Current State Of Rebreather Electronics

[silent running]

IIRC, their is only some reasonable correlation between bubble numbers and DCS. People with lots of bubbles usually don’t get bent and people with few bubbles sometimes get bent, but it’s more common for people who got bent had lots of bubbles.

Correlation yes, but if that correlation points to some kind of real causation, which it probably does, real time Doppler info could be utilized to control bubble size during ascent.

 

[silent running]

If you are diving with a single diluent (most people in CCR), then you can calculate the inspired gas fractions in real time from just the O2 sensors we already have. And we do. The blood gas fractions closely trail the inspired fractions to the point that they are practically the same over any reasonable timescale. Measuring the fraction of helium in the inspired mix doesn’t really add any additional data. I don’t believe that measuring anything in the blood gas mix will substantially improve the data given to the deco algorithm either.

There is no place in ZHL-16 to integrate doppler data even if it existed in real time and we knew what it meant when we got it. The best we could do is increase the gradient factors in some prearranged way.

What you are really proposing is new fundamental technology that has nothing to do with recreational rebreathers but could be used by rebreather divers if it existed. Like most fundamental advancement it will probably need to come from the military (I.e. NEDU) or commercial operations. No rebreather electronics manufacturers are going to do that kind of expensive and speculative work.

I was not speaking of inspired gas fractions, I was concerned with the phase change from saturated gas back into the blood. I was positing that if inert gases coming out of tissues could be measured by percentage, and the bubble size of those gases measured, you could control bubble size growth in real time by holding the diver at depth for however long it took to keep bubble size small enough to predict low chance of DCS.

Actually just real time Doppler input alone into a deco algorithm during ascent could probably reduce DCS, I would think. Knowing what % of the gas was N2 and He might add some further predictive value about the different rates of desaturation and a more accurate TTS. But the Doppler monitoring might be the more valuable measurement and easier to get.

Maybe an underwater Doppler is not so hard to develop? I don't know the mechanics, but it’s an acoustic signal measurement and I don’t see why being underwater would make it harder, aside from the electronics...

 

[tbone1004]

Correlation yes, but if that correlation points to some kind of real causation, which it probably does, real time Doppler info could be utilized to control bubble size during ascent.

see my first comment on this. That implies they would know what to do with it, which they don't because it has never been studied. So if you have 10's of millions of dollars to invest in a. figuring out how decompression in the body actually works, and b. how to monitor it reliably, then by all means, but bubble models have been all but disproven in the last decade, including a lot of Doppler studies. Sure they can be used to predict the odds of you getting DCS, but it doesn't mean they know how to control ascent rates by monitoring bubble size and quantity.

 

[silent running]

see my first comment on this. That implies they would know what to do with it, which they don't because it has never been studied. So if you have 10's of millions of dollars to invest in a. figuring out how decompression in the body actually works, and b. how to monitor it reliably, then by all means, but bubble models have been all but disproven in the last decade, including a lot of Doppler studies. Sure they can be used to predict the odds of you getting DCS, but it doesn't mean they know how to control ascent rates by monitoring bubble size and quantity.

I saw your comment but I don’t really agree that nobody would know what to do with real-time Doppler info. There certainly are a bunch papers published about Doppler and DCS. Here are the most recent ones I found with google, from a journal:

https://www.eubs.org/documents/DHM Vol44 No1.pdf

I’m no expert, but presumably you would slow the ascent rate if high bubble scores are present in say the left side of the heart. I’m sure there are many hurdles to such a device coming to market, but it certainly doesn’t hurt to kick around the idea.

I’d be much more impressed/interested in a dive gear manufacturer partnering with say the NEDU and putting resources into some type of real time physiological monitoring of decompression stress, than a manufacturer reinventing a more high tech wheel...

 

[silent running]

Further on your post:

There is no place in ZHL-16 to integrate doppler data even if it existed in real time and we knew what it meant when we got it. The best we could do is increase the gradient factors in some prearranged way.

I never mentioned a specific algorithm, but I’m sure some would be more or less adaptable to an additional variable. That doesn’t strike me as a very big obstacle. As I said in my last post, I’d guess somebody would know how to implement such information, like hold you at a particular depth till the bubble score went down.

What you are really proposing is new fundamental technology that has nothing to do with recreational rebreathers but could be used by rebreather divers if it existed. Like most fundamental advancement it will probably need to come from the military (I.e. NEDU) or commercial operations. No rebreather electronics manufacturers are going to do that kind of expensive and speculative work.

All rebreathers are recreational, unless you are in the military, work for some government agency or a commercial diver. As far as I know, very few commercial divers use CCRs, so a military/government and private company partnership would probably be the best way to move such an idea forward. That’s how we ended up with civilians diving CCR in the first place.

Remember, OC divers get bent too, sometimes without violating their computers. IMHO, a device which could significantly reduce the chance of DCS would be a huge benefit to all divers, especially those CCR divers pushing time and depth exposures...

 

[tbone1004]

@silent running there is exactly a 0% chance of that ever happening. There is no ROI on that investment for the manufacturers to make money by selling more computers. The only hope would be for the navy or commercial diving industry to fund it, but even if it started now, you're 20+ years away from having something useful.

 

[JohnnyC]

Not to mention the military and commercial divers tend not to bend people on a regular basis. Benefits of having chambers on board and running SurD deco schedules.

 

[tbone1004]

Not to mention the military and commercial divers tend not to bend people on a regular basis. Benefits of having chambers on board and running SurD deco schedules.

well, they tend to bend them somewhat frequently compared to recreational divers, but they can "bend em and mend em" with chambers on board. More importantly for them, they don't really use computers per se so something that is actively monitoring them would not be ideal. They have surface support that takes care of all of that for them....

 

[JohnnyC]

well, they tend to bend them somewhat frequently compared to recreational divers, but they can "bend em and mend em" with chambers on board. More importantly for them, they don't really use computers per se so something that is actively monitoring them would not be ideal. They have surface support that takes care of all of that for them....

I should have been more clear. They're not getting people hurt by bending them. They're doing whatever deco or they're doing whatever deco then SurD, and it looks nothing like a recreational deco profile.

I hate the term "bend and mend." It implies something that it's not.

 

[silent running]

@silent running there is exactly a 0% chance of that ever happening. There is no ROI on that investment for the manufacturers to make money by selling more computers. The only hope would be for the navy or commercial diving industry to fund it, but even if it started now, you're 20+ years away from having something useful.

Whether it happens the way I was positing or another way, I’m pretty sure eventually real time physiological info will determine dive profiles, and that will be a good day. And I will be way more willing to shell out good money for that than I will for an sss or a bunch of consumer grade/cheap sensors that remind me to turn on my gas. I think most life long divers will agree.

I’m assuming the ROI of a civilian/government partnership would be software and hardware based, like many are. So there’s plenty of ROI potential between software and hardware in a properly structured agreement. No need to rely on only selling computers to the military for future revenue.

We wouldn’t have CCRs developed to the level where divers wanted to buy them if it weren’t for the US military/civilian partnership...