# US 8,465,292 B2 · System and method for increased accuracy in determining CPR chest compression depth in real time > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,465,292 B2 - Document ID: US8465292B2 - Status: Granted - Kind: B2 - Application number: 12/032,574 - Filed: 2008-02-15 - Published: 2008-08-28 - Granted: 2013-06-18 - Earliest claimed: 2007-02-15 - Assignees: Laerdal Medical AS - Applicants: Jon Nysæther; Joar Eilevstjønn - Inventors: Jon Nysæther; Joar Eilevstjønn - Web page: https://patentgrep.com/patent/US8465292B2 ## CPC - A61B 5/11: Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb {(A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721)} - A61B 5/6892: {Mats} - A61B 5/7242: {using integration} - A61H 31/005: {with feedback for the user} - A61B 2562/0219: Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches - A61H 2201/5061: Force sensors - A61H 2201/5084: Acceleration sensors - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - A61H: PHYSICAL THERAPY APPARATUS, e.g. DEVICES FOR LOCATING OR STIMULATING REFLEX POINTS IN THE BODY; ARTIFICIAL RESPIRATION; MASSAGE; BATHING DEVICES FOR SPECIAL THERAPEUTIC OR HYGIENIC PURPOSES OR SPECIFIC PARTS OF THE BODY (electrotherapy, magnetotherapy, radiation therapy or ultrasound therapy A61N) ## Abstract Embodiments of the present invention are directed toward a system and method of determining real time chest compression depth of a CPR patient or manikin from acceleration and a reference signal, such as force. In one embodiment, an acceleration signal is filtered and integrated to determine a raw depth signal. A force signal is adjusted to having a similar amplitude, phase, and shape as the raw depth signal. The force signal is filtered. The adjusted force signal is subtracted from the filtered force signal to obtain a compensation signal. The chest compression depth is obtained by adding the raw depth signal to the compensation signal. ## Claims ### Claim 1 A method of determining, using a processor, chest compression depth during CPR being performed on a patient or manikin, comprising: receiving an acceleration signal representing an acceleration value of the chest compression; filtering the acceleration signal at least once; double integrating the filtered acceleration signal; receiving and adjusting an independent reference signal to produce an adjusted reference signal; filtering the adjusted reference signal at least once to produce a filtered adjusted reference signal; determining, using a processor operatively coupled to receive the double integrated filtered acceleration signal, the filtered adjusted reference signal, and the adjusted reference signal, a compensation signal by subtracting the filtered adjusted reference signal from the adjusted reference signal; and determining, using the processor, the chest compression depth by adding the double integrated filtered acceleration signal and the compensation signal. ### Claim 2 (depends on 1) The method of claim 1 wherein the acceleration signal is measured by a chest compression sensor. ### Claim 3 (depends on 1) The method of claim 1 wherein filtering the acceleration signal and filtering the adjusted reference signal are performed using the same filter. ### Claim 4 (depends on 1) The method of claim 1 wherein the independent reference signal is adjusted to have a similar amplitude, shape and phase as the double integrated filtered acceleration signal. ### Claim 5 (depends on 1) The method of claim 1 wherein the reference signal and the acceleration signal are filtered by digital filters. ### Claim 6 (depends on 1) The method of claim 1 wherein the double integration is applied to the acceleration signal before the acceleration signal is filtered. ### Claim 7 (depends on 1) The method of claim 1 wherein at least one of filtering the adjusted reference signal and filtering the acceleration signal is performed using a comb filter. ### Claim 8 (depends on 1) The method of claim 1 wherein the independent reference signal is deduced from at least one of a force signal, an ECG signal, thoracic impedance measurements, and blood pressure measurements. ### Claim 9 (depends on 8) The method of claim 8 wherein the force signal is generated by a force sensor measuring compression force exerted during CPR. ### Claim 10 (depends on 9) The method of claim 9 wherein the force sensor is situated between the palm of a hand of a performer performing CPR and a chest of the patient receiving CPR. ### Claim 11 (depends on 1) The method of claim 1 wherein the independent reference signal is deduced from a combination of a force signal and other measured information producing signals. ### Claim 12 (depends on 1) The method of claim 1 wherein the adjusted reference signal is produced by calculating the difference in phase and amplitude ratio of the independent reference signal and a previously determined chest compression depth signal. ### Claim 13 (depends on 1) The method of claim 1 wherein the acceleration signal and the independent reference signal are synchronized. ### Claim 14 A system for determining real time chest compression depth on a patient or manikin during CPR, comprising: an accelerometer configured to measure acceleration of the chest compression of the patient or manikin and generate an acceleration signal corresponding thereto; a force sensor configured to measure chest compression force and generate a force signal corresponding thereto; and a processor configured to receive the acceleration signal and the force signal, the processor further configured to filter and integrate the acceleration signal, the processor configured to adjust the force signal and filter the adjusted force signal, the processor configured to calculate a compensation signal by subtracting the filtered adjusted force signal from the adjusted force signal, the processor configured to calculate the chest compression depth from the compensation signal and the filtered and integrated acceleration signal. ### Claim 15 (depends on 14) The system of claim 14 wherein the acceleration signal and the force signal are filtered by similar filters. ### Claim 16 (depends on 14) The system of claim 14 wherein the processor is further configured to use a comb filter for filtering at least one of the acceleration signal and the adjusted force signal. ### Claim 17 (depends on 14) The system of claim 14 wherein the processor is configured to adjust the force signal to have a similar amplitude, shape, and phase of the filtered and integrated acceleration signal. ### Claim 18 (depends on 14) The system of claim 14 wherein the processor is configured to synchronize the acceleration signal with the force signal. ### Claim 19 (depends on 14) The system of claim 14 wherein the force sensor is positioned between the palm of the hand of a person performing the CPR and the chest of the patient or manikin. ### Claim 20 (depends on 14) The system of claim 14 wherein the processor is configured to calculate the difference in phase and amplitude ratio of the force signal and a previously determined compression depth signal. ### Claim 21 (depends on 14) The system of claim 14 wherein the processor is configured to filter the acceleration signal before it is integrated. ### Claim 22 (depends on 14) The system of claim 14 wherein the processor is configured to integrate the acceleration signal twice.