gliax / stethoscope

A research-validated stethoscope whose plans are available Freely and openly. The cost of the entire stethoscope is between $2.5 to $5 to produce

Stethoscope

This project aims to create a research-validated stethoscope whose plans are available freely and openly. The goal is for the bell to cost ~USD$1-2 to produce, and the rest of the stethoscope to cost approximately the same. You can see the peer-reviewed publication relating to this stethoscope's validation here:

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193087

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

Bill of Materials

Printed parts:

• 1 stethoscope head (head.stl)
• 2 ear tubes (eartube.stl)
• 1 Y-piece (y_piece.stl)
• 1 Spring (spring.stl)
• 1 Ring (ring.stl)

Other hardware: Some vendors are suggested.

• 40cm - 50cm Silicone 13mm (preferred) or 12mm OD, 8mm ID, 50 durometer

  • 8MM I.D X 13MM O.D NGP60 Clear Translucent Silicone Hose Pipe Tubing (USD$7.34/meter)

• 20cm Silicone 8mm (preferred) or 6mm OD, 4mm ID (cut into 10cm pieces), 60 durometer

  • 4mm ID x 8mm OD

• Diaphragm: 40mm diameter cut from a report cover with approx 0.35mm plastic sheet

  • In Business Report Covers(USD$8.99)
  • You can cut the diaphragm by hand or with a stamp like this one

• Earbuds / Eartips: Any large-sized standard earbuds will do.

  • Silicone Earbuds 7 Pairs - Large size

Optional hardware:

• Metal spring for holding ear tubes together

Print Instructions

INFILL MUST BE 100% INFILL MUST BE 100% INFILL MUST BE 100% INFILL MUST BE 100%

• Use PETG or ABS
• Layer height: 0.2mm
• Use PrusaSlicer 2.0 or above to import 3MF file
• Modify filament and printer settings as needed.
• DO NOT MODIFY PRINT SETTINGS
• Export and print

Troubleshooting

• If the spring and eartubes do not fit well, go ahead and scale the spring as needed
• If the head and ring do not fit well, use caution as you may be modifying the acoustics. You can scale the head a little.

Notes

• We do not use PLA due to deformation in heat and poor plastic quality in the spring causing early failure. PLA may be used, but the lifetime of the stethoscope will decrease significantly.

• We do not use brims, but you may print the eartubes and Y-pieces with a brim of 2mm to ensure that none of the parts lift off.

INFILL MUST BE 100% INFILL MUST BE 100% INFILL MUST BE 100%. Otherwise, the stethoscope will not produce a correct sound.

Assembly Instructions

See this instructional video for assembly instructions.

• Attach the diaphragm (40mm) to the stethoscope head.
• Attach the stethoscope head to the silicone tube.
• Attach the silicone tube to the Y-Piece.
• Attach spring to ear tubes.
• Attach the Y-piece to the ear tubes.
• Attach the ear tubes to the eartips / earbuds.
• Test the stethoscope as per the validation instructions.

Printing the inserts

The inserts are included in the manual directory. Using 8.5 x 11 (Legal) paper, they can be printed at 8.25" page width with 95% scale for the top print and 90% scale for the bottom print using GIMP.

The top insert is cut at 14.5cm and again at 1cm creating two labels of 13.5cm height. These inserts are printed on adhesive material.

The bottom insert is cut at a width of 20cm with a height cuts at 25cm, 15cm, 13.5cm and 3.5cm creating 10cm x 20cm inserts.

Changing and creating SCAD files

CrystalSCAD and OpenSCAD were used to create all STL files. To recreate the stethoscope head, simply do:

gem install crystalscad
ruby source_files/stethoscope_head/stethoscope_head.rb

The SCAD files output from CrystalSCAD are found in source_files/stethoscope_head/output and are named as follows:

• PrintableStethoscopeHead1Assembly_output.scad - The head

Mass Manufacturing

We generally print 4 stethoscopes per plate to ensure that each stethoscope is created out of the same material.

Our serial numbering system consists of two parts. The last number part is the total number of unique stethoscopes created since day 1. All numbers before that dash are spool identifiers involved in that stethoscope. For example:

001-010 would be the tenth stethoscope made with the first spool in our inventory. If the first spool makes a total of 15 stethoscopes, then the first stethoscope of the second spool would be 002-016. If the twentieth stethoscope uses plastic from spool 002 and spool 003, it would be 002-003-020.

Other stethoscopes

Others have made 3D printed stethoscopes too. See:

• https://www.youmagine.com/designs/stethoscope-chestpiece

Licensing notes

As per our understanding, hardware is not covered by copyright. However, we present our work under the TAPR OHL license insofar as it applies.

stethoscope's Issues

Literature review

A review of the literature to figure out where things stand in stethoscope research and design.

eartube.scad warning message

There was a warning message on line 61. Just a syntax error, removed the ,0 at the end of the translate function. It was redundant and already included within the square brackets.
translate([xarray[30]-2,yarray[30]+6.5,0])
rotate([0,90,earbud_rotation])cylinder(r=6,h=9.5);

Field Test

Just field tested your stethoscope, I noticed that you are using 2 different formats for the head the one from OpenScad code is different from the Master list, I have printed both under the prescribed settings for the model. Neither have preformed better than a littmann classic with just a simple test using a medical simulator using breath sounds set to wheezing the printed one sounded more dull than the littmann..My thoughts are that maybe the report cover that I have bought is different, the tubing is the from a cardiac 3 fits perfectly. So I am thinking the diaphragm density my have something to do with it. I would like to work with you to improve your model. My team is considering maybe conducting a study on your stethoscope, so any help to support would be much appreciated.

CAEP presentation

Present this research and the idea of Free hardware at CAEP.

Chris won't be there, so this will be Tarek's responsibility.

To do this, need to:

1. Submit to CAEP
2. Get accepted
3. Make presentation files
4. Present

Describe the properties needed for the diaphragm

It looks like the suggested diaphragm material is not available in a lot of countries (including in the UK, or at least not under that name). It would be really helpful if the properties needed could be described, its unclear how the material should behave, how flexible etc.

Stethoscope head design

A few device designs should be proposed, and then the best of these will be selected to go forward.

Realistically, there's no issue in testing several, since the testing time is not likely to take that long.

Research and Ethics board approval

REB proposal and approval

• Find REB guidelines and application
• Get ROMEO account
• Complete REB proposal on ROMEO
• Send for advice and peer review
• Submit REB proposal to board. Deadlines
• Get approved

eartube file

I'm having a few issues with the eartube file, the segments don't seem to be meshed together properly and they come out separate in the output file. The source file for eartube isn't in the master folder. Is there a way to get the source file?
Regards

Make instructions on assembling the head with diaphragm clearer

I'm a bit stuck with assembling the head, do I need to glue the diaphragm to the ring or does it just get sandwiched and should the membrane be held tight or is it ok if it moves around? Looking at the box insert made it a bit clearer how it fits together but not how it should behave.

Test the device

Hopefully the question of how should have been answered by Issue #4.

In this case, we actually test the device.

Move general testing files out of dated testing folder

Only data taken on 03-31 should remain in that folder. Otherwise, the remainder should be moved into the 'testing' directory in general.

Enhancement request - bill of materials documentation

Hi,

Thanks for sharing this documentation!

A small suggestion: could you please improve the bill of materials section by adding the specific use/purpose, supplier number, order number and price of each bill of material item to make it clearer how much it all costs. Once it becomes visible for everyone, someone might find an alternative supplier that is cheaper with equal or better quality components.....

Here is an example:

http://labs.nortd.com/lasersaur/bom-one-subsystems-eur

Regards,

Mark Rijckenberg

Distinction needed between 3D printed parts and 2D inserts

I'm currently printing the parts and now I'm reading the readme and it says I should print inserts, I assumed they were additional 3D printed inserts of some sort for the stethoscope. Looking at the files and I've worked out they're paper information cards. It would be helpful to readers if a distinction was made between 3D printed parts and paper printed information, maybe call them information cards or something instead of inserts?

Thanks

Decide on a license

In this story on SoylentNews about the stethoscope design, editor "cmn32480" wrote:

[Ed: as of posting there is no license on the Github documents. Thus as per the Berne Convention it is not yet freely available, until explicitly published under an open license such as CC or similar. ]

Under what license will these plans be made available? The GNU project maintains a list of licenses for designs of physical objects.

Alternative material to Acrylonitrile butadiene styrene plastic?

What might be the best alternative material to Acrylonitrile butadiene styrene (ABS) plastic?

Earplug mold should have direction marks

... to see easily which side is the correct one to bolt it on.

Tube design

Tubes used for connections from head to T-connector, then T-connector to earpieces.

Resident research day presentation

RRD presentation to be done by Chris

SAEM presentation

Presentation at the SAEM conference

Size of rubber/silicone ring for diaphragm?

Do you have any specifications for the rubber/silicone ring we should purchase to hold on the diaphragm (similar to the other products you specified)? Thanks!

ear plugs

I bought the xcessor ear plugs but those don't seem to fit with the ear tubes. Which type should I buy?

License

There is no licensing information for the files, especially the .scad files. Please post copyright notice and license.

Ear tube & Y-piece outer diameter?

1. The tube connecting the eartube to the Y-pieace is called for it to be 20cm long in the list of materials, but if I look at the sample in FB it looks shorter, is 20 cm is till the length to go with?
2. I had a really hard time with the outer diameter of ear-tubes and Y-piece and the 4mm inner diameter/6mm OD tubing. It seems to me that this tubing should have a wider ID or the Y and ear-tubes be smaller in diameter. What do you think? Look at the connecting points on my current prototype

Dimensions and drawings for non scad users?

I would like to make customizations/modifications to the design but not doing very well with SCAD (super slow for some reason). The STL gives errors while being imported into Solidworks, so I figure that it would be easier if I could re-design from scratch given the dimensions.
If it would be possible to also upload a pdf of drawing dimensions, it could help others as well :)

What statistical analysis is needed?

What statistical analysis is needed to test the non-inferiority of the device?

For that matter, what kind of study should be done to validate devices?

Objective bench validation done by us

This is done as per https://github.com/GliaX/Stethoscope/blob/master/Testing/2015-03-31/Stethoscope_Validation.md

Verify that analysis was done correctly

After running statistical analysis, run it by somebody very familiar in stats to verify that we've done it right and that it makes sense.

Headpiece design

See https://github.com/GliaX/Stethoscope/blob/master/stethoscope_head/eartube.stl for model and https://github.com/GliaX/Stethoscope/blob/master/stethoscope_head/lib/printed/eartube.rb for source.

Needs:

• Fix bend in stem
• Human testing again.

Patent search

A patent search regarding all USPTO (and Canadian?) patents that deal with stethoscopes. These should be categorized as those expiring within the next 2 years, and those active for 2years+

Patent searches can happen at the following:

• https://www.google.com/?tbm=pts (american)
• http://patft.uspto.gov/ (american)
• http://brevets-patents.ic.gc.ca/opic-cipo/cpd/eng/introduction.html (canadian)

Results should be put on the wiki here:

https://github.com/FreeMedicalHardware/Stethoscope/wiki/Patent-search

tarek : )

Meet with Cindy Langford at PEDs ER

Cindy Langford [email protected]

Eman says ' run it by Rod Lim (peds site chief) as well.'

Source for stethoscope membrane in Europe?

The report cover used as the membrane in GliaX is unfortunately not available in Europe, and I have had difficulty finding a replacement.

The .35mm PVC sheets available from many eBay sellers are far too pliable; I tried these in my printed copies of the stethoscope and the membrane was completely useless. Are any sources apart from this specific Staples product recommended or usable, and procurable within the EU?

Recruit participants

Recruitment strategies:

1. Recruit emergency medicine physicians
2. Recruit cardiologists
3. Recruit anaesthesia
4. ? Multisite:
   • U Toronto?

How will the device be tested?

In the R & D phase, we should also answer the question:

What is the industry standard for testing medical devices such as stethoscopes?

Y-Part does not fit

There is a wired thing: The Y-shaped part will fit with the 8 mm tube to the diaphragma but not to the ear things. I printed it twice. I used petg with a prusa.

Another way to cut diaphragms

I designed a part that can be cheaply 3D printed and holds a #11 X-Acto knife blade to cut diaphragms from PVC report covers: https://gitlab.com/mcdanlj/circlecutter

Feel free to add it as a resource.

What do you think of expanding the membrane drum to 50mm ?

What do you think of expanding the membrane drum to 5mm ?

I think it would be able to funnel more acoustical signal up the pipes , especially if fitted with a modified chest piece scaled up to 50mm : https://www.thingiverse.com/thing:2895115

Some users cannot hear due to shape of ear tube

When we switched to commodity earbuds, the eartube shape became an issue for a small number of users (?5-10%), making the sound of the stethoscope poor.

Upon examination of several of these users' ear canals, they seem to respond poorly to the downward angle and the forward angle of the eartubes.

Device testing protocol

What is the protocol for testing the device?

Equipment list for device testing

What equipment will be needed for testing the device?

Out of hand, I would say:

• Microphone
• Speaker
• experimental stethoscope
• sound-proof room

What else?

[Suggestion]: Add releases using the "releases" GitHub feature

For those who are planning to make derivative works from this repository and other of your projects it would be beneficial to know where exactly in the commit history Version 1.0 or 2.0 etc is. That way it can easily be delineated that if there is some backwards compatibility it is compatible with Version 2.0 for example.

See below image taken for reference in the right hand panel of the GitHub repository.

Happy to help but this requires having collaborator's rights to the repository

Manuscript

Obviously prepare manuscript for publication.

Who are the people we'd send to?

Printing in smaller printing Beds

I encountered this problem while I tried to print the parts using a Fisher RepRap which has a circular printing bed of 150mm.

The parts which need to be changed are the

• stethoscope_eartube.scad
• stethoscope_spring.scad

Spring is too tight when printed in PLA

The spring is too tight initially and needs significant softening to work properly.

Size of Diaphragm

Thanks for the design - this is our new home project.

Sorry if this sounds like a dumb question, but nowhere do I see the diameter of the Diaphragm.

Is it supposed to sit inside the lip on the top of the head ?
Does it extend to the inner edge of the ring ?
Should it be glued to the lip, or does it need to have some play between the lip and the ring ?

Study design

• Email Jon D. to ask re: best contact, best design
• Determine design

Suggested design:

Two studies:

1. Blinded with 10 control, 10 intervention
2. Unblinded, open-label.

Objective bench validation by independent test lab

This is done as per https://github.com/GliaX/Stethoscope/blob/master/Testing/2015-03-31/Stethoscope_Validation.md

? Engineering lab at UWO?

Run statistical analysis

Hopefully this should be informed by Issue #8.

Rendering of Stethoscope_Validation.md

Is this page being used on another website that has a different rendering scheme?

It appears that when trying to view the markdown file in the browser that the images & some titles are not rendering correctly

Happy to make a pull request to make it easier to read in the browser if interested!

Precision loss in CrystalScad math causes "step" in earpiece

Mainly an esthetical error, should be found out why this happens.