Sometimes grabbing the cylinder of a revolver and applying pressure to spin it will prevent the gun from firing. Placing something between the hammer and the firing pin will prevent a revolver from firing; usually this something will be a body part, such as a finger or the web of skin between the thumb and index finger. The finger will not be broken, and you will probably not feel the pain due to the circumstances. The web of skin will probably be punctured and will hurt a lot, but it will not be incapacitating and it will heal later. Pain is better than dead.
Any account of someone cutting their throat to stop choking on something is something of which you should be skeptical. Cutting your throat to stop choking on an object is similar to cutting off your arm because your finger hurts. First, if the object is below the cut, then you now have two serious problems: you will still be choking on the object and now you will also be choking on blood from the cut. Emergency tracheotomies work better on television than in real life.