Body-worn pulse oximeter

Patent metadata

Field	Value
Publication number	US-9775529-B2
Application number	US-55938609-A
Country	US
Kind code	B2
Filing date	Sep 14, 2009
Priority date	Jun 17, 2009
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

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.

First claim

What is claimed is:

1. A method for determining an oxygen saturation value from a patient, comprising the following steps:
(a) positioning a first radiation source, a second radiation source, and a radiation detector on the base of the thumb such that the first radiation source and second radiation source are positioned proximally to one another and the radiation detector is positioned at an included angle of between 35° and 55°, wherein the included angle is the angle formed between a first plane drawn parallel to a planar surface comprising the emitting surface of the first and second radiation sources and a second plane drawn parallel to a planar surface of a circuit board comprising the receiving surface of the radiation detector, and such that a first radiation emitted by the first radiation source and a second radiation emitted by the second radiation source pass through the thumb tissue and are received by the princeps pollicis artery before reaching the radiation detector;
(b) measuring a first time-dependent signal by detecting the first radiation emitted by the first radiation source after the first radiation passes through the thumb tissue;
(c) measuring a second time-dependent signal by detecting the second radiation emitted by the second radiation source after the second radiation passes through a portion of the patient;
(d) measuring a time-dependent motion signal with at least one motion sensor;
(e) measuring a time-dependent electrical signal with an electrical sensor comprising at least two electrodes;
(f) processing the time-dependent electrical signal to determine at least one reference point;
(g) processing the time-dependent motion signal to determine if a motion-related event that affects at least one of the first and second time-dependent signals has occurred that would render the first and second time-dependent signals unreliable for calculation of SpO2;
(h) if the motion event that would render the first and second time-dependent signals unreliable for calculation of SpO2 has not occurred, processing both the first and second time-dependent signals from the reference point to determine processed forms of the first and second time-dependent signals; and
(i) determining the oxygen saturation value from the processed forms of the first and second time-dependent signals.

2. The method of claim 1 , wherein step (g) 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.

3. The method of claim 2 , wherein the motion-related event is posture, and step (g) further comprises determining a parameter corresponding to orientation of the patient's torso.

4. The method of claim 3 , wherein the parameter corresponding to orientation of the patient's torso is a vector.

5. The method of claim 4 , wherein step (g) further comprises processing signals corresponding to three axes of a motion sensor to determine the vector.

6. The method of claim 5 , wherein the motion sensor is an accelerometer.

7. The method of claim 5 , wherein step (g) further comprises comparing the vector to a pre-determined coordinate system to determine an angle.

8. The method of claim 7 , wherein step (g) further comprises comparing the angle to a set of pre-determined values, each corresponding to a different posture, to determine the patient's posture.

9. The method of claim 2 , wherein the motion-related event is activity level, and step (g) further comprises processing time-dependent variations in the motion signal to determine the activity level.

10. The method of claim 9 , wherein the activity level corresponds to one of moving, walking, falling, convulsing.

11. The method of claim 9 , wherein step (g) further comprises performing a mathematical transform of the time-dependent variations to determine a frequency-domain spectrum.

12. The method of claim 11 , wherein step (g) further comprises comparing portions of the frequency-domain spectrum to pre-determined frequency parameters to determine the activity level.

13. The method of claim 9 , wherein step (g) further comprises comparing magnitudes of the time-dependent variations in the motion signal to pre-determined magnitude parameters to determine the activity level.

14. The method of claim 9 , wherein step (g) further comprises taking a mathematical derivative of the time-dependent motion signal to determine the time-dependent variations.

15. The method of claim 2 , wherein the motion-related event is a degree of motion, and step (g) further comprises determining an amplitude of a portion of the time-dependent motion signal to determine the degree of motion.

16. The method of claim 15 , wherein step (g) further comprises performing a mathematical transform of the time-dependent variations to determine a frequency-domain spectrum.

17. The method of claim 16 , wherein step (g) further comprises determining a power of the frequency-domain spectrum to determine the degree of motion.

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

19. The method of claim 18 , wherein step (e) further comprises detecting a QRS complex in the ECG signal to determine the reference point.

20. The method of claim 19 , wherein step (h) further comprises processing both the first and second signals during a pre-determined time period that follows the QRS complex.

21. The method of claim 20 , wherein the predetermined time period is less than 500 ms.

Assignees

• Moon Jim
• Mccombie Devin
• Dhillon Marshal
• Banet Matt
• Sotera Wireless Inc

Inventors

• Moon Jim
• Mccombie Devin
• Dhillon Marshal
• Banet Matt

Classifications

• A61B5/02125

  of pulse wave propagation time · CPC title

• A61B5/6826

  Finger · CPC title

• A61B5/1118 Primary

  Determining activity level · CPC title

• A61B5/1116

  Determining posture transitions · CPC title

• A61B5/022

  by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers · CPC title