Method of determining depth of chest compressions during CPR

• US 7,122,014 B2
• Filed: 05/12/2004
• Issued: 10/17/2006
• Est. Priority Date: 10/25/2002
• Status: Expired due to Term

• Current Assignee: Zoll Circulation Incorporated (Asahi Kasei Corporation)
• Original Assignee: Zoll Circulation Incorporated (Asahi Kasei Corporation)
• Inventors: Berger, Ronald D., Halperin, Henry R., Sherman, Darren R., Palazzolo, James Adam
• Primary Examiner(s): DEMILLE, DANTON D
• Application Number:
  US10/844,660
• Publication Number:
  US 20040210170A1
• Time in Patent Office: 888 Days
• Field of Search: None
• US Class Current: 601/41
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/346 Analysis of electrocardiograms
• 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 5/7242 using integration
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61H 2201/5007 computer controlled
• CPC Class Codes: A61H 2201/501 connected to external computer devices or networks
• CPC Class Codes: A61H 2201/5012 using the internet
• CPC Class Codes: A61H 2201/5043 Displays
• CPC Class Codes: A61H 2201/5048 Audio interfaces, e.g. voice or music controlled
• CPC Class Codes: A61H 2201/5058 Sensors or detectors
• CPC Class Codes: A61H 2201/5084 Acceleration sensors
• CPC Class Codes: A61H 2201/5097 wireless
• CPC Class Codes: A61H 2230/04 Heartbeat characteristics, e.g. E.G.C., blood pressure modulation
• CPC Class Codes: A61H 2230/08 Other bio-electrical signals
• CPC Class Codes: A61H 2230/40 Respiratory characteristics
• CPC Class Codes: A61H 31/005 with feedback for the user
• CPC Class Codes: A61H 31/006 Power driven
• CPC Class Codes: A61H 31/007 : Manual driven
• CPC Class Codes: A61H 31/008 : Supine patient supports or bases, e.g. improving air-way access to the lungs
• CPC Class Codes: A61M 16/00 : Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/0078 : Breathing bags
• CPC Class Codes: A61N 1/39044 : in combination with cardiopulmonary resuscitation [CPR] therapy
• CPC Class Codes: G06F 2218/04 : Denoising
• CPC Class Codes: Y10S 128/901 : Suppression of noise in electric signal
• CPC Class Codes: Y10S 601/08 : Artificial respiration with computer control
• CPC Class Codes: Y10S 601/09 : including biological sensors
• CPC Class Codes: Y10S 601/10 : Artificial respiration combined with non-artificial respiration therapy

Abstract

A method of processing a raw acceleration signal, measured by an accelerometer-based compression monitor, to produce an accurate and precise estimated actual depth of chest compressions. The raw acceleration signal is filtered during integration and then a moving average of past starting points estimates the actual current starting point. An estimated actual peak of the compression is then determined in a similar fashion. The estimated actual starting point is subtracted from the estimated actual peak to calculate the estimated actual depth of chest compressions. In addition, one or more reference sensors (such as an ECG noise sensor) may be used to help establish the starting points of compressions. The reference sensors may be used, either alone or in combination with other signal processing techniques, to enhance the accuracy and precision of the estimated actual depth of compressions.

Claims

1. A method of determining the estimated actual depth of chest compressions during chest compressions, wherein the method comprises the steps of:

providing an accelerometer capable of sensing accelerations caused by chest compressions;

performing chest compressions, wherein the accelerometer measures an acceleration signal during chest compressions;

double integrating the acceleration signal to produce a measured depth signal corresponding to the measured depth of chest compressions;

calculating an autoregressive moving average of the measured compression depth signal;

wherein the estimated actual depth of compressions comprises the autoregressive moving average of the measured compression depth signal.

2. The method of claim 1 comprising the further steps of:

providing a reference sensor capable of identifying the start of a compression;

identifying the start of a compression with the reference sensor; and

calculating estimated actual depth of compressions when the start of a compression has been identified.

3. The method of claim 2 wherein the step of providing the reference sensor comprises providing a sensor capable of measuring an ECG signal of a patient, and wherein the method comprises the further steps of:

measuring the ECG signal of the patient during compressions, wherein the ECG signal comprises a noise component and an actual component;

identifying the noise component of the ECG signal;

wherein the start of each compression is identified by a predetermined change in the noise component of the ECG signal.

4. A method of estimating the actual depth of chest compressions during chest compressions, wherein the method comprises the steps of:

providing an accelerometer capable of measuring the acceleration caused by chest compressions;

performing compressions, wherein the accelerometer produces an acceleration signal corresponding to the acceleration of chest compressions;

providing the acceleration signal to a first filter, said first filter producing a filtered acceleration signal;

providing the filtered acceleration signal to a processor, said processor producing a velocity signal corresponding to the velocity of chest compressions upon integrating the filtered acceleration signal;

providing the velocity signal to a second filter, said second filter producing a filtered velocity signal;

providing the filtered velocity signal to the processor, said processor producing a chest depth signal corresponding to the depth of chest compressions upon integrating the filtered velocity signal;

providing the chest depth signal to a baseline limiter, said baseline limiter producing a chest depth signal with a processed baseline component;

providing the chest depth signal with a processed baseline component to a starting point detector, said starting point detector identifying the starting points of chest compressions, and further providing a starting point signal corresponding to the starting points of chest compressions to a means for combining signals;

providing the chest depth signal with a processed baseline component to a peak limiter, said peak limiter producing a chest depth signal with a processed peak component;

providing the chest depth signal with a processed peak component to a peak detector, said peak detector identifying the peaks of chest compressions corresponding to the maximum depths of compressions, and further providing a peak signal corresponding to the peaks of chest compressions to the means for combining signals;

calculating the estimated actual depth of chest compressions by combining the starting point signal with the peak signal.

5. The method of claim 4 comprising the further step of filtering the chest depth signal with a processed baseline component.

6. The method of claim 4 comprising the further step of filtering the chest depth signal with a processed peak component.

7. The method of claim 4 comprising the further steps of:

providing the estimated actual depth of compressions to a means for user feedback operably connected to the processor; and

providing feedback to a user that indicates whether chest compressions fall within a predetermined range of values.

8. The method of claim 4 comprising the further steps of:

providing a reference sensor capable of identifying the start of a compression;

identifying the start of a compression with the reference sensor; and

calculating estimated actual depth of compressions when the start of a compression has been identified.

9. The method of claim 8 wherein the step of providing the reference sensor comprises providing a sensor capable of measuring an ECG of a patient, and wherein the method comprises the further steps of:

measuring the ECG signal of the patient during compressions, wherein the ECG signal comprises a noise component and an actual component;

identifying the noise component of the ECG signal;

wherein the start of each compression is identified by a predetermined change in the noise component of the ECG signal.

10. A method of estimating the actual depth of chest compressions during chest compressions, wherein the method comprises the steps of:

providing a means for performing chest compressions on a patient;

providing a sensor capable of measuring an ECG signal of the patient and providing an accelerometer capable of measuring the acceleration of chest compressions;

performing chest compressions on the patient, wherein the accelerometer produces an acceleration signal corresponding to the acceleration of chest compressions;

measuring the ECG signal of the patient, wherein the measured ECG signal comprises an actual component and a noise component, and wherein at least part of the noise component is caused by chest compressions;

identifying the noise component of the ECG signal, wherein a starting point of a compression is identified by a change in the noise component of the ECG signal;

calculating the estimated actual depth of compressions by double integrating the acceleration signal when the starting point of a compression has been identified.

11. A method of performing CPR on a patient, wherein the method comprises the steps of:

providing an accelerometer capable of sensing accelerations caused by chest compressions;

performing chest compressions, wherein the accelerometer measures an acceleration signal during chest compressions;

double integrating the acceleration signal to produce a measured depth signal corresponding to the measured depth of chest compressions;

calculating an autoregressive moving average of the measured compression depth signal;

wherein the estimated actual depth of compressions comprises the autoregressive moving average of the measured compression depth signal;

providing a means for ventilating the patient; and

ventilating the patient during CPR.

12. The method of claim 11 wherein the step of providing a means for ventilating the patient comprises providing a means for electro-ventilation.

13. The method of claim 11 comprising the further steps of:

providing a reference sensor capable of identifying the start of a compression;

identifying the start of a compression with the reference sensor; and

calculating estimated actual depth of compressions when the start of a compression has been identified.

14. The method of claim 13 wherein the step of providing the reference sensor comprises providing a sensor capable of measuring an ECG signal of a patient, and wherein the method comprises the further steps of:

measuring the ECG signal of the patient during compressions, wherein the ECG signal comprises a noise component and an actual component;

identifying the noise component of the ECG signal;

wherein the start of each compression is identified by a predetermined change in the noise component of the ECG signal.