Physiological sensor having reduced sensitivity to interference

• US 8,558,178 B2
• Filed: 05/14/2012
• Issued: 10/15/2013
• Est. Priority Date: 05/26/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Gonopolskiy, Oleg, Anderson, Arik
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US13/470,717
• Publication Number:
  US 20120223213A1
• Time in Patent Office: 519 Days
• Field of Search: 600/344, 250/338.1
• US Class Current: 250/338.1
• CPC Class Codes: A61B 2562/182 Electrical shielding, e.g. using a Faraday cage
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/68335 including release sheets or liners
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker

Abstract

A physiological sensor having reduced sensitivity to interference includes a light source, a light detector in optical communication with the light source, and a sensor pad at least partially housing the light source and the light detector. The sensor pad is configured to be capacitively isolated from a patient. Moreover, the physiological sensor may be electrically connected to an amplifier having a signal ground and a monitor.

Claims

1. A sensor comprising:

a sensor pad;

a conductive material disposed on the sensor pad;

a printed circuit board disposed on the conductive material, the printed circuit board including a light source configured to generate light and a light detector configured to receive light generated by the light source,

wherein the sensor pad has a thickness that capacitively isolates the conductive material from a patient.

2. The sensor of claim 1, wherein a capacitance of the conductive material relative to the patient is inversely proportional to a distance between the conductive material and the patient and the distance is based on the thickness of the sensor pad.

3. The sensor of claim 2, wherein the capacitance between the conductive material and the patient is defined as:

C_p=∈

₀∈

_r A/d, wherein C_p is the capacitance in Farads, A is an area of the sensor pad disposed on the patient, d is a distance between the conductive material and the patient, ∈

_r is a dielectric constant between the conductive material and the patient, and ∈

₀ is a permittivity of free space.

4. The sensor of claim 3, wherein the dielectric constant between the conductive material and the patient is greater than 1.

5. The sensor of claim 1, wherein the conductive material is electrically connected to the printed circuit board.

6. The sensor of claim 5, wherein the conductive material and the printed circuit board are electrically grounded.

7. The sensor of claim 1, wherein the printed circuit board includes traces configured to minimize an electromagnetic field generated between the traces.

8. The sensor of claim 1, further comprising a light-blocking pad disposed on the sensor pad and configured to at least partially limit ambient light received by the light detector.

9. A system comprising:

an amplifier configured to receive signals representing physiological information, wherein the amplifier includes a monitor configured to graphically display the physiological information represented by the received signals; and

a sensor having a sensor pad, a conductive material disposed on the sensor pad, and a printed circuit board disposed on the conductive material, the printed circuit board including a light source configured to generate light and a light detector configured to receive light generated by the light source, wherein the sensor pad has a thickness that capacitively isolates the conductive material from a patient.

10. The system of claim 9, wherein a capacitance of the conductive material relative to the patient is inversely proportional to a distance between the conductive material and the patient and the distance is based on the thickness of the sensor pad.

11. The system of claim 10, wherein the capacitance between the conductive material and the patient is defined as:

C_p=∈

₀∈

_r, A/d, wherein C_p is the capacitance in Farads, A is an area of the sensor pad disposed on the patient, d is a distance between the conductive material and the patient, ∈

_r is a dielectric constant between the conductive material and the patient, and ∈

₀ is a permittivity of free space.

12. The system of claim 9, wherein the sensor pad is capacitively isolated from the monitor.

13. The system of claim 9, wherein the conductive material is electrically connected to the printed circuit board.

14. The system of claim 13, wherein the conductive material and the printed circuit board are electrically grounded.

15. The system of claim 9, wherein the printed circuit board includes traces configured to minimize an electromagnetic field generated between the traces.

16. The system of claim 9, wherein the sensor includes a light-blocking pad disposed on the sensor pad, wherein the light-blocking pad is configured to at least partially limit ambient light received by the light detector.

17. The system of claim 9, further comprising a shield electrically disposed between the sensor and the amplifier.

18. The system of claim 9, wherein the amplifier includes a signal ground electrically connected to the sensor and capacitively isolated from the monitor.

19. A sensor comprising:

a sensor pad;

a conductive material disposed on the sensor pad;

a printed circuit board disposed on the conductive material, the printed circuit board including a light source configured to generate light and a light detector configured to receive light generated by the light source,

wherein the sensor pad has a thickness that capacitively isolates the conductive material from a patient and wherein a distance between the conductive material and the patient is based on the thickness of the sensor pad, and

wherein a capacitance of the conductive material relative to the patient is defined as;

C_p=∈

₀∈

_r, A/d, wherein C_p is the capacitance in Farads, A is an area of the sensor pad disposed on the patient, d is a distance between the conductive material and the patient, ∈

_r is a dielectric constant between the conductive material and the patient, and ∈

₀ is a permittivity of free space.