Enhanced analysis of uterine surface electromyography

A new approach for the analysis of uterine activity is based on surface electromyography (EMG). It is assumed, that the rising synchronisation between the muscle cells changes the frequency distribution of the EMG-signals. Although first results are very encouraging, the expressiveness of a standard spectrum based on the fourier transform strongly depends on the parturient’s actual state, such as excitement. Therefore, the authors search for an enhanced analysis, which is less influenced by the skin’s conductivity and capacity.

This contribution presents an enhanced signal analysis of the electromyography taken at the abdomen of the parturient. First, the signal is conditioned to eliminate the noise as well as low-frequent phenomena generated by conductivity effects. It is followed by a reliable detection of the all significant EMG-pulses. At first sight, these pulses exhibits differences in length, magnitude and shape. Now, a stochastic algorithm based on the Karhunen-Loève transform decomposes the ensemble of pulses into uncorrelated components. This method extracts the main pulse shape, which occurs in every single pulse. Additionally, the differences between the pulses not only indicate the lack of synchronisation but also the quality of measurement.

The enhanced signal analysis proposed in this contribution provides more reliable information of the EMG-pulses in time and frequency domain. Characteristic values can be deduced out of the single measurements in order to compare them during the proceeding pregnancy. This supports the physician’s diagnosis esp. with regard to the determination of the point of delivery.