Sensor for intrauterine use

• US 5,247,932 A
• Filed: 10/11/1991
• Issued: 09/28/1993
• Est. Priority Date: 04/15/1991
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Original Assignee: Nellcor Incorporated (Medtronic Plc)
• Inventors: Johansson, Eric, Chung, Christopher, Mannheimer, Paul D., McNamara, Helen M., Ritson, Carl
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): PONTIUS, KEVIN LANE
• Application Number:
  US07/775,315
• Time in Patent Office: 718 Days
• Field of Search: 128/633, 128/634, 128/664, 128/665, 128/642, 128/670, 128/698, 128/700
• US Class Current: 600/338
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1464 specially adapted for foetal tissue
• CPC Class Codes: A61B 5/6853 with a balloon
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure

Abstract

A sensor placement and retention mechanism for use with fetal sensor sites beyond the user'"'"'s reach are disclosed. The preferred embodiment of this invention is a fetal pulse oximetry sensor having an active face through which a light source and a light detector operate. The sensor includes a handle that facilitates placement of the active face at a sensor site in a preferred region beyond the transcervical region and beyond the reach of the user. A pair of electrodes--one disposed against the fetus'"'"' skin and one exposed to the amniotic fluid--are used to confirm that the sensor is firmly in place on the fetus. In an optional sensor retention feature, a self-inflating bladder presses the active face of the sensor against the fetus'"'"' skin to optically couple the sensor with the tissue at the sensor site.

Claims

1. A pulse oximetry apparatus for use in measuring a blood characteristic in fetal tissue during labor and delivery, the apparatus comprising:

a sensor having an active face including a light source and a light detector;

a handle means attached to said sensor for accurately placing the active face of the sensor on a site on a fetus beyond the presenting part and beyond the transcervical region; and

a self-inflating bladder means attached to said sensor for retaining the active face of the sensor in place on the site on the fetus.

2. The apparatus according to claim 1 wherein the bladder means has a compressible, self-expanding, foam disposed therein for inflating the bladder means.

3. The apparatus according to claim 1 wherein the bladder means has an opening disposed on a surface thereof for controlling the rate of self-inflation of the bladder means.

4. The apparatus according to claim 3 wherein the opening is approximately 0.050 inches.

5. A pulse oximetry apparatus for use in measuring a blood characteristic in fetal tissue during labor and delivery, the apparatus comprising:

a sensor having an active face including a light source and a light detector;

a handle means attached to said sensor including a sleeve having a predetermined radius of curvature for accurately placing the active face of the sensor on a site of a fetus beyond the presenting part and beyond the transcervical region; and

a rod removably insertable into the sleeve, the rod being constructed so that the radius of curvature of the sleeve is altered when the rod is inserted into the sleeve.

6. The apparatus according to claim 5 wherein the rod is constructed so that the radius of curvature of the sleeve increases when the rod is inserted into the sleeve.

7. The apparatus according to claim 6 wherein the rod is constructed so that the sleeve is substantially straight when the rod is inserted into the sleeve.

8. The apparatus according to claim 7 wherein the sleeve comprises approximately 0.020 inch steel, and wherein the rod comprises approximately 0.025 inch steel.

9. A pulse oximetry apparatus for use in measuring a blood characteristic in fetal tissue during labor and delivery, the apparatus comprising:

a sensor having an active face including a light source and a light detector;

a handle means attached to said sensor for accurately placing the active face of the sensor on a site of a fetus beyond the presenting part and beyond the transcervical region; and

contact determining means for determining whether the active face is placed firmly in contact with the site on the fetus, the contact determining means including;

a first electrode disposed on the active face of the sensor;

a second electrode; and

current generating means for generating current between the first electrode and the second electrode.

10. The apparatus according to claim 9 wherein the second electrode is located on a surface of the sensor other than the active face of the sensor.

11. The apparatus according to claim 10 wherein the second electrode is located on a surface of the sensor opposite the active face of the sensor.

12. The apparatus according to claim 9 wherein the contact determining means further comprises impedance measuring means, coupled to the current generating means, for measuring the impedance between the first electrode and the second electrode in accordance with the current flowing between the first electrode and the second electrode.

13. The apparatus according to claim 12 wherein the contact determining means further comprises threshold comparing means, coupled to the impedance measuring means, for comparing the measured impedance to a threshold value.

14. The apparatus according to claim 13 wherein the contact determining means further comprises contact indicating means, coupled to the threshold comparing means, for providing a signal when the measured impedance exceeds the threshold value for indicating that the active face is placed firmly in contact with the site on the fetus.

15. The apparatus according to claim 14 wherein the contact indicating means comprises a visual indicator that is activated when the measured impedance exceeds the threshold value.

16. The apparatus according to claim 14 further comprising:

calculating means for calculating a blood oxygen saturation value;

signal communicating means, coupled to the light detector and to the calculating means, for communicating signals corresponding to optical data from the light detector to the calculating means;

wherein the calculating means includes saturation calculating means for calculating a blood oxygen saturation value using the signals corresponding to the optical data; and

wherein the saturation calculating means is coupled to the contact indicating means for altering the calculation of the blood oxygen saturation value in a predetermined manner when the active face is not placed firmly in contact with the site on the fetus.

17. A method of measuring a blood characteristic in fetal tissue during labor and delivery comprising the steps of:

inserting a sensor into a mother'"'"'s uterus, the sensor having an active face;

placing the active face of the sensor on a site on a fetus beyond the presenting part and beyond the transcervical region;

calculating the blood characteristic;

determining whether the active face of the sensor is placed firmly in contact with the site on the fetus; and

altering the calculation of the blood characteristic in a predetermined manner if the active face of the sensor is not firmly in contact with the site on the fetus.

18. The method according to claim 17 wherein the determining step comprises the step of causing current flow between a first electrode disposed on the active face of the sensor and a second electrode.

19. The method according to claim 18 wherein the determining step further comprises the step of measuring the impedance between the first electrode and the second electrode in accordance with the current flowing between the first electrode and the second electrode.

20. The method according to claim 19 wherein the determining step further comprises the step of comparing the measured impedance to a threshold value.

21. The method according to claim 20 wherein the determining step further comprises the step of providing a signal when the measured impedance exceeds the threshold value for indicating that the active face is placed firmly in contact with the site on the fetus.

22. The method according to claim 21 wherein the determining step further comprises the step of activating a visual indicator when the measured impedance exceeds the threshold value.