CARDIOTOCOGRAPH

Typical Number in Hospital: 10

Cost Bands: 4,5

References:

This is essentially a device for recording the uterine contractions during labour. However, the term is normally applied to an instrument which also records the foetal heart rate on a beat-to-beat basis to monitor the progress of labour and in particular the wellbeing of the foetus. Uterine contractions are sometimes monitored using a tocodynamometer lightly strapped on to the mother's abdomen which consists of a central plunger coupled to a force transducer and outer guard ring so that the plunger is pressed during the uterine contractions. This provides a qualitative indication of the strength and occurrence of contractions and this is compared with the foetal heart rates which result. Sometimes an internal transducer is used once the foetal membranes have been ruptured and a recording catheter can be introduced into the uterus. The recording catheter can be a fluid-filled tube connected to an external pressure transducer or it may have a miniature pressure transducer built into the tip of the catheter.

Foetal heart rate is normally monitored by a foetal scalp electrode clamped or screwed into the foetal scalp when exposed through the opening cervix. Alternative methods of recording the foetal heart rate are to have electrodes on the mother's abdomen or an ultrasonic transducer detecting motion of the foetal heart.

The records are presented on a paper trace to identify both the effects of the contractions on foetal heart rate and the trend of these effects. In some modern instruments computer processing is applied to these signals to provide time compression to provide a display indicating the trend of these parameters during the course of labour.

Cardiotocographs are used in the labour ward but variations on these machines are used in the antenatal clinic to assess the state of the foetus in other stages of pregnancy.