The death rattle is where the Terminal respiratory secretions occur as the body's breathing slows down as the person is dying.
The death rattle typically lasts for no more than a few hours but sometimes can last as long as 24 to 48 hours depending on how far the person is to death.
The sound that is created knows as the death rattle occurs as a result of fluids such as saliva and bronchial secretions accumulating in the throat and upper chest.
Most people who do die with the death rattle usually stop the death rattle within a few hours but it's normal for some peoples death rattle to last as long as 48 hours.
It can be a very creepy sound and I was there with my Grandpa in the nursing home as he was dying and I had to leave the room when the death rattle started happening.