An open-source stethoscope that costs between $2.5 and $5 to produce
136 points by 0x54MUR41 7 hours ago | 56 comments

stronglikedan 5 hours ago
The thing is that I can get just as good if not better ones (metal) for $7 all day long, and not have to spend time sourcing and assembling materials, and I don't even have to leave my house to do it.
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andrewla 36 minutes ago
When my kids were little they had a toy doctors set and the fake wooden stethoscope broke; replacing it with a real one was significantly cheaper than paying Melissa and Doug for a new one.
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dieselgate 3 hours ago
Respectfully, as this is HN, I do not believe that is the purpose of the posted Github repository.
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bluGill 4 hours ago
I'm not sure what you are buying, but it wouldn't surprise me if they were done in a factory that does medical grade quality control. While the odds are a medical problem from a non-medical grade stethoscope seem low, it still seems a couple bucks is worth the price. (if we are talking thousands I'd ask for a deeper drive into what that really gets you)
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krispykrem 55 minutes ago
Here is an interview with one of the researchers behind this project:

https://logicmag.io/bodies/tarek-loubani-on-3d-printing-in-g...

It explains the project and its motivations. It's been a while since I read it (2019), but at the time I found it really fascinating and inspiring.

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colinbartlett 5 hours ago
I was shocked to see that a "brand name" stethoscope is $100+ and even generic ones are $30.
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projektfu 40 minutes ago
There are cheap, generic scopes (Sprague-Rappaport types) that are very sensitive but the double tube also causes a lot of noise. There are knock-offs of the Littmann scopes in the market. Then there are the scopes doctors usually buy, which are Littmann, Harvey (made by Welch-Allyn) and Heine, and a few smaller makers. No marketer of a high-quality scope wants to sell it at a $30 or less price point, and if you're going to go higher, might as well place it in the same market as the Littmann ($115+). I'll be honest, for emergency medicine use, the Littmann lightweight scope is good enough and cost about $45 when I bought it. But if I actually want to hear the subtleties in a chest, I'll use my personal scope (a Littmann Cardiology IV). Why choose this one? I already know it and they are very consistent. It doesn't feel cold to the patient and it has the right level of sensitivity without much noise. It is a little heavy. If a dog is bucking around, it can go flying and hurt if it hits someone.
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jcims 4 hours ago
I'm shocked that you're shocked lol.

$100 for a somewhat specialized, durable medical device that has to meet regulatory standards and will be used daily, possibly for years, by healthcare providers to do patient assessments?

A 3D printed option is going to require a 3D printer, appropriate filament and should be unit tested to ensure it's within spec. The durability is going to be suspect no matter what. It's an awesome project and I'm sure would be a welcome addition to the 'boostrap humanity' catalog of 3D printed parts, but for everyday doctors plunking a hundo on a good tool is going to be a no-brainer.

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nomel 3 hours ago
> has to meet regulatory standards

Genuinely curious, what standards exactly, for a stethoscope?

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filoleg 3 hours ago
A commercially sold hospital stethoscope is a legally marketed medical device made under a manufacturer quality system, with labeling/instructions, device listing/registration obligations, adverse-event/complaint processes, cleanability expectations, liability, warranty, consistent materials, and repeatable acoustic performance.

An open-source 3D-printed stethoscope is a cool project, but unless it is produced and controlled as a medical device, it is not equivalent to what hospitals are buying for daily patient care.

Personally, if I was a hospital or a doctor, it would be a no-brainer for me to go with the commercially sold stethoscopes. All those factors I listed above, if neglected, can end up costing a lot more in terms of consequences. I would rather pay a fixed extra overhead price per unit to sleep well, knowing I don't have to worry or think about those factors at all. And, I would assume, most of the patients would be in favor of that as well.

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nomel 2 hours ago
What standard exactly, for a stethoscope?

I know nothing of this, but it looks like stethoscopes are Class 1 medical devices with 501(k) exemption, and fall under the "Good manufacturing practices" guidelines of Quality System Regulation (21 CFR 820), but that seems pretty squishy.

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conception 60 minutes ago
CFR 21 being labeled squishy is a first for me.
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lukko 2 hours ago
In the UK it would be Class Im - so low risk device that sits outside the body, with a measuring functionality.
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duskwuff 3 hours ago
> $100 for a somewhat specialized, durable medical device...

And one which is treated as a status symbol, at that. Part of the reason a good stethoscope costs more is because it looks nicer, not just because it works better.

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harvey9 2 hours ago
You can get a basic littman for not much. I could afford one when I was a rookie EMT and I've still got the same one many years later.
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sonofhans 4 hours ago
Years ago I had my blood pressure taken by a nurse; this was when they did it manually, squeezing the pressure cuff bulb by hand and listening with a stethoscope. The doctor came in later, saw the numbers and frowned, and took my pressure again. She (both were women) ended up with a reading much more within my normal range.

I asked, joking, “So are you just better than her?” “No,” my doctor replied, “She’s better. She gets more practice. I have a better stethoscope.”

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Lalabadie 3 hours ago
The pressure cuff + stethoscope combo is called a sphygmomanometer. It's a pretty fascinating piece of technology: A heartbeat is only audible in the earpiece when the cuff is compressing between someone's systolic and diastolic pressure.

To use it, you get the cuff pressure high enough that you stop hearing a heartbeat in the earpiece. Start releasing pressure slowly. As it comes down, take note of where on the dial you start hearing the heartbeat. That's systolic pressure. Keep listening, and take note of where you stop hearing the heartbeat. That's diastolic pressure.

Using one feels kind of magic.

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devilbunny 3 hours ago
And if you use a mercury sphygmomanometer, you can actually see those pulses appear and then disappear. (It's harder to see them with a gauge-based one.)
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M95D 2 hours ago
The pulses you see are no substitute for a stethoscope. You see them later and they dissappear sooner than what you hear with a stethoscope.
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lukko 2 hours ago
It does feel magical, especially when the first sound comes in. More details here [0].

[0] https://en.wikipedia.org/wiki/Korotkoff_sounds

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Johnny555 2 hours ago
I have a much higher BP when I first go to the office than after I'm sitting in the exam room for a bit.

Usually they call me back to the hallway where they check my weight, then have me sit in a chair and check my temperature, pulse ox and BP, with maybe only a minute sitting down before they do the BP check. My BP is usually in the "hypertension" range there.

But, if they come back to the exam room after I've been sitting in that quiet room for 5 or 10 minutes and check my BP , it's almost always in the "normal" BP range (same as what I see when I check it at home).

Doctor calls it "white coat hypertension", I call it "rushed BP check in the hallway".

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harvey9 2 hours ago
If the nurse got a reading well outside normal range she should have repeated it to confirm, especially if it was inconsistent with your overall presentation.
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nomel 3 hours ago
Or, maybe you have "white coat syndrome" [1]. This is closely related to "pretty lady syndrome".

[1] https://en.wikipedia.org/wiki/White_coat_hypertension

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donaltroddyn 5 hours ago
They can become a lot more expensive than $100, but the difference between a Littman Cardiology and the $15 EMT student stethoscope is night and day.

> Currently, the stethoscope resulting from this project functions as well as the market gold standard, the Littmann Cardiology III

If this is true, it's a major achievement.

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boelboel 4 hours ago
People buying stethoscopes tend to be reasonably affluent. Some of the pricier ones just look better and people usually buy them when you get into med school (at least this was the case for me), it's somewhat symbolic so why not splurge.
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matheusmoreira 3 hours ago
There does seem to be a difference in quality though. It's much easier to hear the important things with my littman than with the cheap generic stethoscopes I usually find lying around in clinics.
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conductr 52 minutes ago
If it’s your everyday carry used in your profession, just pay for a nice one. It’s really not that much.

If someone showed you how to create a functional $30 monitor, you’d still pay more for a nicer commercial one

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deknos 5 hours ago
You probably pay for tests and that the company has to be audited for medical diagnostics standards
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elAhmo 5 hours ago
It is somewhat of a critical tool, so you don't wanna be checked by a doctor who made their own stethoscope or got one for 3 USD on AliExpress.
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NewsaHackO 4 hours ago
It’s funny, most physicians agree that the cheap disposable stethoscopes in isolation rooms are the best, mostly because they are so loud it’s difficult miss anything with them. However, I am not a cardiologist so they may have a different opinion.
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classichasclass 3 hours ago
I've actually found them pretty terrible. I can't hear subtle findings at all with those. My usual stethoscope is an older-model Littman Cardiology III with stiff rubber and a dual pediatric-adult head. I've had it for over 25 years.
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NewsaHackO 3 hours ago
I guess it's different strokes, because I can definitely hear subtle sounds much easier with them. In fact normal sounds sound like it is going to blow out my ears. The only issue I have is consistency; it's difficult to gauge how much something has changed over time with different stethoscopes, especially pulmonary edema and wheezing.
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recursivegirth 4 hours ago
Our one that DIY'd one like one would do a dosing rod in their garage.
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DoctorOetker 3 hours ago
Well-formed sentence one dosed for make benefit understandability not garage DIY'd one?

Written on ether?

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Lalabadie 3 hours ago
My daughter's toy stethoscope has actual tubing, some sort of diaphragm, and that seems to work reasonably well!

I'm not surprised good results are available for a few dollars.

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unsupp0rted 5 hours ago
Is that a lot or a little?
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hungryhobbit 5 hours ago
This "recipe" produces them for $5 ... that's 5% of the market price.
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mikeyouse 5 hours ago
Assuming equivalent capabilities and longevity.. I know physicians who have used their "20x too expensive" Littmann for 30 years.
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Agingcoder 5 hours ago
À lot
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abdullahkhalids 4 hours ago
What's the price per use compared to a standard industrial metal one?
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samantha_greene 5 hours ago
No pictures? Missed opportunity. Seems cool though!
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Modified3019 5 hours ago
Do the design and materials take into account how well it can be sterilized?
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zabzonk 5 hours ago
Never seen a UK doctor or nurse attempt to clean, much les sterilize, one.
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jwcacces 5 hours ago
There are disposable, single-patient stethoscopes, but I've seen my Dr do a casual wipe with an alcohol swab often enough...
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xyzzy_plugh 5 hours ago
I think this is a good point, insofar that how bacterial resistant the stethoscope is relevant. Stethoscopes made of stainless steel are going to beat anything 3d printed by a significant margin.
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bsza 4 hours ago
It definitely doesn’t help that prints from filament printers are very porous, 100% infill or not. Maybe sealing it with epoxy after printing would help?
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bluGill 3 hours ago
This seems like another case where the hobby has discovered the 3d printer hammer and forgot that cnc tools (lathe, milling machines) are often better and faster for the job. Or if plastic is what you want injection molding is something you can do on a hobby scale and it is much better (but unlike the others this isn't something you can go from CAD to widget)
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matheusmoreira 4 hours ago
The usual procedure is to wipe with 70% ethyl alcohol.
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classichasclass 3 hours ago
I regularly wipe my stethoscope, but I have never sterilized it. I doubt many would survive an autoclave.
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jader201 5 hours ago
Instructional video: https://youtu.be/u-KNTc0POLA
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sandworm101 59 minutes ago
I seem to remember a major issue re 3d-printing medical things. Early in the pandemic LTT organied an effort to print some PPE face shields for hospitals. It was all rejected. The microscopic holes left in the print material meant it could not be properly sanitized.

A stethoscope touches both patients and providers. This may be a place where smooth non-printed material may be the only sanitary choice.

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brcmthrowaway 5 hours ago
Are sthethoscopes passive or active devices?
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matheusmoreira 4 hours ago
It's basically a tube that transmits sound waves from a diaphragm to your ears. Pretty much an extension of your own ears.

Nowadays they do make electronic models. Active enough, I suppose. Can even record sounds.

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kfarr 5 hours ago
passive
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onetokeoverthe 3 hours ago
[dead]
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