VITAL SIGN MONITOR FOR CUFFLESSLY MEASURING BLOOD PRESSURE WITHOUT USING AN EXTERNAL CALIBRATION

• US 20080221461A1
• Filed: 03/05/2007
• Published: 09/11/2008
• Est. Priority Date: 03/05/2007
• Status: Abandoned Application

• Current Assignee: Sotera Wireless Incorporated
• Original Assignee: Triage Wireless, Inc.
• Inventors: Visser, Henk, Banet, Matthew John, Zhou, Zhou, Dhillon, Marshal Singh, Terry, Andrew Stanley
• Application Number:
  US11/682,228
• Publication Number:
  US 20080221461A1
• Time in Patent Office: Days
• US Class Current: 600/485
• 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 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

The invention provides a method for measuring a patient'"'"'s blood pressure featuring the following steps: 1) measuring a first time-dependent optical signal with a first optical sensor; 2) measuring a second time-dependent optical signal with a second optical sensor; 3) measuring a time-dependent electrical signal with an electrical sensor; 4) estimating the patient'"'"'s arterial properties using either the first or second time-dependent optical signal; 5) determining a pulse transit time (PTT) from the time-dependent electrical signal and at least one of the first and second time-dependent optical signals; and 6) calculating a blood pressure value using a mathematical model that includes the PTT and the patient'"'"'s arterial properties.

Claims

1. A method for measuring a patient'"'"'s blood pressure comprising:

measuring a first time-dependent optical signal with a first optical sensor;

measuring a second time-dependent optical signal with a second optical sensor;

measuring a time-dependent electrical signal with an electrical sensor;

estimating the patient'"'"'s arterial properties from at least one of the first time-dependent optical signal or a derivative thereof, and the second time-dependent optical signal or a derivative thereof,

determining a pulse transit time from the time-dependent electrical signal or a derivative thereof, and at least one of the first and second time-dependent optical signals, or a derivative thereof, and

calculating a blood pressure using a mathematical model that includes the pulse transit time and the patient'"'"'s arterial properties.

2. The method of claim 1, wherein determining the vascular transit time further comprises analyzing a first time-dependent feature from at least one of the first time-dependent optical signal or a derivative thereof, and a second time-dependent feature from the second time-dependent optical signal or a derivative thereof.

3. The method of claim 2, wherein the first time-dependent feature is comprised by a second derivative of an optical plethysmograph.

4. The method of claim 3, wherein the first time-dependent feature is a ratio of one or more peaks comprised a second derivative of an optical plethysmograph.

5. The method of claim 1, further comprising attaching the first optical sensor to a finger or wrist of the patient.

6. The method of claim 5, further comprising attaching the second optical sensor to a wrist or arm of the patient.

7. The method of claim 1, wherein the electrical sensor comprises at least two electrodes.

8. The method of claim 1, wherein a single sensor comprises at least one electrode and at least the first or second optical sensor.

9. The method of claim 1, wherein estimating the patient'"'"'s arterial properties further comprises comparing a vascular transit time, or a derivative thereof, to a predetermined look-up table.

10. The method of claim 1, wherein estimating the patient'"'"'s arterial properties further comprises comparing a vascular transit time, or a derivative thereof, to a mathematical function.

11. The method of claim 10, further comprising calculating a pulse wave velocity from the vascular transit time and a distance value corresponding to separation of the first and second optical sensors.

12. The method of claim 11, further comprising estimating the patient'"'"'s arterial properties using the pulse wave velocity.

13. The method of claim 12, wherein estimating the patient'"'"'s arterial properties further comprises comparing the pulse wave velocity, or a derivative thereof, to a predetermined look-up table.

14. The method of claim 12, wherein estimating the patient'"'"'s arterial properties further comprises comparing the pulse wave velocity, or a derivative thereof, to a mathematical function.

15. The method of claim 1, wherein determining the pulse transit time further comprises analyzing a first time-dependent feature from the time-dependent electrical signal or a derivative thereof, and a second time-dependent feature from at least one of the first time-dependent optical signal or a derivative thereof, and a second time-dependent feature from the second time-dependent optical signal, or a derivative thereof.

16. The method of claim 15, wherein the first time-dependent feature comprises a peak corresponding to a portion of the time-dependent electrical signal.

17. The method of claim 15, wherein the second time-dependent feature comprises a base of an optical plethysmograph.

18. The method of claim 15, wherein the second time-dependent feature comprises a peak of an optical plethysmograph.

19. A device for measuring a patient'"'"'s blood pressure, comprising:

a first optical sensor configured to measure a first time-dependent optical signal;

a second optical sensor configured to measure a second time-dependent optical signal;

an electrical sensor configured to measure a time-dependent electrical signal; and

a processor, in electrical communication with the first and second optical sensors and the electrical sensor;

the processor configured to receive the first time-dependent optical signal or a derivative thereof, the second time-dependent optical signal or a derivative thereof, and the time-dependent electrical signal or a derivative thereof, the processor comprising a software program configured to;

i) estimate the patient'"'"'s arterial properties from at least one of the first time-dependent optical signal or a derivative thereof, and the second time-dependent optical signal or a derivative thereof,

ii) determine a pulse transit time from the time-dependent electrical signal or a derivative thereof and either the first or second time-dependent optical signal or a derivative thereof, and

iii) calculate a blood pressure value using a mathematical model that includes the pulse transit time and the patient'"'"'s arterial properties.

20. A device for measuring a patient'"'"'s blood pressure, comprising:

a first optical sensor configured to measure a first time-dependent optical signal;

a second optical sensor configured to measure a second time-dependent optical signal;

an electrical sensor configured to measure a time-dependent electrical signal; and

a processor configured to;

i) process the first time-dependent optical signal or a derivative thereof, to generate a first processed optical signal;

ii) process the second time-dependent optical signal or a derivative thereof, to generate a second processed optical signal;

iii) process the time-dependent electrical signal or a derivative thereof, to generate a processed electrical signal;

iv) estimate arterial properties from at least one of the first processed optical signal and the second processed optical signal;

v) determine a pulse transit time from the processed electrical signal and at least one of the first processed optical signal and the second processed optical signal; and

,

iv) calculate a blood pressure value using the pulse transit time and the estimated arterial properties.

21. A method for measuring a patient'"'"'s blood pressure comprising:

measuring a first time-dependent optical signal with a first optical sensor disposed on the patient'"'"'s finger;

measuring a second time-dependent optical signal with a second optical sensor disposed on the patient'"'"'s arm;

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

determining a pulse wave velocity from the first time-dependent optical signal or a derivative thereof, the second time-dependent optical signal or a derivative thereof, and a distance separating the first optical sensor and the second optical sensor;

estimating the patient'"'"'s arterial properties using the pulse wave velocity, or a derivative thereof;

determining a pulse transit time from the time-dependent electrical signal or a derivative thereof and at least one of the first and second time-dependent optical signal, or a derivative thereof; and

,

calculating a blood pressure value using a mathematical model that includes the pulse transit time and the patient'"'"'s arterial properties.