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Temporal dynamics of recurrent airway symptoms and cellular random walk

¹Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215; and ²Pediatric Respiratory Medicine, Department of Pediatrics, University Hospitals of Berne, Berne, Switzerland

Submitted 18 June 2003 ; accepted in final form 1 August 2003

ABSTRACT

Asthma is a complex chronic inflammatory disease of the small airways that has dramatically increased in prevalence in industrialized countries during the last decades. Risk factors for adult asthma have been related to the complex array of gene-environment interactions and exposure of the immune system to allergens in early childhood. In genetically predisposed subjects, continuous exposure to environmental agents such as allergens or infections can lead to recurrent airway symptoms characterized by recurrent episodes of airway inflammation and bronchoconstriction with clinical symptoms of cough, dyspnea, or wheezing. In this study, we report that the longterm temporal dynamics of recurrent airway symptoms in a population of unselected infants display a complex intermittent pattern and that the distribution of interepisode intervals follows a power law. We interpret the data by using a model of the dynamics of attack episodes in which an attack is triggered by an avalanche of airway constrictions. We map the dynamics of this model to the known problem of a random walk in the presence of an absorbing boundary in which the walker corresponds to the fluctuations in contractile state of airway smooth muscle cells. These findings may provide new insight into the mechanisms of otherwise unexplained symptom episodes.

asthma; instabilities; distribution; avalanche; power law

This article has been cited by other articles:

				U. Frey Asthma as a nonlinear complex dynamic system: a novel approach to understand the temporal behaviour of chronic asthma and its response to {beta}-agonists Eur. Respir. Rev., June 1, 2008; 17(108): 67 - 69. [Full Text] [PDF]