Rate of Descent

[windapp]

So, today I had an aborted dive, and I finally figured out why it happened.

I have been doing horizontal, and head first descents recently It has been working for me. Today, I did the same thing but to a deepr depth than I had done this before. When I got to the bottom (28 m), I felt like I couldn't get enough oxygen. Even after relaxing for a minute, the feeling would not go away. I felt myself start to panic so I decided to abort the dive. My buddy paired with another diver, and a rescue diver went up with me. She took control of my inflator hose. I didn't want to give her control of my inflator but I realized I had no way to communicate with her that even though something was wrong,I still had the were-with-all to ascend on my own. At 18 m, I started to feel better but we had not ascended on the buoy line so there was no way to rejoin the group from there. I assumed that I had been narced. I think I did the right thing to abort the dive since I couldn't figure out how to make the situation better, and I was afraid that I might have a full blown panic attack if I waited, which at 28 m would not have been good.

Anyway, after thinking about the incident I realized what really happened. I decended so fast that I spent almost the entire descent equalizing my ears. That equated to one very long breath hold. Yes I was breathing but not enough to clear the carbon dioxide out of my system.

So, the lesson learned was that even though I could equalize going down the fast, I was doing so at the expense of proper breathing. That cost me the dive.

 

[DevonDiver]

Could be a tinge of narcosis... I've noticed that rapid descents, esp head-down, bring about onset sometimes (for me).

 

[TSandM]

Well, nitrogen and carbon dioxide don't make a good combination. Glad everything turned out okay for you.

 

[DivemasterDennis]

Learn from every dive- and you did. And I think your analysis was good, too. You will learn more in each of your first 25 dives, and from your 500th dive. Descent rates and positions can require variance with conditions, equipment changes, and even just how you are feeling. A controlled decent is important in every dive. My wife and I like a head first decent, but sometimes it doesn't work. And remember to breathe constantly, even clearing, on descents and ascents and everything and all the time in between.
DivemasterDennis

 

[beanojones]

Could be a tinge of narcosis... I've noticed that rapid descents, esp head-down, bring about onset sometimes (for me).

When diving air, where do you feel narcosis? I had a diver tell me that anything over 22m and they feel uncomfortable, which was a surprise to me, because she has done a lot of diving at a 33m 'wreck', a place where she has done 20-30 dives.

It made me realize that I may have just long ago acclimatized myself to 30-40m diving by hitting those depths daily when boat guiding, and when solo diving. I either am completely compensating, to the point I no longer know I am compensating, or I have lost enough brain cells that I am no longer smart enough to know I am slow at depth.

 

[Ozwald]

The only advice I would give would be to brush up on your hand signals. Not being able to communicate could very well have led to a less than desirable outcome. Glad you are okay.

 

[spectrum]

Was this in local water?

 

[PfcAJ]

This may or may not have been a factor, but sometimes wetsuits can 'squeeze' similar to how a drysuit can if you don't get water into it/ get the small amount of residual air out of it.

 

[boulderjohn]

I think your own analysis was essentially correct.

The body really doesn't have any signal that it need oxygen. When you feel that you need oxygen, what you are really feeling is too much carbon dioxide. That is usually caused--as you suggested--by poor breathing skills. Even without equalization problems, new divers often have a problem caused by breathing quickly off the tops of their lungs. Long, slow exhalations to get rid of the "bad air" goes a long way to making one feel cool and comfortable during a dive.

 

[Tigerman]

So, today I had an aborted dive, and I finally figured out why it happened.

I have been doing horizontal, and head first descents recently It has been working for me. Today, I did the same thing but to a deepr depth than I had done this before. When I got to the bottom (28 m), I felt like I couldn't get enough oxygen. Even after relaxing for a minute, the feeling would not go away. I felt myself start to panic so I decided to abort the dive. My buddy paired with another diver, and a rescue diver went up with me. She took control of my inflator hose. I didn't want to give her control of my inflator but I realized I had no way to communicate with her that even though something was wrong,I still had the were-with-all to ascend on my own. At 18 m, I started to feel better but we had not ascended on the buoy line so there was no way to rejoin the group from there. I assumed that I had been narced. I think I did the right thing to abort the dive since I couldn't figure out how to make the situation better, and I was afraid that I might have a full blown panic attack if I waited, which at 28 m would not have been good.

Anyway, after thinking about the incident I realized what really happened. I decended so fast that I spent almost the entire descent equalizing my ears. That equated to one very long breath hold. Yes I was breathing but not enough to clear the carbon dioxide out of my system.

So, the lesson learned was that even though I could equalize going down the fast, I was doing so at the expense of proper breathing. That cost me the dive.

When diving air, where do you feel narcosis? I had a diver tell me that anything over 22m and they feel uncomfortable, which was a surprise to me, because she has done a lot of diving at a 33m 'wreck', a place where she has done 20-30 dives.

It made me realize that I may have just long ago acclimatized myself to 30-40m diving by hitting those depths daily when boat guiding, and when solo diving. I either am completely compensating, to the point I no longer know I am compensating, or I have lost enough brain cells that I am no longer smart enough to know I am slow at depth.

The bottomn line is that wether you notice it or not, you ARE impaired at 30m. How it manifest itself is an entirely different matter.
I guess we all know the guy that can drink 10 pints and look like he had one, but that does not make him sober.

Quite possibly both narc and co2 buildup involved in this case, question is which one got hold of you, or if it was the combination.
The combination of the two from my experience seem to be quite a good candidate.


I have a dive that was aborted due to equalization myself, but I never got down to depth. Turned off the AC in my room that afternoon