My Cat Is 12yrs Old He Has Had Asthma For

my cat is 12yrs old he has had asthma for all his life and was on steroids for a bit. he always coughs with difficulty breathing, but then he is fine. been doing this for yrs. today he was breathing a little different, like with his mouth opened a little bit and more like panthing. I called my vet and she asked if I had an inhaler for him, which I do not she said to see how he is and let her know if he getsworse. she also said to put him in a cool room. do you think he is ok or should I see her.