Drago Rudel, Branimir Leskošek, Marjan Pajntar, Gaj Vidmar, Dare Oberžan,
Metod Praprotnik

Uterine EMG in sheep model

Abstract:

Problem:                   
To shorten the duration of the latent phase of labour by properly manage the labour considering well ripeness of the cervix

Our supposition:
Unripe cervix at a term labour expresses conditions that are normal during pregnancy.

Aims:                        
Better characterisation of uterine EMG during pregnancy
Development of an appropriate diagnostic tool to be used routinely in delivery rooms

METHODS
Over 3000 hours of measurements in 35 ewes

1. Spontaneous EMG measured at uterine horn and in the cervix during pregnancy, labour and post partum
2. Modulation of EMG activity by:

   Electrical stimulation (under-threshold electrical stimulation at the cervix and at the horn in 4 sheep)
   pharmacological agents (buscopan, atosiban, oxytocin) – 8 sheep

Measurements

1. 2 pairs + ref EMG/stimulation electrodes implanted to the uterine surface: horn and the cervix (2ch measurements)
2. Electrode wires percutaneously from the body
3. EMG amplification (200x) + filtering (0,03Hz – 5 Hz)
4. Mechanical uterine contractions were not measured.
5. The animal freely moving – highly demanding conditions for reliable EMG recordings (artefacts, pulled electrode wire pins…)
6. 45% success in EMG measurements

EMG signal processing

1. Visual selection of EMG intervals - whole session intervals considered or rejected (0, 1, 2 scale)
2. Artefacts reduction, filtering
3. RMS and FFT calculation
4. Variables observed Urms, MF
5. Statistical methods applied

RESULTS
Spontaneous EMG

1. Changes in spontaneous EMG with approaching labour and after it
2. Increase in Urms at labour
3. EMG pattern at uterine contractions: increase in EMG amplitude at low frequency content and/or superimposed high frequency content

EMG modulation with pharmacological agents

1. Repeatable and scalable increase in amplitude and frequency by oxytotocin proportional to quantity and duration of oxytocin infusion
2. atosiban effectively reduces EMG activity within 1h and prolongs pregnancy above max pregnancy duration (3 sheep)

EMG modulation with electrical stimulation

1. Results of electrical stimulation vary - stimulation increases EMG activity at the side of stimulation or reduces it (habituation)
2. No effect on EMG at the site distant to the place of electrical stimulation

DISCUSSION

• Controversial MF results in different ewes due to processing of long measuring intervals
• The cervix acts differently from the corpus (3-ch EMG measurements started)
• Narrow filtering from 0,3Hz to 3Hz gives better indication on uterine contraction (more equally distributed frequency components in the observed frequency interval)

Contact:
Dr. Drago Rudel
Institute of Biomedical Informatics
Faculty of Medicine
Vrazov trg 2
SI-1104 Ljubljana
Slovenia
e-mail: drago.rudel@mf.uni-lj.si

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