ABSTRACT
I. Introduction 192
II. Physiological Significance of Airway Lining Flows and Surface
Tension in the Lung 192
A. Airway Closure 194
B. Airway Reopening 195
C. Summary 196
III. Interfacial Phenomena 197
IV. Physiological Interfacial Flows 201
A. Liquid Redistribution 202
Airway Geometry 202
Airway Deformability 202
B. Airway Closure 204
C. Airway Reopening 207
Benchtop Experiments 207
Physiological Observations 210
Theoretical Investigations of Fluid-Structure Interactions 210
D. Surfactant and Liquid Delivery 214
Surfactant-Spreading Flows 215
Liquid Bolus Transport 217
Surfactant and Inhaled Particles 219
V. Conclusions 219
Acknowledgments 220
References 220
I. Introduction
Our goal for this chapter is to provide an overview of research related to inter-
facial phenomena and liquid-lining flows in airways. To do so, we first present
the physiological significance of surface-tension-driven phenomena within the
lung. Next, in order to explain the physical mechanisms that are responsible
for physiological responses, we present a brief overview of fundamental
surface-tension-driven interfacial phenomena that are generally responsible for
liquid-lining flows. From this framework, we explore a range of different inter-
facial flows that occur within pulmonary airways, and discuss the importance
of surfactants on these flows.
