What is the death rattle?

As far as know, the 'death rattle' is generally a fluid buildup in the back of the throat. People who are dying, their relaxes are slower and they most generally do not swallow the way that you would to get phlegm down the back of their throat. You'll usually notice that if you clear the persons mouth out from back to front with a swab they will not do it as much. Usually you can see the phlegm in the back of their throat as well which helps you know. Hope that helps some.