Confidence analyzer for an automated external defibrillator (AED) with dual ECG analysis algorithms

1. An automated external defibrillator (AED) for use during cardiopulmonary resuscitation (CPR) comprising:

an input of an ECG signal;

a user interface having at least one of an aural instruction output and a visual display;

an ECG analyzer in communication with the input and operable to determine a shockable cardiac rhythm in the presence of CPR-related signal noise artifact from the input;

a confidence analyzer operable to determine a confidence level in the determined shockable cardiac rhythm; and

a processor in communication with the user interface, the ECG analyzer and the confidence analyzer, the processor operable to execute software instructions to adjust a shock decision criteria if the confidence level is less than a predetermined confidence threshold, decide that a shock is to be delivered by an electrotherapy delivery circuit based on the adjusted shock decision criteria, and arm an electrotherapy delivery circuit responsive to a shock delivery decision,

wherein the predetermined confidence threshold is a distance from a decision surface which is constructed from at least corresponding pairs of one of a CLAS score and a FLATS score, and

wherein the CLAS score is comprised of a score from an ECG buffer from the ECG signal filtered at a center frequency of about 25 Hertz and the FLATS score is comprised of a second score from the ECG buffer filtered at a center frequency of about 35 Hertz.

2. The AED of claim 1 , wherein the software instructions to adjust a shock decision criteria comprise instructions to issue a user prompt to stop CPR via the user interface and to decide that a shock is to be delivered based on a second ECG analyzer output.

3. The AED of claim 2 , wherein the software instructions to issue a user prompt to stop CPR via the user interface are executed prior to the end of a predetermined CPR period.

4. The AED of claim 2 , wherein the software instructions to issue a user prompt to stop CPR via the user interface are executed after the end of a predetermined CPR period.

5. The AED of claim 1 wherein the software instructions to adjust a shock decision criteria comprise increasing a minimum number of a shockable cardiac rhythm determinations from the ECG analyzer.

6. The AED of claim 5 , wherein the minimum number is increased from three to four.

7. The AED of claim 1 , wherein the processor controls the user interface to issue an indication of the confidence level in the determined shockable cardiac rhythm.

8. A method for controlling an electrotherapy output from a defibrillator, comprising the steps of:

receiving an ECG signal data stream from two or more external electrodes in electrical contact with a patient, the ECG signal data comprising a cardiac signal characterized by corruption from a CPR compressions noise artifact;

obtaining an ECG signal data stream buffer, the buffer corresponding to a predetermined time segment;

analyzing the ECG signal data stream buffer to determine a shockable cardiac rhythm with a first ECG analysis algorithm;

calculating a confidence level of the determined shockable cardiac rhythm;

adjusting a shock decision criteria if the confidence level is less than a predetermined confidence threshold, wherein the predetermined confidence threshold is a distance from a decision surface;

deciding that a shock is to be delivered by an electrotherapy delivery circuit based on the analyzing step and the adjusting step; and

arming an electrotherapy delivery circuit responsive to the deciding step.

9. The method of claim 8 , wherein the deciding step is further based on a plurality of analyzing steps of different ECG signal data stream buffers, and further wherein the adjusting step comprises increasing a criteria of a minimum number of analyzing steps required for a shock decision.

10. The method of claim 9 , wherein the adjusting step increases the minimum number of analyzing steps from three to four.

11. The method of claim 8 , wherein the adjusting step further comprises switching from using the first ECG analysis algorithm to using a second ECG analysis algorithm, and following the adjusting step comprising the steps of;

receiving a second ECG signal data stream comprising a cardiac signal without corruption from a CPR compressions noise artifact;

obtaining a second ECG signal data stream buffer, the buffer corresponding to a second predetermined time segment; and

analyzing the second ECG signal data stream buffer to determine a shockable cardiac rhythm with the second ECG analysis algorithm,

wherein the deciding step that a shock is to be delivered by an electrotherapy delivery circuit is further based on the analyzing the second ECG signal data step.

12. The method of claim 11 , further comprising the step of issuing a user prompt 219 to stop CPR just prior to the receiving a second ECG signal data stream step.

13. The method of claim 12 , wherein the issuing step occurs prior to the end of a predetermined CPR period.

14. The method of claim 12 , wherein the issuing step occurs at the end of a predetermined CPR period.