Advanced Technology

[EFX]

Now for the Fun Stuff
In any case, this tiny piece of history will hopefully be even more academic before I’m dead. I have to agree with predictions that foresee the demise of decompression algorithms. They hypothesis is computer and sensor technology will allow direct reading of individuals to determine the safest and most efficient decompression. Ascent rates will be variable, slowing down closer to the surface. Stops will probably still exist but won’t be limited to even 3 meter or 10' intervals.

Computers will also control ascent rates on all chambers, as they do on more advanced systems today. Surface supplied diving isn’t likely to go away but all it will take is a faster/slower display to guide the tender. Scuba, freedivers, non-divers, and medical professionals will all know blood O2 and CO2 levels in addition to dissolved gas in tissues and blood.

Predictions I have read on sensors range from built into the suit to imbedded at birth. Bubble formation being a minor part of their overall function and not intended for divers. Just think how archaic, indirect, and inconsistent measuring blood pressure readings are. The whole “wearable technology” movement is just the very beginning. This is a very big deal for society and will ultimately have useful applications for divers.

I think smart sensors are the way to go. There would have to be a sensor in representative (compartment) tissue areas to get at least the functionality predicted by the algorithms. All those sensors can relay the data to a DC mounted on your wrist. The power for the sensors can come from the blood flowing through a turbine driving a small alternator. A transmitter running at an ultrasonic frequency similar to what tank pressure transmitters do should suffice. The power, controller, and sensor can all be embedded on one chip.

A better technology which has already been tried on small mammals is TLV or "Total Liquid Ventilation". Flood the lungs with perflurocarbon (PFC) or another highly oxygenated liquid. There is no uptake of inert gasses and theoretically no deco for extreme depths. Another benefit would be much higher ascent rates or possibly no maximum rate. The downside of course is it's highly invasive; the lungs haven't evolved to handle a liquid (chemical) in close contact with the aveoli.

 

[ajduplessis]

.... and I will still be diving slates with a Petrel backup.

 

[fire_diver]

A better technology which has already been tried on small mammals is TLV or "Total Liquid Ventilation". Flood the lungs with perflurocarbon (PFC) or another highly oxygenated liquid. There is no uptake of inert gasses and theoretically no deco for extreme depths. Another benefit would be much higher ascent rates or possibly no maximum rate. The downside of course is it's highly invasive; the lungs haven't evolved to handle a liquid (chemical) in close contact with the aveoli.

The only problem is that we can't physically move it in and out of our lungs on our own, it requires dedicated "ventilators" as well as heater and oxygen inducer. There is also the problem with death from acidosis after removing the PFCs form the lungs.

 

[EFX]

The only problem is that we can't physically move it in and out of our lungs on our own, it requires dedicated "ventilators" as well as heater and oxygen inducer. There is also the problem with death from acidosis after removing the PFCs form the lungs.

To move CO2 out of the blood requires about 70 ml/kg/min volume of liquid. This is about 5 l/min for a 70 kg adult. This would require an electric motor and small pump to move the liquid through tubes inserted into the airway, one longer than the other, with the longer supplying and the shorter the return line. If the pump fails a lever (one on each side of the unit) can be used to move the liquid. A small heater would be needed to keep the liquid warm. A method is needed to oxygenate the liquid and remove CO2. The acidosis is a huge problem -- haven't figured that out yet.

---------- Post added September 9th, 2014 at 03:26 PM ----------

.... and I will still be diving slates with a Petrel backup.

The Petral is no good on liquid and you can't switch to gas underwater so you won't need to take bailout bottles -- another advantage. If things go horribly wrong and there is no max on ascent rate just pull the emergency rip cord which fills your BCD and enjoy the elevator to the surface. This can also alert the team on the surface to get you out of the water and hang you upside down to drain the liquid and start O2.

Relax. I got it figured out.

 

[Akimbo]

I think smart sensors are the way to go. There would have to be a sensor in representative (compartment) tissue areas to get at least the functionality predicted by the algorithms...

To predict, maybe — but probably not to measure the actual decompression required. It really doesn’t matter which tissues are outgassing, only that the diluent is accumulating faster than the body can clear it. The sensor research I am aware of is targeting blood clots and air emboli in the medical setting, not DCS. However it “should” work for DCS too.

Of course that is assuming that dominant decompression theory is correct. I have read that there is some debate among physiologists that actual bubble formation may not be the root cause of DCS. Apparently some believe it is possible to get bent without bubbles in the blood stream. The logic presented was way over my head.

…A better technology which has already been tried on small mammals is TLV or "Total Liquid Ventilation"...

I remember reading an article in Skin Diver Magazine around 1962/63 on the first small mammal experiments. The subject came up about 10 years later with one of the diving medical officers on the team that studied it at EDU (US Navy Experimental Diving Unit)… we had days to talk during sat decompression. The first major hurdle was (is?) figuring out how to dry out the lungs after total liquid ventilation. All the mammals basically died of pneumonia when they tried to bring them back.

According to him, the real show stopper was hypo and hyperthermia. Somewhere around 50% of our normal heat loss is through respiration and plays a key role in controlling our core temperature. Thermal conductivity of a suitable liquid like perfluorocarbon is around 25x higher than air so the physical mechanics of circulating/ventilating the fluid and controlling the temperature that precisely is a huge practical barrier. They calculated that shock would set in within a minute or two if heating were lost or wondered too far.

We can’t reliably keep hot water flowing to tethered saturation divers within that window. The heat loss requirements, like today, make an untethered deep working dive impractical.

The next problem he brought up was how would the diver communicate? Vocal cords won’t work immersed in fluid. It sounds like a small thing until you start analyzing the work you want to diver to accomplish.

Adding salt water intrusion to the failure mode analysis was enough for the EDU to stop funding their work. That sobering conversation pretty well ended my standing offer to volunteer for that project. Too bad, it would be very cool.

 

[boulderjohn]

More than 10 years ago, I had a neighbor who was an engineer whose work dealt in some way (beyond my understanding) with detecting gas levels in the body. He was not a diver. We had a conversation in which he talked about those simple little clips you place on your finger that can detect the current O2 levels in a couple of seconds. I bought one for home use a while ago--it was dirt cheap. He wondered if there was any market for a similar detector for nitrogen levels in diving. He was wondering about the feasibility of inventing such a device and making some money. He indicated that even back then it would not be that hard to do. I think such ability would have a number of uses.

 

[Nirvana]

More than 10 years ago, I had a neighbor who was an engineer whose work dealt in some way (beyond my understanding) with detecting gas levels in the body. He was not a diver. We had a conversation in which he talked about those simple little clips you place on your finger that can detect the current O2 levels in a couple of seconds. I bought one for home use a while ago--it was dirt cheap. He wondered if there was any market for a similar detector for nitrogen levels in diving. He was wondering about the feasibility of inventing such a device and making some money. He indicated that even back then it would not be that hard to do. I think such ability would have a number of uses.

Don't those O2 sensors work based on the difference in transparency in oxygenated red blood cells and cells with no oxygen? As nitrogen does not react chemically with our blood, I would imagine a nitrogen sensor would have to work on very different parameters.

---------- Post added September 9th, 2014 at 10:58 PM ----------

I think smart sensors are the way to go. There would have to be a sensor in representative (compartment) tissue areas to get at least the functionality predicted by the algorithms. All those sensors can relay the data to a DC mounted on your wrist. The power for the sensors can come from the blood flowing through a turbine driving a small alternator. A transmitter running at an ultrasonic frequency similar to what tank pressure transmitters do should suffice. The power, controller, and sensor can all be embedded on one chip.

The problem is that we would still have to predict how much decompression would be needed before the dive, so that we could bring enough gas.

 

[boulderjohn]

Don't those O2 sensors work based on the difference in transparency in oxygenated red blood cells and cells with no oxygen? As nitrogen does not react chemically with our blood, I would imagine a nitrogen sensor would have to work on very different parameters.

I do not have the foggiest idea how they work.

I do know that my friend did not think it would be any problem figuring out a way to do it. He was only wondering if the demand for such a device would be such that it would make the R & D work worth while. There would not be much demand for it at all outside of scuba, and since the DCS statistics for NDL diving are something like 0.002%, there would not be much call for it there. I doubt it would make money unless made cheaply, and that is what I told him.

 

[Akimbo]

... He was only wondering if the demand for such a device would be such that it would make the R & D work worth while...

Get him busy on CO2 and CO blood sensors. The market would be relatively huge in general and emergency medicine plus divers could use it too.

 

[flots am]

I have to agree with predictions that foresee the demise of decompression algorithms. They hypothesis is computer and sensor technology will allow direct reading of individuals to determine the safest and most efficient decompression.

I don't think you'll ever be able to get away from some sort of algorithm, since even if the devices precisely measure bubbles and declare a perfect ascent rate, you still need something to breathe.

It's not a lot of help if I know that a 45 minute ascent from 130' to the surface would be awesome if I have a 30 minutes of gas left. Even with perfect measurements, it's still necessary to predict things ahead of time to ensure sufficient gas.

flots.