He probably meant "sucking chest wound"
If memory serves, Tom was never in the military so he may have messed up the terminology. In Army Basic, everyone was trained how to treat sucking chest wounds as part of combat first aid. A piece of cellophane is handy to get a good seal. In the old days when a lot of people smoked, they used to recommend the cellophane from a cigarette pack. I first heard of this trick when an off-duty soldier used it to save the life of someone shot in a robbery in my hometown. It can work, but don't forget to check for exit wounds.