When the squad leaves the station on its "man down" call, the engine shown in its adjoining bay is the Crown engine from the first two seasons, and not the Ward LaFrance engine used from season 3 forward.
In both cardiac cases, they read the v-fib EKG with using the quick-look feature of the paddles, but after defibrillating they read the rhythm while the paddles are not in contact with the patient.
When the dispatcher is shown giving Squad 51 its "man down" call, he says the time out is 8:20, but the clock above him says 11:44.