Well, since I first heard it, I have always thought of it meaning as I described: but then I was a medic, and that's how medical minds work! To me, it has never meant anything other than that. But, as fiddle-chick Charlie said, there may be double meanings in it, as in "You're talking a load of bollocks".
The sad thing about the song is the line about "when you're lying there in traction" as it might have been a premonition of what was to come for Andy.