CESA limits

[mannydib]

if i can free-dive to 50' should i really be doing a CESA from 100' ?
i know padi teaches CESA for depths of 40' or less.
i would think there might be a risk of DCS especially after a good amount of on-gassing and then theres always the risk of AGE if you panic and dont let go of your breath.
i have heard first hand of at least 3 cases where a quick ascent was done from 80' - 90' after significant on-gassing without dcs but others have told me there have been cases of dcs from that profile.

my questions to the group are:
at what depth do you start carrying a redundant gas supply.
what do you think the likely-hood of dcs or age is with CESAs between 60' - 100'.

 

[captain]

Would you rather drown or suffer a case of DCS. Seems like a no brainer.
I'll get to the surface and worry about the DCS later

 

[Rick Murchison]

Would you rather drown or suffer a case of DCS. Seems like a no brainer.
I'll get to the surface and worry about the DCS later

Indeed...
The key word in CESA is "Emergency" - saving your life, not DCS, is the concern.
If you are at a depth which you feel is deeper than the depth for your ability to perform a CESA, you should have a redundant source of gas available. This might be in the form of a pony, an "H" valve with two regulators, doubles or at the very least a dependable buddy close at hand.
AGE isn't a problem during a properly performed CESA. And since the delta(P)/P is greater closer to the surface, the likelihood of AGE from an improperly performed CESA is probably higher from 30' than from 100, as you'd more likely remember to exhale before damage from 100 than from 30.
Rick

 

[SDAnderson]

my questions to the group are:
at what depth do you start carrying a redundant gas supply.

Solo or not, I always have a redundant air supply. Without a buddy (the backup gas for recreational divers) I bring my own along.​

what do you think the likely-hood of dcs or age is with CESAs between 60' - 100'.

Too high to risk it, especially since there are options available that aren't onerous to make an emergency ascent, controlled or otherwise, necessary.​

 

[Nemrod]

This thread may be an outgrowth of the "old rule" I mentioned in another thread about never diving solo beyond twice your free diving depth without solid redundancy. The idea is emergency only and more than that rules are made to be modified--lol. I would have to say as you appproach depths like 100 or more feet then you are getting into a range where redundancy is needed other than a CESA. I should think still that if a person where working off the Navy tables with a 10% margin and had a total failure and required an CESA (padi term right?) then it should be successful with no bends--no need to hurry to the surface, keep the head back and ascend at as close to 60 feet a minute as possible. This statement assumes that your free dive limit is approx 50 feet thus using the "old rule" 100 feet is your no redundancy limit. As an aging fellow myself you may wish to to take that into consideration as well, 100 feet is getting deep for us old guys--lol!!!!! The problem with rules is when you try to applyn them uniformly to every circumstance, at 100 feet I would suggrest redundancy even if you can free dive that depth if you are out of shape, getting older, or diving with a deco computer that seem to allow longer bottom times I suppose with the assumption you don't have to immdediantly make a direct ascent to the surface! . N

 

[Scuba]

at what depth do you start carrying a redundant gas supply.

I would say beyond the point where one can consistently and comfortably make a CESA, or to play it safer all the time. Be it pony, doubles or buddy.

The general "old rule" Nemrod mentioned may make sense but requires further analysis before application. Is your 50 ft free dive depth the limit, something you do with ease, or somewhere in between? Consider you start a free dive with a full lung, and may begin a CESA with an empty one. Gas will expand on ascent, and you should be able to get at least a partial breath on the way up. These are positives, the negatives are the stress from emergency situations which may hinder proper response. Unpredictable and unlikely obstacles not accounted for in planning are always possible.

The increasing nitrogen load accumulated with time at depth will increase the chances of DCS from rapid ascent even within so called NDL dives.

The main benefit of an adequate redundant system is to provide continuance and/or extrication in a normal or close to normal operating mode - not in emergency mode. Emergency exits do not leave much room for error.