WO2017049184A1 - Noise cancelling heart monitor - Google Patents

Noise cancelling heart monitor Download PDF

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Publication number
WO2017049184A1
WO2017049184A1 PCT/US2016/052283 US2016052283W WO2017049184A1 WO 2017049184 A1 WO2017049184 A1 WO 2017049184A1 US 2016052283 W US2016052283 W US 2016052283W WO 2017049184 A1 WO2017049184 A1 WO 2017049184A1
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WO
Grant status
Application
Patent type
Prior art keywords
power line
signal
ecg
heart monitor
noise cancelling
Prior art date
Application number
PCT/US2016/052283
Other languages
French (fr)
Inventor
Frank G. Cooper
Eric J. Hoffman
Mark N. GRIGORAKI
Original Assignee
Celf Techonologies Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

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Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/04Detecting, measuring or recording bioelectric signals of the body or parts thereof
    • A61B5/0402Electrocardiography, i.e. ECG
    • A61B5/0452Detecting specific parameters of the electrocardiograph cycle
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/72Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7203Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
    • A61B5/7217Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F19/00Digital computing or data processing equipment or methods, specially adapted for specific applications
    • GPHYSICS
    • G16INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
    • G16HHEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA
    • G16H40/00ICT specially adapted for the management or administration of healthcare resources or facilities; ICT specially adapted for the management or operation of medical equipment or devices
    • G16H40/60ICT specially adapted for the management or administration of healthcare resources or facilities; ICT specially adapted for the management or operation of medical equipment or devices for the operation of medical equipment or devices
    • G16H40/63ICT specially adapted for the management or administration of healthcare resources or facilities; ICT specially adapted for the management or operation of medical equipment or devices for the operation of medical equipment or devices for local operation

Abstract

Systems, methods, and devices are generally describe which may realize high bandwidth (fidelity) in a low level (1mV) ECG waveform throughput (in the range of 0.05 to 150Hz), while phase locking to, and cancelling, a local power line (typically 1500mV). The local power line may reside within the desired bandwidth which may be 47-63Hz beyond the common mode rejection capabilities of the classic ECG differential amplifier front end. The amplitude of the cancellation signal may be variable to accommodate differences in the power line signal.

Description

NOISE CANCELLING HEART MONITOR

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 62/219,966 filed on September 17, 2015. The U.S. Application is hereby incorporated herein by reference in its entirety.

BACKGROUND OF INVENTION:

The electrophysiology of the human heart is known and has been studied and quantified dating back to the early 1900s. The pacing node ("SA"), initiates the electrical activity in the atria causing the atria to contract. At the same time, SA excites the second dominant node ("AV") through the bundle of His (a nerve connection) to contract the lower ventricles.

Thereafter repolarization occurs and the heart is readied for its next beat cycle.

The electrocardiogram ("ECG") is the electrical measurement of time versus amplitude during the cyclical heartbeat. The ECG is known to provide an electrical signature that quantifies electrical functionality (SA, AV nodes and heart muscle functions). The ECG remains a gold standard - non-invasively enhancing cardiac care/diagnosis. It is a challenge to obtain high fidelity electrical measurement of the human heart's ECG using two electrodes, in situ, absent a lab or clinical setting (affording signal grounds and up to 12 leads). In traditional heart monitors, detrimental complex power line pick-up (similar in nature to microphone "hum") may interfere with and/or obscure a subject's ECG. One technique for eliminating power line noise includes use of a classical "notch" filter to attenuate power line frequencies residing within the ECGs frequency range. Use of notch filters for power line cancellation in heart monitors may be equated to having a stereo amplifier for audio that is flat from 20 Hz to 20 kHz yet the midrange tone is set to— lOdB. In the audio amplifier analogy, perceived audio quality would suffer, much as with the use of a notch filter in the ECG context, which attenuates mid-range frequencies within the ECG's frequency bandwidth.

In an electrocardiogram device, a third lead which serves as a signal ground may be used to optimize common mode rejection in all variants of standard 3 lead, 5 lead, and 12 lead (electrode) measurements typical in clinical settings, with 2-3 lead ECG serving halter monitoring and hospital cardiac care unit ("CCU") telemetry monitoring. Beyond the differential common mode rejection characteristics of the ECG measurement amplifier discussed, an electronic notch filter, being either 50 Hz (European) or 60 Hz (US & Canada) band extended to +/- 3Hz of the target power line frequency may be used to further negate background power line pickup.

DETAILED DESCRIPTION

Signal processing techniques may be employed which utilize a combined architecture of Analog and Digital Signal Processing ("DSP") modes. The signal processing techniques may effect cancellation of detrimental complex power line pick-up without the use of notch filters. Notch filters, or band-stop filters, may attenuate power line frequencies residing within the ECG's desired frequency range. The signal processing techniques and heart monitor architecture described below may effect "flat" frequency response, presenting the highest ECG waveform clarity without coloration. Additionally, the signal processing techniques and heart monitor architecture described below may dynamically negate power line pickup and may auto null/calibrate to a lmV reference standard assuring best possible waveform amplitude certainty.

The noise cancelling heart monitor may be employed as a "wearable bio sensor". The noise cancelling heart monitor may exact measurement of ECG for purposes of "Wellness & Fitness" exercise physiology that would otherwise not be possible except in a controlled clinical environment with multi-lead (5 to 12) electrodes and/or an earth- grounded fixed instrumentation setting. The noise cancelling heart monitor described herein may afford a simple two electrode wearable sensor that may ride the host during measurement and wirelessly transmit ECG - making the noise cancelling heart monitor ideal for exercise physiology. The architecture of the noise cancelling heart monitor described herein may allow for an inexpensive (approximately $50) wearable heart monitor, in stark contrast to existing fixed electrophysiology ECG clinical installations, which may exceed $10,000 in cost.

In order to "see" a cardiac electrical signal without power line noise, two measurement electrodes may be placed on the patient's skin. The two electrodes may form an electrical (low impedance) circuit to the heart. A differential voltage measurement to acquire the l-5mV full scale signal may be employed. Differential amplifiers, by design, ideally "see" only the differential voltage, and reject input signals of the same amplitude and phase which are equally presented to both differential amplifier inputs. This characteristic of differential amplifiers is known as "common mode rejection". It is by this methodology that ECG measurement of relatively low level signals (l-5mV) may minimize detrimental pickup of local power line induced components (which reside in the area of 1500mV according to the American Heart Association). The noise cancelling heart monitor may use two (2) low impedance field effect transistor ("FET") switches (See, for example, Fig 1.0 depicting switches SW1 & SW2), to electrically remove and isolate the two patient electrode ECG input lines for two purposes (described in further detail below): 1) generation of a noise cancelling signal, and 2) to allow for calibration of the differential amplifier using a lmV reference signal.

Generation of Noise Cancelling Signal

After removing and isolating the patient's ECG input signal, a FET switch (Fig 1.0 SW3) may electrically terminate the ECG differential amplifier inputs. DSP hardware, including an analog to digital converter ("ADC"), and a processor (e.g., an ARM processor) may be employed to determine the remaining power line carrier's amplitude and frequency which exists beyond the common mode rejection of the differential amplifier front end. As depicted in FIG 2.0, the frequency and phase angle of the power line signal may be precisely acquired using a digital phase locked loop ("PLL"). The frequency and phase angle of the power line signal may be digitally programmed into a precision frequency tunable amplifier ("FT A"). The FTA's resulting output may be proportional to the real-time prevailing power line carrier magnitude, and may be employed to control the amplitude of a digitally synthesized, equal and opposite (180 degrees out of phase) sinusoidal cancellation signal.

Accordingly, undesirable power line carrier effects, detrimental to realizing high quality ECG beyond the common mode rejection of the input differential amplifier, may be eliminated without the use of traditional analog or digital domain notch filters, affording flat frequency response in the ECG range of 0.05 Hz to 150 Hz. The noise cancelling heart monitor eliminates the traditional +/- 3 Hz standard notch filter for 50 and/or 60 Hz power line frequency being detrimental to ECG waveform clarity as it cuts out meaningful information within the spectral range where the ECG waveform resides.

1 mV Reference Signal for Differential Amplifier Calibration

FET switches SW4 & SW5 (depicted in FIG 1.0) may be closed to apply a lmV precision reference signal to the ECG differential amplifier at device initialization in order to assure a sum-check for absolute front end amplifier calibration. Such a calibration may be required to assure dosimetry if employed beyond Wellness and Fitness as a qualified Food and Drug Administration ("FDA") part 21 medical device. The resulting digital "trim" of the overall wearable sensor's gain (employing lmV reference) at each use assures dosimetry for accurate ECG amplitude measurement over time and temperature, accounting for variations including aging of components, temperature coefficients of resistors, and/or error.

Claims

Claim
1. A method for producing a power line noise cancellation signal in a heart monitor device, the method comprising:
isolating an electrocardiogram signal received from one or more electrodes;
identifying a frequency and a phase angle of a power line carrier signal using a phase locked loop, wherein the power line carrier signal exists beyond the common mode rejection capability of a differential amplifier; and
programming a frequency tunable amplifier to produce a noise cancellation signal that is 180 degrees out of phase with the power line carrier signal, wherein a first magnitude of the noise cancellation signal is proportional to a second magnitude of the power line carrier signal.
PCT/US2016/052283 2015-09-17 2016-09-16 Noise cancelling heart monitor WO2017049184A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US201562219966 true 2015-09-17 2015-09-17
US62/219,966 2015-09-17

Publications (1)

Publication Number Publication Date
WO2017049184A1 true true WO2017049184A1 (en) 2017-03-23

Family

ID=58289703

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2016/052283 WO2017049184A1 (en) 2015-09-17 2016-09-16 Noise cancelling heart monitor

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WO (1) WO2017049184A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5903615A (en) * 1998-03-30 1999-05-11 3Com Corporation Low complexity frequency estimator and interference cancellation method and device
US20130069780A1 (en) * 2006-05-12 2013-03-21 Bao Tran Health monitoring appliance
US20140100467A1 (en) * 2006-11-01 2014-04-10 Welch Allyn, Inc. Body worn physiological sensor device having a disposable electrode module

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5903615A (en) * 1998-03-30 1999-05-11 3Com Corporation Low complexity frequency estimator and interference cancellation method and device
US20130069780A1 (en) * 2006-05-12 2013-03-21 Bao Tran Health monitoring appliance
US20140100467A1 (en) * 2006-11-01 2014-04-10 Welch Allyn, Inc. Body worn physiological sensor device having a disposable electrode module

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