HL7 = cow dung.
Thousands of pages of documentation to define code values and what they mean.
That's not a protocol. It's just a list of values.
If HL7 had any elegance to it, it might pass for a protocol. As it is, it's just a pile of shit for which you have to pay hundreds of dollars just to read the description of every undigested leaf of grass and the amorphous goo that holds them together.