Source: Annual Congress 2003 - Respiratory structure and mechanisms: current concepts
Disease area: Airway diseases, Respiratory critical care

Abstract

The structure of air flow through the first generations of the bronchial tree can be very complex because of inertial effects. This could be responsible for an heterogeneous distribution of flow profiles within the bronchi, which in turn could affect acinar ventilation (see [1]). However, inertial effects are largely influenced by time-dependent conditions.
Numerical simulations of time-dependent Navier-Stokes equations have been performed to study the evolution of flow distribution during a respiratory cycle. We studied a tree geometry made of two or three generations of rigid cylinders. The end branches are coupled to bottle-like structures which act like pistons to simulate the mechanism of respiration.
The results show that flow in the tree structure does not respond identically during the two phases of the respiratory cycle. In a symmetrical tree of three generations, inertial effects at inspiration imply that flow profiles through cylinders slices are strongly distorted. On the contrary, at expiration, velocity profiles are more homogenous, exhibiting a parabolic shape. This shows that inspiration and expiration are not symmetrical even for a sinusoidal excitation. These effects could be increased for a non-symmetrical and more realistic respiration cycle.
[1] B. Mauroy, M. Filoche, J.S. Andrade Jr and B. Sapoval, Interplay between geometry and flow distribution in an airway tree, Physical Review Letters in Press, http://arxiv.org/abs/physics/0302050

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Citations should be made in the following way:
B. Mauroy, T. Similowski, C. Straus, B. Sapoval (Cachan, Paris, Palaiseau, France). Asymmetry of inspiratory and expiratory fluid dynamics in a branched model of the lung. Eur Respir J 2003; 22: Suppl. 45, 161

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