Here is a link to an article that addresses this very subject...
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In-flight Death of a Passenger Requires a
Thoughtful Response from Flight Attendants
New studies of passenger deaths during flight will help airlines to update policies and procedures in light of data that are more accurate and current. The probability of the in-flight death of a passenger on any specific flight is low. Nevertheless, given the volume of passengers and changing demographics, a cabin crewmember could be called upon to respond appropriately if a death occurs."
Flight Safety Foundation - Cabin Crew Safety