Method and apparatus for detecting artifact signals in the electrocardiogram of a patient caused by CPR and/or patient motion using patient impedance

• US 20060025825A1
• Filed: 07/29/2005
• Published: 02/02/2006
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: Scion Medical Ltd. (Siemens AG)
• Original Assignee: Limar Medical Inc.
• Inventors: Bowers, Kyle R.
• Granted Patent: US 7,822,471 B2
• Time in Patent Office: Days
• US Class Current: 607/5
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• 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 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61N 1/39044 in combination with cardiopulmonary resuscitation [CPR] therapy

Abstract

Medical apparatus for detecting the presence of artifact signals generated in the electrocardiogram of a patient by CPR and/or other patient motion. The presence of artifact signals is determined by analyzing variations in a measured electrical signal that represents the patient'"'"'s transthoracic impedance. Such detection is important because the presence of CPR and/or motion artifacts can disrupt a patient'"'"'s electrocardiogram (ECG) signal. The patient'"'"'s impedance signal data is stored in the apparatus and analyzed to determine if the characteristics are indicative of the presence of CPR and/or motion artifacts. This analysis is performed independently of ECG data and may be used as an indicator of the underlying ECG rhythm classification. In essence, if the impedance exceeds some threshold amount, so as to indicate the presence of CPR or patient motion which can render the ECG data unreliable, the normal interpretation of the ECG data is interrupted. Applications of the invention include, but are not limited to, advising or not advising, defibrillation therapy, CPR or intravenous medicinal therapy.

Claims

1. A method for detecting artifact signals in the electrocardiogram of a patient caused by CPR and/or patient motion, the method comprising:

acquiring impedance signal data from the patient; and

analyzing variations in the acquired impedance signal data for characteristics indicative of artifact signals caused by CPR and/or patient motion.

2. A method according to claim 1 wherein the analyzed variations are compared to a predetermined threshold for a given time period.

3. A method according to claim 2 wherein the predetermined threshold comprises a 10.5 ohm threshold.

4. A method according to claim 2 wherein the given time period comprises 0.5-second segments over a three-second period.

5. A method according to claim 4 wherein a multiple 0.5-second segments are considered over the three-second period.

6. Apparatus for detecting artifact signals in an electrocardiogram of a patient caused by CPR and/or patient motion, the apparatus comprising:

a signal circuit for passing an impedance-sensing signal through a patient;

an impedance measuring circuit connected to the signal circuit for measuring the impedance-sensing signal;

a conversion circuit for digitizing the impedance-sensing signal; and

a microprocessor for analyzing the digitized signal data for characteristics indicative of CPR and/or patient motion.

7. Apparatus according to claim 6 wherein the digitized signal data is evaluated for variations that are compared to a predetermined threshold for a given time period.

8. Apparatus according to claim 7 wherein the predetermined threshold comprises a 10.5 ohm threshold.

9. Apparatus according to claim 7 wherein the predetermined threshold is varied dependent on the operating mode of the device.

10. Apparatus according to claim 7 wherein the given time period comprises 0.5-second segments over a three-second period.

11. Apparatus according to claim 10 wherein multiple 0.5-second segments are considered over the three-second period.

12. Apparatus according to claim 6 wherein the digitized signal data is stored in memory prior to analyzing the signal data.

13. A method for determining if a patient is undergoing CPR and/or motion, the method comprising:

passing an impedance-sensing signal through the chest of the patient; and

analyzing variations in the impedance-sensing signal to determine when the patient is undergoing CPR and/or motion.

14. A method for treating a patient, the method comprising:

measuring the electrocardiogram of the patient and measuring variations in the transthoracic impedance of the patient;

determining when the patient is undergoing CPR and/or motion from variations in the transthoracic impedance;

applying conventional defibrillation therapy to the patient only if variations in the transthoracic impedance indicate that the patient is not undergoing CPR and/or motion.

15. A method according to claim 14 wherein conventional defibrillation therapy comprises applying a defibrillation shock to the patient when the patient is in VF, but not applying a defibrillation shock to the patient when the patient is in fine VF below the shockable threshold or asystole.

16. A method for treating a patient, the method comprising:

measuring the electrocardiogram of the patient and measuring variations in the transthoracic impedance of the patient;

determining when the patient is receiving CPR from a rescuer, by analyzing variations in the transthoracic impedance;

allowing the rescuer to perform CPR therapy for a predetermined period of time;

stopping the rescuer from performing CPR after the predetermined period of time;

applying conventional defibrillation therapy to the patient only if variations in the transthoracic impedance indicate that the patient is not undergoing CPR and/or motion.