Methods for improving data acquisition and signal processing for monitoring the ECG

The electrocardiogram (ECG) is a recording of the electrical activity of the heart and is widely used by clinicians as a diagnostic tool and during life-saving resuscitation efforts. The traditional 12-lead silver chloride ECG remains the gold standard in healthcare, despite promising advances in sensor technology and signal processing that have the potential to improve quality and ease of recording. The primary aim of this research is to improve the data acquisition and signal processing of the ECG. To achieve this, methods were developed to improve the utility and range of applications for non-contact electric potential sensors (EPS). These sensors allow for rapid, high resolution ECG recording and can be incorporated into passive monitoring systems and wearable devices. Dry flexible textile electrodes and hardware/software filtering systems were developed for use with EPS. These were characterised using simulated and pre-recorded ECGs, cardiac phantoms, and real world data through live human recording. Firstly, dry flexible textile electrodes were developed and characterised for EPS ECG sensing. These electrodes were shown to have the capacity to for the rapid acquisition of high quality ECG suitable for the calculation of heart rate, with an accuracy within ±1 beat per minute, and a 99% beat detection confidence compared to reference electrodes. Secondly, a novel adaptive filtering technique was developed and validated using a novel neonate phantom developed for EPS testing. Using the noise profile from the injection of a known signal, an algorithm for an adaptive ECG filter was generated. This filter was highly effective in removing the predominant mains power line noise that EPS sensors are particularly susceptible to, with average of 22 dB reduction. Additionally, this filtering method introduced no significant alteration of the ECG morphology, with a mean square error equal to that of traditional filtering techniques. This work advances the development of applications for EPS technology by demonstrating and characterising textile electrodes and novel filtering methods. Textile electrodes allow for the integration of these devices into convenient and comfortable devices, as explored in the proof of concept for a smart ECG sensing mattress for use in the neonatal intensive care unit. The novel filtering techniques displayed here are tailored to the characteristics of EPS sensors, and provide ECG signal quality that can compete with the high standards required in clinical practice.