  Sleep Apnea Syndrome (SAS) is defined as a partial or total closure of the
patient upper airways during sleep. The term "collapsus" (or collapse) is used
to describe this closure. From a fluid mechanical point of view, this collapse
can be understood as a spectacular example of fluid-walls interaction. Indeed,
the upper airways are delimited in their largest part by soft tissues having
different geometrical and mechanical properties: velum, tongue and pharyngeal
walls. Airway closure during SAS comes from the interaction between these soft
tissues and the inspiratory flow. The aim of this work is to understand the
physical phenomena at the origin of the collapsus and the metamorphosis in
inspiratory flow pattern that has been reported during SAS. Indeed, a full
comprehension of the physical conditions allowing this phenomenon is a
prerequisite to be able to help in the planning of the surgical gesture that
can be prescribed for the patients. The work presented here focuses on a simple
model of fluid-walls interactions. The equations governing the airflow inside a
constriction are coupled with a Finite Element (FE) biomechanical model of the
velum. The geometries of this model is extracted from a single midsagittal
radiography of a patient. The velar deformations induced by airflow
interactions are computed, presented, discussed and compared to measurements
collected onto an experimental setup.
