Very tough for me to comment.
As a guess, only a guess, the vet must be referring to laryngeal paralysis
, which is seen in this breed.
The goal is to ensure a pet is not in a hot environment and to keep the quiet to ease the breathing.
There is a surgical procedure that can be done called a laryngeal tie-back that can help breathing. In fact, my father's own labrador had this procedure done.
The procedure helps to keep the airway open.
Sometimes, cough suppressants or sedatives will be used to help calm pets to slow the breathing.
But, if I am correct about laryngeal paralysis, there are treatment options, so I would consult another vet or a surgical specialist for another opinion.