breathing space vs elbow room

breathing space and elbow room both are nouns.

Word	Noun	Adjective	Verb	Adverb
breathing space	Yes	No	No	No
elbow room	Yes	No	No	No

As nouns, elbow room is a hypernym of breathing space; that is, elbow room is a word with a broader meaning than breathing space:

Other hypernyms of breathing space include room, way.

breathing space (noun)	elbow room (noun)
sufficient room for easy breathing or movement	space for movement
a short respite