Dedicated Algorithm for Unobtrusive Fetal Heart Rate Monitoring Using Multiple Dry Electrodes

Abstract

Multi-channel measurements from the maternal abdomen acquired by means of dry electrodes can be employed to promote long-term monitoring of fetal heart rate (fHR). The signals acquired with this type of electrode have a lower signal-to-noise ratio and different artifacts compared to signals acquired with conventional wet electrodes. Therefore, starting from the benchmark algorithm with the best performance for fHR estimation proposed by Varanini et al., we propose a new method specifically designed to remove artifacts typical of dry-electrode recordings. To test the algorithm, experimental textile electrodes were employed that produce artifacts typical of dry and capacitive electrodes. The proposed solution is based on a hybrid (hardware and software) pre-processing step designed specifically to remove the disturbing component typical of signals acquired with these electrodes (triboelectricity artifacts and amplitude modulations). The following main processing steps consist of the removal of the maternal ECG by blind source separation, the enhancement of the fetal ECG and identification of the fetal QRS complexes. Main processing is designed to be robust to the high-amplitude motion artifacts that corrupt the acquisition. The obtained denoising system was compared with the benchmark algorithm both on semi-simulated and on real data. The performance, quantified by means of sensitivity, F1-score and root-mean-square error metrics, outperforms the performance obtained with the original method available in the literature. This result proves that the design of a dedicated processing system based on the signal characteristics is necessary for reliable and accurate estimation of the fHR using dry, textile electrodes.

An Overview of the Sensors for Heart Rate Monitoring Used in Extramural Applications

“…Although contact electrodes provide good signal quality, they require skin abrasion to minimize the skin impedance and can cause adverse reactions (e.g., allergic reactions and skin irritation) especially if the electrodes are worn for a long time. In addition, the quality of the acquired signal decreases with dehydration of the gel as a result of prolonged use [27].…”

“…Capacitive electrodes are comfortable and suitable for long-term monitoring because they do not cause skin irritation. On the other hand, the lack of gel between the skin and the electrode increases the contact impedance, resulting in a reduced signal amplitude [27]. Furthermore, the presence of the insulator material involves a large discrepancy in terms of shape between the actual physiological signal and the signal obtained through capacitive electrodes [30].…”

Wearable Fetal ECG Monitoring System from Abdominal Electrocardiography Recording

“…Currently, several devices are available that can acquire FECG signals [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], such as Avalon (with wireless transducer) [ 7 ] and AN24 [ 8 ]. In addition, Fanelli et al [ 10 ] developed remote fetal care to monitor fetal health during pregnancy.…”

“…Yuan et al [ 12 ] established a fetal ECG monitoring system based on the android smartphone. Galli et al [ 13 ] developed a fetal heart rate monitoring using multiple dry electrodes.…”

Applying Noncontact Sensing Technology in the Customized Product Design of Smart Clothes Based on Anthropometry

“…However, many dry electrodes still encounter the issue of higher electrode–skin interface impedance because of the poorer contact between the skin and the electrode. Various types of conductive material and structure have been applied in the development of dry electrodes [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ], such as a carbon nanotube (CNT)/polydimethylsiloxane (PDMS) flexible electrode [ 12 , 13 ], 3D-printed electrode [ 14 ], and an ethylene propylene diene monomer electrode [ 15 ]. In 2012, Jung et al proposed CNT/polydimethylsiloxane (PDMS) composite flexible dry electrodes [ 8 ].…”