First off I definitely wouldn’t think anything badly of you for euthanizing your horse! But I just wanted to mention that if you have him a while longer you might want to consider not buying any more ventipulmin and just increasing the dex if possible. I had an older TB gelding who has similar sounding breathing issues and the last few years of his life he had dex every second day as needed and higher doses every day if needed, I believe we started him on 3cc every second and 6cc when he had a bad day. After a few years he got 10cc when needed, even if this was a few days in a row. Definitely more affective than the ventipulmin , and much less expensive!! My gelding was on dex until age 23 , when he has to be euthanized due to a broken (kicked) leg in his retirement 
as horrible as it was, in a way I’m glad we didn’t have to deal with hard decisions of old age (he had developed Cushings) and dealing with his breathing getting worse!
Thank you so much for your message and sharing your story. I am sorry about the loss of your horse. I can afford to increase his dex for now since it is fairly cheap and I will talk to my vet about doing so. I am not ready to give up just yet as I should have a little more time before I have to make the final decision. Thank you again
