| Abbreviation / other names What does "Cardiotocograph" mean?
|
CTG = Cardiotocograph , “Toco” or Tocodynamometer
Fetal Monitors Cardio = heart Toco = contractions (of uterus during labour) |
| What does it do? | Cardiotocograph can monitor the fetus’ heart rate,
the mother’s heart rate, the mother’s contractions
and the pressure inside the uterus during labour. |
| Physiology |
During labour the fetus can become stressed. The heart rate
of the fetus is monitored throughout labour so stress can be
detected early. The contractions are monitored also so that
the midwife and mother know when the contraction is occurring
and also to check for fetal distress during the contraction. |
| How it works | The Cardiotocograph has a disc-shaped ultrasound transducer,
which is strapped onto the mother’s abdomen over the area
of the uterus. The transducer has several crystals (usually
about 7), which emit ultrasound waves into the uterus and also
detect the waves that are reflected back. The ultrasound waves
are reflected from different surfaces in the uterus and detected
by the transducer. The fetal heart moves every time it beats and this beating movement is detected by the changing ultrasound waves being reflected back to the transducer. From this the cardiotocograph can calculate the fetal heart rate. A second ultrasound transducer can also be used at the same time so that twins can be monitored. The second transducer has a different frequency so the two signals can be separated. The Cardiotocograph also has a different type of transducer to monitor the uterine contractions (the toco transducer). This transducer is also disc-shaped and is strapped around the uterus. The patient’s abdominal muscles depress the transducer’s central section during a contraction. A strain gauge behind the moving part measures the movement. The size of the contraction is proportional to the amount of change in the strain gauge. The Cardiotocograph can also monitor fetal heart rate and contractions invasively. Fetal heart rate can be measured by using a special ECG electrode on the scalp of the baby. The mother’s ECG can also be recorded by a maternal ECG leads. (See Electrocardiograph for explanation). The pressure inside the uterus can be monitored invasively by a Intra Uterine Pressure (IUP) transducer (see invasive blood pressure for explanation) |
| Units of measurement | Fetal heart rate (ultrasound/FECG): BPM (beats per minute) |
| Typical values |
Fetal heart rate: 100 – 200 BPM Contractions: 0 to 100% IUP: 0 - 100 mmHg |
Picture of equipment |
|
 HP ECG &
Tocograph |