a cool mist vapourizer for my pug when she was really sick. it worked good
sometimes they need antibiotic as well
my pugs did too

kept in the room where he spends most of his time and/or sleeps, using this often helps break down some of the thick mucous and lets them breathe easier. Just be sure the vapor is pointing upward and not directly on the dog. Some add Vicks or Musinex or similar to the vapor. If he becomes lethargic, stops eating or has fever (should be no higher than 102) then he needs medication from your vet to prevent/treat pneumonia.

have him in the bathroom with you to breathe in the steam. This helps our little guy and that was recommended by a vet surgeon here in our area.