Investigation of Lung Ventilation Inhomogeneity in Pediatric Asthma
Condition: Asthma
MeSH terms: Asthma
Study type: Observational

Summary: 
      The primary objective of this study is to determine if well-controlled asthmatic patients
      followed in subspecialty asthma clinics between the ages of 3 - 18 years can be distinguished
      from healthy controls using lung clearance index, a parameter from the multiple breath
      washout test. Also, to correlate lung clearance index with asthma sputum cell counts.
    

Detailed description: 
      Clinical studies are underway which are examining the utility of the LCI in obstructive
      respiratory disease (cystic fibrosis and asthma). However, the majority of studies have
      examined asthmatics with ongoing evidence of reversible disease on spirometry. There is a
      very limited body of research comparing LCI values in well-controlled asthmatics to healthy
      controls. Furthermore, the type of inflammation occurring in asthma may have a different site
      of action, we will prospectively study whether there is a difference in LCI between
      eosinophilic and neutrophilic inflammation to give us an indication of whether the site of
      non-eosinophilic inflammation is primarily in the small airways as well.
    

Intervention name(s): Sodium Chloride Inhalation
Intervention type(s): Drug
Intervention description(s): Spirometry: all subjects Plethysmography and exhaled nitric oxide: >6 years Multiple Breath Washout: Tidal breathing using a facemask <9 years or mouthpiece >9 years. Wash-in phase: gas mixture containing 4% SF6, 4% He, 21% oxygen and balance nitrogen inhaled until steady state. Bias flow stopped during expiration by removal of T-piece. Wash-out phase: patient inspires room air and exhales tracer gas until SF6 reaches <0.1%.
Bronchodilator response: Bronchodilator (Salbutamol 400 mcg) to asthma subjects, spirometry and MBW repeated after 15 minutes.
Induced sputum in asthma subjects >10 yrs. Post-bronchodilator spirometry, subject inhales concentrations of 3, 4 and 5% hypertonic saline for 7 minutes for 3 cycles until expectorating sputum.
Other intervention name(s): Salt, NaCl
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Asthma patients will be recruited from the Respiratory Medicine clinic at the Hospital for
        Sick Children. A member of the medical team in the Asthma Clinic, known to the patient,
        will introduce the study, and obtain permission for the patient/caregiver to meet with
        study personnel. Subjects will then be approached by the Principal investigator or her
        delegate. They will be informed that enrolment is voluntary and that they can withdraw from
        the study at any time.
      
Biospecimen description: 
      samples will be processed and divided into two categories: eosinophilic (% eosinophils >2.5%)
      and non-eosinophilic (<2.5% eosinophils). The two categories of asthmatics will be used to
      categorize asthmatics for comparison on parameters such as SnIII analysis of SF6, LCI etc. In
      addition, % eosinophilia will be considered as a continuous measure in those with %
      eosinophils > 2% and correlated with LCI.
    
Keywords: pediatric; lung ventilation inhomogeneity