NO is the answer to your final question
I read about your 7 year old. I have an 8 year old with similar issues. He was diagnosed with asthma by the pediatrician. I ended up taking him to a pediatric specialist in asthma/allergies. He did a blood test which showed that my son had "Mycoplasma." He was treated with BIAXIN. We were told that he probably had this condition in his nose, but it went undiagnosed and therefore, untreated. Once Mycoplasma settles in your lungs, it is hard to get it out and SOME children end up having Asthma as a result. After my son was treated with the Biaxin he was taken off of the nebulzer. He was given Singulair once a night and an inhaler called "Maxair" to be used before PE and sports. The doctor said that this fall and winter we would see if any viruses would then cause asthma. He had two viruses, which we managed by increasing his Maxair to 2 or 3 times a day for a couple of days. Now recently he caught another virus that affected more seriously. However, the doctor still has not diagnosed him as having asthma. Right now the diagnosis he is using is "reactive airway disease." My son is 8 years old, 52 inches tall and 68 punds. His best peak flow is 250, which by the standards of this specialist, are "beyond excellent." When he got sick this week he went down to 150. I don't understand why your doctor thinks your child needs to be at 320 to be healthy.
This time, my son is being treated with oralpred for 5 days, zythromax for the mycoplasma. He was also given a different inhaler called combivent. This inhaler helps to reduce the need to cough.
Hope this is helpful. I am hoping very much that my son doesn't develop asthma. My advice to you is to get a second opinion from a specialist.
The only tests they are doing now are Peak Flow readings. Over the last 10 days his best has been 250. He is 7 years only but 57 inches tall and 80 pounds. His doctor says she expects him to improve over the next few weeks and we are to go back if he doesn't get up to 320.