I think the LABA can make quite a difference based on experience we had with our dog! She had the worse cough and it went on for many years. We tried everything. We thought we would have to put her down it was so bad. And her lungs sounded terrible and looked terrible on X ray. We had been trying Fluticasone inhaler but it was not helping. Then we tried Fluticasone and Salmeterol combined inhaler. It helped right away and after a couple of weeks her cough completely went away. This is the first time in over a decade she is cough free. She acts and looks great now. The change has been miraculous. I guess prior to the LABA the steroids were not getting into her lungs to help her and now they do?