NECKLACE-SHAPED PHYSIOLOGICAL MONITOR

• US 20140235979A1
• Filed: 02/19/2014
• Published: 08/21/2014
• Est. Priority Date: 02/20/2013
• Status: Abandoned Application

• Current Assignee: OtoSense, Inc. (Analog Devices, Inc.)
• Original Assignee: Perminova Inc.
• Inventors: Banet, Matt, Pede, Susan, Dhillon, Marshal, Terry, Drew, Hunt, Robert
• Application Number:
  US14/184,612
• Publication Number:
  US 20140235979A1
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/6822 Neck

Abstract

The invention provides a neck-worn sensor (referred to herein as the ‘necklace’) that is a single, body-worn system that measures the following parameters from an ambulatory patient: heart rate, pulse rate, pulse oximetry, respiratory rate, temperature, thoracic fluid levels, stroke volume, cardiac output, and a parameter sensitive to blood pressure called pulse transit time. From stroke volume, a first algorithm employing a linear model can estimate the patient'"'"'s pulse pressure. And from pulse pressure and pulse transit time, a second algorithm, also employing a linear algorithm, can estimate systolic blood pressure and diastolic blood pressure. Thus, the necklace can measure all five vital signs along with hemodynamic parameters. It also includes a motion-detecting accelerometer, from which it can determine motion-related parameters such as posture, degree of motion, activity level, respiratory-induced heaving of the chest, and falls.

Claims

1. A method for measuring pulse transit time (PTT) using a necklace system configured to be worn around a patient'"'"'s neck, comprising:

measuring an analog ECG waveform with the necklace system, the analog ECG waveform measured with an ECG system housed in the necklace system and comprising an analog ECG circuit in electrical contact with at least two ECG electrodes;

measuring an analog impedance waveform with the necklace system, the analog impedance waveform measured with an impedance system housed in the necklace system and comprising an analog impedance circuit in electrical contact with at least two impedance electrodes;

measuring a motion signal with the necklace system, the motion signal measured with a motion sensor housed in the necklace system;

digitizing the analog ECG and impedance waveforms with a digitizing system comprising an analog-to-digital converter and housed in the necklace system, the digitizing generating a digital ECG waveform and a digital impedance waveform; and

,

processing the digital ECG and impedance waveforms with a processing system comprising a microprocessor and housed in the necklace system when the motion signal or a processed version thereof is below a pre-determined threshold value, the processing configured to determine a first time point from the digital ECG waveform, a second time point from the digital impedance waveform, and a PTT from the difference between the first and second time points.

2. The method of claim 1, wherein the motion sensor is an accelerometer.

3. The method of claim 1, wherein the pre-determined threshold value indicates a degree of motion that may corrupt waveforms measured by the impedance system.

4. The method of claim 1, wherein the processing further comprises taking a mathematical first derivative of the digital impedance waveform, and then processing the mathematical first derivative to determine the second time point.

5. The method of claim 4, wherein the processing further comprises finding a maximum value of the mathematical first derivative, the maximum value representing the second time point.

6. The method of claim 4, wherein the processing further comprises finding an inflection point of the mathematical first derivative, the inflection point representing the second time point.

7. The method of claim 6, wherein the processing further comprises finding a zero point crossing of the mathematical first derivative, the zero point crossing representing the second time point.

8. The method of claim 1, wherein the processing further comprises determining a maximum value of a QRS complex comprised by the digital ECG waveform, the maximum value of the QRS complex representing the first time point.

9. The method of claim 1, wherein the processing further comprises processing the PTT to determine an estimate of a blood pressure value.

10. The method of claim 9, wherein the estimate of a blood pressure value is a trend in blood pressure.

11. The method of claim 9, wherein the processing further comprises processing the PTT with a calibration value to determine a blood pressure value.

12. The method of claim 11, further comprising wirelessly receiving the calibration value with a wireless transceiver housed in the necklace system.

13. A method for measuring pulse transit time (PTT) using a necklace system configured to be worn around a patient'"'"'s neck, comprising:

measuring an analog ECG waveform with the necklace system, the analog ECG waveform measured with an ECG system housed in the necklace system and comprising an analog ECG circuit in electrical contact with at least two ECG electrodes;

measuring an analog plethysmogram waveform with the necklace system, the analog plethysmogram waveform measured with an SpO2 system housed in the necklace system and connected to an optical sensor;

measuring a motion signal with the necklace system, the motion signal measured with a motion sensor housed in the necklace system;

digitizing the analog ECG and plethysmogram waveforms with a digitizing system comprising an analog-to-digital converter and housed in the necklace system, the digitizing generating a digital ECG waveform and a digital plethysmogram waveform; and

,

processing the digital ECG and plethysmogram waveforms with a processing system comprising a microprocessor and housed in the necklace system when the motion signal or a processed version thereof is below a pre-determined threshold value, the processing configured to determine a first time point from the digital ECG waveform, a second time point from the digital plethysmogram waveform, and a PTT from the difference between the first and second time points.

14. The method of claim 13, wherein the motion sensor is an accelerometer.

15. The method of claim 13, wherein the pre-determined threshold value indicates a degree of motion that may corrupt waveforms measured by the SpO2 system.

16. The method of claim 13, wherein the processing further comprises taking a mathematical first derivative of the digital plethysmogram waveform, and then processing the mathematical first derivative to determine the second time point.

17. The method of claim 16, wherein the processing further comprises finding a maximum value of the mathematical first derivative, the maximum value representing the second time point.

18. The method of claim 16, wherein the processing further comprises finding an inflection point of the mathematical first derivative, the inflection point representing the second time point.

19. The method of claim 18, wherein the processing further comprises finding a zero point crossing of the mathematical first derivative, the zero point crossing representing the second time point.

20. The method of claim 13, wherein the processing further comprises determining a maximum value of a QRS complex comprised by the digital ECG waveform, the maximum value of the QRS complex representing the first time point.

21. The method of claim 13, wherein the processing further comprises processing the PTT to determine an estimate of a blood pressure value.

22. The method of claim 21, wherein the estimate of a blood pressure value is a trend in blood pressure.

23. The method of claim 21, wherein the processing further comprises processing the PTT with a calibration value to determine a blood pressure value.

24. The method of claim 23, further comprising wirelessly receiving the calibration value with a wireless transceiver housed in the necklace system.