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Implications for Long-Duration Space-Based Activity
a Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA b Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA c Institute for Translational Medicine and Therapeutics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA d Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
Key Words: gas embolism • air embolism • surfactant • decompression • protein adsorption • surface active • interfacial mechanics • fluid dynamics • front tracking
Address for correspondence: David M. Eckmann, M.D., Ph.D., Department of Anesthesiology and Critical Care, University of Pennsylvania, 3400 Spruce Street, Dulles 6-HUP, Philadelphia, PA 19104, USA. Voice: 215-349-5348; fax: 215-349-5078. e-mail: eckmanndm{at}uphs.upenn.edu
Intravascular gas embolism can occur with decompression in space flight, and it commonly occurs during cardiac and vascular surgery. Intravascular bubbles may be deposited into any end organ such as the heart or the brain. Surface interactions between the bubble and the endothelial cells lining the vasculature result in serious impairment of blood flow and can lead to heart attack, stroke, or even death. Surfactant-based intervention is a novel treatment for gas embolism. Intravascular surfactant can adsorb onto the gas–liquid interface and compete with blood-borne macromolecules for interfacial occupancy. Surfactants can retard the progress of pathophysiological molecular and cellular events stimulated by the bubble surface, including endothelial cell injury and initiation of blood clotting. Bulk and surface transport of a surfactant to provide competition for interfacial occupancy is a therapeutic strategy because surfactant adsorption can dominate protein (or other macromolecule) adsorption. The presence of surfactant along the gas–liquid interface also induces variation in the interfacial tension, which in turn affects the blood flow and the bubble motion. We describe the interplay between biological transport processes and physiological events occurring and the cellular and molecular level in vascular gas embolization. Special consideration is given to modeling the transport and hydrodynamic interactions associated with surfactant-based intervention.
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