persistant cough

My 4 y/o has had a dry cough since June.  She was tx in may for a bad sinus inf.  and placed on orapred and augmentin.  She improved but then the dry cough started.  we have been to a pulmonologist who has tx her w/ xopenex and pulmacort.  The cough was just in the mng after she woke up.  Never at night and insignificant during the day.  There was no fever, no wheezing---her spirometry testing has been unremarkable.  Allergy tx was negative-skin and blood, however this cough persists.  4 weeks ago I brought her back and they placed her on maintenence of xopenex tid and pulmacort 110 bid.  The cough (seal like in nature) is now all day instead of only the am, though still not at night.  I brought her back and they did a cxr which showed increased markings and hyperinflation, according to the pulmonologist--read by radiologist to be normal.  They then placed her on orapred again.  7 days later--no improvement.  Now they placed her on atrovent in addition to the above.  She has also been on nasonex since May for a itchy, runny nose-which did work.  3 days after the atrovent ---no improvement. Actually in the last month the cough has never loosened but has become more freq. I have always thought it was a nasal issue--post nasal drip etc.  Back to pulmonologist, now she has a sinus infection. That is where we are at this point.  I am not convinced it is asthma--iam an rn and i do understand that she has had a cough for a long time which places her in that category.  Bottom line is, she is on all these meds which are not helping, and i really would like an outside view.  Please, any advise?