Airway constriction pattern is a central component of asthma severity - The role of deep inspirations

Measurements of lung resistance and elastance (RL and EL) from 0.1 to 8 Hz reflect both the mean level and pattern of lung constriction. The goal of t his study was to establish a relation between a deep inspiration (DI) and t he heterogeneity of constriction in healthy versus asthmatic subjects. Cons triction pattern was assessed from measurements of the RL and EL from 0.1 t o 8 Hz in seven healthy subjects and in 12 asthmatics. These data were acqu ired before and after a DI and before and after a standard methacholine cha llenge versus a modified challenge in which a DI is prohibited. Generally, avoidance of a DI increased responsiveness. In healthy subjects and in thos e with mild-to-moderate baseline asthma a bronchial challenge, especially d uring self-inhibited DI, produced a heterogenous pattern of constriction in clusive of randomly distributed airway closures or near closures. Neverthel ess, such subjects were able to reopen their airways via a DI. In contrast, in subjects with severe baseline asthma, there is a more extreme heterogen eous constriction pattern with random airway closures even at baseline. Fur ther, there is no residual bronchodilatory effect of a DI either before or after bronchial challenge. We conjecture that inflammation and wall-remodel ing facilitate a dangerous degree of heterogeneous constriction inclusive o f airway closures or near closures, and contribute to the prevention of a D I from having a residual bronchodilatory effect.