Surgery – Truss – Pad
Patent
1993-06-22
1995-08-22
Cohen, Lee S.
Surgery
Truss
Pad
128698, 12866107, 128775, 30441303, A61B 502
Patent
active
054429404
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an apparatus for evaluating the fetal condition prior to or under birth comprising first detection means for detecting the fetal heart rate from a first signal indicative of said fetal heart rate and generating a fetal heart rate trace; second detection means for detecting maternal labour from a second signal indicative of said maternal labour and generating a toco trace; processing means for evaluating said fetal heart rate trace and said toco trace, said processing means generating quantities representative of possible diagnostic information; and rule based operating means for extracting, validating, classifying or scoring said quantities or derived parameters, or said fetal heart rate trace or said toco trace. It also relates to a corresponding method for evaluating the fetal condition.
In gynecology and obstetrics, two medical parameters are important to assess the condition of the fetus. These parameters are the fetal beat-to-beat heart rate and uterus (or labour) activity. Simultaneous assessment of the fetal heart rate (FHR) and uterus activity (TOCO) allows determination of the fetal condition. Monitors measuring and recording both parameters are called fetal monitors or cardiotocographs (CTG monitors).
To obtain a signal indicative of the fetal heart rate, a so-called fetal scalp electrode may be applied to the fetal skin. These electrodes are usually spiral electrodes which are screwed into the fetal epidermis, see for example U.S. Pat. No. 3,827,428. Such direct electrodes allow very accurate measurements due to the excellent signal quality. Unfortunately, the internal or direct measurement can only be used after rupture of the membranes. Prior to that point in time (in particular, during gestation), indirect methods have to be used. These indirect measurements are performed abdominally, e.g. by listening the fetal heart sound or by measuring the Doppler shift of an ultrasound wave reflected by the moving parts of the fetal heart, particularly the heart walls and/or the heart valves. Further methods for recording the fetal heart rate are the abdominal electrocardiogram (recorded with electrocardiogram electrodes placed on the abdomen of the mother), the registration of fetal heart sounds with a microphone ("Phono") and the like. The present invention relates to all of these signals.
However, neither the electrocardiogram (in the case of a spiral electrode), nor the received ultrasound signal (in the case of an ultrasound transducer), nor any other signal indicative of the fetal heart beat, are of major diagnostic importance. What is in fact required to assess the fetal condition is the beat-to-beat heart rate. This means that heart beats have to be detected in the above signals and that the heart rate is calculated as the inverse of the time interval between two consecutive beats, i.e. the heart rate is calculated from beat to beat. This gives quite accurate information particularly on high-frequency variations in the fetal heart rate trace, which in turn is important for diagnosis.
Uterus activity, on the other hand, may be measured--in the antepartum phase--by means of an external toco transducer (tocodynamometer) placed externally on the fundus uteri of the mother, i.e. approximately centrally on the abdomen. Such toco transducer is a tension-measuring device, most commonly one or more resistive wire strain(s). The theory of what is really measured by these transducers is complex as uterus "hardness" as well as uterus deformation (and sometimes also respiration) influence the tension, but still it is possible to obtain clinically meaningful results, i.e. to discover frequency, amplitude-and shape of a contraction.
After rupture of the membranes, an intravaginal toco transducer may be used, which is essentially a hose connected with a direct pressure transducer and introduced into the uterus. This second transducer generates very accurate and reliable readings.
Stand-alone fetal monitors usually record the fetal heart rate and TOCO time traces on paper, most co
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Herrmann Andreas
Hornung Guenter
Secker Herbert
Takacs Zoltan
Ulmer Friedemann
Cohen Lee S.
Hewlett--Packard Company
Nasser Jr. Robert L.
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