BODY-WORN PULSE OXIMETER

• US 20100324386A1
• Filed: 09/14/2009
• Published: 12/23/2010
• Est. Priority Date: 06/17/2009
• Status: Active Grant

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Sotera Wireless Incorporated
• Inventors: MOON, Jim, BANET, Matt, DHILLON, Marshal, McCOMBIE, Devin
• Granted Patent: US 9,775,529 B2
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/1118 Determining activity level
• 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 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• 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 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

The invention provides a body-worn system that continuously measures pulse oximetry and blood pressure, along with motion, posture, and activity level, from an ambulatory patient. The system features an oximetry probe that comfortably clips to the base of the patient'"'"'s thumb, thereby freeing up their fingers for conventional activities in a hospital, such as reading and eating. The probe secures to the thumb and measures time-dependent signals corresponding to LEDs operating near 660 and 905 nm. Analog versions of these signals pass through a low-profile cable to a wrist-worn transceiver that encloses a processing unit. Also within the wrist-worn transceiver is an accelerometer, a wireless system that sends information through a network to a remote receiver, e.g. a computer located in a central nursing station.

Claims

1. A method for determining an oxygen saturation value from a patient, comprising the following steps:

(a) measuring a first time-dependent signal by detecting radiation emitted by a first radiation source after it passes through a portion of the patient;

(b) measuring a second time-dependent signal by detecting radiation emitted by a second radiation source after it passes through a portion of the patient;

(c) measuring a time-dependent motion signal with at least one motion sensor;

(d) measuring a time-dependent electrical signal with an electrical sensor comprising at least two electrodes;

(e) processing the time-dependent electrical signal to determine at least one reference point;

(f) processing the time-dependent motion signal to determine a motion-related event that affects at least one of the first and second time-dependent signals;

(g) processing both the first and second time-dependent signals from the reference point and outside of the motion-related event to determine time-dependent signals; and

(h) processing the time-dependent signals to determine a value of oxygen saturation.

3. The method of claim 1, wherein step (f) further comprises processing the time-dependent motion signal to determine a motion-related event selected from the patient'"'"'s posture, activity level, and degree of motion.

4. The method of claim 3, wherein the motion-related event is posture, and step (f) further comprises determining a parameter corresponding to orientation of the patient'"'"'s torso.

5. The method of claim 4, wherein the parameter corresponding to orientation of the patient'"'"'s torso is a vector.

6. The method of claim 5, wherein step (f) further comprises processing signals corresponding to three axes of a motion sensor to determine the vector.

7. The method of claim 6, wherein the motion sensor is an accelerometer.

8. The method of claim 6, wherein step (f) further comprises comparing the vector to a pre-determined coordinate system to determine an angle.

9. The method of claim 8, wherein step (f) further comprises comparing the angle to a set of pre-determined values, each corresponding to a different posture, to determine the patient'"'"'s posture.

10. The method of claim 3, wherein the motion-related event is activity level, and step (f) further comprises processing time-dependent variations in the motion signal to determine the activity level.

11. The method of claim 10, wherein the activity level corresponds to one of moving, walking, falling, convulsing.

12. The method of claim 10, wherein step (f) further comprises performing a mathematical transform of the time-dependent variations to determine a frequency-domain spectrum.

13. The method of claim 12, wherein step (f) further comprises comparing portions of the frequency-domain spectrum to pre-determined frequency parameters to determine the activity level.

14. The method of claim 10, wherein step (f) further comprises comparing magnitudes of the time-dependent variations in the motion signal to predetermined magnitude parameters to determine the activity level.

15. The method of claim 10, wherein step (f) further comprises taking a mathematical derivative of the time-dependent motion signal to determine the time-dependent variations.

16. The method of claim 3, wherein the motion-related event is a degree of motion, and step (f) further comprises determining an amplitude of a portion of the time-dependent motion signal to determine the degree of motion.

17. The method of claim 16, wherein step (f) further comprises performing a mathematical transform of the time-dependent variations to determine a frequency-domain spectrum.

18. The method of claim 17, wherein step (f) further comprises determining a power of the frequency-domain spectrum to determine the degree of motion.

19. The method of claim 1, wherein step (d) further comprises measuring an ECG signal.

20. The method of claim 19, wherein step (e) further comprises detecting a QRS complex in the ECG signal to determine the reference point.

21. The method of claim 20, wherein step (g) further comprises processing both the first and second signals during a pre-determined time period that follows the QRS complex.

22. The method of claim 21, wherein the predetermined time period is less than 500 ms.

2. A method for determining both oxygen saturation and blood pressure values for a patient, comprising:

(a) measuring at least one optical signal with a first sensor;

(b) measuring an electrical signal comprising a time-dependent marker with a second sensor;

(c) measuring a motion signal with a motion sensor;

(d) processing both the motion and optical signals from the time-dependent marker to a later point in time to determine AC signals and a transit time; and

(e) determining a blood pressure value from the transit time, and an oxygen saturation value from the AC signals.