Apparently The Chicago Manual of Style disagrees with the claim that "respectively" must always go at the end. Here are some examples of their usage (and it is always set off by commas when used in the middle of a sentence):
Thus, for example, the numbers 4.8 and 4.12 signify, respectively, the eighth section and the twelfth section of chapter 4.
The multiple-numeration system may also be used for illustrations, tables, and mathematical equations (see, respectively, 3.11,3.51, and 12.24--25).
Also, they use a comma before it at the end of a sentence every time it appears in that form:
A table normally consists of rows and columns, which are analogous to the horizontal (x) and vertical (y) axes of a graph, respectively.