BODY-WORN PULSE OXIMETER

• US 20100324384A1
• 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 8,554,297 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• 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 monitoring a patient, comprising:

(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) processing the time-dependent motion signal to determine at least one of the patient'"'"'s posture and activity state;

(e) processing both the first and second time-dependent signals to determine an oxygen saturation value for the patient; and

,

(f) suppressing an alarm based on the oxygen saturation value due to at least one of the patient'"'"'s posture and activity state.

3. The method of claim 1, wherein step (e) further comprises processing one of the patient'"'"'s posture and activity state in combination with a parameter resulting from the comparison of the oxygen saturation value to the predetermined alarm criteria to suppress the alarm.

4. The method of claim 3, wherein step (e) further comprises suppressing the alarm if the patient'"'"'s posture is standing upright.

5. The method of claim 3, wherein step (e) further comprises suppressing the alarm if the patient'"'"'s posture changes from lying down to one of sitting and standing upright.

6. The method of claim 3, wherein step (e) further comprises suppressing the alarm if the patient'"'"'s posture changes from one of standing upright and sitting to lying down.

7. The method of claim 1, wherein step (d) further comprises analyzing three time-dependent motion signals, each corresponding to a unique axis, to determine at least one of the patient'"'"'s posture and activity state.

8. The method of claim 7, wherein step (d) further comprises determining a vector from components of the three time-dependent motion signals.

9. The method of claim 7, wherein step (d) further comprises comparing the vector to a coordinate space defined by three positional vectors, each indicating an orientation of the motion-detecting sensor on the patient.

10. The method of claim 9, wherein a first positional vector corresponds to a vertical axis in the coordinate space, a second positional vector corresponds to a horizontal axis in the coordinate space, and the third positional vector corresponds to a normal axis extending normal to the patient'"'"'s chest.

11. The method of claim 10, wherein step (d) further comprises determining an angle associated with the vector.

12. The method of claim 11, wherein step (d) further comprises comparing the vector to the coordinate space to determine the angle between the vector and at least one of the three positional vectors.

13. The method of claim 11, wherein step (d) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a vertical axis, or a property of the angle between the vector and the vector corresponding to the vertical axis.

14. The method of claim 13, wherein step (d) further comprises comparing the angle to a threshold value that is substantially equivalent to 45 degrees, and wherein the patient'"'"'s posture is estimated to be upright if the angle is less than the threshold value.

15. The method of claim 13, wherein step (d) further comprises comparing the angle to a threshold value that is substantially equivalent to 45 degrees, and wherein the patient'"'"'s posture is estimated to be lying down if the angle is greater than the threshold value.

16. The method of claim 15, wherein step (d) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a normal axis extending normal to the patient'"'"'s chest, or a property of the angle between the vector and the vector corresponding to a normal axis extending normal to the patient'"'"'s chest.

17. The method of claim 16, wherein step (d) further comprises comparing the angle to a threshold value that is substantially equivalent to 35 degrees, and wherein the patient'"'"'s posture is estimated to be supine if the angle is less than the threshold value.

18. The method of claim 16, wherein step (d) further comprises comparing the angle to a threshold value that is substantially equivalent to 135 degrees, and wherein the patient'"'"'s posture is estimated to be prone if the angle is greater than the threshold value.

19. The method of claim 15, wherein step (d) further comprises comparing the vector to the coordinate space to determine the angle between the vector and a vector corresponding to a horizontal axis, or a property of the angle between the vector and the vector corresponding to the horizontal axis.

20. The method of claim 19, wherein step (h) further comprises comparing the angle to a threshold value that is substantially equivalent to 90 degrees, and wherein the patient'"'"'s posture is estimated to be lying on a first side if the angle is less than the threshold value.

21. The method of claim 19, wherein step (h) further comprises comparing the angle to a threshold value that is substantially equivalent to 90 degrees, and wherein the patient'"'"'s posture is estimated to be lying on a side opposite the first side if the angle is greater than the threshold value.

22. The method of claim 1, wherein step (c) further comprises detecting a set of time-dependent motion signals with at least one motion-detecting sensor positioned on the patient'"'"'s chest.

23. The method of claim 1, where the at least one motion-detecting sensor is an accelerometer.

2. A method for determining an oxygen saturation value for a patient, comprising:

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

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

(c) processing the optical signal to determine an oxygen saturation value;

(d) processing the motion signal to determine at least of one of the patient'"'"'s posture and activity state; and

(e) suppressing an alarm based on the oxygen saturation value due to at least one of the patient'"'"'s posture and activity state.