ABSTRACT
In order to conceptualize what lung function parameters should be measured in the evaluation of the child with asthma, the physiological changes that take place in asthma should be considered. The physiological changes in asthma can be summarized as follows: (1) increased resistance to air flow; (2) decreased flows and timed expiratory volumes, abnormal flow-volume relationships with decreased flows at all lung volumes; (3) abnormal pressure-volume relationships, resulting in premature airway closure, altered lung volumes (gas trapping), and increased work of breathing; (4) increased airway responsiveness to provocation by both allergenic and nonspecific stimuli; and (5) variability of airway tone, resulting in airway flow measures that may change dramatically during the day. The purpose of lung function testing in asthmatic children is to determine the existence of these physiological abnormalities so as to assist in the diagnosis of asthma, to provide ongoing monitoring of patients, and to continue to evaluate the effects of therapy.
