Fluctuations and noise in respiratory and cell physiology

Bela Suki
Department of Biomedical Engineering, Boston University

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     Last modified: May 12, 2006

Abstract
Physical measurements of the structure of respiratory system display fluctuations at scales spanning several orders of magnitude. Also, various physiological time series originating from the respiratory system are non-stationary, fluctuating in an irregular and complex manner. In disease, the statistical properties of these fluctuations undergo changes that can be used to trace the origins of diseases or, alternatively, to predict the probability of certain pathophysiological conditions. In this presentation, the focus will be on the interpretation of the various scaling behaviors and their relation to structure-function in the normal and diseased states. In particular, we first overview fluctuations and scaling in breathing pattern and how it changes asthma. We will present a physiological model of asthma attacks based on avalanche propagation of airway collapse. We will show how the model can be mapped to cellular random walk with absorbing boundaries and how to use the data and the model to predict the likelihood of asthma attacks. Finally, we will discuss the effects of adding noise to stretching epithelial cells. We find experimentally that a stretch pattern that is irregular can induce cell signaling to produce surfactant lipids at an optimum level of noise. This may have implications to all cellular phenomena that are sensitive to stretch.