Medical device with enhanced electrocardiogram channel selection
A wearable cardioverter defibrillator system includes a support structure that a patient can wear. The system also includes electrodes that contact the patient, and define two or more channels from which ECG signals are sensed. A processor may evaluate the channels by analyzing their respective ECG signals, to determine which contains less noise than the other(s). The analysis can be by extracting statistics from the ECG signals, optionally after first processing them, and then by comparing these statistics. These statistics may include tall peak counts, amplitudes of peaks compared to historical peak amplitudes, signal baseline shift, dwell time near a baseline, narrow peak counts, zero crossings counts, determined heart rates, and so on. Once the less noisy signal is identified, its channel can be followed preferentially or to the exclusion of other channels, for continuing monitoring and/or determining whether to shock the patient.
1 . An external defibrillator, comprising:
a pulse sensor configured to detect a first pulse of a subject during a first time and a second pulse of the subject during a second time;
a discharge circuit configured to output an electrical shock to the subject; and
a processor configured to:
determine that the second pulse is weaker than the first pulse;
identify, in a first electrocardiogram (ECG) channel detected during the first time, a first number of peaks with widths narrower than a threshold width;
identify, in a second ECG channel detected during the first time, a second number of peaks with widths narrower than the threshold width;
determine that the first number of peaks is higher than the second number of peaks;
in response to determining that the second pulse is weaker than the first pulse and determining that the first number of peaks is higher than the second number of peaks, determine that the first ECG channel detected during the second time is indicative of ventricular fibrillation (VF); and
in response to determining that the first ECG channel detected during the second time is indicative of VF, cause the discharge circuit to output the electrical shock to the subject.
2 . The external defibrillator of claim 1 , wherein the first ECG channel corresponds to a first vector, and wherein the second ECG channel corresponds to a second vector, the first vector being nonparallel to the second vector.
3 . The external defibrillator of claim 1 , wherein the pulse sensor is further configured to detect a third pulse of the subject during a third time, and wherein the processor is further configured to:
in response to causing the discharge circuit to output the electrical shock, determine that the third pulse is stronger than the second pulse; and
in response to determining that the third pulse is stronger than the second pulse, determine that a condition of the subject is improving.
4 . A medical device, comprising:
a sensor configured to detect a parameter; and
a processor configured to:
determine, in a first ECG channel detected from a subject during a first time, a first selection criterion;
determine, in a second ECG channel detected from the subject during the first time, a second selection criterion;
determine that the first selection criterion is preferred over the second selection criterion;
in response to determining that the first selection criterion is preferred over the second selection criterion, determine whether the first ECG channel detected during a second time is indicative of a condition;
determine, by analyzing the parameter, whether the first ECG channel accurately reflects a state of the subject; and
in response to determining whether the first ECG channel detected during the second time is indicative of the condition and determining whether the first ECG channel accurately reflects the state of the subject, output a determination of whether to shock the subject.
5 . The medical device of claim 4 , wherein the sensor is configured to detect the parameter during the second time.
6 . The medical device of claim 4 , wherein the parameter is a patient parameter detected from the subject, a system parameter, or an environmental parameter.
7 . The medical device of claim 6 , wherein the patient parameter comprises a blood oxygen level, a blood flow, a blood pressure, a blood perfusion, a pulsatile change in light transmission or reflection properties of perfused tissue, heart sounds, a heart wall motion, breathing sounds, a pulse, an ejection fraction, a stroke volume, cardiac output, or a movement.
8 . The medical device of claim 6 , wherein the system parameter comprises a system identification, a battery status, system date, a system time, a report of self-testing, a record of data entered, a record of an episode, or a record of an intervention, or
wherein the environmental parameter comprises a temperature or a humidity.
9 . The medical device of claim 4 , wherein the first selection criterion or the second selection criterion comprises a baseline shift, a dwell time, a ratio of peak amplitude, a number of peaks with widths narrower than a threshold width, a number of peaks with amplitudes above a threshold amplitude, a number of zero crossings, or a heart rate.
10 . The medical device of claim 4 , wherein the processor is configured to:
determine whether the first ECG channel detected during the second time is indicative of the condition by determining that the first ECG channel detected during the second time is indicative of VF or ventricular tachycardia (VT);
determine whether the first ECG channel accurately reflects the state of the subject by determining that the first ECG channel does not accurately reflect the state of the subject; and
output the determination by outputting the determination to not shock the subject.
11 . The medical device of claim 4 , wherein the parameter is a first parameter detected during the second time,
wherein the sensor is configured to detect a second parameter during a third time, and
wherein the processor is configured to:
determine whether the first ECG channel detected during the second time is indicative of the condition by determining that the first ECG channel detected during the second time is indicative of VF or VT;
determine, by analyzing the first parameter, whether the first ECG channel accurately reflects the state of the subject by:
comparing the first parameter and the second parameter; and
in response to comparing the first parameter and the second parameter, determining that the first ECG channel accurately reflects the state of the subject; and
output the determination by outputting the determination to shock the subject.
12 . A method, comprising:
determining whether a non-ECG parameter is indicative of a condition of a subject;
determining, in a first ECG channel detected during a first time, a first selection criterion;
determining, in a second ECG channel detected during the first time, a second selection criterion;
determining that the first selection criterion is preferred over the second selection criterion;
in response to determining that the first selection criterion is preferred over the second selection criterion, determining whether the first ECG channel detected during a second time is indicative of the condition; and
in response to determining whether the non-ECG parameter is indicative of the condition and determining whether the first ECG channel detected at the second time is indicative of the condition, outputting a determination of whether to shock the subject.
13 . The method of claim 12 , wherein comparing the first selection criterion and the second selection criterion comprises:
comparing a first baseline shift of the first ECG channel detected during the first time and a second baseline shift of the second ECG channel detecting during the first time;
comparing a first dwell time of the first ECG channel detected during the first time and a second dwell time of the second ECG channel detected during the first time;
comparing a first ratio of peak amplitude of the first ECG channel detected during the first time and a second ratio of the second ECG channel detected during the first time;
comparing a first number of peaks with widths narrower than a threshold width of the first ECG channel detected during the first time and a second number of peaks with widths narrower than a threshold width of the second ECG channel detected during the first time;
comparing a first number of peaks with amplitudes above a threshold amplitude of the first ECG channel detected during the first time and a second number of peaks with amplitudes above a threshold amplitude of the second ECG channel detected during the first time;
comparing a first number of zero crossings of the first ECG channel detected during the first time and a second number of zero crossings of the second ECG channel detected during the first time; or
comparing a first heart rate determined from the first ECG channel detected during the first time and a second heart rate determined from the second ECG channel detected during the first time.
14 . The method of claim 12 , wherein determining that the non-ECG parameter is indicative of the condition comprises determining that the non-ECG parameter is not indicative of VF or VT;
wherein determining whether the first ECG channel detected during the second time is indicative of the condition comprises determining that the first ECG channel detected during the second time is indicative of VF or VT; and
wherein outputting the determination comprises outputting the determination to not shock the subject.
15 . The method of claim 12 , wherein determining that the non-ECG parameter is indicative of the condition comprises determining that the non-ECG parameter is indicative of VF or VT;
wherein determining whether the first ECG channel detected during the second time is indicative of the condition comprises determining that the first ECG channel detected during the second time is indicative of VF or VT; and
wherein outputting the determination comprises outputting the determination to shock the subject.
16 . The method of claim 12 , wherein the non-ECG parameter is a first non-ECG parameter detected at the first time, the method further comprising:
determining whether a second non-ECG parameter detected at the second time is indicative of the condition; and
in response to determining whether the second non-ECG parameter is indicative of the condition, determining that a state of the subject is deteriorating,
wherein determining that the first ECG channel detected during the second time is indicative of the condition comprises determining that the first ECG channel detected during the second time is indicative of VF or VT, and
wherein outputting the determination comprises outputting a determination to shock the subject.
17 . The method of claim 12 , wherein the non-ECG parameter is a first non-ECG parameter detected at the first time, the method further comprising:
detecting the first ECG channel during the first time and the second time;
detecting the second ECG channel during the first time;
determining whether a second non-ECG parameter detected at a third time is indicative of the condition;
in response to determining whether the second non-ECG parameter is indicative of the condition, determining that a state of the subject is deteriorating; and
in response to determining that the condition of the subject is deteriorating, detecting the first ECG channel during the second time.
18 . The method of claim 12 , further comprising:
in response to outputting the determination of whether to shock the subject, causing a discharge circuit to output an electrical shock to the subject.
19 . The method of claim 12 , wherein the non-ECG parameter is a patient parameter detected from the subject, a system parameter, or an environmental parameter.
20 . The method of claim 12 , wherein the non-ECG parameter is a first non-ECG parameter detected during the second time, the method further comprising:
identifying a second non-ECG parameter detected during a third time;
determine whether the first ECG channel detected during the second time is indicative of the condition by determining that the first ECG channel detected during the second time is indicative of VF or VT;
determine, by analyzing the first non-ECG parameter, whether the first ECG channel accurately reflects a state of the subject by:
comparing the first non-ECG parameter and the second non-ECG parameter; and
in response to comparing the first non-ECG parameter and the second non-ECG parameter, determining that the first ECG channel accurately reflects the state of the subject; and
output the determination by outputting the determination to shock the subject.