Non Invasive Foetal Monitoring with a Combined ECG - PCG System

Abstract

Although modern ultrasound provides remarkable images and biophysical measures, the technology is expensive and the observations are only available over a short time. Longer term monitoring is achieved in a clinical setting using ultrasonic Doppler cardiotocography (CTG) but this has a number of limitations. Some pathologies and some anomalies of cardiac functioning are not detectable with CTG. Moreover, although frequent and/or long-term foetal heart rate (FHR) monitoring is recommended, mainly in high risk pregnancies, there is a lack of established evidence for safe ultrasound irradiation exposure to the foetus for extended periods (Ang et al., 2006). Finally, high quality ultrasound devices are too expensive and not approved for home care use. In fact, there is a remarkable mismatch between ability to examine a foetus in a clinical setting, and the almost complete absence of technology that permits longer term monitoring of a foetus at home. Therefore, in the last years, many efforts (Hany et al., 1989; Jimenez et al., 1999; Kovacs et al., 2000; Mittra et al., 2008; Moghavvemi et al., 2003; Nagal, 1986; Ruffo et al., 2010; Talbert et al., 1986; Varady et al., 2003) have been attempted by the scientific community to find a suitable alternative. The development of new electronic systems and sensors now offers the potential of effective monitoring of the foetus using foetal phonocardiography (FPCG) and foetal electrocardiography (FECG) with passive, fully non-invasive low cost digital recording systems that could be suitable for home monitoring. These advances provide the opportunity of extending the recordings of the current commonly used CTG from relative short to long term, and provide new previously unavailable measures of cardiac function. In this chapter, we present highlights of our research into non-invasive foetal monitoring. We introduce the use of FECG, FPCG and their combination in order to detect the foetal heart rate (FHR) and potential functional anomalies. We present signal processing methodologies, suitable for longer-term assessment, to detect heart beat events, such as first and second heart sounds and QRS waves, which provide reliable measures of heart rate, and offer the potential of new information about measurement of the systolic time intervals and foetus circulatory impedance.