Deep diving advice that goes against conventional thought?

[PfcAJ]

Its also the one that's least recoverable.

 

[Subcooled]

Its also the one that's least recoverable.

Without a FFM

 

[Akimbo]

Its <Oxygen Toxicity> also the one that's least recoverable.

Not nearly as unmanageable as most people indicate here. IMHO fear and overstatement is not a useful substitute for understanding. There is a vast disconnect between real-world experiences with Oxygen Toxicity and what appears to be the wide-spread belief in recreational diving. Sure it is dangerous, but not as fatal as massive barotrauma.

Its also the one that's least recoverable.

Without a FFM

A FFM has its own problems. They are great to have if there is a rapid-onset convulsion, but not so great for barfing&#8230; nausea is a more common OxTox symptoms among healthy divers.

Far too many recreational divers ignore or are unaware of the VENTIDC symptoms.

&#8230;

V: Visual symptoms. Tunnel vision, a decrease in diver&#8217;s peripheral vision, and other symptoms, such as blurred vision, may occur.

E: Ear symptoms. Tinnitus, any sound perceived by the ears but not resulting from an external stimulus, may resemble bells ringing, roaring, or a machinery-like pulsing sound.

N: Nausea or spasmodic vomiting. These symptoms may be intermittent.

T: Twitching and tingling symptoms. Any of the small facial muscles, lips, or muscles of the extremities may be affected. These are the most frequent and clearest symptoms.

I: Irritability. Any change in the diver&#8217;s mental status including confusion, agitation, and anxiety.

D: Dizziness. Symptoms include clumsiness, incoordination, and unusual fatigue.

C: Convulsions. The first sign of CNS oxygen toxicity may be convulsions that occur with little or no warning.​

&#8230;

&#8230; Even though he was on a very aggressive trimix ratio when he died, when you are below 800 feet, narcosis is still a factor...

It probably was &#8220;a&#8221; factor, along with high gas density, CO2 buildup, Compression Arthralgia, and HPNS (High Pressure Nervous Syndrome). Gas density is problematic on HeO2 used by commercial saturation divers at that depth. Trimix density would be crazy. I know that some studies indicate that Trimix &#8220;might&#8221; be useful in controlling HPNS, but not at this depth. Joint pain from Compression Arthralgia alone is pretty debilitating.

http://www.scubaboard.com/forums/te...triox-trimix-heliox-question.html#post6528589

 

[MXGratefulDiver]

Far too many recreational divers ignore or are unaware of the VENTIDC symptoms.

... we use the mnemonic ConVENTID, but it's the exact same thing (except we put Convulsions first) ... and it's a standard part of recreational EANx training ...

... Bob (Grateful Diver)

 

[Akimbo]

... we use the mnemonic ConVENTID, but it's the exact same thing (except we put Convulsions first) ... and it's a standard part of recreational EANx training ...

The problem is that convulsion is the only one people seem to remember or remain aware of and is, in my experience, the least common symptom... unless you ignore all the others until convulsions set in too.

 

[MXGratefulDiver]

The problem is that convulsion is the only one people seem to remember or remain aware of and is, in my experience, the least common symptom... unless you ignore all the others until convulsions set in too.

Actually the problem is that those other symptoms are a lot like the symptoms you can get from other scuba-related maladies. And because a person can experience one or more of those symptoms and rationalize it away as not scuba-related at all, what often gets people in trouble is a symptom known as "denial".

But as your own post indicates, convulsions can be the first symptom to appear ... with little or no warning. Since it's the one that will have the most serious impact, it's the easiest one for people to think about.

... Bob (Grateful Diver)

 

[John C. Ratliff]

During the spring of 1975, I participated as a divemaster and safety diver in the Warm Mineral Springs Underwater Archaeological Project. Warm Mineral Springs was the site where a 10,000 year-old spear-throwing tool (atenlatal, sp?) was found in the spring. This as headed by Sonny Cockrell and Larry Murphy. We conducted shallow dives (45-80 feet) around the periphery of the springs to collect pollen samples and look at layers of deposits, and dives to the deep ares where there was a derbies pile at between 190 and 220 feet. These deep dives were decompression dives, and we set up several measures to ensure the safety of the scientific divers. These measures included:

--A detailed Dive Master's Log, which contained emergency information (nearest doctor, chamber, ambulance service, helicopter rescue service) with their phone numbers.
--Oxygen decompression from thirty feet to the surface using an O2 cylinder bank and long hoses with regulators on them at the 30, 20 and 10 foot stops.
--Strict buddy system.
--for multiple dives, recording and tracking the repetitive group designation for each diver.
--Mandatory use of regulators with octopus second stages, and pressure gauges.
--Use of twin 90 cubic foot scuba.
--Divemaster and safety diver on standby for deep dives.
--At the time, I was an active EMT-Paramedic, and also a USAF Reserve Pararescueman; I therefore set up the helicopter rescue protocol with Detachment 14, 48th Aerospace Rescue and Recovery Squadron, McDill Air Force Base, in Tampa, Florida in case we had a decompression emergency.

We conducted these dives successfully, and had only one incident, and that happened on a shallow, fifty-foot dive. The incident was a complete failure of the Cyclone 300 regulator, so that neither the primary or secondary regulator functioned (could pass air). We never determined why this regulator failed, but it did. On March 23rd, I did a safety check dive of two minutes duration for two teams of deep divers when they conducted a 40 foot stop prior to going onto oxygen decompression at 30 feet.

I'll reproduce one of our dive log sheets to show some of what we were doing there. But this is a case of a non-commercial dive operation which successfully used air between 190 and 220 feet in depth.

SeaRat

 

[Akimbo]

…Actually the problem is that those other symptoms are a lot like the symptoms you can get from other scuba-related maladies. And because a person can experience one or more of those symptoms and rationalize it away as not scuba-related at all, what often gets people in trouble is a symptom known as "denial"…

My Navy instructor in First Class Diving School had a simple cure for that. There was very little risk of drowning because we were in Mark V deep sea gear but he managed to make a lasting impression anyway (paraphrasing here since I can’t remember exactly).

“Immediately report any suspicion of Oxygen Toxicity symptoms and we’ll switch you to an air break. It will take several minutes to purge the Oxygen out of your umbilical after we switch (300-600' long hose) so don’t hesitate. You will beat the crap out of your head in the hat and probably bite your tongue off if you convulse.”

It is simpler and faster for a Scuba diver to take an air-break (or Nitrox) when decompressing on pure or high O2. Those “other symptoms” are not like “other scuba-related maladies” because you are on high PPO2 Oxygen and progression of symptoms can easily kill you!

It is fantastically rare that convulsion is the first symptom. I have never seen a convulsion nor have any of the other military or commercial diving supervisors I have discussed it with. Convulsions are also very rare in combat swimmers even though they violate the 25' rule with considerable frequency and under fantastic stress.

The point is not that convulsions aren’t dangerous because they are. The point is that convulsion is preventable the great majority of the time with decent training. Unfortunately, the attempt by the recreational training industry to simplify and sugar-coat reality is ultimately a bigger hazard.

 

[DCBC]

...commercial diving does not equal recreational (as in 'for fun') diving.

I think what's missed is that divers that use SB come from all walks of life. There are three commercial divers on this thread who dive recreationaly (as you're aware).

Using surface supply or SCUBA on air doesn't change how inert gas narcosis effects anyone. My point is that many of us have experience diving in over 150 FSW for extended periods of time without IGN affecting us to such a degree that we were unsafe or unable to complete the job. Have you ever been incapable at 200' because of IGN?

I agree that commercial equipment (surface supply, comms, etc.) provide additional safety for the diver, but that's not what's in-question. Can a person be safe and competent on SCUBA over 150' with proper training and adequate experience?

 

[MXGratefulDiver]

We all live in our own worlds. What is called "common knowledge" is usually what falls within your particular realm of experience. I don't personally want to try diving in the manner described in the OP ... nor would I recommend it to anyone interested in asking my opinion on the subject. How it pertains to the world of commercial diving isn't anything I either need or particularly care to know about either.

I think that explains why the disparity exists most of the time.

Personally, I'm more concerned about the disparity between common knowledge and common sense ...

... Bob (Grateful Diver)