What Explains My Daughter's Low Peak Flow Level At Night?

Question

I have been experiencing a problem of my peak flow levels dropping down to the red zone every night. I find that my daughter’s peak flow levels during the day time are about a 100 more than the normal level in the green zone, but at night it drops down to the red zone. This has been going on for some days. She is eight years old and has just been discharged from the hospital the previous night. We have to go to the ER two times the previous week. Even though, my doctor’s peak flow levels were low and she was experiencing severe constriction in her chest. Her doctor is really confused about what to do about her condition and he has put her on Xopenex breathing therapies thrice a day apart from her other medications. We have decided to take her to a Pulmonologist tomorrow. Any way we would be grateful if someone could shed some light on the matter as soon as possible and clear me out of this quandary.