Coroners Report. What do you think!

[The Chairman]

Ascending from "just" 12 feet still means you lungs will undergo a fairly large volume increase if you inadvertently hold your breath. You're definitely in embolism territory.

There was an instructor candidate in South Florida who argued against this, Ken. This was before the turn of the century, and he went down to the bottom of the pool they were using for their IDC, took a breath, and ascended while holding his breath. He never woke up from his coma. The very first thing you are taught after doing a vertical CESA is to check your student's pupils and make sure they are responsive. Nobody checks yours.

However, not to be picky, all such embolisms are barotraumas, but not all barotraumas are embolisms. It's the same mechanism, so it's a picky, picky point. Mediastinal emphysema comes to mind here.

 

[Celt]

Fine. You win. You're way smarter than I'll ever be. I'll quit instructing, quit diving, and quit this conversation.

I wouldn’t worry about it to much some of the best divers I’ve ever worked with underwater wouldn’t know the medical explanation for an embolism, and neither would I.

 

[The Chairman]

wouldn’t know the medical explanation for an embolism, and neither would I.

An embolism is any obstruction of a blood vessel. It can be either a blood clot or a bubble. If it happens in your butt, you'll probably never know. If it lodges in your brain, it can cause a stroke. Embolisms in divers are caused by

AGE: Arterial Gas Embolism caused by an overly rapid decompression and too much gas in your system. The closer you are to your NDL, the more likely this is to happen. Even more so, if you exceed your NDLs.
POPS: Pulmonary OverPressurization Syndrome caused by occluding your glottis and ascending.
Bubble Pumping: Rapid re-compression which allow venus proto-bubbles to bypass the alveoli and coalesce into real bubbles on the arterial side.​

 

[EFX]

This is simply not true. I teach the CESA horizontally but think doing it vertically is exceptionally nuts given the damage it can and has done to students and instructors. Either you don't understand what I state, or you're intentionally distorting it. There's been enough distortions in our election campaigns: no need to do it here.

I'm confused. From my understanding a CESA is a "Controlled Emergency Swimming Ascent". Swimming to the surface involves kicking. If you're horizontal and kicking I would think you would move horizontally and not be making an ascent to the surface. What am I missing?

 

[The Chairman]

I'm confused. From my understanding a CESA is a "Controlled Emergency Swimming Ascent". Swimming to the surface involves kicking. If you're horizontal and kicking I would think you would move horizontally and not be making an ascent to the surface. What am I missing?

An embolism.

Obviously, if you run out of air IRL, you go to the surface. There are dangers associated with doing this once, much less how many times instructors do it to teach a class. In the pool, you can practice the techniques of doing a CESA horizontally until you get it right.

 

[Ken Kurtis]

I'm confused. From my understanding a CESA is a "Controlled Emergency Swimming Ascent". Swimming to the surface involves kicking. If you're horizontal and kicking I would think you would move horizontally and not be making an ascent to the surface. What am I missing?

Horizontal is a simulated CESA. I suppose it could be renamed CESH.

There is definite danger, and potential life-threatening danger at that, in performing a CESA. You are relying on the student to exhale all the way to the surface AND to exhale at a rate that matches or exceeds the rate of lung over-expansion that they will undergo during the ascent. If they do it wrong (hold their breath or don't exhale enough), it's extremely difficult for an instructor - even when you've got them firmly in your grasp and you're going right up with them - to force them to exhale. Should they embolise on the way up, you are now faced with an immediate life-threatening situation rather than an "Atta-boy!!"

By doing it horizontally, you are eliminating the ascent, which eliminates the lung-expansion, which eliminates the danger of embolism. Another way to look at it would be that instead of considering it an ascent, you're teaching them how to swim and exhale over a certain distance. It has application both horizontally and vertically. But since we know there's embolism danger in a vertical ascent, this eliminates that.

And if you REALLY want to nitpick about mitigating risk, unless you have them swim side-to-side in the pool, do you have them go deep end to shallow or shallow to deep? In going deep to shallow, you're still doing an ascent (over the 75' length of a standard pool) since you're likely going from 8-10' deep to about 3' and then surfacing. Chance of embolism exists. If you go shallow to deep, and instruct them (assuming you're doing this with reg-in-mouth) to follow the bottom and stop when they hit the deep end wall (at which point they can inhale off of their reg), you've totally eliminated the chance of embolism.

 

[johndiver999]

Horizontal is a simulated CESA. I suppose it could be renamed CESH.

There is definite danger, and potential life-threatening danger at that, in performing a CESA. You are relying on the student to exhale all the way to the surface AND to exhale at a rate that matches or exceeds the rate of lung over-expansion that they will undergo during the ascent. If they do it wrong (hold their breath or don't exhale enough), it's extremely difficult for an instructor - even when you've got them firmly in your grasp and you're going right up with them - to force them to exhale. Should they embolise on the way up, you are now faced with an immediate life-threatening situation rather than an "Atta-boy!!"

By doing it horizontally, you are eliminating the ascent, which eliminates the lung-expansion, which eliminates the danger of embolism. Another way to look at it would be that instead of considering it an ascent, you're teaching them how to swim and exhale over a certain distance. It has application both horizontally and vertically. But since we know there's embolism danger in a vertical ascent, this eliminates that.

And if you REALLY want to nitpick about mitigating risk, unless you have them swim side-to-side in the pool, do you have them go deep end to shallow or shallow to deep? In going deep to shallow, you're still doing an ascent (over the 75' length of a standard pool) since you're likely going from 8-10' deep to about 3' and then surfacing. Chance of embolism exists. If you go shallow to deep, and instruct them (assuming you're doing this with reg-in-mouth) to follow the bottom and stop when they hit the deep end wall (at which point they can inhale off of their reg), you've totally eliminated the chance of embolism.

I agree with most everything you said, however I think that (unless someone has some sort of anatomical "problem") it is nearly impossible to exhale too slowly on ascent. As long as you are exhaling, any extra pressure developed from the rapid ascent will just naturally vent from the lungs. If the airway is open, then excess pressure will vent.

 

[Ken Kurtis]

As long as you are exhaling, any extra pressure developed from the rapid ascent will just naturally vent from the lungs.

This didn't sound correct to me so I checked with my friend who runs the Catalina Hyperbaric Chamber. The semi-short version is that when you are exhaling, you're actually still using muscles to restrict airflow. And the increasing pressure of expanding air will not just overcome that. So you CAN exhale at too slow a rate on the way up and still embolise because the air expands (and then over-expands through the alveoli which burst) more rapidly than you're venting off.

If the airway is open, then excess pressure will vent.

The only truly open airway would be that of an unconscious diver being brought up, assuming they haven't gone into laryngospasm and their larynx locked up, and then the expanding air will naturally vent off as you ascend.

 

[Celt]

An embolism is any obstruction of a blood vessel. It can be either a blood clot or a bubble. If it happens in your butt, you'll probably never know. If it lodges in your brain, it can cause a stroke. Embolisms in divers are caused by

AGE: Arterial Gas Embolism caused by an overly rapid decompression and too much gas in your system. The closer you are to your NDL, the more likely this is to happen. Even more so, if you exceed your NDLs.
POPS: Pulmonary OverPressurization Syndrome caused by occluding your glottis and ascending.
Bubble Pumping: Rapid re-compression which allow venus proto-bubbles to bypass the alveoli and coalesce into real bubbles on the arterial side.​

Thank you. I did an emergency assent from 142 feet, not nice and something I definitely wouldn’t practice from any depth. It is and should be a life or death decision.

 

[johndiver999]

This didn't sound correct to me so I checked with my friend who runs the Catalina Hyperbaric Chamber. The semi-short version is that when you are exhaling, you're actually still using muscles to restrict airflow. And the increasing pressure of expanding air will not just overcome that. So you CAN exhale at too slow a rate on the way up and still embolise because the air expands (and then over-expands through the alveoli which burst) more rapidly than you're venting off.

The only truly open airway would be that of an unconscious diver being brought up, assuming they haven't gone into laryngospasm and their larynx locked up, and then the expanding air will naturally vent off as you ascend.

Thanks for looking into it for me. It is my understanding that there are no pain receptors in the alveoli. If so, how does a diver know how much air to vent on ascent (if keeping the airway open and actively venting air) is insufficient to prevent injury during an ascent made at a reasonable rate?