Thinking about DCS

Think of decompression illness as an immune phenomenon, says Cmdr., W. A . (Bill) Bateman, MD, head of the Aerospace Life Support at the Defense and Civil Institute of Environmental Medicine (DCIEM) in Canada. At a talk last year in front of members of the Underwater Hyperbaric Medical Society, he had these provocative comments to make:

“ Twenty years ago, we thought that if bubbles evolve when you reduce pressure, they cause disease. However, we now think that ‘Mr. Bubble’ is not all of the cause.”

Five key advances in the past 20 years that have been o b s e rved and changed our way of thinking are as follows:

1.) Immune responses probably complicate bubble formation and their effects. Bubbles in blood are not the same as bubbles in a beer bottle. Platelets are affected and interact with the bubble. Bubbles reflect stress but the immune response equals strain on the system.

2.) The shunting of bubbles from the right side of the heart to the left as in a patent foramen ovale (PFO) may be critical in some cases.

3.) Relatively small bubbles can have disproportionate effects when lodged in gas-loaded tissues.

4.) There are at least three distinct bubble types: circulating bubbles, obstructive bubbles and autochthonous bubbles, which means bubbles in the tissues. There is a distinct clinical picture caused by each type or they may all be present and give a mixed picture .

5.) Decompression illness should be viewed as probabilistic as opposed to deterministic.

These five advances point to a much more complex and less predictable model for decompression and make it difficult to postulate where decompression illness is improbable. Think of decompression illness as a continuum from no symptoms or signs to severe multi-system involvement.