1. An electrode contact sensing system that provides information indicative of contact between an electrode and tissue, the system comprising
an electrode housed within a distal portion of a catheter shaft;
at least one electromechanical sensor operatively associated with the electrode and adapted to generate an electrical signal in response to a mechanical load on said sensor resulting from contact between said electrode and the tissue; and
an output device electrically connected to said at least one sensor, the output device being adapted to receive the electrical signal and to present to a user of the system an indicator of contact between the electrode and the tissue.
2. The system of claim 1, wherein said electrical signal generated by said at least one electromechanical sensor is a variable electrical signal that varies in response to variations in said mechanical load.
3. The system of claim 2, wherein said variations of said mechanical load are indicative of contact stress between said electrode and the tissue, and said indicator of contact presented by said output device indicates to the user the contact stress between the electrode and the tissue.
4. The system of claim 2, wherein said variable electrical signal has a strength, and wherein said strength of said variable electrical signal is proportional to contact stress.
5. The system of claim 2, wherein said variable electrical signal has an amplitude, and wherein said amplitude of said variable electrical signal is proportional to the magnitude of contact stress.
6. The system of claim 2, wherein said variable electrical signal has a periodicity.
7. The system of claim 6, wherein said periodicity of said variable electrical signal corresponds to the periodicity of contact stress.
8. The system of claim 1, wherein the at least one electromechanical sensor includes a piezoelectric film.
9. The system of claim 1, wherein the at least one electromechanical sensor is laminated on a support structure and the support structure is connected directly to the electrode.
10. The system of claim 1, wherein the at least one electromechanical sensor is laminated on a support structure and the support structure is provided in a spaced-apart relation from the electrode.
11. The system of claim 1, wherein multiple electrically-isolated, electromechanical sensors are laminated on a single support structure operatively associated with the electrode.
12. The system of claim 10, wherein the multiple electrically-isolated, electromechanical sensors provide information concerning the directionality of the electrode-tissue contact.
13. The system of claim 1, wherein the at least one electromechanical sensor is housed within the electrode.
14. The system of claim 13, wherein the at least one electromechanical sensor is substantially arcuate.
15. The system of claim 13 further comprising a plurality of electromechanical sensors housed within the electrode, said electromechanical sensors comprising a first electromechanical sensor and an adjacent electromechanical sensor, said first electromechanical being radially offset from said adjacent electromechanical sensor by about 30 to about 180 degrees.
16. The system of claim 15, wherein the plurality of electromechanical sensors are a plurality of electrically-isolated piezoelectric sensors.
17. The system of claim 1, wherein the at least one electromechanical sensor contacts the electrode without being mounted to the electrode.
18. A method of sensing electrode-tissue contact comprising
contacting a tissue with an electrode housed within a distal portion of a catheter;
generating electric signals in an electromechanical sensor in response to contact stress of the electrode with the tissue; and
outputting the electrical signals to a monitoring device.
19. The method of claim 18 further comprising assessing contact stresses between the electrode and tissue based on the electric signals.
20. The method of claim 19 further comprising determining contact based on strength of the electric signals.
21. The method of claim 19 further comprising determining contact based on an amplitude of the electric signals.
22. The method of claim 19 further comprising determining contact based on periodicity of the electric signals.
23. The method of claim 19 further comprising reducing noise artifacts during distal portion movement.
24. The method of claim 19 further comprising reducing noise effects from intermittent contact of the electrode.
25. The method of claim 19 further comprising detecting stress of the electrode in any direction.
26. The method of claim 19, wherein the electromechanical sensor comprises at least two piezoelectric sensors, and further comprising determining direction and plane of tissue contact with the electrode based on relative magnitude and direction of signals obtained from each of the at least two piezoelectric sensors.
27. A system comprising
an electrode means for applying ablative energy to a tissue;
a means for generating electromechanical signals corresponding to contact stress of the electrode means; and
a means for assessing contact between the electrode means and the tissue based on the electromechanical signals.
28. The system of claim 27 further comprising a means for reducing noise artifacts.
29. The system of claim 27 further comprising a means for reducing noise effects from intermittent tissue contact.
30. The system of claim 27 further comprising a means for determining direction and plane of tissue contact with the electrode means based on relative magnitude and direction of a signal obtained from each of at least two electro-mechanical sensors operatively associated with the electrode means.
31. The system of claim 30, wherein the at least two electro-mechanical sensors are two or more electrically-isolated piezoelectric sensors.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1-14. (canceled)
15. A method for gas generation comprising:
(a) providing a circuit comprising a power source;
(b) connecting first and second electrodes to said circuit; and
(c) providing an aqueous electrolyte fluid between said electrodes comprising an azide having a formula XN3 for generation of a gas containing nitrogen in an electrochemical reaction, said electrolyte fluid containing a magnesium salt for chemical binding of hydroxide ions formed during the electrochemical reaction.
16. The method according to claim 15, wherein the azide comprises sodium azide.
17. The method according to claim 15, wherein the magnesium salt comprises magnesium sulfate.
18. The method according to claim 15, wherein the magnesium salt comprises magnesium perchlorate.
19. The method according to claim 15, wherein the magnesium salt is added stoichiometrically or in excess with regard to the amount of azide.
20. The method according to claim 15, further comprising an anti-freeze agent added to the electrolyte fluid.
21. The method according to claim 20, wherein the anti-freeze agent comprises a member selected from the group consisting of ethylene glycol, dimethyl sulfoxide, and mixtures thereof.
22. The method according to claim 15, wherein the electrolyte fluid contains nickel sulfate to prevent a hydrogen over-voltage of one of said first and second electrodes that forms a cathode.
23. The method according to claim 15, wherein the electrodes comprise steel.
24. The method according to claim 23, wherein the electrodes comprise chrome-nickel steel.
25. The method according to claim 15, wherein the electrodes comprise graphite.
26. The method according to claim 15, wherein the electrodes comprise plastic with embedded graphite powder.
27. The method according to claim 15, wherein the magnesium salt comprises magnesium sulfate.
28. The method according to claim 15, wherein the magnesium salt comprises magnesium perchlorate.