As an insulin user, I know that air injected into your subcutaneous fat won’t kill you and as far as I know, won’t even do any harm, at least not in the amounts you find in your average insulin needle. But what DOES happen to that air? Does it just slowly absorb into the fat, or does it go into the bloodstream (but wouldn’t that be harmful?) or what?
Anyone?
The gas slowly dissolves into the surrounding tissue fluid. If I had to guess, I would say that the oxygen dissolves the fastest (because oxygen is more soluble in blood than nitrogen due to the presence of hemoglobin). This would leave a nitrogen-enriched bubble that would be absorbed more slowly. This does not mean that there would be tiny bubbles in the bloodstream. As an analogy, think of a glass of Coke that has gone flat at room temperature; even though there aren’t bubbles fizzing out of it anymore, there is still a lot of CO2 dissolved in the liquid. If you were to heat the flat Coke, or put it into a vacuum chamber, you could drive out some of that dissolved CO2 as more bubbles. Similarly, you have a small amount of nitrogen gas dissolved in your bloodstream, but not enough to make your blood fizzy unless the outside pressure drops suddenly (see “the bends”).
Thanks, brossa! This came about because I was telling my brother-in-law that it was okay to have an air bubble in an insulin syringe (I mean in terms of having a movie-style instant embolism; it’s still not good to have one because of course then you’re getting less insulin than you think you are) and he wanted to know where the air went, then, and I realized I had no idea. Ignorance has been successfully fought!