A question about diving and going up

[gabbydiver]

Hello all!
Say I am after a wonderful diving liveaborad(4 days and each day is about 4 dives).After I finish I am driving with a car to a height of 1000 meters.I understand it is dangerous,why is it? and can you refer me to any relevent matiral on this subject?

Many thanks in advance.

 

[John A]

Going from multiple dives over a period of days to an altitude of close to a mile would be troublesome, because the sounding pressure is decreasing as you ascend, just like ascending from diving (only not to the same extent, less pressure gradient in air). Any diving manual will explain this in detail.
But from reading your post, there seems that there will be a time lag between your last dive and the time the boat gets to the dock, off load the gear, ect…, also I doubt the road goes straight up and you will be diving an Enzo? So, you have time to off gas and a slow accent, in my opinion your chances of any off gas problems are probably non-existent.

 

[UKDiver]

Why is it dangerous ?

Couldn't find any articles for you I'm afraid, but basically as you ascend the ambient pressure drops below 1bar (1 atmosphere) so you need to off gas more for the tissues to reach equilibrium.

 

[Alison]

I think as John says, if your driving, the acent will be slow slow its going to have the same effect as decomp stops. If a problem is going to arrise it would be on an aircraft, where the cabin is pressurized to ~ 2000 metres and you reach that pressure in about 5 - 10 mins, which depending on your recent dive history, that may or may not be enough time. Certainly a risk I would never take but I wouldnt worry over the car journey

 

[UKDiver]

Good point Alison, didn't mean to scaremonger with my previous post.

Was just pointing out, the "why" bit

 

[Alison]

Sorry I didnt mean to imply that, you are totaly right in what you said and wouldnt argue with you in any way. I was just trying to give a bit of input from 24 years of daily flying, wich was the reason I took to freediving (or probably more accurately snorkelling)

 

[londonsean69]

Isn't it possible (although I know it would be hard) to get a bend freediving? Well, not necessarily a bend, but get onto the tables a bit.

I understand that you would obviously only ongas a little at such a depth on the minimal amount of nitrogen in your lungs, but if you were say spearfishing all afternoon at 20-30m, wouldn't there be quite a lot of residual nitrogen. Also (pardon my ignorance) but how do people ascend when freediving, fast/slow??

I have in my imagination the following sequence (please forgive me for the waffle but I am at work and bored);
-Big breath in (N2 in)
-freedive to 25m (N2 starts being absorbed by blood)
-swim around a bit (2-3mins of N2 being absorbed)
-come up pretty quick (N2 tries to diffuse back into lungs but some stays in blood)

repeat all afternoon.

What is a typical freediving session, ie bottom times, surface times, depths etc. and how long would that session last eg all afternoon??

Sorry if I got a bit off topic but this will provide an answer that myself and another instructor (both non-freediving) have discussed

 

[UKDiver]

In short yes it is a concern for freedivers, have a look at this thread.

 

[londonsean69]

Thanks for the thread, thats is basically what I thought, just wanted someone else to confirm my thinking.

By the way, repetitive freedives to 300ft+, thats some crazy talk:duh I know she is/used to be world champion but that seems to me like going deep just to go deep. I think the spearfishermen/women deserve the greatest of respect.

 

[Alison]

It all holds for freediving the same as scuba, no matter where you breath in, at x depth the partial pressure of N2 will be the same, it is possible and sometimes even likely that freedivers will get bent to some degree or other.
Brilliant subject this, there has been a fair bit of talk about this on DB in the past, have a trawl through the freediving section, theres some good stuff

 

[mps798]

what i have to add is that in dive accidents helicopters carring diver are ment to fly max 300 m over sea level (just because bubbles in the sea , the same in the air , also the same in the blood ) the higher they go the bigger they become and stops blood circulation (nitrogen - in - blood )