The defibrillators.
Bob with 72bpm.
Heart Rate is a gimmick introduced in Surgeon Simulator Touch. Bob has a heart rate, which increases with damage but can be lowered by the anesthetic button. However, if you use too much anesthetic, Bob will flatline. If Bob flatlines, the player needs to charge up the defibrillators and aim them both towards Bob. If it is done successfully, Bob's heart rate will reset. Be aware; the defibrillators make Bob lose 200ml. Thus, if Bob has 200ml or less and you use the defibrillators, he will die upon contact. This is needed to get the achievement "The Instructions Lied!"
Bob flatlining with 0bpm.
Bob starts with a heart rate of 72bpm. Once his heart rate reaches 200bpm, he will go down to 0bpm and begin to flatline. If Bob dies because of flatlining, it will not say brutal murder but instead, "Heart attack achieved in --:--, watch those BPMs!"
In the Alien Surgery, you cannot let Gworb get to 200bpm, as there are no defibrillators. You must use the anesthetic button to lower his heart rate, but be careful; if you use too much anesthetic, Gworb will flatline.