From Longman Dictionary of Contemporary Englishat (a) breathless pace/speedat (a) breathless pace/speedextremely fast → breathless
Examples from the Corpus
at (a) breathless pace/speed• Though she has had little education, her vocabulary is excellent: she fountains out ideas and observations at breathless speed.• Indeed, Moffett worked at a breathless pace to ensure that those issues were addressed before the annual meeting took place. 