Deep inhalation (DI) induces changes in airway calibre that may last beyond the manoeuvre itself. The mechanisms involve mechanical interaction between conducting airways subjected to parenchymal tethering and lung parenchyma itself. Healthy children usually show small bronchodilation after DI. Increased airway calibre after DI has been documented in wheezy preschool children with mild airway obstruction and, after methacholine challenge, in preschool and school children with normal lung function but has not yet been demonstrated in infants. The DI also induces bronchodilation in children with mild exercise induced airway obstruction. In the presence of severe airway obstruction, the bronchodilatory effect of DI may be blunted or reversed. The bronchodilatory effect of DI appears to be larger in children and adults than infants and elderly and larger in girls than boys. It is inversely related to the degree of airway hyperresponsiveness and the blunted bronchodilatory response to DI in acute or severe asthma is restored by steroid therapy or allergen avoidance. The airway effects of DI may in the future prove a valuable tool in assessing the mechanisms of airway obstruction and reactivity in children.
Keywords: Conducting airways, lung parenchyma, respiratory or airway resistance, methacholine, exercise, asthma, bronchodilation, bronchoconstriction, airway responsiveness, lung volume
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