Whether the domains of lung function for asthma severity previously defined in the guidelines (EPR – 2 1997) do apply to children has been questioned in cross-sectional studies that have found normal EEVs (well over 90 percent predicted) in a majority of children aged 5 to 18 years, regardless of their severe asthma, classified on the basis of symptoms (Bacharier et al. 2004; Paull et al. 2005; Spahn et al. 2004). Two of these studies indicated that, unlike fevric measures, VEV1/FVC decreased as asthma severity increased and therefore appeared to be a more sensitive measure of severity (Bacharier et al. 2004; Paull et al. 2005). On the other hand, analysis of a large longitudinal study in children confirmed a link between the severity of airflow obstruction and the risk of exacerbation (Rhlbrigge et al. 2001).