anymore. I don't care how sick I feel or how high my fever is. The last time I went to the doctor with some persistent heartburn (from binge eating) I ended up going to the hospital for $4k worth of unneccesary tests when a little bit of therapy for my eating disorder was all I needed. The physician didn't even ask about any medical history, my eating habits, or ANYTHING. He asked what the problem was. I said I had had heartburn consistently for 3 or 4 days, and he wrote up the Rx and shoved me out of his office. That was the end of medical care for me - about 2 years ago.
There's no reason for any of this crap to be going on. If there were no insurance companies or lawyers, human medicine would cost about the same as veterinary medicine, which is much more reasonable.
The cost of ECG machines run $10,000-$15,000 (US). One of the biggest reasons for these cost is not the actual hardware or software cost, but the liability involved of selling such an item.
The problem with noise (more correctly called artifact) is that it can't be distinguished from the signal by filtering - it's in the same band as the signal. These artifacts come from chest muscle movement - breathing, bending, etc. Remember - the signal you're looking for is electrical impulses in muscle tissue. There are always concerns that lowpass filtering of DC offsets will affect the fidelity of the waveform - some of the data of interest is the slow-moving S-T segment (the area just after the 'blip'), used to monitor for some heart conditions. If the low-pass filter is set too high it distorts this part of the waveform. Filtering doesn't impact arrhythmia monitoring, tho, so the filters for devices that just monitor for heart rate anomalies can use less exotic filtering, which means that the dynamic range of the A/D can be less - 9-12 bit samples. Also, real in-hospital EKG monitors usually sample five to twelve channels, at up to 500Hz sampling rates.
Storage is the other issue for ambulatory cardiac monitors. These typically monitor three channels. At 12 bits/channel, 240 samples/second, three channels requires 1080 bytes of storage per second. A patient being monitored for 48 hours will require 186 MBytes of storage. We used flash memory in a device I helped develop. Some of the older devices stored their data on magnetic tape.
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