Mechanism(s) of Airflow Limitation During Exacerbation of Asthma
Mechanism(s) of Airflow Limitation During Exacerbation of Asthma
The purpose of this study is to evaluate the site and mechanisms responsible for expiratory
 airflow limitation in chronic, treated, non-smoking, stable asthmatics with moderate to
 severe persistent expiratory airflow obstruction. Treatment will include inhaled
 corticosteroids and long acting beta2agonists. The investigators are interested in
 determining whether the large and/or small airways are the predominant site of airflow
 limitation. The investigators are also interested in determining whether intrinsic small
 airways obstruction and/or loss of lung elastic recoil is responsible for expiratory airflow
 limitation. The investigators are also interested to evaluate the role of varying doses of
 inhaled corticosteroids to suppress large and small airway inflammation using exhaled nitric
 oxide as surrogate markers of inflammation. For comparison purposes, spirometry and
 measurements of exhaled nitric oxide will also be obtained if possible during a naturally
 occurring exacerbation of asthma.
In addition we will also obtain above studies in asthmatics during naturally occuring
 exacerbation of asthma and following treatment. If available, results of lung function
 studies including measurements of lung elastic recoil will be compared to pathologic analyses
 of formalin fixed, air inflated lungs obtained at autopsy in asthmatics who die from asthma
 related or non-asthma related death. This kind of lung structure-function study will provide
 potential mechanism(s) to explain the loss of lung elastic recoil in acute and chronic
 asthmatics who are non-smokers. We will also obtain voxel quantification of high resolution
 thin section CT of lung obtained without IV contrast. Also, we will use fiberoptic
 bronchoscopy to obtain optical coherence tomography in stable asthmatics with mild to
 moderate to severe expiratory airflow limitation to assess integrity of the lung parenchyma.
Inclusion Criteria:

 -  Current non-smoking (<10 pack yr smoking history)

 -  Stable, treated asthmatics

 -  Age 10-80 yr

 -  post 180ug albuterol by MDI: FEV 1/FVC < 70% and FEV 1 <80% predicted

 Exclusion Criteria:

 -  Pregnancy