MAP should not be a foreign concept to EMTs as most of todays hospital and ambulances use automated blood pressure devices that display the MAP in addition to the pulse, systolic and diastolic pressures.
The MAP value is fairly easy to calculate. If you double the diastolic pressure, add the systolic number to it and divide that number by 3 you will have a very close approximation. Don't worry about minor variations from automatic devices as they may incorporate a more complicated formula that takes heart rate into consideration. For most instances in EMS, this is not critical and does not change the value a great deal.
MAP = [(2*D)+S] / 3