Faculty Collaboration Database

Airflow limitation in a collapsible model of the human pharynx: physical mechanisms studied with fluid-structure interaction simulations and experiments. Physiol Rep 2019 May;7(10):e14099

Date

05/23/2019

Pubmed ID

31116516

Pubmed Central ID

PMC6530458

DOI

10.14814/phy2.14099

Scopus ID

2-s2.0-85066466799 (requires institutional sign-in at Scopus site)   24 Citations

Abstract

The classical Starling Resistor model has been the paradigm of airway collapse in obstructive sleep apnea (OSA) for the last 30 years. Its theoretical framework is grounded on the wave-speed flow limitation (WSFL) theory. Recent observations of negative effort dependence in OSA patients violate the predictions of the WSFL theory. Fluid-structure interaction (FSI) simulations are emerging as a technique to quantify how the biomechanical properties of the upper airway determine the shape of the pressure-flow curve. This study aimed to test two predictions of the WSFL theory, namely (1) the pressure profile upstream from the choke point becomes independent of downstream pressure during flow limitation and (2) the maximum flowrate in a collapsible tube is VImax=A3/2(ρdA/dP)-1/2 , where ρ is air density and A and P are the cross-sectional area and pressure at the choke point respectively. FSI simulations were performed in a model of the human upper airway with a collapsible pharynx whose wall thickness varied from 2 to 8 mm and modulus of elasticity ranged from 2 to 30 kPa. Experimental measurements in an airway replica with a silicone pharynx validated the numerical methods. Good agreement was found between our FSI simulations and the WSFL theory. Other key findings include: (1) the pressure-flow curve is independent of breathing effort (downstream pressure vs. time profile); (2) the shape of the pressure-flow curve reflects the airway biomechanical properties, so that VImax is a surrogate measure of pharyngeal compliance.

Author List

Le TB, Moghaddam MG, Woodson BT, Garcia GJM

Authors

Guilherme Garcia PhD Assistant Professor in the Biomedical Engineering department at Medical College of Wisconsin
B Tucker Woodson MD Chief, Professor in the Otolaryngology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Airway Obstruction
Airway Resistance
Biomechanical Phenomena
Compliance
Computer Simulation
Elastic Modulus
Female
Humans
Magnetic Resonance Imaging
Middle Aged
Models, Anatomic
Models, Biological
Pharynx
Pressure
Respiration
Rheology
Sleep Apnea, Obstructive