How deep is dangerous?

[24940]

this may sound like a stupid question, but what about holding breath while in a stable fixed position ... hiding behind a rock for a photo for example

What do you think?

As long as both you and the water column above are static, what could go wrong? The point of "NEVER HOLD YOUR BREATH" is similar to how we teach lil children street safety: "NEVER GO NEAR THE STREET!". No instructor is going to tell you when it's OK to hold your breath, but there are time when it is not only OK, but necessary.

In the example you give, you don't mention surface conditions. Can you see how they would be an issue?

One thing worth mentioning is lungs don't have to be full to over expand. You can hold your breath with any volume of air and it would be like squeezing a partially filled balloon in your hand: compression, then a lil blip out the side of your hand.

 

[ianr33]

Nobody has answered the original question from a DCS (bends) point of view .

So,if a BC inflator sticks on and you rocket to the surface (but DO NOT hold your breath) how much nitrogen loading is dangerous?

My guess,and it is just a WAG,is that anything over half way to NDL at a particular depth is asking for trouble. e.g shooting to the surface after 10 minutes at 100 feet is probably going to end badly.

 

[24940]

My guess,and it is just a WAG,is that anything over half way to NDL at a particular depth is asking for trouble. e.g shooting to the surface after 10 minutes at 100 feet is probably going to end badly.

Depends on physiology actual ascent rate and a whole lot more, I guess.

I did a free ascent from 115', day 2, dive 5, :08 BT. I was 18 or 19 and thought barotrauma was the only concern. We used to practice free ascents all the time from 80'. We'd end dives with free ascents. AOW required a 60' free ascent. Just blow and go.....

I have never missed a dive as a result of an injury, but I (and many others) were very lucky.

 

[Diver Dennis]

this may sound like a stupid question, but what about holding breath while in a stable fixed position ... hiding behind a rock for a photo for example

Breath holding is fine but you can practice holding your breath and still keep your airway open in case something unexpected happens. I do it all the time taking photos. The problem is getting in the habit of closing your airway while breath holding. It's not dangerous in the situation you describe but there is a better way.

 

[RJP]

Nobody has answered the original question from a DCS (bends) point of view .

So,if a BC inflator sticks on and you rocket to the surface (but DO NOT hold your breath) how much nitrogen loading is dangerous?

My guess,and it is just a WAG,is that anything over half way to NDL at a particular depth is asking for trouble. e.g shooting to the surface after 10 minutes at 100 feet is probably going to end badly.

Of course the real answer is "there's no way to know for sure" but based on the theory behind use of dive tables and diving within recreational "no-stop" dive limits you should be able to safely ascend to the surface at any point during a no-deco dive.

Of course individual variables related to physiology and the specific dive might "over-rule" the tables at any time.

:11doh:

 

[ianr33]

Of course the real answer is "there's no way to know for sure" but based on the theory behind use of dive tables and diving within recreational "no-stop" dive limits you should be able to safely ascend to the surface at any point during a no-deco dive.

:11doh:

Well,yes,but that is at a rate of 30 feet/min.

A runaway ascent can be much faster,maybe 100 feet/minute? More??

And what about the infamous "mandatory safety stop" ?

 

[DevonDiver]

I have a medical report on my pc that illustrates the case of a young Austrian diver who suffered a double pneumothorax (burst lung) while ascending from 1m deep and holding his breathe.

So, in the case of breath holding (can happen if you are task loaded and ascending rapidly in shallow water)....any depth below 75cm can kill you.

Of course, if you were holding your breath in a static position and a 1m swell passed overhead........

In terms of the bends... I've heard cases (from our local chamber) of people getting bent on dive 2 of their OW courses. Normally, it is because of a fast ascent, coupled with several pre-disposing factors (alcohol, fatigue and dehydration). So - in a worst case scenario.. a fast ascent from 10m could give you bubbles.

 

[DevonDiver]

Breath holding is fine but you can practice holding your breath and still keep your airway open in case something unexpected happens. I do it all the time taking photos. The problem is getting in the habit of closing your airway while breath holding. It's not dangerous in the situation you describe but there is a better way.

IDIOT



This rates as the stupidist, most complacent, most ignorant statement I've yet to read on this board....

Holding your breath means that you are 'locking' your Diaphragm. An 'open airway' is when your Glottis is open to your lungs and closed to your stomach. If your Glottis is closed, then your lungs are sealed. The Glottis is naturally closed when you are not in the process of respiring and cannot be manually 'held open' unless you are actually breathing in or out. Thus...if you hold your breath, your airway is CLOSED. Given that the pressures required to rupture the lungs are tiny - whereas the Diaphragm is a very powerful muscle and the Glottis is naturally closed when not respiring (and you have no in-built pressure sensors in your lungs) you WILL be risking a lung-overexpansion injury when you hold your breath.

 

[Charlie99]

The Glottis is naturally closed when you are not in the process of respiring and cannot be manually 'held open' unless you are actually breathing in or out.

Ummmmm. YOU may not be able to control your glottis, but most people can easily learn to do so.

I have no trouble consciously controlling my glottis. I have no difficulty in maintaining an open airway, even while pausing my breathing by use of chest muscles and the diaphram.

I make it a habit to never close my glottis underwater except momentarily when swallowing or coughing.

IMO, OW instructors are doing their students a disservice if they do not fully explain the difference between pausing breathing using muscles and closing of the airway.

 

[lamont]

Can anyone tell me, what is the maximum depth before an uncontrolled ascent becomes dangerous ? Last August, I had been using my own BCD with no problems but on the last day of holiday diving, I stupidly used a BCD from the back of a dive schools supply. I confess that I did not test the deflate properly. Yep ..... you've guessed it, it wouldn't. I was only about 14m and slowly rising, trying to let air out of the BCD but it would not deflate. I tried everything I could think of as well as splaying out for drag and exhaling as much as poss before taking in a short breath and exhaling. I could not stop the uncontrolled ascent. unfortunately, I was in mid water and there was nothing to hang onto. Anyway, on surfacing, I waited, checking out if I felt anything different, I didn't. I klept aware of my body for the next 36 hours but I was fine. So .... this is making me think that maybe there is a depth at which these problems begin. Is this true ? . not that I would push my luck ever, but it would be good to know the facts. Can anyone help ?

If you were only "slowly rising", why not kick down, compress the gas in the BC and find a depth where you were neutral? You've got big fins on your feet right?