1. Lung Airway Closure:
Airways are liquid-lined, flexible tubes and can be subject to surface-tension instabilities which cause the liquid lining to form a plug. The plug obstructs the airway and reduces the ability to exchange gas. Our research deals with the mechanical analysis of the instability in an effort to understand the fundamental nature of the phenomenon and to seek ways of preventing its occurrence. Particular attention is given to airway closure in the micro-gravity environment and astronaut safety.
2. Lung Airway Re-opening.
Closed airways due to liquid plugs must be re-opened, often by deep inspiration. The dynamics of liquid plug flow and rupture are being studied to determine their characteristics and how they are influenced by surfactants, airway flexibility, airway bifurcations and other physiological effects. Rapid rupture can create crackling sounds in the lungs, a common clinical finding in many lung diseases.
3. Pulmonary Liquid and Surfactant Delivery.
Increasingly more medical procedures involve delivery of liquids into the lung airways by direct instillation. These include surfactant replacement therapy, lung lavage, delivery of drugs, delivery of genetic materials for gene therapy, partial and total liquid ventilation, and resuscitation. We study the transport mechanisms ranging from liquid plug flows, gravity drainage in bifurcating tubes, Marangoni flows of small airways and alveolar dynamics. Animal experiments, bench-top models and mathematical analysis are used for these studies.
5. Partial and Total Liquid Ventilation.
A methodology to enhance pulmonary gas exchange during acute respiratory distress is liquid ventilation. Although it sounds odd that breathing through a liquid could be an alternative to air, some liquids (e.g. fluorocarbons) have high gas solubilities that make them viable for respiratory support. In total liquid ventilation, the lungs are completely filled and ventilated using a liquid ventilation system while in partial liquid ventilation, only the alveoli are filled and the lungs are gas-ventilated using a standard mechanical ventilator. The aim of this research is to show the ability of these liquid ventilation techniques to improve gas exchange, pulmonary function, and reduce acute lung injury, as well as to develop an optimized treatment methodology.
6. Ocular Flows.
Through collaboration we are investigating the outflow of aqueous humor through incomplete channels created in the sclera. We examine the pressure-flow relationship of the poro-elastic sclera for various configurations of the channels and the effect of multiple channels. The intent is to develop a therapy for glaucoma which may provided long term reduction of intra-ocular pressures to the normal range.
7. Implantable Artificial Lung.
This work involves development of a membrane oxygenator which consists of a bundle of hollow micro-fibers that have an internal gas flow with blood flowing externally between the fibers. The blood flow would be supplied by the right ventricle of the heart, so is pulsatile and non-Newtonian. We are using computational fluid dynamics to study the gas exchange through the fiber walls for oxygen and carbon dioxide. The transport depends on the heart cycle, the fluid properties and the geometric arrangement of the fiber arrays.