We have previously developed an adsorption-limited model to describe the exchange of lung surfactant and its fractions to and from an air–liquid interface in oscillatory surfactometers. Here we extend this model to allow for diffusion in the liquid phase. Use of the model in conjunction with experimental data in the literature shows that diffusion-limited transport is important for characterizing the transient period from the start of oscillations to the achievement of steady-state conditions. Matching previous data shows that upon high levels of film compression, large changes occur in adsorption rate, desorption rate, and diffusion constant, consistent with what one might expect if the subsurface region was greatly enriched in DPPC. Collapse of the surfactant film that occurs during compression leads to a significant elevation of surfactant concentration immediately beneath the interface, consistent with the subsurface depot of surfactant that has been postulated by other investigators. Modeling studies also uncovered a phenomenon of surfactant behavior in which the interfacial tension remains constant at its minimum equilibrium value while the film is compressed, but without collapse of the film. The phenomenon was due to desorption of surfactant from the interface and termed “pseudo-film collapse.” The new model also gave improved agreement with steady-state oscillatory cycling in a pulsating bubble surfactometer.
Dynamic Behavior of Lung Surfactant
Contributed by the Bioengineering Division for publication in the JOURNAL OF BIOMECHANICAL ENGINEERING. Manuscript received by the Bioengineering Division August 31, 1999; revised manuscript received August 24, 2000. Associate Editor: S. E. Rittgers.
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Morris, J., Ingenito , E. P., Mark, L., Kamm , R. D., and Johnson, M. (August 24, 2000). "Dynamic Behavior of Lung Surfactant ." ASME. J Biomech Eng. February 2001; 123(1): 106–113. https://doi.org/10.1115/1.1336146
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