The rat sniffs the air a few times, and within a minute, his naturally twitchy movements are almost still. On a monitor that shows his rate of breathing, the lines look like a steep mountain slope, going down.
At first glance, that looks bad. We need oxygen to live. If you don't get it for several minutes -- for example, if you suffer cardiac arrest or a bad gunshot wound -- you die. But something else is going on inside this rat. He isn't dead, isn't dying. The reason why, some people think, is the future of emergency medicine.
