BLOOD PRESSURE MEASUREMENT SYSTEM

• US 20120059267A1
• Filed: 08/25/2011
• Published: 03/08/2012
• Est. Priority Date: 08/26/2010
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Lamego, Marcelo, Kiani, Massi Joe E., Dalvi, Cristiano, Vo, Hung, Lam, Ken
• Granted Patent: US 9,649,054 B2
• Time in Patent Office: Days
• US Class Current: 600/483
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• 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

Abstract

A blood pressure measurement system that non-invasively determines an individual'"'"'s blood pressure can include a noninvasive blood pressure sensor having an optical sensor and a motion sensor. The optical sensor can provide a photoplethysmograph signal obtained from a patient to a processor. The motion sensor can provide a motion signal to the processor responsive to motion of the patient. In one embodiment, the processor calculates or estimates the blood pressure of the patient based on the photoplethysmograph signal and the motion signal. Advantageously, the system can obtain this blood pressure measurement without an occlusive cuff, thereby reducing patient discomfort. In other implementations, the processor calculates a blood pressure-related parameter from the photoplethysmograph and motion signal. The processor can occasionally trigger an occlusive cuff measurement as this parameter changes, thereby reducing the frequency of occlusive cuff measurements.

Claims

1. A sensor for measuring blood pressure, the sensor comprising:

an optical sensor comprising an emitter configured to emit light on a measurement site of a patient and a detector configured to detect the light after attenuation by the measurement site and to output a photoplethysmograph signal responsive to the attenuated light; and

a motion sensor configured to sense motion of the patient at the measurement site and to provide a motion signal responsive to the sensed motion;

wherein the photoplethysmograph signal and the motion signal are configured to be used to derive a blood pressure of the patient.

2. The sensor of claim 1, wherein the photoplethysmograph signal comprises a deformed portion due to the motion, and wherein the deformed portion of the photoplethysmograph signal is indicative of blood pressure.

3. The sensor of claim 2, wherein a higher magnitude of the deformed portion reflects a lower blood pressure and wherein a lower magnitude of the deformed portion reflects a higher blood pressure.

4. The sensor of claim 1, wherein the motion sensor comprises an accelerometer.

5. The sensor of claim 1, further comprising a motion inducer configured to induce the motion at the measurement site.

6. The sensor of claim 5, wherein the motion inducer comprises a motor.

7. A method of measuring blood pressure, the method comprising:

obtaining a photoplethysmograph signal from an optical sensor coupled with a patient at a measurement site that is in motion;

obtaining a motion signal from a motion sensor coupled with the measurement site; and

calculating a blood pressure measurement based at least in part on the photoplethysmograph signal and the motion signal.

8. The method of claim 7, further comprising identifying a motion component of the photoplethysmograph signal due to the motion.

9. The method of claim 8, wherein said calculating the blood pressure measurement comprises calculating a lower blood pressure for a higher magnitude of the motion component and a higher blood pressure for a lower magnitude of the motion component.

10. The method of claim 8, wherein said identifying the motion component comprises adaptively filtering the photoplethysmograph signal with an adaptive noise filter, such that noise filtered by the adaptive noise filter comprises the motion component.

11. The method of claim 8, further comprising normalizing the motion component with respect to one or more of the following:

the motion, perfusion, and a second motion component derived from a wavelength of light other than a wavelength used to obtain the photoplethysmograph.

12. The method of claim 11, wherein said calculating further comprises using the normalized motion component to obtain the blood pressure measurement from a calibration curve.

13. The method of claim 12, further comprising using the blood pressure measurement to trigger an occlusive cuff to obtain an occlusive blood pressure measurement.

14. The method of claim 7, wherein said calculating further comprises applying one or more basis functions to the motion signal, such that the blood pressure measurement is based on an output of the one or more basis functions.

15. A method for measuring blood pressure, the method comprising:

attaching an inflatable cuff to a person;

inflating the cuff at an approximately constant rate using gas from a gas reservoir; and

measuring blood pressure of the person while the cuff is inflating.

16. The method of claim 15, wherein said measuring is configured to be performed prior to occlusion of an artery of the person during inflation of the inflatable cuff.

17. The method of claim 15, wherein said measuring comprises filtering the blood pressure data to generate filtered blood pressure data.

18. The method of claim 17, wherein the filtered blood pressure data comprises pressure oscillations in the inflatable cuff due to blood flow in an artery of the person.

19. The method of claim 17, wherein said measuring further comprises determining the blood pressure based on at least one of the slope of the filtered blood pressure data and the amplitude of the filtered blood pressure data.

20. The method of claim 15, wherein the gas from the gas reservoir is used to generate electricity for the blood pressure monitoring system.