Method for measuring blood oxygen content under low perfusion

• US 7,471,970 B2
• Filed: 12/22/2005
• Issued: 12/30/2008
• Est. Priority Date: 03/10/2005
• Status: Active Grant

• Current Assignee: Shenzhen Mindray Bio-Medical Electronics Co., Ltd. (Excelsior Union Ltd.)
• Original Assignee: Shenzhen Mindray Bio-Medical Electronics Co., Ltd. (Excelsior Union Ltd.)
• Inventors: Zhang, Xu, Ye, Jilun
• Primary Examiner(s): Winakur; Eric F
• Assistant Examiner(s): Berhanu; Etsub D
• Application Number:
  US11/316,060
• Publication Number:
  US 20060206019A1
• Time in Patent Office: 1,104 Days
• Field of Search: 600/322, 600/323, 356/39, 356/41
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7242 using integration

Abstract

A method for measuring blood oxygen content under low perfusion, which is used in a device for measuring blood oxygen content, includes the steps of: initializing the device that is applied with power, collecting and processing data with a driving circuit of light emitting device, a bias circuit, a gain circuit and an A/D sampling circuit, which are controlled under a core control module; calculating blood oxygen saturation based on the collected data with a data processing module which integrates the collected data in a period of time with an area integration method; and outputting from a communication functional module results of the blood oxygen saturation or pulse rate calculated with the data processing module. The method further includes a decision step of deciding the two results acquired from the data processing module with the waveform method and the integration method respectively based on the intensity of the measured signal and generating the final measured result, performed by a decision unit included in the device. By adopting the above method, the disturbance to effective signal by noise can be eliminated. As a result, the measuring accuracy of blood oxygen content under low perfusion can be improved without increasing the production cost for the measuring device.

Claims

1. A method for measuring blood oxygen content under low perfusion, which is used in a device for measuring blood oxygen content, including the steps of:

a. initializing the device that is applied with power;

b. collecting and processing data with a driving circuit of a light emitting device, a bias circuit, a gain circuit and an A/D sampling circuit, which are controlled under a core control module;

c. calculating blood oxygen saturation based on the collected data with a data processing module which integrates the collected data in a period of time with an area integration method, wherein the collected data is cyclical and the period of time for integration includes more than one cycle; and

d. outputting from a communication functional module a result of the blood oxygen saturation or pulse rate calculated with the data processing module.

2. The method for measuring blood oxygen content under low perfusion according to claim 1, wherein in the step of c, the data processing module further fits envelope waveform of a pulse wave and finds out the maximum value and minimum value of the pulse wave to calculate the blood oxygen saturation with a waveform method based on the collected data.

3. The method for measuring blood oxygen content under low perfusion according to claim 2, wherein the method, between the steps of c and d, further includes a decision step of deciding between the two results acquired from the data processing module with the waveform method and the integration method respectively based on the intensity of measured signals and generating a final measured result, performed by a decision unit included in the device.

4. The method for measuring blood oxygen content under low perfusion according to claim 3, wherein a precondition for the decision and calculation in the decision step is:

A=a*A₁+(1−

a)*A₂,

where “

A₁”

is the result of the blood oxygen saturation acquired with the waveform method, “

A₂”

is the result of the blood oxygen saturation acquired with the integration method, “

A”

is the final measured result of the blood oxygen saturation, and “

a”

ranges from 1 to 0.

5. The method for measuring blood oxygen content under low perfusion according to claim 2, wherein the device performs the sampling and measuring by making two lights pass through end parts of tissues, wherein one is red light, and the other is infrared light;

and in the step of c, the data of the two lights is integrated respectively to calculate the ratio of integration result of the red light to that of the infrared light for replacing the ratio of AC peak value of the intensity of the red light Red_AC to that of the infrared light Ir_AC received during the period of time.

6. The method for measuring blood oxygen content under low perfusion according to claim 5, wherein:

in the step of c, the calculation of the data processing module also depends on a forgetting factor λ

which ranges from 0 to 1, and the ratio of the AC peak value Red_AC to Ir_AC of the current two lights is

7. The method for measuring blood oxygen content under low perfusion according to claim 6, wherein the value of the forgetting factor λ

is 0.8.

8. The method for measuring blood oxygen content under low perfusion according to claim 3, wherein the device performs the sampling and measuring by making two lights pass through end parts of tissues, wherein one is red light, and the other is infrared light;

and in the step of c, the data of the two lights is integrated respectively to calculate the ratio of integration result of the red light to that of the infrared light for replacing the ratio of AC peak value of the intensity of the red light Red_AC to that of the infrared light Ir_AC received during the period of time.

9. The method for measuring blood oxygen content under low perfusion according to claim 8, wherein:

in the step of c, the calculation of the data processing module also depends on a forgetting factor λ

which ranges from 0 to 1, and the ratio of the AC peak value Red_AC to Ir_AC of the current two lights is

10. The method for measuring blood oxygen content under low perfusion according to claim 9, wherein the value of the forgetting factor λ

is 0.8.

11. The method for measuring blood oxygen content under low perfusion according to claim 4, wherein the device performs the sampling and measuring by making two lights pass through end parts of tissues, wherein one is red light, and the other is infrared light;

and in the step of c, the data of the two lights is integrated respectively to calculate the ratio of integration result of the red light to that of the infrared light for replacing the ratio of AC peak value of the intensity of the red light Red_AC to that of the infrared light Ir_AC received during the period of time.

12. The method for measuring blood oxygen content under low perfusion according to claim 11, wherein:

in the step of c, the calculation of the data processing module also depends on a forgetting factor λ

which ranges from 0 to 1, and the ratio of the AC peak value Red_AC to Ir_AC of the current two lights is

13. The method for measuring blood oxygen content under low perfusion according to claim 12, wherein the value of the forgetting factor λ

is 0.8.

14. The method for measuring blood oxygen content under low perfusion according to claim 1, wherein the device performs the sampling and measuring by making two lights pass through end parts of tissues, wherein one is red light, and the other is infrared light;

and in the step of c, the data of the two lights is integrated respectively to calculate the ratio of integration result of the red light to that of the infrared light for replacing the ratio of AC peak value of the intensity of the red light Red_AC to that of the infrared light Ir_AC received during the period of time.

15. The method for measuring blood oxygen content under low perfusion according to claim 14, wherein:

in the step of c, the calculation of the data processing module also depends on a forgetting factor λ

which ranges from 0 to 1, and the ratio of the AC peak value Red_AC to Ir_AC of the current two lights is

16. The method for measuring blood oxygen content under low perfusion according to claim 15, wherein the value of the forgetting factor λ

is 0.8.

17. The method for measuring blood oxygen content under low perfusion according to claim 1, wherein in the step of c, the period of time for integration is 2-3 seconds.

18. The method for measuring blood oxygen content under low perfusion according to claim 1, wherein the integration determines an area between the collected data and a normalized value of the collected data.