- Messages
- 13,450
- Reaction score
- 10,055
- Location
- Port Orchard, Washington State
- # of dives
- 1000 - 2499
There are no CESA's (required) in any courses after open water. At least for all the major worldwide agencies.
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
You do not need a full breath to start a CESA. In fact, if you look at the US Navy video I posted, you will see that they are taught to exhale before starting the ascent so they don't have too much air in the lungs when they start. Not only do you not need a full breath, you don't want a full breath. That can be done from 300 feet. Look at how much air is being exhaled in those videos.Think I follow all that. I practice my CESA from 30' starting with lungs about half full. I figure if I am able to grab a full breath from my tank, then I probably could start up doing a normal ascent. Is this sound reasoning?
In an earlier post, someone mentioned that you have a minute (really more) of O2 in the body, implying that you have a minute to get to the surface. That is only true if there is no O2 exchange going on in the lungs.
Understood. Do you agree that if you have enough air in your tank for a complete breath but it feels like there might not be much (or any ) more, you should begin with a normal (breathing) ascent and take it from there?You do not need a full breath to start a CESA. In fact, if you look at the US Navy video I posted, you will see that they are taught to exhale before starting the ascent so they don't have too much air in the lungs when they start. Not only do you not need a full breath, you don't want a full breath. That can be done from 300 feet. Look at how much air is being exhaled in those videos.
Now, those are videos of buoyant ascents, so they are ascending faster than you would on a CESA, when you are supposed to ascend at a "normal" ascent rate, even dumping air from the BCD as you become buoyant.. That rate of ascent is really the only difference between a CESA and a buoyant ascent. What does "normal" mean? When PADI first used that language, decades ago, pretty much everyone was ascending at 60 FPM as the "normal" rate. When I took my instructor exam, the examiner said it was perfectly fine to allow students to ascend faster than that, which is likely what would happen in a real OOA event.
PADI training as to when you should use a buoyant ascent rather than a CESA is vague--it really comes to your judgment as to what you need to do to get to the surface. A lot of people will use 30 feet or 60 feet as a hard line below which they will use a buoyant ascent. The reason for using the CESA rather than the buoyant ascent is to minimize the dangers of a fast ascent, but reaching the surface is always the primary goal, and if you are not sure you can do that at a "normal" rate, then go buoyant at any depth.
In an earlier post, someone mentioned that you have a minute (really more) of O2 in the body, implying that you have a minute to get to the surface. That is only true if there is no O2 exchange going on in the lungs. The fact that air is gushing out of the lungs as you ascend means that you have air (and therefore O2) in the lungs, so a normal O2 echange is happening. You have plenty of O2 (and therefore time) to make it to the surface from any depth.
Yes.Understood. Do you agree that if you have enough air in your tank for a complete breath but it feels like there might not be much (or any ) more, you should begin with a normal (breathing) ascent and take it from there?
As was explained to me by an emergency room physician and diver named Lynne Flaherty, you have a minute to a minute and a half of O2 in your tissues, with no oxygen exchange in the lungs adding to it. If you are doing a breath hold dive, there is continual oxygen exchange with whatever you inhaled before the dive, which is why you can hold our breath for more than a minute or two. As you noted, at 130 feet, you are starting with 5 times as much oxygen as you would have on a breath hold dive.That was said by my swimming coach way back when, explaining the "15 metre rule". I've no idea if it included air in the lungs or not. But even if it did, at 130' you'll have 5 times more of it so you'll certainly much more than a minute of O2.
As you noted, at 130 feet, you are starting with 5 times as much oxygen as you would have on a breath hold dive.
And a hat-tip to @TSandM. She is still missed.
...and that is why I would personally choose to do a normal ascent, a CESA, or a buoyant ascent rather then try buddy breathing in a real OOA emergency. The only exception on an NDL dive would be if the other diver was someone with whom I had practiced buddy breathing, and since I don't practice buddy breathing, that is not a likely scenario. (I can imagine a tech scenario where I would have to do it because none of the other options were available; in a recent fatality in a cave, it is possible that the two sidemount divers shared their last functioning regulator, but we will never know.)When I couldn’t get the reg back I had to make an emergency assent with him