Look at the diagram. He likely had a cover for it at the elbow. What you are seeing is it slipped or he was uncomfortable with the protective elbow cover and insisted the line dangle (for lack of a better word).
The diagram shows an insert at the elbow area. I’ve had them. I’ve had IVs in the back of the hand. There’s NO WAY either would show up as a small head at the bottom of the inside of the wrist. This is absurd. It’s fruitless, and stupid.