It doesn't seem like a pleasant way to go, it seems like if there is an air bubble going through your bloodstream (I'd imagine it would be unpleasant) and it reaches your heart, you could get some sort of embolism (air embolism) and I don't think it would be comfortable. Then again, I am only basing my knowledge of this on what I read/heard about people who went to get a vaccine and air (accidentally) got into the syringe while administering the vaccine.