Sprayable foam that slows bleeding could save lives

For some serious injuries to arms and legs, medics can apply pressure to keep bleeding in check. But for major trauma to the torso, particularly when it affects vital organs, compression can make the situation worse. Currently, first responders have no way to stop this kind of bleeding, which is a leading cause of death among young adults.
The researchers developed a sprayable foam made of modified chitosan, a biopolymer derived from the shells of shrimp and other crustaceans that is already being used in other types of non-foam wound dressings. In tests, the spray reduced blood loss by 90 percent.
When sprayed, the foam has a consistency like whipped cream, the scientists write. It expands to nearly twice its original size into the body’s crevices and becomes "solid-like," making a barrier that prevents blood from leaking out. 
When the foam encounters blood cells they cluster together and gel up, so they don’t spill out of the open wound. The crucial ingredient that makes this happen is a modified version of the molecule chitosan, a material naturally in the shells of shrimp and other crustaceans. The modification adds special "tails" to the molecule that stick into blood cells and make them clump together, the scientists hypothesize.