why hate safety devices?

[Crush]

That is the real bottom line, even the DAN article contains the caveat:

The missing link of this research is the unknown relationship between Doppler-detectable bubbles and neurological DCS. For the moment, it is our hope that by eliminating the 30 percent so-called silent bubbles in the heart, we will also be stopping their occurrence in the spinal cord too. More research is needed in this regard.
​

I lament the fact that DCI is so well-studied, yet so poorly understood. Through analogy, I understand how complicated the worlds of biochemistry and physiology are. I am not casting stones at those who study DCI. I only wish that they were better-funded and had an over-abundance of excellent grad students.

 

[bvanant]

Can Doppler be used to measure bubbles in the lymphatic system? We have only used Doppler for blood flow measurements in the subcutaneous tissues in the arm, never for bubbles.
thanks
Bill

 

[bvanant]

That is the real bottom line, even the DAN article contains the caveat:

The missing link of this research is the unknown relationship between Doppler-detectable bubbles and neurological DCS. For the moment, it is our hope that by eliminating the 30 percent so-called silent bubbles in the heart, we will also be stopping their occurrence in the spinal cord too. More research is needed in this regard.
​

So what study should be done? Is there a relevant animal model? Is there some relatively simple non-invasive approach (nerve conduction velocity or something like that) or is there some imaging modality in the nervous system that can be used?
The issue I have is that if turns out that there is minimal correlation between microbubbles and DCS then using microbubbles as an endpoint in studies designed to change diving habits to those that are more safe will be useless.

Bill

 

[lamont]

So what study should be done? Is there a relevant animal model? Is there some relatively simple non-invasive approach (nerve conduction velocity or something like that) or is there some imaging modality in the nervous system that can be used?

if it was simple, someone would have thought of it.

The issue I have is that if turns out that there is minimal correlation between microbubbles and DCS then using microbubbles as an endpoint in studies designed to change diving habits to those that are more safe will be useless.

correct.

that's the issue everyone has with using microbubbles.

 

[bvanant]

if it was simple, someone would have thought of it.

Maybe, maybe not. In the last few years medical technology, particularly imaging technology has grown enormously, yet a PubMed search on Doppler and DCI yields only a few articles that try to understand the mechanism. For example there are no Pubmed citations that describe any nerve conduction studies when microbubbles might be present. Is that because "everyone knows" that it won't work or because no one has looked. My take from outside (but inside the medical world) is that this is a difficult field that is underfunded and not particularly well studied. I don't know why but suggesting that we shouldn't think about what experiments to do because they are hard makes no sense.

Bill

 

[captain]

Sooner or later you get to the point of diminishing return dollar wise doing research. DCS is probably a minuscule fraction of medicine, treatment is fairly well established and so is prevention. In most fatality cases even treatment would have been futile. We have spent billions on cancer research and people still get cancer but the cure isn't as easy as curing DCS or preventing it.

 

[String]

but the cure isn't as easy as curing DCS or preventing it.

At the blunt end of things a cure for DCS is easy - don't breathe gases under pressure. Ie don't dive. Its completely avoidable.

 

[Jim Malone]

Replying to the OP as a licensed pilot and engineer. Some pilots like innovations but ONLY if it makes their taskload lighter, like HUD or a Glass Cockpit, or increase their safety. One thing is certain, you learn flying in small single engine planes with low tech instruments. They when you transfer to bigger multi engine airplanes and you go to IFR (Instrument Flight Rules) were you fly strictly on instruments. Watching 20 dails at the same time is very difficult, so they integrate them in a "glass cockpit" with one or two screens. They still have basic mechanical gauges as back-up. Pilots hate alarms and beeps. The reason is that most pilots don't remember all the different horns, beeps etc especially those who are rare (like fire) and under stress. That's why they have voice commands! "Pull Up" "Too Low Terrain" "gear up" "overspeed"in dangerous situations. These audible signals are so loud that they are clearly heard above the loudest possible sound levels in a cockpit. When you test them on the ground they are soo loud you have to wear hearing protection. Also the alarm indicators are placed in direct line of sight in front of the pilot.

I have dived with students on their first dives that were so focused on their task that they had no idea they even had an spg. I had to sit in front of them, make eyecontact, and show my gauge and point at it, before they realised that somewhere there should be a gauge with a needle on. They have tried to show me air 2's, Octopus second stages, compasses and depth gauges instead of their SPG. I always ask them how much air. Sometimes they look about 30 seconds at the gauge before the signal me the (sometimes wrong) content. Replacing these simple gauges with a small instrument that beeps and chirps every five seconds is a disaster waiting to happen.
I have a Wireless D9 and a Vytec AI computer and a mechanical pressure gauge. I don't like the idea of diving with Murphy as my buddy, getting caught in a very fine fishnet on the ascend and then realising your only Air integrated dive computer is showing a blank screen. No idea how deep you are, how long you have been diving, how much air left, any decostops, etc.
A fancy dive computer should always have a mechanical low tech back-up.
I have had 2 dive computers quit on me during diving, and just went to my back-up.
Like in an airplane every critical life support system under normal conditions should be at least double redundant preferably tripple redundant.
This means in my opinion
- 2 seperate airsources ( in my case 3, one 12 liter 300 bar bottle with double valve and 2 MK17's first stages, and a 4 liter 300 bar pony bottle filled with Nitrox 32 with a MK2 first stage)
The Nitrox is never used during the dive but serves as an emergency airsource with high oxygen contents to help degassing and as a added safety margin if a decostop is missed, or an ascend rate was too high, or to help an exhausted or scared diver or myself oxygenate his blood if hyperventilating. The air and Nitrox are from 2 different filling stations. I fill it with air when doing deep air dives to avoid oxygen intoxication.
- 2 seperate pressure gauges ( i have 3 (Wireless Suunto D9 + Vytec) + mechanical on the pony)
- 2 seperate bouyancy compensators ( 1 bcd and 1 drysuit)
- 2 ways of calculating decompression ( i have 3, 2 divecomputers and air/nitrox tables)
- 2 depth gauges ( i have 3, 2 computers, one bottomtimer)
- 2 timers ( 3 myself)
- At least 2 cutting tools (I have 1 knife, 1 shear, and a small wire cutter) accessible from both sides (i dive in net and fishing line infested water)
- At least 2 lightsources ( i take , you guessed it 3, 1 main and 2 back-ups)
- I replaced my rubber finstraps with springstraps
- I Carry 2 SMB in different colours ( one with a dropshot, one with a reel), a strobe, a wistle and cyalume sticks
-I carry a snorkel ( it's much more relaxing breathing from a snorkel face down if you get have to swim long distances due to unforseen occurences)
- I carry a back-up mask and 2 small reels

Do i look like a mule, dragging useless **** around? Yes.
Do i need it? I hope not
Would my chance of survival be higher when the excrement hits the ventilator? I think it would.
Do they mock me sometimes because i look like a walking store? yep, but better safe then sorry.

Now you should realise that i do most of my dives in a drysuit in cold 40 to 50°F water with strong currents, around the North Sea with limited natural light penetration and low visibility ( 30 feet visibility is fantastic, 6 feet is the norm).

So don't take my safety precautions as the norm. Tropical diving doesn't need these extreme precautions.

 

[sdiver68]

For example, a pilot should know to watch the altitude gauge. Also, pilots of aircraft with retractable landing gear should know to extend said landing gear prior to landing. I am not a pilot, but I am sure that warning systems exist in aircraft to alert pilots to low altitude and retracted landing gear, irrespective of how good the pilot is.

What makes scuba different?

Scuba is not different. Some people just don't understand the safety principles of redundancy.

 

[Rhone Man]

As I understand it, the main problem with studying DCI is the huge variables. When Haldane first pressurised his goats to 6 ATA (about 165 fsw equivalent), kept them there for 30 minutes, and then brought them to surface pressure immediately, two died almost immediately, three died within a few hours and one was asymptomatic. When your variables are that wide, it is pretty hard to draw bright white lines.