Lead set filter for a patient monitor

• US 6,246,902 B1
• Filed: 05/04/1999
• Issued: 06/12/2001
• Est. Priority Date: 05/04/1999
• Status: Expired due to Term

• Current Assignee: Draeger Medical Systems Incorporated (Dragerwerk AG)
• Original Assignee: Siemens Medical Systems, Inc. (Siemens AG)
• Inventors: Naylor, Thomas Kipling, Newell, Scott W., Kelly, Clifford
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US09/304,378
• Time in Patent Office: 770 Days
• Field of Search: 607/63, 600/509, 128/901
• US Class Current: 600/509
• CPC Class Codes: A61B 2562/182 Electrical shielding, e.g. using a Faraday cage
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/303 Patient cord assembly, e.g. cable harness
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A shielded conductor path comprising: a first signal conductor having an input end for acquiring a physiological signal and an output end for coupling the physiological signal to a physiological signal input of a patient monitor, and a second signal conductor positioned with respect the first signal conductor for acting as a shield therefore. An inductance connected in series between an output end of the second signal conductor and the reference signal input of the patient monitor forms a filter circuit which attenuates the level of an interference signal in the second signal conductor. In one preferred embodiment of the invention, the inductance is part of an RLC filter circuit contained in a housing which is selectively insertable between an EKG lead set and the EKG signal input of a patient monitor. The selectively insertable filter permits the use of standard EKG lead sets in the presence of RF electrosurgery procedures, without risk of burning the patient at the site of the EKG electrodes.

Claims

1. An apparatus for coupling physiological signals acquired from a patient to a physiological signal processing circuit in a patient monitor, in the presence of an interference signal acquired by the apparatus, said apparatus comprising:

a first signal conductor having an input end adapted for coupling to a physiological signal sensor coupled to a medical patient for acquiring a physiological signal, and having an output end adapted for coupling the physiological signal to a physiological signal input of a physiological signal processing circuit in a patient monitor;

a second signal conductor positioned for shielding the first signal conductor from the input end to the output end, the second signal conductor having an output end adapted for coupling to a reference point associated with the physiological signal processing circuit of the patient monitor; and

a first inductance connected in series with the second signal conductor for forming a filter circuit which attenuates the level of the interference signal in the second signal conductor, wherein there is no series coupled inductance in the first conductor corresponding to the first inductance in the second conductor.

2. The apparatus of claim 1, comprising a plurality of shielded conductor paths, with the first signal conductor of each path adapted to be coupled to a physiological signal sensor mounted on a patient, and an inductance connected in series between the output end of each of the second signal conductors and associated reference point inputs of the patient monitor for forming a plurality of filter circuits, each filter circuit for attenuating the level of the interference signal in a respective one of the shielded conductor paths.

3. The apparatus of claim 1, further including:

a switching arrangement coupled to the inductance for selectively removing the attenuating effect of the filter circuit on the interference signal.

4. The apparatus of claim 1, wherein the inductance is part of an RLC filter, comprising:

a resistance connected in series between the output end of the first signal conductor and the physiological signal input of the patient monitor, and a capacitance for bridging the first and second signal conductors at the point between the series connections of both of the resistance and inductance to the patient monitor.

5. The apparatus of claim 4, further including:

a switching arrangement coupled to the RLC filter for selectively removing the attenuating effect of the filter circuit on the interference signal.

6. The apparatus of claim 5, wherein the switching arrangement comprises a first switch for selectively bridging the resistance, and a second switch for selectively disconnecting the capacitance, the first switch being open and second switch being closed for causing said RLC filter circuit to operate so as to attenuate the interference signal.

7. The apparatus of claim 1, wherein the inductance is located in a housing adapted for being selectively coupled between the output end of the second signal conductor and the associated reference point input of the patient monitor.

8. The apparatus of claim 2, wherein the inductance is located in a housing adapted for being selectively coupled between the output end of the second signal conductor of each of the plurality of shielded conductor paths, and reference signal inputs of the patient monitor.

9. The apparatus of claim 8, wherein the housing is adapted for being selectively coupled between an EKG lead wire set adapted for being coupled to a plurality of EKG signal sensors mounted on the medical patient, and EKG signal inputs of a patient monitor.

10. The apparatus of claim 8, wherein the housing includes a switch arrangement in the leadwire set for selectively removing the attenuating effect of the filter circuit on the interference signal.

11. A conductor path for coupling a physiological signal acquired from a patient to a physiological signal processing circuit in a patient monitor, in the presence of an interference signal acquired by the conductor path, said conductor path comprising:

a first signal conductor path having an input end adapted for coupling to a physiological signal sensor coupled to a medical patient for acquiring a physiological signal, and having an output end adapted for coupling the physiological signal to a physiological signal input of a physiological signal processing circuit in a patient monitor;

a second signal conductor positioned for shielding the first signal conductor from the input end to the output end, said second signal conductor having an output end adapted for coupling to a reference point associated with the physiological signal processing circuit of the patient monitor; and

a first inductance coupled in series with the second signal conductor wherein there is an absence of a series coupled inductance in the first conductor corresponding to the first inductance in the second conductor.