Traditionally, blood had to be moved from one container to another as it was collected, freeze-dried, stored, then reconstituted. Each time blood changed containers, it was exposed to the air and possible contamination. A new blood bag developed for the Army by Foster-Miller Inc., Waltham. Mass., (fostermiller.com), lets health workers keep the blood in the same container as it is collected and used.

One of the major challenges was designing a bag that would prevent blood from contacting the membrane, where it clogs and impedes freeze-drying. A diaphragm on the new bag expands when a vacuum is applied to freeze dry the blood. This creates a one-inch gap between the membrane, which lets water escape. Air leaves via a one-way vent. Once freeze-drying is finished, the diaphragm permanently reseals, the membrane is removed, and the bag stores the blood. The bag is made of micro-porous polyurethane, which resists penetration by viruses. Blood in the bag can also be freeze-dried at -20°C, an improvement over the -40°C temperatures previously