Skin bends...

[Storker]

I have seen some portable doppler devices for sale on doing Google searches, but they do not appear to be specific for the bubbling in divers, and maybe more for use on pregnant women

Doppler ultrasound for use on pregnant women? Are you sure you're not thinking of ultrasound imaging? The Doppler instrument only outputs audio, and while ultrasound imaging is used a lot on pregnant women, I haven't heard of the use of Doppler measurements. What would that be for?

If you're seriously considering trying out ultrasound measurements on yourself, you might want to read
Doolette, DJ (2016): "Venous gas emboli detected by two-dimensional echocardiography are an imperfect surrogate endpoint for decompression sickness", Diving and Hyperbaric Medicine 46(1), 4-10 and Møllerløkken A, Blogg SL, Doolette DJ, Nishi, RY, Pollock NW (2016): "Consensus guidelines for the use of ultrasound for diving research", Diving and Hyperbaric Medicine 46(1), 26-32. Dr. Doolette's paper is about imaging measurements, but if I remember correctly it also contains references to the seminal articles on Doppler measurements.

The full issue of Diving and Hyperbaric Medicine 46(1) can be downloaded from here.

 

[Miyaru]

Detecting bubbles using Doppler in a hospital examination room is something else than detecting these on a boat right after a dive. And if you detect anything, what's your next action?

I'd suggest a different approach: use a high nitrox percentage during the dive and, as @Germie suggested, breathe oxygen post-dive. For $500 you can get the equipment and several oxygen refills. Even more effective would be to get some training in handling decotanks and switching gasses and do a long safety stop at ~15ft on oxygen after every single dive.
Prevention is better than treatment. If you get skin bends regularly, there might be consequences from the inflammatory reactions in your tissues. Diagnosing bubbles post-dive is not the first choice of action.....

 

[Storker]

I'd suggest a different approach: use a high nitrox percentage during the dive and, as @Germie suggested, breathe oxygen post-dive.

Or even simpler: Use nitrox on all dives, allow for generous surface intervals, limit yourself to one or perhaps two dips per day and take a surface break of a day after a couple of days diving. IOW, follow what's generally regarded as sound practice according to some agencies

32% allows for some 50% longer NDLs, so if you're usually gas limited on your dives, you'll be backing off your saturation quite a bit by switching to nitrox. And if you breathe down the tank on the boat, you'll desaturate even faster and more efficiently.

 

[michael-fisch]

Ebay has good and dirt cheap 8mhz dopplers. I bought mine new for less than $100 back about 10 years ago, and they have to be cheaper now. Make sure to buy with an 8Mhz head, lower frequency heads penetrate way too deep.
Familiarize yourself with the speed of bubbles in the various Spencer grades, and try to stay at Grade 2 or lower.

Michael

This is the doppler that I bought back then, and it works very well.
Vascular Sonotrax Ultrasonic Pocket Doppler W/ 8 MHz & Batteries, Case, Gel | eBay

Find the carotid vein on the side of your neck and you will hear blood flowing by, if there are bubbles they are easy to hear - but if you aren't focused on the vein you don't hear anything.

Michael

Unfortunately, many of us that learned tech diving in the last few years, never really learned it, but are sure that they know everything about everything.
Since they know everything about everything they are as opinionated as George Irvine III was, but without his knowledge and experience, and cannot learn.
The old saying "You can lead a horse to water, but you can't make it drink" still holds.

Sad,

Michael

 

[Duke Dive Medicine]

Unfortunately, many of us that learned tech diving in the last few years, never really learned it, but are sure that they know everything about everything.
Since they know everything about everything they are as opinionated as George Irvine III was, but without his knowledge and experience, and cannot learn.
The old saying "You can lead a horse to water, but you can't make it drink" still holds.

Sad,

Michael

Michael,

When you say carotid vein, I assume you're talking about the internal jugular vein, is that correct? If so, is there literature that supports jugular venous gas emboli as a measure of decompression stress? The modern ultrasound studies looking at venous gas emboli visualize either the right heart or the pulmonary artery, since that's where the venous gas emboli coming from the various parts of the body all collect. By only using the internal jugular, you're getting a picture of venous bubbles coming from your head. Arguably if that's bubbling, you're under considerable decompression stress and may find even higher grade bubbles in the rest of your body.

Best regards,
DDM

 

[michael-fisch]

Dear DDM, as you have to well know, hearing bubbles on the carotid vein, when using a 8mhz probe is easy enough that anybody can do it and is indicitive of the decompression stress found after a trimix dive using decompression gasses, or any other real decompression dive. It's also a pretty good indication of the reason rec divers sleep so well after their 3rd dive of the day, as long as they are diving deeper that the standard 30' dives so common in Florida for 2nd and 3rd dives.

Being in good shape, BMI<25, knowing that you don't have an open PFO, and staying below a Spence grade of 2- 3, usually results in a costfree evening - if not then the costs start climbing with surface O2, calling DAN, travelling to a chamber or heaven forbid a hospital filled with ignorant doctors who want to stay ignorant and treat you with 1lpm of O2 untill the window of opportunity has closed before finally sending you to a treatment chamber as they should have done 6 hours earlier.
Been there, had it happen to me 4 years ago and now I advise that you only go to the hospital with an armed buddy to make sure that you get the STAT treatment you need, that way, you might save the 6-7 hours of crippling and useless intensive care before you end up in a chamber that can save your life or keep you from becoming permanently crippled.
My experience was, doctors in a hospital usually have a hearing problem and are incapable of listening to a prone patient who knows what needs to be done to save his life, with breathing difficulties, nausia, mottled skin between the ears and thighs, and the inability to touch his nose with open or closed eyes. But they are good about giving you 1 lpm of O2 even though the pulse oximeter shows 98%, and keeping the IV drip open just enough that it doesn't clog. Thankfully they eventually gave up on me and sent me via helicopter, but without O2, to the Croatian Naval hospital in Pula that had a great chamber and very good hyperbaric doctors who knew what they were doing.

Michael

 

[Duke Dive Medicine]

Dear DDM, as you have to well know, hearing bubbles on the carotid vein, when using a 8mhz probe is easy enough that anybody can do it and is indicitive of the decompression stress found after a trimix dive using decompression gasses, or any other real decompression dive. It's also a pretty good indication of the reason rec divers sleep so well after their 3rd dive of the day, as long as they are diving deeper that the standard 30' dives so common in Florida for 2nd and 3rd dives.

Being in good shape, BMI<25, knowing that you don't have an open PFO, and staying below a Spence grade of 2- 3, usually results in a costfree evening - if not then the costs start climbing with surface O2, calling DAN, travelling to a chamber or heaven forbid a hospital filled with ignorant doctors who want to stay ignorant anf treat you with 1lpm of O2 untill the window of opportunity has closed before finally sending you to a treatment chamber as they should have done 6 hours earlier.
Been there, had it happen to me 4 years ago and now I advise that you only go to the hospital with an armed buddy to make sure that you get the STAT treatment you need, that way, you might save the 6-7 hours of crippling and useless intensive care before you end up in a chamber that can save your life or keep you from becoming permanently crippled.
My experience was, doctors in a hospital usually have a hearing problem and are incapable of listening to a prone patient who knows what needs to be done to save his life, with breathing difficulties, nausia, mottled skin between the ears and thighs, and the inability to touch his nose with open or closed eyes. But they are good about giving you 1 lpm of O2 even though the pulse oximeter shows 98%, and keeping the IV drip open just enough that it doesn't clog. Thankfully they eventually gave up on me and sent me via helicopter, but without O2, to the Croatian Naval hospital in Pula that had a great chamber and very good hyperbaric doctors who knew what they were doing.

Michael

Hi Michael,

I'm sorry to hear about your experience and glad it had a good resolution.

Re the bubbles, I do well know that bubbles can be heard in veins, but they can also be localized. That is, if you're hearing bubbles in the vein that's coming from your head, it means that there are bubbles coming from your head. I'm not aware of any literature that correlates that with general decompression stress and would not endorse it as a measure of such. From an intuitive perspective, your brain is a fast tissue, and if you're hearing audible Doppler bubbles coming from there on the surface, it could that that area was under considerable decompression stress. How long after the dive are you doing your measuring?

Best regards,
DDM

 

[michael-fisch]

With trimix as the limiting tissue the bubbles seem to reach theim maximum 10 minutes after surfacing. If nitrogen is the limiting tissue, bubbles seem to hit a peak after 45 minutes.
You can really cause a bubble spike 30 seconds after doing 2 pushups though so doing hard exercise shortly after diving should be avoided.
I have never noticed 2 peaks (for helium and nitrogen) in the same diver after the same dive, but assume that it would be possible.
Several divers have also had spiral CTs done of their brain without signs of damaged braintissue, which could also be expected to show up after repeated aggressive trimix decompression.
15 years ago, GFhigh at 150% was normal in my crowd, I didn't feel quite right the couple of times I tried it but GFhigh 125% worked well for me.
Now years later, after a bad DCS incident, several minor skinbends hits, BMI>25, and age over 60, I'm much more conservative, and start slowly ascending from my last stop at 6M with a GFhigh of 85% or less. After 2 and a half days of aggressive diving I also skip the afternoon deco dive and let my tissues recover, before restarting the next morning.

Michael

 

[kelemvor]

You can build a DIY ultrasound imager relatively easily for under $500. Instructions here: Introduction · Hacking ultrasound with a DIY dev kit

You don't get nearly the resolution of expensive commercial ultrasound machines, but you don't get the same cost either.

Probably also great for checking scuba tanks for cracks, if you were so inclined.

 

[Storker]

With trimix as the limiting tissue the bubbles seem to reach theim maximum 10 minutes after surfacing. If nitrogen is the limiting tissue, bubbles seem to hit a peak after 45 minutes.

Sorry, but what does this mean? Nitrogen isn't a tissue, it's a gas. Trimix isn't a tissue, it's a gas mix. And "limiting tissues" are, as far as I understand, theoretical constructs in a decompression model.