Objective monitoring tools are urgently required to address the large healthcare burden of asthma, the most common chronic respiratory condition among children in the developed world, with 300 million sufferers worldwide and significant ongoing morbidity and mortality. Attempts to reduce ongoing exacerbation risks with early use of increased inhaled cortiscosteroids have been unsuccessful, resulting in a call to better understand the nature of asthma in adults but is of limited use in pediatric asthma owing to its effort-dependent nature. A more pratical and clinically informative signal of lung function variability is needed to capture the degree of variable airflow obstruction present, which, in addition to airway hyperresponsiveness, is a fundamental physiological characteristic of asthma.
The forced oscillation technique (FOT) is an effort-independent tidal breathing test of lung me
chanics that is highly feasible in pediatric patients. Respiratory system resistance (Rrs) reflects airway caliber, and reactance (Xrs) reflects lung stiffness and is sensitive to heterogeneity of airway narrowing and closure. Using physician-supervised FOT measurements over a 1-week period, we demonstrated increased day- to-day variability of FOT indices in patients with asthma versus healthy control subjects, and an ability to differentiate asthma severity and symptom control (6), both of which were missed by peak expiratory flow variability and FEV . In ongoing prospective observational work, 1 we are exploring the longer-term relationships between home-based, parent-supervised daily FOT measurements over 4 months with asthma control and the ability of these measurements to predict future asthma exacerbations. Here we present illustrative cases highlighting the potential of this approach to better characterize asthma exacerbations and detect changes in asthma control. [...]