I have two boarded horses in my barn that both had major COPD episodes at separate occasions.  Both were on Dexamethosone for a brief time to help bring down the inflammation.  Neither one of them gets hay anymore, instead  they get tim/alf hay cubes.  Occasionally, they will get a supplement called Ani-hist if they seem to be starting to have any issues.  Knock on wood, the gelding hasn't had to have anything in almost a year.  The mare, who had her major episode late this spring still needs the Ani-hist on occasion, seems to coinside with the weather changing.  Both horses are outside as much as possible. They both are also still on regular bedding, and they aren't having any issues.  I am trying to convince the owner to put them both on MSM, but so far no luck. 

Finish Line has a cough syrup that has menthol/eucalpytus, not sure if that might be what Quantum was thinking of.