Can you explain the heimlich maneuver?

Windpipe obstruction: The heimlich maneuver is a way to assist someone whose throat is blocked with (usually) food and occasionally other stuff. Since they cannot inhale either, they cannot increase the pressure in their chest too much. You reach around them, clench your hands and forcefully compress the chest to get a rush of air to push out the object in the throat. It is a lifesaver and you can be a hero.