MOTION ARTIFACT MITIGATION METHODS AND DEVICES FOR PULSE PHOTOPLETHYSMOGRAPHY

• US 20140058217A1
• Filed: 08/23/2013
• Published: 02/27/2014
• Est. Priority Date: 08/25/2012
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Giovangrandi, Laurent B.
• Granted Patent: US 10,881,310 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• 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

Aspects of the present disclosure are directed toward devices, apparatus, and methods for interfacing a PPG apparatus with the skin surface of a patient and sensing artifacts due to surface motion attributable to contact-based surface motion at or near where the apparatus in contact with the skin surface of the patient. The devices, apparatus, and methods include circuitry that contacts the skin surface of the patient, illuminates tissue at the surface, and senses a pulse photoplethysmography (PPG) signal of the patient in response thereto. Further, the circuitry senses artifacts due to surface motion, and responds to the sensed PPG signal by processing the sensed PPG signal relative to the sensed artifacts to produce a version of the sensed PPG signal that is indicative local blood volume and composition of the patient, and filtered to suppress noise therein due to the contact-based surface motion.

Claims

1. An apparatus for interfacing with a patient, the apparatus comprising:

a housing including a first circuit, the housing being configured and arranged to contact the skin surface of the patient,

via the first circuit, illuminate tissue at the skin surface of the patient by sending light toward the surface, the light being characterized by a first wavelength range, and

sense a pulse photoplethysmography (PPG) signal of the patient in response to the light being sent toward the surface while the housing is in contact with the skin surface of the patient; and

a second circuit configured and arranged to sense artifacts attributable to contact-based surface motion at a portion of the housing where the housing is in contact with the skin surface of the patient, the artifacts being characterized as also affecting the light in the first frequency range, and configured and arranged to respond to the sensed PPG signal by processing the sensed PPG signal relative to the sensed artifacts to produce a version of the sensed PPG signal that is indicative of local blood volume and blood composition of the patient and that is filtered to suppress noise therein due to the contact-based surface motion.

2. The apparatus of claim 1, wherein the second circuit includes an impedance-based sensor configured and arranged to measure the surface motion artifacts, and wherein the second circuit is further configured and arranged to sense artifacts attributable to contact-based surface motion at a portion of the housing in response to the housing in sufficient proximity of the skin surface to transfer energy between the skin surface and the impedance-based sensor.

3. The apparatus of claim 1, wherein the second circuit includes an impedance-based sensor configured and arranged to measure the surface motion artifacts, and wherein the impedance-based sensor is configured and arranged to determine electrical properties via the surface of the patient.

4. The apparatus of claim 1, wherein the second circuit includes:

an impedance-based sensor, including capacitance circuitry, configured and arranged to measure physiological and mechanical surface motion artifacts of the patient; and

a computer that is electrically coupled to the capacitance circuitry and configured and arranged to measure physiological and mechanical surface motion artifacts of the patient and produce the filtered version of the sensed PPG signal.

5. The apparatus of claim 1, wherein the second circuit is configured and arranged to send light toward the surface, the light being characterized by a second wavelength range that is different than the first wavelength range.

6. The apparatus of claim 1, wherein the second circuit includes an impedance-based sensor configured and arranged to measure surface motion artifacts of the patient that are both physiological and mechanical, and the second circuit is configured and arranged to illuminate tissue at the surface at a second wavelength.

7. The apparatus of claim 1, wherein the second circuit is configured and arranged to send light toward the surface, the light being characterized by a second wavelength range that is different than the first wavelength range, and wherein the second circuit is further configured and arranged to measure transmitted or reflected light being characterized by a second wavelength range and, in response thereto, measure physiological and mechanical surface motion artifacts of the patient and produce the filtered version of the sensed PPG signal.

8. The apparatus of claim 1, wherein the second circuit is further configured and arranged to measure a transmitted or reflected PPG signal, and the second circuit generates a noise-reference signal based on the sensed artifacts, the noise-reference signal being characterized to correlate predominantly with the artifacts and minimally to the sensed PPG signal.

9. An apparatus for interfacing with a patient, the apparatus comprising:

first means, including a housing, for

contacting the skin surface of the patient via the housing,

illuminating tissue at the skin surface by sending light toward the skin surface, the light being characterized by a first wavelength range, and

sensing a pulse photoplethysmography (PPG) signal of the patient in response to the light being sent toward the skin surface while the housing is in contact with the skin surface of the patient; and

second means, including impedance circuitry, for sensing artifacts due to contact-based surface motion at a portion of the housing where the housing is in contact with the skin surface of the patient, the artifacts being characterized as also affecting the light in the first frequency range, and responding to the sensed PPG signal by processing the sensed PPG signal relative to the sensed artifacts, and therefrom producing a version of the sensed PPG signal that is indicative of local blood volume and blood composition of the patient as filtered to suppress noise therein due to the motion at the skin surface.

10. A method of interfacing with a patient, the method comprising:

contacting the skin surface of the patient via an apparatus having a housing for a light source,

using the light source to illuminate tissue at the skin surface, thereby sending light thereat, the light being characterized by a first wavelength range;

sensing a pulse photoplethysmography (PPG) signal of the patient in response to the light being sent toward the skin surface while the housing is in contact with the skin surface of the patient; and

sensing artifacts due to contact-based surface motion at a portion of the housing where the housing is in contact with the skin surface of the patient, the artifacts being characterized as also affecting the light in the first frequency range, and in response to the sensed PPG signal, processing the sensed PPG signal relative to the sensed artifacts to produce a version of the sensed PPG signal that is indicative local blood volume and blood composition of the patient as filtered to suppress noise therein due to the skin surface motion.