Complex sentence: The first helicopter was a Eurocopter BO 105 which was later replaced with the more advanced Eurocopter EC 135, which used extensively in an air ambulance capacity throughout the world.
Split into simpler sentences: The first helicopter was a Eurocopter BO 105 which was later replaced with the more advanced Eurocopter EC 135. The EC 135 is used extensively in an air ambulance capacity throughout the world.