1995-04-11
1997-06-03
Sykes, Angela D.
Surgery
Truss
Pad
128642, A61B 500
Patent
active
056344597
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to obstetrics and in particular to probes for fetal monitoring.
The monitoring of the fetus is a vital aspect of modern labour management. Assessment of the fetal heart rate is a mainstay of such monitoring and can be done externally or by internal electrodes. In certain circumstances, internal monitoring is preferred and provides a more accurate representation of the fetal heart rate pattern for analysis. Internal monitoring probes are usually made of arcuate or spiral metal needles which perforate the scalp skin and are thus secured to obtain electrical signals from the fetal heart. Such probes can be considered invasive to the fetus.
Alternatively, intrauterine probes have been designed which do not have to perforate the fetal skin and which have contact electrodes that lie apposed to the surface of the fetal body and scalp. Reference is directed for example to U.S. Pat. No.-3,326,207 and GB-A-2,195,897. These probes are long and have several built-in electrodes to ensure that at least one of them is in sufficient contact with the fetal skin to obtain an adequate signal. Another sensor, some distance away, is used as a reference electrode. Unless already ruptured spontaneously, the membranes of the amniotic sac have to be ruptured artificially before such a probe is inserted. Because of this aspect and its overall length, such probes can be considered invasive to the mother and the uterine environment of the fetus.
The probe disclosed in GB-A-2,195,897 comprises an elongate flexible strip having a series of protruding electrodes. The strip is of sufficient length (approximately 50 cm) to extend past the fetal head and along the trunk of the fetus. U.S. Pat. No.-3,326,207, issued in 1967, proposed a fetal probe having two inflatable balloons positioned as to contact the shoulder and hip/thigh regions of the fetus, respectively. Each balloon is spherical and carries six or so equatorially spaced electrodes. Additionally, each electrode is provided with a port for the local discharge of a conductive solution. The construction and operation of this probe is considered to be far too elaborate and cumbersome for practical application.
It is an object of this invention to provide an improved fetal probe which is not invasive to the mother or the fetus.
SUMMARY OF THE INVENTION
Accordingly, the present invention consists in one aspect in a fetal probe comprising an elongate body portion adapted for insertion into the cervix around the presenting part of the fetus, the body portion carrying fetal sensor means; characterised in that the body portion is insertable into the cervix to a length of between 10 and 20 cm and preferably about 15 cms enabling positioning of the probe such that the sensor is held against the fetal presenting part by the pressure of maternal tissue with the amniotic membrane intact.
The probe according to this invention can be inserted through the vagina into a cervical opening of 1 cm or more dilatation, with the most distal part of the probe extending into the lower part of the uterus only, inside the cervix and just above the presenting part. The amniotic membranes do not necessarily have to be ruptured to enable this insertion.
The probe can be a vehicle for a variety of monitoring functions, and the probe sensor means can take a variety of forms. Principally, the sensor means would comprise a contact electrode for obtaining the fetal heart rate signal, using a second, reference electrode positioned on the maternal surface of the near end of the probe, to be in contact with vaginal tissues. In addition, the probe can contain the sensors (photodiode and light emitting diodes (LED's)) for transcutaneous pulse oximetry. Other sensors can also be built in to measure other parameters. It has been found that most sensors can detect a satisfactory signal through intact amniotic membranes.
According to this invention, the probe can be held in place by the pressure of maternal tissues (cervix, vagina) against the fetal presenting part; but a
REFERENCES:
patent: 3326207 (1967-06-01), Egan
patent: 4873986 (1989-10-01), Wallace
patent: 5109849 (1992-05-01), Goodman et al.
patent: 5247932 (1993-09-01), Chung et al.
patent: 5377675 (1995-01-01), Ruskewicz et al.
Corometrics Medical Systems, Inc.
Sykes Angela D.
Yarnell Bryan K.
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