Looking at: https://journals.plos.org/plosone/article/figure?id=10.1371/...
I'm not sure I believe the graphs.
For example, here's another frequency response chart of some stethoscopes: https://www.researchgate.net/figure/a-Frequency-response-of-...
How is it that professional stethoscopes can be that different, and yet this 3D printed one can match a gold-standard one almost exactly?
From what I can tell there's no audio engineering / modelling that's been done here -- It's just some crude openSCAD tubes. And it's not even optimized for 3D printing; a 3D printed tube with a circular cross-section is going to have bridging issues at the top which will result in internal roughness. I have to imagine that results in attenuation. (A better internal shape for a tube is something that looks like "ô". The ^ will print much better)
The type of plastic used and its frequency response, the thickness / stiffness of the silicone tubing, the height / width of the bell... There are so many variables that I think would make significant differences in performance. The fact that they see basically no difference is highly suspect.
This feels like one of those "3D-print everything" fads that was popular a few years ago. Yes, you can make a 3D-printed adjustable wrench, but even the most miserable dollar-tree metal version will beat it in every possible metric.
Likewise, on Alibaba, if you order 200 pieces, I'm seeing metal ones as low as $1.22/pc. I don't believe that this 3D printed one will even be as good as those.
It would require abject incompetence on the part of jellybean stephoscope manufactorers for this to make sense.
On the other hand the reason Litmann stephoscopes are expensive is target market (doctors), build quality and amortization of cost over probably a decade of use. Stephoscopes are a metanym for doctor, and doctors don't want cheap stephoscopes.
It reminds me of the product to make budget incubators for developing markets. I can't find a link but it failed for two reasons, if you can't afford medical grade systems. You probably don't have the highly trained teams needed anyways.
Medicine is in large part a trust based endeavour you need to trust the system you are putting your life at the hands of.
Long story short, this solves an imagined problem. When you consider why X doesn't have Y medical system. It's not because of the price of the kit. It's the entire system that is too expensive. If you can't afford a brand incubator you probably can't afford the it intense cleaning regime needed for the room to put that incubator in!
For example, I like coding on a nice keyboard, and I think I am not the only one here. But realistically, the cheap keyboards that litter offices everywhere work just as well. Simply, I don't enjoy using them, and when it is something you work with every day on a job that pays well, you can afford a few hundred dollars worth of luxury once in a decade.
As someone said, there is also the question of image. If you are a professional, your customers (/patients if you are a doctor) expect you to have professional tools. For example, a contractor arriving with that $10 Ikea toolbox may rise a few eyebrows. Maybe that's all he needs and he can do a terrific job with it, but he may not be taken seriously.
I normally wouldn't comment just to correct a misspelling, but it's pretty consistent and it's an entirely different sound, as well as being what the thread is about.
BTW: I found the 3M Littmann page on Amazon. The prices are wild: https://www.amazon.com/stores/3MLittmannStethoscopes/page/42...
IIRC in 2010 a Litmann Classic II was $60 today it's $100. That's what most medical students and doctors might use early in their career and it's probably nearly all the benefits of the premium lines.
But even ~$200 for their top tier lines are not expensive given their the tool of the industry.
That's a single year of JetBrains subscription? Or a single month of Claude? For something they could use for 10+ years.
The ~$500-700 electronic with recording stethoscopes always seemed gimmicky to me. But are legitimately useful for people with a hearing impairment.
> I would bet that there is a 10 USD model that is 98% as good as 200 USD models from 3M Littmann
I'd take this in a different direction, a common adage is that diagnosis is 80% history 15% examination, 5% investigation. In this case too the stethoscope performance is a slice of that 15%, and is dominated by the knowledge and experience of the user. If you don't know what to listen for and why (and many doctors won't compared to say a experienced cardiologist) they won't be able to hear it from a perfectly recorded FLAC file.
It's the same as every other field, cars, phones, or computer cases, you name it. Something can be artificially expensive, but it can also be because it uses better materials, has more features, is built to higher standards. And some things can't be tested properly in a small scale review. Longevity, for example.
But there are factors that influence the premium price. The build construction - quality of the construction, quality and feel of materials, flexibility/rigidity of components, comfort of the ear tips and why not, even color options or the logo that shows you don't cheap out on equipment. Functionality - amplification, frequency response, double sided, 2 diaphragms can be used on children and adults. And then you have nice features like tunable diaphragms, or warm rims/sleeves for making it more comfortable for the patient.
Like for any other product, you'll save on the things you don't care about. The neck is stiff, the earpiece is uncomfortable, the tubing degrades, it's ice-cold, not great for kids or thin patients, but the sounds come in loud and clear enough and it's half the price.
Within that space you get things like soft-seal eartips , where as most cheaper models came with hard rubber, a stiffer spring that holds its shape better, and great acoustics (though most users will know what to listen for by the time they pick one up). You also get less tube noise from movement, less rubbing and scratching under the head, and longer listening time without having to fiddle.
The diaphragm on expensive stethoscopes is more complex, often "floating" — not under tension at rest, but when you press down, a ring tightens it. This gives you both bell (low frequency) and diaphragm (high frequency) response from a single side, so you modulate pressure rather than rotating the head.
Why do expensive stethoscopes fail?
1. You lose them. 2. Wear and tear many parts are replaceable, but repairing the whole head often isn't worth it. Rotating heads can become a failure point, growing lax over time, with grit accelerating the damage. 3. Neck oils degrade the PVC tubing. 4. Alcohol/cleaning wipes also degrade the PVC tubing.
Surprisingly, Littmann hasn't released a dedicated long-term care wipe for occasional use.
(taxonomy) A name that is rejected because a valid name (based on another member) already exists for the same group.
metonymy
(rhetoric) The use of a single characteristic or part of an object, concept or phenomenon to identify the entire object, concept, phenomenon or a related object.
Assuming the usual Amazon, distributor and retailer markups, these probably cost around 50 cents to make in China.
https://www.amazon.in/BPL-Medical-Technologies-ST-01-Stethos...
Many poor countries are perfectly capable of manufacturing their own medical equipment
Background: I have worked in hospitals in Bihar & Vellore Tamilnadu, and have university mates, friends and family who worked in hospitals in Mizoram, PNG, Libya, Nepal, Uganda and even South Sudan.
Even the doctors who worked in South Sudan had no difficulty sourcing basic equipment. They did however, have enormous trouble sourcing funding and trained personnel who were willing to work in a potentially lethal situation.
It is adorable!
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.
One day everyone will truly be against this.
Feels like the real value here is not beating commercial stethoscopes, but accessibility and local manufacturing. even if performance is slightly worse, being able to produce something “good enough at scale in low-resource environments could still have huge impact.
Curious though has anyone tested consistency across multiple prints? I’d expect variation in material + print quality to affect acoustic performance quite a bit.
$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.
Genuinely curious, what standards exactly, for a stethoscope?
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.
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.
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.
> It doesn't feel cold to the patient
That's like a little over $3/yr. Can't complain
They last forever. Why would they break? This is like asking how long floor speakers last.
The adhesives can age. Foam surrounds can disintegrate. (Ask a Bose 901 owner about foam rot.)
They also can also die from use, and abuse. And finger-poking. And environmental conditions like moisture and UV light.
I know enough enough about old speakers to know that lasting forever isn't one of their usual traits.
Are stethoscopes really as bad as that?
Littmann sells repair kits.
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.”
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.
Or go slower.
I'm an anesthesiologist; we will sometimes use a pulse oximeter below the cuff as a quick estimate. With practice you can estimate SBP to within 5 mm Hg or so, which is more than enough for our needs.
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".
https://www.heart.org/en/health-topics/high-blood-pressure/u...
Then you will notice when your HCP ignores those instructions, like wrapping the cuff around your shirt-sleeve, or prompting you to talk while the measurement is taken, or allowing you sit with your legs crossed.
BP monitors are often poorly calibrated. The instructions for my home monitors suggest bringing the device into the clinic for calibration, and then the clinician says "we don't do that!"
Manual sphygmomanometer readings won't have an automatic digital readout, and require the human HCP to interpret, announce and record the numbers.
> 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.
I'm not surprised good results are available for a few dollars.
Written on ether?
If someone showed you how to create a functional $30 monitor, you’d still pay more for a nicer commercial one
However I am comfortable with my Littmann.
Littmann's last for 20 plus years.
The 3d printer is always ready and always has material in the right shape. It doesn't make a lot of noise, it doesn't make a lot of waste, the parts come off the machine clean and dry and ready to use. It's really hard to overstate the convenience of 3d printing.
I believe, in practice you should avoid putting it directly onto the heart, keep a layer of healthy skin in-between. Given the scope of the scope, that may be acceptable, considering the alternative may be direct skin2skin contact with your patient...
But yeah, generally, 3D printed objects are not easy to sanitize properly.Eg. their porosity makes them not safe for repeated food contact. I mean, the glass transition temperature of ABS is 105°, so you could dip it in boiling water, but that's not enough for making it sterile and consequent water inclusions are a welcoming place to start a new family a few hours later for any remaining spores. You could try fractional pasteurization and heat drying, in a pinch, at the end of times.
(if eBay kills that link, then for future HNers it's a link to an inexpensive bright yellow single-use plastic stethoscope by a company called Valuemed, which have been available basically forever and are for when you cannot risk getting something nasty on your good Littman)
£1.99 in single unit quantities from a dude on eBay.
These things are so cheap in bulk that they'd ship two in every box of Orthogon Gemini microwave links that I used to fit something like 20 years ago before VDSL was a thing to link fast sites to places that'd otherwise be on dialup. They emitted a quiet beeping to help you align them when they were in aiming mode; the cheap plastic stethoscope made it possible to hear that over wind noise, air handling units, and other such clatter.
I still have a box full of them, despite giving a bunch to the nursery my son went a couple of years ago.
What's the point in 3D printing something for $3 when you can buy them in a bulk box for a tenth of that?
A stethoscope touches both patients and providers. This may be a place where smooth non-printed material may be the only sanitary choice.
Nowadays they do make electronic models. Active enough, I suppose. Can even record sounds.