Devices and techniques for cutting and coagulating tissue

A surgical system, comprising:

• a surgical instrument, comprising:
• an ultrasonic transducer;
• and
• an ultrasonic end effector coupled to the ultrasonic transducer;
• and
• a surgical generator, the surgical generator comprising:
• at least one processor programmed to:
• receive data describing an electrical signal provided by the surgical generator to the surgical instrument;
• compare an ultrasonic impedance of the surgical instrument to an impedance threshold;
• determine that the ultrasonic impedance of the surgical instrument is greater than an impedance threshold;
• determine that a present resonant frequency slope of at least one electrical signal generated by the surgical generator differs from a past resonant frequency slope by more than a frequency slope threshold;
• and
• trigger a first response.

A method of driving an end effector coupled to an ultrasonic drive system of a surgical instrument, the method comprising:

• generating, by a surgical generator, at least one electrical signal;
• monitoring, by the surgical generator, the at least one electrical signal against a first set of logic conditions;
• detecting, by the surgical generator, a load event at the end effector by comparing an ultrasonic impedance of the surgical instrument to an impedance threshold, wherein the load event is detected when an ultrasonic impedance of the surgical instrument exceeds an impedance threshold and a present resonant frequency slope differs from a past resonant frequency slope by more than a frequency slope threshold parameter;
• determining, by the surgical generator, that the first set of logic conditions are met;
• and
• triggering, by the surgical generator, a first response.

A surgical system, comprising:

• a surgical generator, the surgical generator comprising:
• an amplifier;
• a transformer;
• and
• at least one processor, wherein the at least one processor is programmed to:
• monitor at least one electrical signal generated by the surgical generator against a first set of logic conditions, wherein the at least one electrical signal is provided to a surgical instrument to drive an end effector of the surgical instrument;
• detect a load event at the end effector by comparing an ultrasonic impedance of the surgical instrument to an impedance threshold, wherein a load event is detected when an ultrasonic impedance of the surgical instrument exceeds an impedance threshold, and a present resonant frequency slope differs from a past resonant frequency slope by more than a frequency slope threshold parameter;
• determine that the first set of logic conditions is met;
• and
• trigger a first response of the surgical generator.

A method of driving an end effector coupled to an ultrasonic drive system of a surgical instrument, the method comprising:

• generating, by a surgical generator, at least one electrical signal;
• monitoring, by the surgical generator, the at least one electrical signal against a first set of logic conditions;
• detecting, by the surgical generator, a load event at the end effector, wherein detecting the load event comprises comparing an ultrasonic impedance of the surgical instrument to an impedance threshold, and wherein the load event is detected when the ultrasonic impedance of the surgical instrument exceeds the impedance threshold for at least a threshold time and a present resonant frequency slope differs from a past frequency slope by more than a frequency slope parameter;
• determining that the first set of logic conditions is met;
• and
• triggering a first response of the surgical generator.