Breathing 100% O2 at depth...

[kinetic]

Dear All,

I posted up and asked a question about breathing inert gas in a dire situation, just so you could breathe something so as to make your way up on a rapid ascent, for example.

My next question is what could/would happen if say, you had to take one or two breaths from a 100% stage bottle at depths below the recommended for 100%.

Scenario, all back gas (air) is gone and your only option is to fly from 120 feet, or deeper within air limits, upto 20 feet (6m) breathing once or twice from pure O2 and then deco as best as you can with what's left at safe depth.

What would happen or is that an impossible question?

I understand the limits but I am just asking about those "no choice" situations, like the inert gas question I posted previously, same scenario.


Thanks in adavnce.

kinetic

[john]

your dead.

http://www.sptimes.com/News/82399/He...bars_acc.shtml

More recently, in April, Guido Gaudenzi of Italy died in a sinkhole under the Sand Hill Scout Reservation on a dive led by Derksen; he accidentally sucked air from a tank full of pure oxygen at 120 feet, a depth at which it is toxic.

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Mistake costs diver his life:[STATE Edition]
GRAHAM BRINK. St. Petersburg Times. St. Petersburg: Apr 28, 1999. pg. 1
Full Text (1380 words)
Copyright Times Publishing Co. Apr 28, 1999



(ran ET edition of TAMPA & STATE)

An Italian tourist apparently inhaled from the wrong tank during a dive in the Diepolder cave system Monday.

Guido Gaudenzi recently traveled from his hometown in Italy to Florida, lured by one of the world's largest and most spectacular networks of underwater caves.

The experienced diver came with plans to write a magazine article and take photos of the gin-clear waters and strange marine life that lurks in the porous limestone.

Instead, a spring-fed cave at the Sand Hill Scout Reservation off State Road 50 claimed Gaudenzi on Monday night as its second drowning victim this decade. Gaudenzi, 29, apparently breathed from the wrong tank, sucking in toxic pure oxygen, on the way up from what one of his partners described as an uneventful dive.

The fatality illustrates the perils of cave diving, an increasingly popular activity with many more risks than traditional open-water diving.

"It's unforgiving," said Chris Grant, director of the O2 Wound Care & Hyperbaric Center in Inverness and former editor of Scuba Times. "Making a mistake in a cave is often the last mistake you make."

Gaudenzi, his Italian friend Simone Roncoli, and their guide, Spring Hill resident Sandra Derksen, arrived at the sinkhole that leads into the underground caves about 5 p.m., according to a Hernando County sheriff's report. They signed the release - a requirement for diving at the Diepolder cave system, named for the man who owned the land - donned their cumbersome gear and plunged into the murky entrance.

They descended about 190 feet through a chute before entering a cave the size of a basketball stadium full of crystal-clear water. Once there, they swam to the top of the cave and made their way around most of the circumference before exiting and ascending through the same chute.

Divers who go deeper than 200 feet often use different gas mixes in their tanks than the compressed air used for more shallow dives. The mixes, a combination of oxygen, nitrogen and helium, allow them to stay longer at deeper depths, among other things. Some deep divers carry four separate tanks filled with different mixes.

Even with the complex gas mixes, deep divers must make decompression stops several times at different depths on their ascent to help dispel nitrogen and other gases from their bodies. If they don't stop and instead go straight to the surface, they likely will die.

Deep divers often take a bottle of pure oxygen with them, which helps them decompress in less time. The oxygen, however, should only be used at the last decompression stop, usually at 10 to 20 feet below the surface. Below 66 feet, oxygen becomes toxic to humans, so many divers secure the tank at the 20-foot level on the descent to avoid mistakes.

Gaudenzi took his with him. He was at the prearranged 120-foot decompression stop when the problems arose, the report said. He apparently switched mouth pieces and took a breath from the wrong tank, the report said. He immediately began convulsing. The regulator fell out of his mouth. His teeth clenched. Derksen and Roncoli swam to help their shaking partner, but it was too late.

At 120 feet under water, one deep breath of pure oxygen would shut a person's central nervous system off like a light switch, said Bruce Ryan, a cave diving specialist with the National Speleological Society.

"It would have been over in seconds," Ryan said. "There's nothing anyone can do, including an experienced guide, when someone does that."

Derksen and Roncoli realized they could do little for Gaudenzi, whose body began to float toward the surface, the report said. They made their decompression stops every 10 feet and exited the water about an hour after Gaudenzi drowned. The ranger who lives on the reservation called the Sheriff's Office. A dive team retrieved the body late Monday night. An autopsy was performed Tuesday.

Gaudenzi's family in Brescia, Italy, could not be reached for comment. Derksen did not return phone messages left by the St. Petersburg Times.

"It looks like a tragic accident, nothing suspicious," sheriff's spokeswoman Deanna Dammer said.

The surreal rock formations and wildlife, including albino crayfish, entice divers into the caves. Many call the experience spiritual and calming. Like a trip to space, say others.

For those reasons, the number of people cave diving in Florida is increasing, Ryan said. Hernando has at least a half-dozen dive shops and guides, and several more are in Citrus and Pasco counties. The diving in Spring Hill and Weeki Wachee was mentioned in an 18-page article about exploring Florida's caves that appeared in the March issue of National Geographic.

Cave-diving enthusiasts usually enter the water with no less than $6,000 in equipment strapped to their bodies. There are tanks, safety lines, lights, computers, bottom timers - backup systems for backup systems. The mix of danger, exploration and scenery is too much for some to resist

"It's an incredible experience. Once you do it, you're addicted," said Ryan, who has logged more than 500 cave dives, including the one where Gaudenzi died. "I'm sure that addiction is what brought him to this area."

Florida's caves are also some of the most difficult to negotiate in the world. They are tighter, siltier, deeper and more extensive, all of which can disorient divers and lead to panic and accidents.

"If you can cave dive in Florida, you can do it anywhere," said Grant, a 17-year diving veteran who has lost five friends to cave- diving accidents.

Hernando County and in particular the Diepolder system, which contains two main sites, have not been immune to accidents.

Lloyd Morrison, 25, of Hudson drowned in May 1990 after he drifted away from a group exploring the same sinkhole where Gaudenzi died. Morrison was a licensed cave diver but had little experience diving in the sinkhole where he drowned.

Three months later, 29-year-old Tallahassee resident Brent Potts was killed and another man was injured in a scuba diving accident at the Eagle's Nest sinkhole off Ostrom Way north of Weeki Wachee. Potts died while diving about 200 feet below the surface of the 320-foot- deep sinkhole.

In 1987, Springstead High School student Jason Tuskes, 17, drowned in a silty network of caves in a spring near Jenkins Creek. Tuskes, apparently aware of his fate, removed the harness from his body and used a knife to scratch a message to his parents and brother on the tank: "I love you Mom, Dad and Christian." He had little training in cave diving.

Experts estimate that about 400 people have died cave diving in the past three decades. Fatalities peaked in the mid-1970s, but the numbers have dropped since cave training has become widely available and the equipment has improved.

Still, about half of the deaths can be attributed to young divers venturing into underwater caves without proper training or equipment. Fully certified cave divers undergo specific cave training that includes at least 16 instructor-led dives and several hours of classroom training.

But it's not just the inexperienced who perish. The ones driven to explore new areas - called by industry insiders the "Star Trek syndrome," a desire to boldly go where no one has gone before - or try to set depth records are also vulnerable. Sheck Exley, considered by many people in diving circles to be the world's premier deep-cave diver, died in 1994 while trying to break his own depth record of 881 feet in a cave on Mexico's Yucatan Peninsula.

Gaudenzi had four years of cave diving under his belt, Dammer said. The scout reservation requires divers to dive at least twice at the easier of the two sites before trying the cave where Gaudenzi died, said Tony Davidson, who runs Down Under Dive in Spring Hill.

"The industry is well-regulated and for the most part safe as long as people do not exceed their training or experience," he said. "Everyone has close calls, and it's the ones who have the training who survive. There's not much margin for error."

- Information from Times files was used in this report.

[Illustration]
Caption: (1991) A diver explores one of Florida's caves, which are deeper and siltier than others, and can disorient divers and lead to panic. (ran HT); Photo: COLOR PHOTO, MIKE PEASE




Reproduced with permission of the copyright owner. Further reproduction or distribution is prohibited without permission.
Dateline: SPRING HILL
Section: HERNANDO TIMES; CITY & STATE; METRO & STATE; TAMPA & STATE
Text Word Count 1380

[andrebasso]

Technically, in a state of perfect calm, your body can tolerate high levels of oxygen far above the PP02 diving limit of 1.4. In a typical table 6 chamber ride for example, the pure O2 in the chamber can reach PPO2 levels as high as 3.00. Anyone who has ever taken a chamber ride can attest that you feel perfectly fine at this level. Actually, in a chamber you might not start convulsing until you hit PPO2 of around 4.00 or maybe even slightly greater. The body's response to oxygen is very strange though and is unpredictable, especially when under stress or heavy breathing - hence the tighter margins of safety when diving.

Is it possible to breathe high PPO2's when diving? Well, it has been done in the past. The macho fad of "going deep" using AIR in the 70 and 80's proved that many people can actually get close to PPO2 of 2.5 while diving, without convulsing. Guess what, many people also died while attempting this. If you consider that people have died while getting close to PPO2 of 2.5 you would be TOTALLY INSANE to use pure oxgen at 120' -- the PPO2 level would be exactly 4.636. One breath - you're dead!!

As for ascending in open water if you run out of air...
There's a reason why they teach CESA in open water scuba class. It works. Try doing a controlled swimming ascent from 70' or 80', you'll be surprised how far you can go without feeling the urge to breathe. If you do feel desparate to breathe - take a swig from your reg - you'll be surprised to find that the expanding air in the reg, hoses and tanks will provide one good and final inhalation.

Bottom line, pure O2 below 20' - BAAAAAD!

[Gibby]

Based on your questions I’m going to interject on andrebasso and recommend that you DON'T try a swimming ascent from 70 or 80 feet.

I can see that going south real fast.

[andrebasso]

Based on your questions I’m going to interject on andrebasso and recommend that you DON'T try a swimming ascent from 70 or 80 feet.

I can see that going south real fast.

IMHO, practicing a swimming ascent from within recreational limits is perfectly vaild and helps to build the OW diver's confidence. In fact, knowing that you can do it in an emergency is the best way to put an end to nonsense about breathing Argon or Oxygen...

[divindoubles]

I tried one from forty feet once, it was not all that hard. I must confess though that I took one hell of a breath before I shot maniacally toward the surface. I would hate to have started after an exhale.

[Tegg]

You may just want to focus on not running out of gas at depth.

Things like diving 1/3rds, carry AL when solo with backmount, gas management, etc...

If you run out of backgas at depth, you did more then one thing wrong already.

[bigbaldberg]

hey knitec,
while there is an abundance of reasearch in chambers, in water research is somewhat limited. the principles i argree with most are that breathing 100% deeper that 20ft is more dangerous than say breathing air at 250. the reason being is that some speculate, myself included, that narcosois actually helps defend against ox tox. high po2's are dangerous, howver canbe mitigated. some research idicates that anti anxiety prescriptions actually help prevent ox tox. the mis-firings in the brain are basically because of the added oxygen increaseing the amount of "activity" in the brain, and perhaps narcosis and anti-anxiety drugs slow down this process. i am a strict believer in 1.4 working, and 1.6 deco limits. i have however "had" to breathe gasses at higher po2's. more tothe point of your question though, my brother and i worked on a "different" configuration last year. typicaly in Guam, we can do300ft shore dives. on the mid-range stuff 130-200 we were playing with a single back cylinder and a 40ft deco/bailout bottle. the thought being if a catistrophic failure occured, we could do a CESA to the mod of the bailout, usually 40%. i tried this several times and from 200-100 with nothing to kickoff from is somewhat difficult, but do-able under most circumstances. obviously we'd prefer to share gasses and ascend slowly, but alot of our diving was solo. (i'm not interested in flames to this approach). one of my mentors lost his mid-mix gas on a "bigboy" dive and actually blended his back (15-50) with his deco (100) in his lungs in an emergency. this is not ideal, but certainly beat a cns hit. dive enough and #### will go wrong, but think through the problems and you'll survive, probably.

[Cave Ranger]

I concur with Tegg. Having to do a free assent from any significant depth is a very BAD option. Even as a new "Openwater" diver I had read enough on the subject and hung out with enough Tech guys to know that doing an emergency free assent while humming Ahhhhhhh through your Regulator was not the best self rescue plan. I bought and used a 30 cu ft Pony on every dive.
While on a Cattle Boat down in Pompano Beach this big smarmy guy thought it was funny that I felt the need to carry such a large Pony Bottle. I was the only one with one on the Boat.
Besides looking like 350 lbs of lumpy Oatmeal stuffed in a Neoprene wetsuit he had one of those 1.5 cu ft "Spare Airs" attached to his B.C. with a coily cord. Since the first dive was on the "Rodeo 25" wreck which is at around 130 fsw, I pointed out to him that if something went wrong at that depth that the only way that "Spare Air" was going to save him is if he stuck it where the Sun never shines, breaks the valve off and maybe if he was lucky it would blast him up to the surface. It was funny at the time but after the Boat was back at the dock he told me that after thinking about it he was going to upgrade to a Pony.
Carrying a Pony early on also got me used to carrying Deco bottles as I became a more advanced diver.
IMHO: Not just Tech and Cave but EVERY Scuba Diver should dive plan with the mindset of "Problems that occur underwater......get solved underwater" and equip themselves accordingly.

[JDostal]

I pointed out to him that if something went wrong at that depth that the only way that "Spare Air" was going to save him is if he stuck it where the Sun never shines, breaks the valve off and maybe if he was lucky it would blast him up to the surface.

ROTFLMAO!!!

That is the BEST description of a Spare Air I have ever heard!! HAHA!