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.

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.

Inclusion Criteria:

• Asthma Subjects:

  • 3 - 18 years of age at enrolment
  • Clinically stable at enrolment
  • Physician diagnosis of asthma and attending follow-up in the Asthma Clinic

Exclusion Criteria:

• Asthma Subjects:

  • Born premature (before 37 weeks gestational age)
  • Low birth weight (less than 2.5 kilograms)
  • History of congenital heart disease, neuromuscular disorder or bone disease
  • History of any chronic lung disease other than asthma
  • Respiratory infection in last three weeks
  • Change in medication in last three weeks (including oral steroids)
  • Current or previous history of smoking

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.

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