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Hydrodynamic Cleansing of Pulmonary Alveoli

Zelig, D; Haber, S; (2002) Hydrodynamic Cleansing of Pulmonary Alveoli. SIAM Journal on Applied Mathematics , 63 (1) pp. 195-221. 10.1137/S0036139901386090. Green open access

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Abstract

The inside wall of the pulmonary alveolus is lined with a thin viscous fluid layer and a monolayer of surfactants. Inhaled foreign particles that reach the lung alveoli are normally neutralized by macrophages and remain inside the lung. Nevertheless, Podgorski and Gradon [Ann. Occup. Hyg., 37 (1993), pp. 347–365] suggested that a hydrodynamic cleansing mechanism may exist in which particles are swept out by the net fluid flow from the alveolar viscous layer to the adjacent airways. Hawgood [The Lung: Scientific Foundations, 2nd ed., R. G. Crystal and J. B. West, eds., Lippincott-Raven, Philadelphia, 1997, pp. 557–571] has also reported that surfactants exit the alveoli during every breathing period. Based upon the foregoing observations, we examine a possible mechanism of hydrodynamic cleansing and predict its effectiveness. Our central assumption is that the amount of surfactant remains periodic during breathing and that a certain regulatory mechanism exists that causes excess surfactant (reported by Hawgood) to leave the alveoli. Owing to the latter, surfactant concentration gradients are induced inside the alveoli, which in turn generate fluid motion (a Marangoni effect) and concomitant fluid discharge. Our analysis predicts that a typical value of the outflow velocity is 10−9[m/sec]; i.e., it takes a fluid particle almost two days to travel a distance equal to an alveolar radius. It is also shown that the outflow velocity depends almost linearly on the discharge rate of the surfactants. Hence, a small artificial addition of surfactants into the lung may enhance alveolar cleansing, provided that a biological mechanism exists that maintains normal surfactant concentration over the lining fluid layer.

Type: Article
Title: Hydrodynamic Cleansing of Pulmonary Alveoli
Open access status: An open access version is available from UCL Discovery
DOI: 10.1137/S0036139901386090
Publisher version: https://doi.org/10.1137/S0036139901386090
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: lung alveoli, hydrodynamic cleansing, surfactants
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > UCL School of Management
URI: https://discovery.ucl.ac.uk/id/eprint/1575574
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