Saheim originally gave me the idea of using tampons to seal GSWs (gun shot wounds); as tampons absorb fluid they expand. Of course my inner hippy told me that non-bleached cotton would help prevent toxic shock syndrome if the wound did not receive immediate attention. I asked an ER nurse about this idea and she said that it would stop the the external bleeding but the major tissue damage caused by GSWs would cause continual internal bleeding.
A Gulf War One combat medic veteran recently gave me more information on the subject. He said that it would work and was very similar to many products used by medics. His job, and that off all combat medics is to stabilize the wounded, patch them up well enough to survive the trip to the field hospital. An example of how something like a tampon would work on a "sucking chest wound" (a wound he brought up) i.e. the bullet punctures the lung and exited the body; insert the tampon in the exit wound and bandage it up, then covering the entrance wound with a solid material like a plastic gauze packing or an ID card and taping it three sides. This allows the air to escape during exhalation but does not allow for more air to enter during inhalation.
So add a couple to your bug out med kit.
