External defibrillator
An external defibrillator estimates the phase of ventricular defibrillation (VF) by deriving, from an ECG exhibiting VF, at least one quality marker representing the morphology of the ECG and, therefore, the duration of the VF. The duration of the VF is calculated as a function of the value (s) of the quality marker (s). The quality marker (s) may comprise any one or more of the median slope of the ECG, the average slope of the ECG, the ratio of the power in relatively high and low frequency bands of the ECG, and a measure of the density and amplitude of peaks in the ECG, over a predetermined period.
1. An external defibrillator comprising:
a processor;
a pair of electrodes; and
a non-transitory computer-readable storage medium having instructions stored which, when executed by the processor, perform operations comprising:
receiving electrical signals from the pair of electrodes when the pair of electrodes are in contact with a patient;
determining, from the electrical signals, an electrocardiogram of the patient; and
when, based on the electrocardiogram, the patient is in a state of ventricular fibrillation:
identifying an average of slopes over a period of time in the electrocardiogram based on duration of the ventricular fibrillation and one or more quality marker(s);
estimating a current phase of ventricular fibrillation based on the average of slopes; and
outputting an instruction based on the current phase of ventricular fibrillation.
2. The external defibrillator of claim 1 , wherein the estimating of the current phase of ventricular fibrillation is further based on a median slope over the period of time.
3. The external defibrillator of claim 2 , wherein the estimating of the current phase of ventricular fibrillation is further based on a frequency ratio of the ventricular fibrillation over the period of time.
4. The external defibrillator of claim 1 , wherein the outputting of the instruction comprises outputting an audible signal.
5. The external defibrillator of claim 4 , wherein the audible signal indicates the patient is not in an electrical state of ventricular fibrillation and cardiopulmonary resuscitation should begin.
6. An external defibrillator comprising:
a processor;
a pair of electrodes; and
a non-transitory computer-readable storage medium having instructions stored which, when executed by the processor, perform operations comprising:
receiving electrical signals from the pair of electrodes when the pair of electrodes are in contact with a patient;
determining, from the electrical signals, an electrocardiogram of the patient; and
when, based on the electrocardiogram, the patient is in a state of ventricular fibrillation;
identifying an average of slopes over a period of time in the electrocardiogram;
estimating a current phase of ventricular fibrillation based on the average of slopes; and
outputting an instruction based on the current phase of ventricular fibrillation, wherein the average of slopes is calculated based on duration of the ventricular fibrillation and using quality marker(s), as follows:
t
=
-
B
+
C
[
-
ln
(
Q
-
D
A
)
]
E
where t represents the duration of the ventricular fibrillation, A, B, C, D, and E are constants, and Q represents a value of the quality marker, if only one, or a linear combination the values of the quality markers if more than one.
7. The external defibrillator of claim 6 , wherein the estimating of the current phase of ventricular fibrillation is further based on a median slope over the period of time.
8. The external defibrillator of claim 7 , wherein the estimating of the current phase of ventricular fibrillation is further based on a frequency ratio of the ventricular fibrillation over the period of time.
9. The external defibrillator of claim 6 , wherein the outputting of the instruction comprises outputting an audible signal.
10. The external defibrillator of claim 9 , wherein the audible signal indicates that the patient is not in an electrical state of ventricular fibrillation and cardiopulmonary resuscitation should begin.
11. An external defibrillator comprising:
a processor;
a pair of electrodes; and
a non-transitory computer-readable storage medium having instructions stored which, when executed by the processor, perform operations comprising:
receiving electrical signals from the pair of electrodes when the pair of electrodes are in contact with a patient;
determining, from the electrical signals, an electrocardiogram of the patient; and
when, based on the electrocardiogram, the patient is in a state of ventricular fibrillation:
identifying an average of slopes over a period of time in the electrocardiogram;
identifying a frequency ratio of power in a high frequency band over power in a low frequency band within the electrocardiogram over the period of time;
estimating a current phase of ventricular fibrillation based on the average of slopes and the frequency ratio of power; and
outputting an instruction based on the current phase of ventricular fibrillation.
12. The external defibrillator of claim 11 , wherein the outputting of the instruction comprises outputting an audible signal.
13. The external defibrillator of claim 12 , wherein the audible signal indicates the patient is not in an electrical state of ventricular fibrillation and cardiopulmonary resuscitation should begin.