B737-800
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Confusion; Situational Awareness; Time Pressure; Training / Qualification
Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury
Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Declared Emergency
Human Factors; Manuals
Shortly after takeoff we received chimes from the flight attendants. When I answered I received a very loud and frantic voice repeating this 'XXXX; XXXX; we must land immediately.' I tried to gain more information to no avail. I declared an emergency and asked for a return to the airport. When asked what the nature of the emergency was; I stated that is was unclear; however; it could be a fire type of situation. During the 180 degree turn back we received a second chime and got the same verbiage from the flight attendants. 'XXXX; XXXX; we must land immediately.' Soon thereafter I took the control of the airplane and radios and asked the First Officer to get more information from the back. We eventually found out that is was an ill passenger who was having a heart attack and CPR was being administered. I then stated to ATC what type of emergency we had and entered a downwind for the landing runway.The phrase 'XXXX' is mentioned one time in our operations manual. It is a Flight Attendant to Flight Attendant reference only. Simple English; with details; need to be used when describing a situation in the cabin of the airplane. Due to the severity of the ill passenger (heart attack; no pulse; no breathing and CPR being done) the flight attendants were under a lot of stress. They performed very well and I would like to acknowledge they probably saved this mans life! GREAT JOB! However; I feel there needs to be much more awareness of the fact that we are not privy to or trained in some of their references; acronyms etc. My perception of what was maybe a fire or other [question of airworthiness] type of situation; even though for a very short time; is very concerning due to the [lack of specificity] from the flight attendants.
Air carrier Captain reported a passenger had a heart attack shortly after takeoff; an emergency was declared and the flight returned to the departure airport.  Captain stated the flight attendants were utilizing unique to the flight attendant group language to describe the situation which resulted in an inaccurate assessment of the needs between the flight crew and ATC.