Method of detecting signal clipping in a wearable ambulatory medical device

• US 9,456,778 B2
• Filed: 11/03/2015
• Issued: 10/04/2016
• Est. Priority Date: 03/25/2011
• Status: Active Grant

• Current Assignee: Zoll Medical Corporation (Asahi Kasei Corporation)
• Original Assignee: Zoll Medical Corporation (Asahi Kasei Corporation)
• Inventors: Kaib, Thomas E., Volpe, Shane S., Macho, John D.
• Primary Examiner(s): Gedeon, Brian T
• Assistant Examiner(s): Tejani, Ankit D
• Application Number:
  US14/931,399
• Publication Number:
  US 20160051186A1
• Time in Patent Office: 336 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0204 Acoustic sensors
• CPC Class Codes: A61B 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/303 Patient cord assembly, e.g. cable harness
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: A61B 5/6805 Vests
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock
• CPC Class Codes: H03G 7/002 in untuned or low-frequency amplifiers, e.g. audio amplifiers H03G7/007, H03G7/001, H03G7/008, H03G7/02, H03G7/06 take precedence
• CPC Class Codes: H03G 7/005 using discontinuously variable devices, e.g. switch-operated

Abstract

A wearable medical device and method of detecting clipping of ECG signals is disclosed. In one embodiment, the wearable medical device comprises a plurality of ECG sensing electrodes configured to sense an ECG of a patient and an ECG acquisition circuit electrically coupled to a pair of the plurality of ECG sensing electrodes and configured to provide an amplified and conditioned analog ECG signal, a programmable attenuation/gain stage electrically coupled between a first gain stage and a second gain stage, an ADC electrically coupled to the ECG acquisition circuit to receive and digitize the amplified and conditioned analog ECG signal and provide a digitized ECG signal, and a signal conditioning and control unit electrically coupled to the ECG acquisition circuit and the ADC to receive and monitor the digitized ECG signal and to detect clipping of the amplified and conditioned analog ECG signal based upon the digitized ECG signal.

Claims

1. A wearable medical device, comprising:

at least one sensing electrode configured to sense a cardiac signal of a patient;

an acquisition circuit, operatively coupled to the at least one sensing electrode, configured to process the cardiac signal; and

a signal conditioning and control unit, operatively coupled to the acquisition circuit, configured to monitor the cardiac signal during processing by the acquisition circuit and mark one or more portions of the cardiac signal as compromised to prevent misdetection of the cardiac signal by the wearable medical device, wherein the marking is based on one or more predetermined clipping thresholds for the cardiac signal;

wherein the acquisition circuit comprises at least one programmable attenuation/gain stage;

wherein the signal conditioning and control unit comprises an automatic level control unit to vary an amount of attenuation/gain provided by the at least one programmable attenuation/gain stage; and

wherein the signal conditioning and control unit is configured to temporarily disable functionality of the automatic level control unit responsive to marking one or more portions of the cardiac signal as compromised.

2. A wearable medical device, comprising:

at least one sensing electrode configured to sense a cardiac signal of a patient;

an acquisition circuit, operatively coupled to the at least one sensing electrode, configured to process the cardiac signal; and

a signal conditioning and control unit, operatively coupled to the acquisition circuit, configured to monitor the cardiac signal during processing by the acquisition circuit and adjust at least one of a gain and an attenuation applied by the acquisition circuit to the cardiac signal based on one or more predetermined clipping thresholds for the cardiac signal, wherein at least one of the one or more predetermined clipping thresholds is determined based on at least two of a voltage range of an ECG of a human patient, a maximum output voltage level of one or more gain stages of the acquisition circuit, and a current gain setting of the one or more gain stages of the acquisition circuit.

3. The wearable medical device of claim 2, wherein the acquisition circuit is configured to process the cardiac signal by at least one of amplifying and attenuating the cardiac signal.

4. The wearable medical device of claim 2, wherein the acquisition circuit comprises at least one programmable attenuation/gain stage and wherein the signal conditioning and control unit comprises an automatic level control unit to vary an amount of attenuation/gain provided by the at least one programmable attenuation/gain stage based on the processed cardiac signal and the one or more predetermined clipping thresholds.

5. The wearable medical device of claim 4, wherein the automatic level control unit is configured to increase a gain of the at least one programmable attenuation/gain stage responsive to the processed cardiac signal being below at least one of the one or more predetermined clipping thresholds.

6. The wearable medical device of claim 4, wherein the automatic level control unit is configured to decrease a gain of the at least one programmable attenuation/gain stage responsive to the processed cardiac signal being above at least one of the one or more predetermined clipping thresholds.

7. The wearable medical device of claim 2, further comprising an analog to digital converter, electrically coupled to the acquisition circuit, to digitize the processed cardiac signal and provide a digitized cardiac signal.

8. The wearable medical device of claim 2, wherein the acquisition circuit comprises at least one filter to remove high frequency noise from the cardiac signal.