Chamber dive today

[Hoag]

@Marie13, sounds like you had a fun day. Over the years, I have done a number of chamber rides for work, but we always went the other direction. We would start off at the local altitude & and breathe 100% O2 for 30 minutes to reduce our N2 levels as much as possible, then "climb" on a specific profile to a specific altitude. In some cases, we went up to (simulated) 30,000 feet and took our masks off and had to do a test to show us the effects of Hypoxia. (In many people it is similar to the effects of Nitrogen Narcosis, but the truth is that it manifests itself differently in every person.) In other cases, it was an almost instantaneous (less than 1/2 second) "climb" from surface to (simulated) 25,000 feet to simulate explosive decompression. Maybe I am a bit twisted, but I always looked forward to the chamber training and had a fun afternoon. (Spatial disorientation training on the other hand ... not so much fun.)

 

[Marie13]

We only breathed regular air. No O2.

 

[TMHeimer]

My wife asked if unnecessary chamber rides are prudent? A valid question since we always read that you can get the bends on very rare occasions even if you are well within your table/DC limits.

 

[Marie13]

My wife asked if unnecessary chamber rides are prudent? A valid question since we always read that you can get the bends on very rare occasions even if you are well within your table/DC limits.

Over 1000 divers have done this chamber dive since 1994, and there has only been one DCS hit. There are risks, but this has a very good safety record.

I consider it invaluable to get some idea of what being narced is like in a controlled environment.

 

[Killerflyingbugs]

In my experience you get more narked in the chamber than in water. The first chamber drop I did was to 130 and my voice cracked me up so much. The next one was to 190 for a HeO2 test, we rode to depth on air and were LIT! Constant uncontrolled laughter but it went away after the switch to helium.

 

[Hoag]

The biggest risk as far as getting bent in a chamber ride is probably not from a dive profile, but from an aircrew profile. As I said in a previous post, one of the chamber profiles I did was to go from surface to a simulated pressure of 25,000 feet in 1/2 second. This "explosive decompression" is so dramatic that it causes a loud bang, all the water vapor in the air instantly condenses into fog and the pressure changes from 14.7psi to 5.5 psi all in 1/2 second.

That type of profile has the potential to cause DCS and barotrauma. To mitigate this, two steps are typically done. The first is that you go on 100% O2 for about 30 minutes. This will greatly reduce the risk of DCS. While you are one 100% O2, they will do a gentle profile up to about 15000-20000 feet to ensure that nobody has any sinus issues at all. They they bring the chamber back to sea level and start chatting. When enough people are distracted, BANG! and the explosive decompression run is all over except to repressurize and bring the chamber back to local pressure and see how everybody is.

Everytime I have done this profile, there was an "AMT" an Aeromedical Tech in the chamber with us.

 

[Magnus Lundstedt]

My wife asked if unnecessary chamber rides are prudent? A valid question since we always read that you can get the bends on very rare occasions even if you are well within your table/DC limits.

If you get bent, no better place to be.. ;-)

 

[Kevrumbo]

Over 1000 divers have done this chamer dive since 1994, and there has only been one DCS hit. There are risks, but this has a very good safety record.

I consider it invaluable to get some idea of what being narced is like in a controlled environment.

In my experience you get more narked in the chamber than in water. The first chamber drop I did was to 130 and my voice cracked me up so much. The next one was to 190 for a HeO2 test, we rode to depth on air and were LIT! Constant uncontrolled laughter but it went away after the switch to helium.

It gets pretty silly at 50m/165ft (scroll through 53min video below):

Every year the Fire Suppression system of the USC Catalina Hyperbaric Chamber is tested under pressure. Anything that we do not want to get wet is either removed or sealed in plastic. The Chamber Crew, wearing wetsuits enter and the Chamber is compressed to 165 fsw (6 ATA, 50 msw). At depth the deluge system and the fire hoses are tested. When the ascent from 165 fsw to the first decompression stop at 30 fsw begins the fog starts to roll in as the moisture condenses out of the air. The Total Decompression Time following the dive to 165 fsw for a 12 minute Bottom Time (time from start of descent to beginning of ascent) is about 33 minutes.

USC Dornsife Scientific Diving: The Catalina Hyperbaric Chamber

 

[TMHeimer]

One case of bends in 1,000 in the chamber is very low, but I believe so are the overall stats of divers getting bent on dives.
The idea of checking out being Narced in a controlled environment does make sense. And yes, the chamber is the best place to be if narced. Don't think I'd take the ride though. I have absolutely no fear of flying either, but I only get on a plane to get somewhere--no sense being that one in a million on a crash. But hey, just talkin'--even with possible human error I guess taking the chamber ride has it's advantages.

 

[Marie13]

I'd have to say that the most fascinating part of the presentation were the two case histories from the early 90s that the RT who runs the chamber mentioned. I actually took pics of the slides.

1st case history:

More details: woman had done multiple dives to 75 ft without proper surface intervals. She flew back to Chicago from Mexico about 11 hours after last dive. Her symptoms presented on the plane back. She notified the flight attendant and was put on O2. Pilot was notified who notified emergency personnel at O'Hare. She was transported to the ER at this hospital as soon as the flight landed. The hospital is maybe 10 minutes from ORD.

2nd case history:

More details: woman was in the midst of her OW class at the local YMCA. She and husband were practicing buddy breathing in 5 ft of water. She had a full breath, but when it was her turn, husband refused to give her the reg. She panicked, stood up quickly, and ended up with an AE.