Fetal Monitoring by Transabdominal Electrocardiogram Recording: the ELAINE Pilot Project (ELectronic fetAl monitorINg System)

Cardiotocography (CTG), or electronic fetal monitoring (EFM), is the most common procedure used for fetal assessment before and during labour and largely replaced the use of intermittent heart rate auscultation with the Pinard stethoscope or intrapartal analysis of fetal pH by scalp sampling. It relies on acoustic methods in the audible (auscultation) and inaudible range of the sound spectrum (ultrasound). Ever since its introduction in the late 1960s, the benefit of the method has been controversial. Not only the great inter- and intra-observer variability due to visual interpretation of CTG traces seems to be an issue, but also the technical difficulties of the method: data assessment in adipose patients, active fetuses or multiple gestation, confusions between fetal and maternal pulse, assessment during water delivery, strong contractions or changing labour positions of the parturient. It is common knowledge that CTG leads to unnecessary medical interventions such as caesarean section and vaginal-operative deliveries, with the associated health consequences and economic costs.

Despite the continuous progress made in CTG technology in the past 50 years, CTG devices still have drawbacks, namely their bulkiness (including cables and bedside computers), combined with the limited informative value and suboptimal reliability of the measured signals. The assessment can be uncomfortable for the pregnant patient, due to the fact that the patient is bound to a machine and implicitly to the bed, particularly when a longer surveillance is needed. Long periods of immobility can lead to further medical and psychical problems during pregnancy.

Wireless methods of fetal monitoring exist; nevertheless, the technical difficulties of the assessment seem to be more pronounced when these are employed.

Routine continuous monitoring of physiological signals in normal and extraordinary environments provides useful insides for better understanding and modelling of human physiology. Under contract by the European Space Agency (ESA), the Swiss Centre for Electronics and Microtechnology (CSEM) has designed and developed the LTMS system (Long Term Medical System) system. In 2003, ESA commissioned CSEM to do a definition study for a prototype of LTMS. Following the outcomes of this study, in 2006 CSEM built a first prototype (LTMS-2) for ESA, which was validated at Bern University Hospital in 2008. In the subsequent phase (LTMS-3, 2009-2010), CSEM manufactured a set of upgraded systems which were validated in Antarctica (Concordia Station) in 2010 and during the Rio-Tinto field test of the Austrian Space Forum spacesuit simulator in 2011. In 2015, CSEM delivered to ESA a new sensor system (LTMS-S) with yet improved measuring functionalities and higher overall integration in an easy to-wear vest. The system has been shipped to the Concordia Station in Antarctica for the scientific investigation for monitoring the physiological adaptation of manned crews in remote, isolated, and extreme environments. An in-depth clinical validation study at the University Hospital in Lausanne has shown that the performance of the system was within the contractual specifications and that it fulfilled the requirements set by international medical standards.

Although it has initially been proposed to adapt and use LTMS-S for fetal ECG (fECG) measurements, reconsidering the required noise level and resolution to capture fECG, it has been decided to modify and use the ECGi-CDWe system, which has evolved from LTMS-S and belongs to the cooperative sensors family of CSEM. This system outperforms LTMS-S in terms of noise level, resolution, and also number of electrodes that can be connected (>200). The said system has been designed in the frame of an industrial mandate by respecting the requirements of medical device development. Therefore a reduced version of ECGi-CDWe has been developed, hereafter called ELAINE system.