Embolism bubbles

I be been leafing through the navy diving manual & have found standard treatment for AGE is o2 initially (to reduce bubble size) & chamber ( to reduce size further) . I have 3 questions about Air bubbles if you folks would be so kind :



1 Can an air bubble at chamber pressures be dissolved into the blood , like how nitrogen is absorbed into blood



2 or Does the treatment depend on making the air bubbles small enough so they dislodge from whatever they are blocking & travel back to the lungs to be exhaled.



3 Failing this,can an air bubble be absorbed by tissues directly over time of days or weeks, or will a lodged bubble remain unabsorbed forever? Thx

B

Firstly, some general comments. The chamber treatment works on the following principles:
- Forcing gas from bubbles back into solution;
- Reducing the size of the bubbles so they may more easily circulate through the bloodstream and be eliminated in the lungs (whether after coming into solution again or not);

The person in the chamber is also made to breath pure O2 (for most of the time, controlling O2 toxicity) to maximize both the amount of oxygen available to the organism and the net flow of inert gas out of the body.

So, to answer your questions more directly:

1. Yes, the bubbles can be absorbed. They are made up from gases that were once in solution, and they can return to that state, provided that the relation between external pressure and content of dissolved gas in the blood is favorable.

2. Getting the bubbles to the lungs and getting the gas from the bubbles dissolved back into the blood - and then to the lungs and out of the body.

3. Inert gas is absorbed by other tissues, but this is a constant flux, from the lungs to the blood to other tissues, from these tissues back to the blood, to the lungs and out. The is no permanent pooling of inert gas anywhere.

To further help you understand as well. Those bubbles are generally nitrogen.
The nitrogen you absorbed in your tissues during your dive expands on ascent. Too fast an ascent and you're a soda pop.

Get that soda pop in your blood stream and you get an embolism.

Bubbles have what is called a "critical radius", below which they will collapse, and above which they will expand. The goal of hyperbaric treatment with regards to bubbles, is to compress them to a size below that critical radius, so that they will collapse, and the gas contained in them will return to solution. (Gas in bubbles is not gas in solution.). So the answer to BOTH of your first questions is yes; bubbles are compressed and get smaller and may stop causing embolic symptoms, and the gas in them may return to solution as a result of treatment.

And yes, bubbles will eventually resolve, even without treatment at all. The problem is that the damage they cause by interrupting circulation may become permanent in the interim.

g1138:

To further help you understand as well. Those bubbles are generally nitrogen.

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Since the query was about embolism, wouldn't the bubble in that case be air and not nitrogen?

Ricky B:

Since the query was about embolism, wouldn't the bubble in that case be air and not nitrogen?

Click to expand...

The gas in bubble for AGE is predominantly nitrogen. The composition of air is 79% nitrogen, 20% oxygen, and 1% other gasses. Under pressure you have nitrogen dissolving into the blood. The amount of nitrogen dissolving also is time dependent, the longer you are at depth the more your nitrogen load. The ambient pressure not only drive the gas to dissolve into you blood but keeps,the bubbles from forming. But, as you ascend from your dive the ambient pressure drops which allows the dissolved nitrogen to start forming bubbles.

You limit the risk by limiting depth (pressure), time (limits amount gas to dissolve) and slow ascent rate (allows gas to come out solution without forming bubbles). It is also why you spend time in between dives to "off gas."

Plus O2 can be absorbed readily by your red blood cells and tissues.
Nitrogen is inert in your body, O2 is not.

Worth pointing out that embolists get treated as foreign bodies and the thought is/was that the nittrogen bubble can "helpfully" be covered to the point that the internal space is not longer nitrogen but the shape is still there.

Where that line of research currently stands though..

Here is why I suggested that the gas in an AGE would be air, not nitrogen.

Diving Science is a book written by Michael Strauss, MD, and Igor Aksenov, MD, PhD. Both authors have excellent credentials in the field of hyperbaric medicine. On page 24, Diving Science says (emphasis mine):

... arterial gas embolism, which is a medical condition in which air bubbles introduced into arteries block their circulation (see chapter 15).

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In chapter 15, under the heading of Arterial Gas Embolism, on page 294, Diving Science says:

Arterial gas embolism results when air-carrying structures (alveoli and bronchial tubes) rupture explosively from sudden overexpansion. ... Free air then enters the lung circulation and is carried to the left side of the heart, where it is pumped into the arterial circulation. Once free air enters the bloodstream, the results can be catastrophic, as noted in figure 15.3. The air forms boluses or emboli. The emboli are too large to pass through small blood vessels and thus act as obstructions just as a cork would in a pipe that progressively narrows.

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Having read the book, I am confident that these guys know the difference between air and nitrogen.

This is not to say that nitrogen can't in some cases cause AGE, but my understanding is that the main cause is an overexpansion injury that results in air entering the blood stream, not nitrogen coming out of solution.