Imaging Study of the Lungs During an Allergic Asthma Attack
Condition: Asthma; Atopy
MeSH terms: Asthma
Study type: Interventional

Summary: 
      Asthma is a disease of rapidly increasing incidence that already affects more than 17 million
      people in the United States alone. It has long been known that areas of severely reduced
      airflow occur in asthma and contribute significantly to the impairment of gas exchange in
      this disease. However, the extent to which local blood flow changes during an asthmatic
      attack is unclear. The purpose of this study is using Positron Emission Tomography - Computed
      Tomography imaging to evaluate how the blood flow changes in the lungs during an asthma
      attack induced by allergens.
    

Detailed description: 
      Asthma is a disease of rapidly increasing incidence that already affects more than 17 million
      people in the United States alone. It is of major importance to understand the mechanisms
      responsible for underlying mechanical and physiological changes that occur during asthma
      exacerbations. The effect of asthma on the pulmonary vasculature is virtually unknown. It has
      long been known that areas of severely reduced airflow occur in asthma and contribute
      significantly to the impairment of gas exchange in this disease. However, the extent to which
      local blood flow changes during an asthmatic attack is unclear. This proposal is designed to
      evaluate the relevance of potential mechanisms responsible for the blood flow defects seen in
      our Positron Emission Tomography studies of subjects with asthma and identify factors
      modifying that perfusion distribution. With this knowledge, it is hoped that a more focused
      basic research is motivated to understand the fundamental mechanisms behind these processes
      ultimately targeted to improved asthma therapy. Comparing these measures in healthy subjects
      and asthmatics patients may lead to methods to improve patient care.
    

Intervention name(s): Standardized Cat Allergen Extract and Standardized Dust Mite Allergen; Computed Tomography imaging, functional Positron Emission Tomography imaging; Nebulized methacholine inhalation
Intervention type(s): Biological; Radiation; Drug
Intervention description(s): The route of administration will be topical application of the titrated allergen via nebulized droplets to the lungs. The starting dose of allergen will be 3 dose dilutions below the estimated provocative concentration of allergen that causes a 20% fall in Forced Expired Volume in 1 second delivered for 5 minutes at tidal breathing, followed by Forced Expired Volume in 1 second at 10-minute intervals until the lowest Forced Expired Volume in 1 second is established. If the percent of Forced Expired Volume in 1 second fall is < 20%, the next concentration is given, until the Forced Expired Volume in 1 second falls ≥ 20 percent. When this happens the Forced Expired Volume in 1 second will be followed at 10, 20, 30, 45, and 60 minutes, then hourly for 7 hours. The early asthmatic response is the maximum percent of Forced Expired Volume in 1 second fall between 0 and 3 hours and the late asthmatic response between 3 and 7 hours post allergen challenge.; Physiology study using Computed Tomography and Positron Emission Tomography imaging with Nitrogen-13 saline as radiotracer; images obtained during the early and late phases after allergen challenge; Standard methacholine challenge performed once to determine the subject's dose that causes a 20% fall in Forced Expired Volume in 1 second from baseline.
Other intervention name(s): •Reagents from Greer will be used:; •Standardized Cat Hair Extract; •Standardized mite extract-Dermatophagoides farinae; •Standardized mite extract-Dermatophagoides pteronyssinus; MethaPharm Provocholine
Intervention MeSH terms: Methacholine Chloride
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Asthma; Allergen Challenge; Cat allergen; Dust mite allergen; Airway Hyper-responsiveness; Positron Emission Tomography - Computed Tomography; Nitrogen isotopes; Blood flow