Carey,
I think you'll get different answers on this one. If your child with CF "baseline" or normal day does not include a cough, than a cough could indicate something is brewing. A barking cough sounds like it could be viral, or inflammation, or bacterial or a combo. When Maggie gets a cough, I up her nebs/VEST. If her cough is sounding deep, keeping her up at night, she has a fever, or just not acting right, I call the pulmonologist. Depending on her last sputum culture, we'll do antibiotics for at least 2 weeks while keeping up with nebs/VEST. If it's been a while since her last culture, I'll ask to have her cultured to make sure she's not growing something new. When Maggie was 2 1/2 she had such a cough and she was not treated aggresively enough and needed the works, bronch, IV's, hospital. Some docs assume CF'ers cough and they do; but the philosophy of treating aggressively the flare-ups is to keep our CF'ers lungs as healthy as possible to the next best treatment comes out. The reason maybe the CF nurse isn't giving you a straight answer is likely because each CF'er is so different. Or maybe she doesn't know the answer? Anyhow you do what you think is right.