Combination ultrasonic and electrosurgical instrument with adjustable energy modalities and method for limiting blade temperature

1. A method of limiting an ultrasonic blade temperature of a surgical instrument with an ultrasonic blade configured to apply ultrasonic energy to tissue, the method comprising:

(a) increasing the temperature of the ultrasonic blade toward an upper temperature limit;

(b) in response to determining that the temperature of the ultrasonic blade has reached the upper temperature limit, setting a predetermined frequency parameter change threshold;

(c) adjusting at least one power parameter of the ultrasonic energy in response to reaching the predetermined frequency parameter change threshold in the ultrasonic blade to limit the ultrasonic energy to the predetermined frequency parameter change threshold; and

(d) limiting the temperature of the ultrasonic blade to the upper temperature limit.

2. The method of claim 1 , further comprising:

(a) measuring a first ultrasonic frequency of the ultrasonic blade;

(b) measuring a second ultrasonic frequency of the ultrasonic blade after measuring the first ultrasonic frequency; and

(c) calculating a frequency parameter change between the measured first and second ultrasonic frequencies of the ultrasonic blade.

3. The method of claim 2 , wherein the first ultrasonic frequency of the ultrasonic blade is an initial ultrasonic frequency of the ultrasonic blade.

4. The method of claim 2 , further comprising correlating the frequency parameter change of the ultrasonic blade to the temperature of the ultrasonic blade.

5. The method of claim 4 , wherein correlating the frequency parameter change further includes correlating the frequency parameter change of the ultrasonic blade to the temperature of the ultrasonic blade based on a plurality of predetermined data correlations of blade temperature to frequency parameter stored on a controller of the surgical instrument.

6. The method of claim 4 , further comprising determining that the temperature of the ultrasonic blade has increased to the upper temperature limit.

7. The method of claim 6 , wherein limiting the temperature of the ultrasonic blade further includes limiting the temperature of the ultrasonic blade to thereby inhibit transection of a tissue.

8. The method of claim 6 , further comprising measuring a third ultrasonic frequency of the ultrasonic blade.

9. The method of claim 8 , further comprising determining that a tissue engaged with the ultrasonic blade is not sealed.

10. The method of claim 9 , further comprising:

(a) determining that the third ultrasonic frequency of the ultrasonic blade reached the predetermined frequency parameter change threshold; and

(b) further adjusting the at least one power parameter of the ultrasonic energy in response to reaching the predetermined frequency parameter change threshold in the ultrasonic blade.

11. The method of claim 9 , further comprising:

(a) determining that the third ultrasonic frequency of the ultrasonic blade is less than the predetermined frequency parameter change threshold; and

(b) remeasuring the third ultrasonic frequency of the ultrasonic blade.

12. The method of claim 8 , further comprising determining that a tissue engaged with the ultrasonic blade is sealed.

13. The method of claim 12 , further comprising terminating the ultrasonic energy based on the determination that the tissue engaged with the ultrasonic blade is sealed.

14. The method of claim 1 , wherein limiting the temperature of the ultrasonic blade further includes inhibiting damage to a clamp arm configured to compress a tissue against the ultrasonic blade.

15. The method of claim 1 , further comprising setting the predetermined frequency parameter change threshold.

16. A method of determining an ultrasonic blade temperature of a surgical instrument having an ultrasonic blade configured to be driven by an ultrasonic energy, the method comprising:

(a) measuring a first ultrasonic frequency of the ultrasonic blade;

(b) measuring a second ultrasonic frequency of the ultrasonic blade after measuring the first ultrasonic frequency;

(c) calculating a frequency parameter change between the measured first and second ultrasonic frequencies of the ultrasonic blade;

(d) correlating the frequency parameter change of the ultrasonic blade to the temperature of the ultrasonic blade to thereby determine the temperature of the ultrasonic blade;

(e) in response to determining that the temperature of the ultrasonic blade has reached a predetermined temperature limit, setting a predetermined frequency parameter change threshold; and

(f) adjusting at least one power parameter of the ultrasonic energy based on the determined temperature of the ultrasonic blade to limit the ultrasonic energy to the predetermined frequency parameter change threshold.

17. The method of claim 16 , wherein correlating the frequency parameter change further includes correlating the frequency parameter change of the ultrasonic blade to the temperature of the ultrasonic blade based on a plurality of predetermined data correlations of blade temperature to frequency parameter stored on a controller of the surgical instrument.

18. A method of limiting an ultrasonic blade temperature of a surgical instrument with an ultrasonic blade configured to apply ultrasonic energy to tissue, the method comprising:

(a) activating the ultrasonic energy to initiate sealing of the tissue;

(b) measuring an initial ultrasonic frequency of the ultrasonic blade;

(c) measuring a first interrogation ultrasonic frequency of the ultrasonic blade;

(d) calculating a frequency parameter change based on the measured initial ultrasonic frequency and the measured first interrogation ultrasonic frequency;

(e) correlating the calculated frequency parameter change to a current temperature of the ultrasonic blade based on a plurality of predetermined data correlations of blade temperature to frequency parameter change;

(f) determining whether the current temperature of the ultrasonic blade has reached a predetermined temperature limit;

(g) in response to determining that the current temperature of the ultrasonic blade has reached the predetermined temperature limit, setting a predetermined frequency parameter change threshold; and

(h) adjusting at least one power parameter of the ultrasonic energy to limit the ultrasonic energy to the predetermined frequency parameter change threshold.

19. The method of claim 18 , further comprising:

(a) measuring a second interrogation ultrasonic frequency of the ultrasonic blade;

(b) determining whether the tissue is sealed;

(c) in response to determining that the tissue is not sealed, determining whether the measured second interrogation ultrasonic frequency exceeds the predetermined frequency parameter change threshold; and

(d) in response to determining that the measured second interrogation ultrasonic frequency exceeds the predetermined frequency parameter change threshold, readjusting the at least one power parameter of the ultrasonic energy to limit the ultrasonic energy to the predetermined frequency parameter change threshold.

20. The method of claim 19 , further comprising in response to determining that the tissue is sealed, terminating the ultrasonic energy.