A.G.E. Questions and answers

[Cave Diver]

I'm posting this in response to some questions that have been raised in a few threads.
Mods, please feel free to move or edit this for content as necessary.

Most divers are taught the first rule of SCUBA in their openwater class; Never hold your breath.

The reason for this is the potential for lung over expansion injury and a serious condition called Arterial Gas Embolism, or AGE.

***Note: The term "gas" is used in the following description because many divers use breathing mixes other than air such as Nitrox or Trimix. ***

AGE is one of the most serious potential injuries divers face. It's caused when excess gas is unable to vent from the lungs on ascent, causing the lungs to overexpand.

Lung overexpansion can cause ruptures in the air sacs and blood vessels in the lungs, forcing gas into the blood stream where it is pumped through the heart and into arteries.

If a bubble is too large to go through an artery, it will form a blockage, causing any tissue beyond that point to become oxygen starved. The actual consequence of such a blockage depends on the area of the body that is being deprived of oxygen.

If the brain is affected by the blockage, the effects can be devastating.

Symptoms are usually seen immediately after surfacing and can include paralysis, unconciousness, convulsions, visual disturbances, dizziness, speech difficulties and even death unless the victim can be recompressed immediately, reducing the size of the offending bubble so that blood flow can return to normal.

Anyone have anything to add?

 

[scubapolly]

Great post John!

It is important to note that when dealing with the brain the symptoms can vary greatly depending on the portion of the brain that is effected, and the size of the artery that becomes blocked. This is also going to play a role in the outcome as well.

Immediate treatment for a suspected AGE is Oxygen, and the victim needs to be taken to a chamber as soon as possible.

 

[Cacia]

I would like to hear the physiology of large gas emboli, in the arterial circulation, and the various paths the gas takes before becoming lodged somewhere. (spinal cord blood supply, brain, etc). Lamont spoke of venous bubbles getting recompressed and re-appearing on the arterial side....

 

[Kevrumbo]

I would like to hear the physiology of large gas emboli, in the arterial circulation, and the various paths the gas takes before becoming lodged somewhere. (spinal cord blood supply, brain, etc). Lamont spoke of venous bubbles getting recompressed and re-appearing on the arterial side....

. . .that would be via a Patent Foramen Ovale (PFO):
http://www.diversalertnetwork.org/news/article.asp?newsid=462

 

[Cacia]

I know what that is....most babies have it and it closes at birth. My handle on hemodynamics is really pretty okay. (Intraaortic balloon pump, etc)

I want to know when a diver takes a gas bubble hit in the arterial bed, and it did not come from an overexpansion injury....where is the orgin most likely?

Don't microbubbles collect to make bigger, more dangerous bubbles? Where are they most likely to lodge? What variables affect where they lodge?

Lamont was describing what happens when you bounce or freedive with a nitrogen load, I THOUGHT.

 

[Diver Dennis]

That is exactly what I would like to find out too Catherine.

 

[Jcsgt]

I would also like to know if having previous surgery of the brain or head injury can make one more susceptible.

 

[Cacia]

one more try...I cannot word it well.


If you have large gas bubbles in the arterial circulation, and there was not an overexpansion injury, but an aggregation of smaller bubbles, collecting into a larger bubble, from good ol' decompression....where are they most likely to appear, and then, where do they usually lodge first, based on the anatomy and pressures found in the circulatory tree?...whew, my vocabulary sucks.

"aggregation" may not be the best word. Some medical type would know.

Guess I could whip out a book.

 

[Cave Diver]

Lamont was describing what happens when you bounce or freedive with a nitrogen load, I THOUGHT.

When you bounce or do a free dive, you can temporarily reduce the size of a bubble and it may have time to pass through the heart to the other side (forget the technical name) where when it expands it can cause problems.

I've also been taught by several instructors, that at the end of the dive to hang out and float on the surface for at least two minutes before climbing onto the boat or shore. This allows time for your blood to circulate one complete time and reduce the risk of any of those bubbles growing or causing problems because of the extra exertion.

 

[Kevrumbo]

I know what that is....most babies have it and it closes at birth. My handle on hemodynamics is really pretty okay. (Intraaortic balloon pump, etc)

I want to know when a diver takes a gas bubble hit in the arterial bed, and it did not come from an overexpansion injury....where is the orgin most likely?

Don't microbubbles collect to make bigger, more dangerous bubbles? Where are they most likely to lodge? What variables affect where they lodge?

Lamont was describing what happens when you bounce or freedive with a nitrogen load, I THOUGHT.

Other possible causes other than frankly "holding one's breath during ascent", or a forceful Valsalva during ascent:

Trauma Causing IGE/AGE
1. Penetrating injury to the heart or major vessels.
2. Blunt injury to the chest with closed epiglottis

Iatrogenic Injury Causing IGE/AGE
1. Pulmonary over pressurization by positive ventilation of a patient or diving barotrauma victim.