Fetal spiral electrode sleeve and wire interconnect system

Details Fetal spiral electrode sleeve and wire interconnect system Fetal spiral electrode sleeve and wire interconnect system

2000-03-21

2001-11-20

Dvorak, Linda C. M. (Department: 3739)

Surgery

Diagnostic testing

Structure of body-contacting electrode or electrode inserted...

C600S511000, C439S669000, C439S675000, C439S909000

Reexamination Certificate

active

06321103

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to systems used to monitor the health of a fetus during labor and deliver and, more particularly, to an interconnection arrangement for safely monitoring fetal heart rate. The arrangement electrically interconnects a remote fetal monitor with bipolar fetal electrodes.
BACKGROUND OF THE INVENTION
It is desirable to monitor the biological functions (such as heart rate) of a fetus continuously during labor and delivery in order to detect fetal distress. Devices which are external to the mother's body are insufficiently sensitive. In the case of heart rate signals, such devices do not adequately isolate the fetal and maternal heartbeats. Consequently, devices which attach directly to the fetus during labor are used. U.S. Pat. No. Re. 28,990, issued to Hon et al., discloses a fetal spiral electrode assembly historically used to monitor fetal heart rate during birth.
The conventional fetal spiral electrode assembly includes a curved guide tube of adjustable shape for insertion of the fetal spiral electrode through the mother's cervix and into contact with the fetus during labor. A nonconductive plastic tip or holder is slidably received in the guide tube. A sharp, pointed, fetal spiral electrode is mounted on the forward end of the holder for contacting the fetal epidermis.
A reference (maternal) electrode in the form of a flat fin or plate is electrically isolated from the fetal electrode and located on the rear end of the holder. A flexible, hollow drive tube with a cutout on its forward end fits inside the guide tube and engages the holder. The drive tube has a diameter smaller than the diameter of the guide tube. The cutout of the drive tube engages the reference electrode in the holder to impart translation and rotation to the holder and, hence, to the fetal spiral electrode. A handle on the opposite end of the drive tube allows the user to push, pull, and rotate the drive tube within the guide tube. A forward-twisting force is applied to the drive tube to affix the fetal spiral electrode in the fetal epidermis.
The two electrodes are connected to separate wires which are threaded through the common center of the drive and guide tubes until they ultimately exit at the rear end of the drive tube. The wires connected to the electrodes are twisted about each other so that any induced voltages caused by external electromagnetic interference will be the same in each and therefore will not adversely affect the measurement of the galvanic potential difference between the electrodes. After the fetal spiral electrode is secured to the fetal epidermis, the drive tube and guide tube are removed by pulling the tubes longitudinally over the wires and away from the mother. Removal of the drive and guide tubes leaves the electrodes, the holder, and the wires in place inside the mother. The bare, uninsulated ends of the wires are then connected, via an intermediate support or leg plate, to a fetal monitor.
To use the fetal spiral electrode product, the shape of the guide tube is adjusted and the guide tube is inserted through the mother's cervix and into contact with the fetus. Once the guide tube contacts the fetus (and is held against the fetus using one of the user's hands), the drive tube is advanced (using the second hand) until the fetal spiral electrode contacts the fetus. While pressure is maintained against the fetus by the guide tube and drive tube, the drive tube is rotated, using the second hand and the handle, until the fetal spiral electrode is secured to the fetal epidermis. Typically, one full revolution suffices to secure the fetal spiral electrode. Then the drive tube and guide tube are removed by sliding them over the electrode wires.
U.S. Pat. No. 5,680,859 issued to Urion et al. is an improvement over the device disclosed in the '990 patent. Manual connection of the uninsulated ends of the wires is cumbersome and risks shorting the wires. If shorted, the wires cannot transmit correct signals from the fetal and reference electrodes. Accordingly, the '859 patent adds a connector to the wire ends of the fetal spiral electrode assembly disclosed in the '990 patent.
FIG. 6
is a side view of the fetal spiral electrode system
110
disclosed by Urion et al. Electrode system
110
includes a sharp, pointed fetal spiral electrode
120
for contacting the fetal epidermis; a reference (maternal) electrode
122
in the form of a flat fin or plate which is electrically isolated from fetal spiral electrode
120
; a holder
124
; and two electrode wires
126
a
and
126
b.
Holder
124
is an electrically insulating plastic and is adapted to be slidably received inside an introducer
140
. Fetal spiral electrode
120
is mounted on the forward end of holder
124
. Reference electrode
122
is attached to the rearward end of holder
124
.
A drive rod
130
is slidably received in introducer
140
. Drive rod
130
has a clutch
128
at its forward end. Clutch
128
engages reference electrode
122
in holder
124
to impart translation and rotation to holder
124
and, hence, to fetal spiral electrode
120
. A handle
150
on the opposite end of drive rod
130
allows the user to push, pull, and rotate drive rod
130
. Drive rod
130
, clutch
128
, and handle
150
are integrally molded together.
Electrode wires
126
a
and
126
b
are separately coupled to respective electrodes
120
and
122
. Electrode wire
126
a
(typically green in color) connected to fetal spiral electrode
120
and electrode wire
126
b
(typically red) connected to reference electrode
122
form a twisted wire strand
118
which extends from electrodes
120
and
122
along the entire length of drive rod
130
and handle
150
. A retainer
166
is provided near the end of handle
150
opposite drive rod
130
. Retainer
166
locks wire strand
118
in a fixed position. The ends of wires
126
a
and
126
b
opposite holder
124
terminate in a male connector
132
.
Turning to
FIG. 7
, wires
126
a
and
126
b
(which are typically about 450 mm or 18 inches in length) are provided with an untwisted length
116
along a short distance (25-50 mm or 1-2 inches) of wire strand
118
. Untwisted length
116
allows the clinician to separate wires
126
a
and
126
b
without cutting them. The individual wires
126
a
and
126
b
are separately connected to first and second terminal (or ring) contacts
134
and
136
in connector
132
. Contacts
134
and
136
are electrically and physically separated by a spacer
138
. Connector
132
has a forward tapered tip
142
which plugs into a longitudinal passage in the end of handle
150
(connector
132
is shown plugged into the passage in FIG.
6
).
Connector
132
is designed to be inserted into a support or leg plate
170
which is affixed to the mother (typically to the thigh). Support plate
170
is connected, via a cable
176
, to a monitor
178
. Upon insertion of connector
132
into the opening of support plate
170
, ring contacts
134
,
136
on connector
132
click into physical and electrical contact with two corresponding barrel contacts in support plate
170
. Moreover, tip
142
of connector
132
abuts a wall in support plate
170
to prevent over-insertion of connector
132
.
Support plate
170
carries its own ground electrode
180
. Insertion of connector
132
in support plate
170
connects electrodes
120
and
122
to monitor
178
. Consequently, three electrical circuit paths are created upon interconnection of connector
132
of fetal spiral electrode system
110
and support plate
170
: (1) fetal electrode
120
to green wire
126
a
to terminal
134
to a first barrel contact to a first output terminal to monitor
178
; (b) reference electrode
122
to red wire
126
b
to terminal
136
to a second barrel contact to a second output terminal to monitor
178
; and (c) ground electrode
180
to a third output terminal to monitor
178
.
Connector
132
has a grip
144
with an ergonomically designed shape to permit the user to grasp it easily and to ensure a

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