External defibrillator

• US 9,238,146 B2
• Filed: 12/05/2014
• Issued: 01/19/2016
• Est. Priority Date: 11/29/2010
• Status: Active Grant

• Current Assignee: Stryker European Operations Limited (Stryker Corporation)
• Original Assignee: Heartsine Technologies Limited (Stryker Corporation)
• Inventors: Navarro-Paredes, Cesar Oswaldo, Anderson, John McCune, Anderson, Janice
• Primary Examiner(s): Wieland, Robert N
• Application Number:
  US14/561,571
• Publication Number:
  US 20150088215A1
• Time in Patent Office: 410 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/3918 characterised by shock pathway, e.g. by electrode configuration
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3931 Protecting, e.g. back-up systems
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

An external defibrillator includes patient electrodes (20) for obtaining the patient'"'"'s electrocardiogram (ECG) and for applying a shock to the patient. A microprocessor (24) analyses the patient'"'"'s ECU using a diagnostic algorithm to detect if the patient'"'"'s heart is in a shockable rhythm, and shock delivery circuitry (10) is enabled when a shockable rhythm is detected by the diagnostic algorithm. The patient electrodes also allow obtaining a signal (Z) which is a measure of the patient'"'"'s transthoracic impedance and the microprocessor is responsive to Z to detect conditions likely to cause the diagnostic algorithm to generate a false detection of a shockable rhythm. If such detection is made, the microprocessor prevents detection of a shockable rhythm by the diagnostic algorithm, at least for a period of time.

Claims

1. A defibrillator comprising:

electrodes;

a processor; and

a circuit connecting the processor and the electrodes, wherein, when the electrodes are in contact with a patient, the processor performs operations comprising;

receiving a signal from the patient;

determining, from the signal, a measure of transthoracic impedance of the patient;

identifying, based on the measure of transthoracic impedance, that an interference condition is present, wherein the interference condition causes a false detection of a shockable rhythm in the patient; and

performing, based on the interference condition, one of;

inhibiting the circuit from delivering a shock to the patient and preventing a diagnostic algorithm from detecting a shockable rhythm.

2. The defibrillator of claim 1, wherein the interference condition is one of a movement of the patient and a touching of the electrodes by an operator.

3. The defibrillator of claim 1, wherein when the electrodes are in contact with a patient, the processor performs further operations comprising:

establishing an electrocardiogram of the patient.

4. The defibrillator of claim 3, wherein inhibiting the circuit from delivering a shock to the patient is independent of the electrocardiogram.

5. The defibrillator of claim 1, wherein inhibiting the circuit from delivering a shock to the patient is performed for a predefined period of time.

6. The defibrillator of claim 1, wherein when the electrodes are in contact with a patient, the processor performs further operations comprising:

identifying that the interference condition is present by forming a first derivative of the measure of transthoracic impedance with respect to a period of time to yield a first derivative; and

deriving a quantity of interference related to the first derivative.

7. The defibrillator of claim 6, wherein when the electrodes are in contact with a patient, the processor performs further operations comprising:

determining if the quantity of interference exceeds a threshold level.

8. The defibrillator of claim 7, wherein the quantity of interference is a measure of the number of times the amplitude of the first derivative exceeds the threshold level.

9. The defibrillator of claim 1, wherein when the electrodes are in contact with the patient, the processor performs additional operations comprising:

converting the measure of transthoracic impedance from analog to digital, to yield a digital signal; and

using the digital signal for the identifying that the interference condition is present.

10. A method comprising:

receiving a signal from a patient via electrodes;

determining, from the signal and via a processor, a measure of transthoracic impedance of the patient;

identifying, based on the measure of transthoracic impedance, that an interference condition is present, wherein the interference condition causes a false detection of a shockable rhythm in the patient; and

performing, based on the interference condition, one of;

inhibiting the circuit from delivering a shock to the patient and preventing a diagnostic algorithm from detecting a shockable rhythm.

11. The method of claim 10, wherein the interference condition is one of a movement of the patient and a touching of the electrodes by an operator.

12. The method of claim 11, further comprising:

establishing an electrocardiogram of the patient.

13. The method of claim 12, wherein inhibiting the circuit from delivering a shock to the patient is independent of the electrocardiogram.

14. The method of claim 11, wherein inhibiting the circuit from delivering a shock to the patient is performed for a predefined period of time.

15. The method of claim 11, further comprising:

determining when the interference condition is present by forming a first derivative of the measure of transthoracic impedance with respect to a period of time to yield a first derivative; and

deriving a quantity of interference related to the first derivative.

16. The method of claim 15, further comprising:

determining if the quantity of interference exceeds a threshold level.

17. The method of claim 16, wherein the quantity of interference is a measure of the number of times the amplitude of the first derivative exceeds the threshold level.

18. The method of claim 11, further comprising:

converting the measure of transthoracic impedance from analog to digital, to yield a digital signal; and

using the digital signal for the identifying that the interference condition is present.