Another PONY Q!

[John C. Ratliff]

uncfnp,

Thanks for that discussion. Having suffered from shallow water blackout, I know that it is easy to overcome the oxygen driver for breathing. I was in high school swim team, and we had a contest to swim underwater. My competition, a good friend and very good swimmer, had just swam 20 yards time 4 lengths, or 80 yards underwater. I was determined to beat him. So I hyperventilated for about two minutes (memory, may have been less), and dove in. I started out swimming a modified breaststroke underwater, made my first turn feeling lightheaded. As I come to my second turn I was feeling really good. Approaching my third turn (at 60 yards) I was starting to feel that I should breath. As I approached my fourth turn to beat Tom Lengyl, my buddy, I told myself that I would make the turn, take one stroke, and surface. And, that's exactly what I did. Only I don't remember anything after the turn. I don't remember taking that last stroke, or surfacing, or swimming to the side of the pool (which everyone says I did). My first recollection was breathing heavily at the side of the YMCA pool in Salem, Oregon. This was about the year 1963. I told our coach, Margarette Lengyl (who was a Silver Medalist in breaststroke in the 1950s Olympic competition from Hungry), about my experience, and she shut down the competition for underwater swimming. I firmly believe that had I not told myself to surface, I would not have and would have died that day. There is a lot more to the physiology of shallow water blackout, including doing it at depth, which I won't get into right now.

But it's not the same for an emergency swimming ascent without air. Why? Because the air breathed at depth (130 feet) is pressurized. Let me quote another noted diver about this, Jacque Cousteau. He, in his book The Silent World, discussed how Frédéric Dumas trained divers.

At the end of the course the honor students swim down to a hundred feet, remove all equipment and return to the surface naked. The baccalaureate is an enjoyable rite. As they soar with their original lungful, the air expands progressively in the journey through lessening pressures, issuing a continuous stream of bubbles from puckered lips.

I'll look more closely at your concerns about partial pressure, but realize that at the surface, the partial pressure is much less, and at 130 feet the partial pressure oxygen in air is equal to breathing pure oxygen at the surface.

Yes, 16% (.16 atm) at the surface is considered hypoxic. For diving, it depends upon the depth, as with really deep diving the percentage of oxygen is very low to keep the partial pressure of oxygen in the breathing gas below 2 atm. Just realize that the percentage of oxygen in the breathing air and the partial pressure of oxygen are different, depending upon the depth.

Figure 1-15.--Partial pressure. At 5 atmospheres absolute, partial pressure of oxygen in air is approximately equal to the partial pressure of pure oxygen at the surface.

This is from a figure on the next page of the U.S. Navy Dive Manual (I may be able to scan that fugure for you). But that means that at 132 feet (5 atm absolute), air is equivalent to pure oxygen on the surface. This shows how much more effective oxygen transfer would be in an ascent, and also shows that somewhere below 264 feet (I've heard 296 feet) the partial pressure of oxygen in air is considered toxic to a diver.

By the way, this is why I would not breathe pure oxygen, even in an OOA emergency, at a depth of 5 atmospheres absolute--it is definitely toxic at that depth. I like the idea of saving that oxygen bottle to be breathed at shallow depth during the ascent.

So far as how long it would take to have a reaction, remember that Peter Small and Hannes Keller, on their record 1,000 foot dive in the 1960s, accidentally breathed ordinary air at 1,000 feet, and almost immediately were unconscious. Peter Small passed out within two minutes, and died on that dive.
The Keller Dive

SeaRat

 

[John C. Ratliff]

I have just made a calculation on the Keller dive:

1000 feet divided by 33 feet per atmosphere equals 30.3 atmospheres plus one atmosphere for the absolute pressure.

1000 ft / 33 ft/atm = 33.3 atm. + 1 atm = 34.3 atm absolute

Air is composed of 21% oxygen, or a 0.21 oxygen mixture with nitrogen.

Partial Pressure is equal to the absolute pressure times the percentage of the gas in the mixture, in this case 21% oxygen.

PPO2 = 34.3 atm X 0.21 = 7.2 atm

Now, look at how close that is to 5 atmospheres partial pressure for pure oxygen at 132 feet. I don't think a diver breathing pure oxygen at 132 feet would last long even attempting a controlled emergency swimming ascent (CESA).
The Keller Dive

SeaRat

 

[Gareth J]

To answer the first post, I would say you can just put air in and forget about it, thats the simplest solution.

You 'could' put 32% Nitrox in, personally, much beyond 30m and I would be on twins (if I was diving OC), so I wouldn't see it as an issue.

For a while, I had a 3l strapped to the side of my CCR as independent bailout. That had 27%, good for 40m. With the CCR I effectively had the onboard DIL as bailout and an off board 3litre. Part of the reason for the 3l was so my OC buddies had something they could use, if pressed, but most buddies I dive with either have a pony or twins.
Most of my diving I carry an Ali80, be it 20m or 50m, frankly I'm so used to an Ali80, that I don't really notice it.

 

[NAUI Wowie]

uncfnp,

Thanks for that discussion. Having suffered from shallow water blackout, I know that it is easy to overcome the oxygen driver for breathing. I was in high school swim team, and we had a contest to swim underwater. My competition, a good friend and very good swimmer, had just swam 20 yards time 4 lengths, or 80 yards underwater. I was determined to beat him. So I hyperventilated for about two minutes (memory, may have been less), and dove in. I started out swimming a modified breaststroke underwater, made my first turn feeling lightheaded. As I come to my second turn I was feeling really good. Approaching my third turn (at 60 yards) I was starting to feel that I should breath. As I approached my fourth turn to beat Tom Lengyl, my buddy, I told myself that I would make the turn, take one stroke, and surface. And, that's exactly what I did. Only I don't remember anything after the turn. I don't remember taking that last stroke, or surfacing, or swimming to the side of the pool (which everyone says I did). My first recollection was breathing heavily at the side of the YMCA pool in Salem, Oregon. This was about the year 1963. I told our coach, Margarette Lengyl (who was a Silver Medalist in breaststroke in the 1950s Olympic competition from Hungry), about my experience, and she shut down the competition for underwater swimming. I firmly believe that had I not told myself to surface, I would not have and would have died that day. There is a lot more to the physiology of shallow water blackout, including doing it at depth, which I won't get into right now.

But it's not the same for an emergency swimming ascent without air. Why? Because the air breathed at depth (130 feet) is pressurized. Let me quote another noted diver about this, Jacque Cousteau. He, in his book The Silent World, discussed how Frédéric Dumas trained divers.

I'll look more closely at your concerns about partial pressure, but realize that at the surface, the partial pressure is much less, and at 130 feet the partial pressure oxygen in air is equal to breathing pure oxygen at the surface.

Yes, 16% (.16 atm) at the surface is considered hypoxic. For diving, it depends upon the depth, as with really deep diving the percentage of oxygen is very low to keep the partial pressure of oxygen in the breathing gas below 2 atm. Just realize that the percentage of oxygen in the breathing air and the partial pressure of oxygen are different, depending upon the depth.

This is from a figure on the next page of the U.S. Navy Dive Manual (I may be able to scan that fugure for you). But that means that at 132 feet (5 atm absolute), air is equivalent to pure oxygen on the surface. This shows how much more effective oxygen transfer would be in an ascent, and also shows that somewhere below 264 feet (I've heard 296 feet) the partial pressure of oxygen in air is considered toxic to a diver.

By the way, this is why I would not breathe pure oxygen, even in an OOA emergency, at a depth of 5 atmospheres absolute--it is definitely toxic at that depth. I like the idea of saving that oxygen bottle to be breathed at shallow depth during the ascent.

So far as how long it would take to have a reaction, remember that Peter Small and Hannes Keller, on their record 1,000 foot dive in the 1960s, accidentally breathed ordinary air at 1,000 feet, and almost immediately were unconscious. Peter Small passed out within two minutes, and died on that dive.
The Keller Dive

SeaRat

Awesome post! I had always worried that at say even 80 ft deep id never be able to surface. I did my 30ft to surface single breath in my OW training and always ran out of air to breath about 5 ft until about the 4th try so thought at 80 id just be dead. This leads me to believe I am incorrect.

 

[uncfnp]

I have just made a calculation on the Keller dive:

1000 feet divided by 33 feet per atmosphere equals 30.3 atmospheres plus one atmosphere for the absolute pressure.

1000 ft / 33 ft/atm = 33.3 atm. + 1 atm = 34.3 atm absolute

Air is composed of 21% oxygen, or a 0.21 oxygen mixture with nitrogen.

Partial Pressure is equal to the absolute pressure times the percentage of the gas in the mixture, in this case 21% oxygen.

PPO2 = 34.3 atm X 0.21 = 7.2 atm

Now, look at how close that is to 5 atmospheres partial pressure for pure oxygen at 132 feet. I don't think a diver breathing pure oxygen at 132 feet would last long even attempting a controlled emergency swimming ascent (CESA).
The Keller Dive

SeaRat

So John, I am Lisa by the way, it is your contention that Peter Small’s death while decompressing aboard the Eureka was the result of his oxygen exposure at depth? (thanks for the link)

And by your own words, it was minutes of oxygen at that level for unconsciousness, not one breath before ascent.

Don’t get me wrong. Just playing devils advocate. I already said I would (and did) start the ascent then breathe when needed, at a “safer” level.

 

[John C. Ratliff]

So John, I am Lisa by the way, it is your contention that Peter Small’s death while decompressing aboard the Eureka was the result of his oxygen exposure at depth? (thanks for the link)

And by your own words, it was minutes of oxygen at that level for unconsciousness, not one breath before ascent.

Don’t get me wrong. Just playing devils advocate. I already said I would (and did) start the ascent then breath when needed, at a “safer” level.

Lisa,

Apparently Hannes Keller was unconscious within 30 seconds. Peter Small stayed conscious a bit longer. Here is a different description from a different source:

...Keller explained that four tanks supplied mixtures to theAtlantis. Tank 1 had been intended to take the two from 250–1000 ft, then back to 500 ft; Tank 2 from 500–300 ft, and Tank 3 from 300–130 ft. Tank 4 was a reserve.

During the early stages of the dive, Keller noticed that Tank 1 was showing only 80 bar instead of 150. The two were using semi-closed-circuit breathing sets with 3 litre tanks, and their reserve at 1000 ft would therefore be reduced to four minutes instead of 10 or 12.

Their dilemma, therefore, was whether to continue the dive and keep refilling their tanks, or to abort. They decided to keep on refilling, but instead of staying at 1000 ft for five minutes, as originally planned, to cut their bottom time to three.

In Keller’s opinion, this decision was one of two which probably caused Peter Small’s death. The second mistake was to exit to drop the flags on the ocean floor at 1020 ft. In the circumstances, this should never have been attempted.

Keller said he was exhausted and dizzy when he climbed back into the chamber, and also felt some fear. In retrospect, he wondered if he should have promptly refilled the apparatus, but decided to close the hatch first instead. He tried to do this but a fin got caught in the hatch, so it wouldn’t close properly.

All he could then do was to open the air-pressure valves to blow the water out of the chamber to prevent them drowning while unconscious. He then opened his face-mask and took his mouthpiece away to breathe ordinary air so that he wouldn’t die from lack of oxygen. Peter Small tried to help him and also removed his mouthpiece, but failed to refill his own apparatus and, apparently, remove his face mask.

Within 30 seconds of re-entering the chamber, Keller lost consciousness and remained that way for half an hour, suffering from oxygen hallucinations. Small’s pulse rate was low and his breathing shallow. He lost consciousness for 90 minutes, after which he began to speak and appeared reasonably normal.

However, he was exhausted and couldn’t stand. He was given a drink and was suffering from heat, so Keller cut away his suit and underwear. He was in touch with Dr Buehlmann and finally reported that everything seemed OK.

Decompression continued for six hours and Small began to sleep. He kept changing positions and was very uncomfortable and nervous. When the bell was lifted onto the pier and laid down, Keller changed Small’s position and noticed that he was not breathing. He failed to respond to mouth-to-mouth respiration. The chamber was opened and Small was rushed to the Navy’s hospital ship, where he was pronounced dead on arrival.

A post mortem was to follow, with a high-level inquiry in the USA. This concluded that, with the exception of a serious gas embolism, Peter Small’s condition was physically sound, with no evidence of cardiac diseases.

The committee agreed with Dr Buehlmann’s conclusion that Small’s circulation was seriously impaired through possible prolonged anoxia with loss of consciousness. He was therefore not able adequately to eliminate the nitrogen from his body, and so developed the symptoms of decompression illness.

One conclusion was that the whole experiment was fraught with potential hazard, caused by the complexity of pressure groups: magazine commitments; public announcements; navy contracts; borrowed items, including ship and closed- circuit TV; timetables; weather factors; limited individual time and expectant creditors.

Nevertheless, the committee concluded that the dive had produced a significant scientific achievement, if one that had saddened the worldwide diving fraternity.

Peter Small’s death was not, of course, the only tragedy. What must not be forgotten was the courage and heroism of his friend and fellow-diver Christopher Whittaker.

Whittaker was one of the two safety divers who went to the aid of Peter and Hannes Keller when they were lying unconscious in the diving chamber. It was impossible to raise them to safety until the leak in the chamber, caused by the trapped fin, had been sealed.

No one will know just how exhausted Chris Whittaker felt, or what his thoughts were, after the unsuccessful first dive to 200 ft to close the hatch. But one thing we know is that, against advice and with an unselfish disregard for his own safety, he turned his back on those aboard the Eureka and plunged 200 ft down again to the leaking bell. He was never seen again.

There was to be a deeply sad and distressing ending to this saga. The young and beautiful Mary Small had been married to Peter for only 12 weeks before his untimely death. She found life without him unbearable, and nine weeks later ended her life in a gas-filled room at home, surrounded by photographs of her husband strewn on the floor.

Bernard Eaton is the Publisher and Editor-in-Chief of ‘Diver’ magazine in the United Kingdom.
Eaton Publications,
55 High Street, Teddington,
Middlesex TW11 8HA, England.
http://archive.rubicon-foundation.o...e/123456789/8128/SPUMS_V33N4_9.pdf?sequence=1

This article is archieved in the Rubicon Foundation database:
The Atlantis affair.

 

[uncfnp]

After I read your first linked article I went searching for more and it was the second linked article that actually made me wonder how much of a role high O2 played in Mr Small’s death since he did regain consciousness and “the committee agreed with Dr Buehlmann’s conclusion that Small’s circulation was seriously impaired through possible prolonged anoxia with loss of consciousness.”
Bold added by me.

Without doubt it seems the loss of consciousness was directly related to the inspired ppo2 at depth and I do take your warning seriously, as I hope others do as well.

 

[uncfnp]

Back to the CESA...

You have peaked my interest in the feasibility of a *safe* CESA at recreational limits for the average diver.

I am seriously interested in putting it to the test with an older, vacation diver in reasonably good health that is very comfortable in the water but in no way a freediver. My next trip to Bonaire would be the best testing ground if I can get my safety diver partner to agree.

 

[John C. Ratliff]

Back to the CESA...

You have peaked my interest in the feasibility of a *safe* CESA at recreational limits for the average diver.

I am seriously interested in putting it to the test with an older, vacation diver in reasonably good health that is very comfortable in the water but in no way a freediver. My next trip to Bonaire would be the best testing ground if I can get my safety diver partner to agree.

I thought you were talking me into doing another test.

I thought Keller's description was very interesting: "...Within 30 seconds of re-entering the chamber, Keller lost consciousness and remained that way for half an hour, suffering from oxygen hallucinations. Small’s pulse rate was low and his breathing shallow. He lost consciousness for 90 minutes, after which he began to speak and appeared reasonably normal...". Imagine suffering oxygen hallucinations for half an hour!

SeaRat

 

[GJC]

So your slinging a pony doing recreational dives. The pony is strictly for OOA emergencies for anyone in our group of divers...The divers are mostly on O2, i'm wearing a computer set to Ean 32.

I'm diving Nitrox....what air should go in the PONY? Why?

I only dive rec and carry a pony for solo. My tanks are almost always filled with 32% and that's what's also in my pony.

My solo course recommended filling the pony with the same nitrox mix you are diving with. That makes sense to me since I would only use the pony in an emergency and during an emergency I don't want any additional nitrogen loading to occur (which would happen if I switched to a tank with 21%).

If I was planning a dive in the 110-130 ft range, I would use a leaner mix and match it in the pony.

If I was planning a wall dive with potential down currents, I would use air and also have it in the pony.

But since I got my pony, I haven't done any diving beyond 110' with a hard bottom and my pony has always been filled and topped off with 32%.

As far as sharing your pony in an emergency with a buddy that may not be diving with nitrox, it's not going to hurt them and may be beneficial for them to get nitrox instead of the air they had in their tank before things went bad. Same thing would happen if I dive with nitrox and had to share my octopus with someone using air.