Rattling breathing is a common symptom when death is near. In the case of a dying person, rattling breathing is often caused by a build-up of mucus in the throat and lungs as the cough and swallowing reflexes become weaker.
If mucus rising up to the mouth and upper parts of the throat is bothering the patient, it can be removed with gentle suction using a suction machine. Taking a suction tube further into the throat feels unpleasant. Additionally, mucus can be controlled with medication reducing its production. Rattling breathing may sound upsetting and cause loved ones to become concerned, but it usually does not bother the dying person themselves.