Creating a Thin, Flexible Biopotential Electrode to Measure dEMG in Preterm Infants

Abstract

Introduction:
High impact respiratory conditions are common amongst preterm infants. Measuring the electromyogram of the diaphragm (dEMG) is a very promising technique to accurately measure respiratory state. However, the currently used Ag/AgCl electrodes are reported to be big and thick, making them less suitable to measure dEMG in preterm infants. Therefore, the aim of this study was to create a prototype for a thin, flexible electrode that could measure dEMG in preterm infants with at least the same signal quality as the currently used Ag/AgCl electrode.
Methods:
To do so, design requirements and wishes were set. Literature and three tests were used to assess whether a certain prototype met the design requirements. If one of the design requirements was not met, an iteration cycle was started and the prototype was redesigned. With the final version of the prototype, a proof of principle test was performed, where dEMG measurements were conducted on a healthy female adult using the prototype and the standard Ag/AgCl electrodes simultaneously.
Results:
The final design was created from two layers of Shieldit conductive fabric ironed onto cotton and one insulating layer of TPU. These layers were connected to a shielded cable by weaving the copper wire through the fabric.
Ultimately, not all design requirements were met. The frequency plot of the final prototype still showed a peak at 50 Hz, indicating insufficient shielding from electromagnetic interference. However, the final prototype was indeed dry, thinner, and more flexible than the Ag/AgCl electrode. The RMSE value for the prototype (0,5984 mV) was smaller than that for the Ag/AgCl electrode (0,5998 mV), although the opposite was true for the SD (prototype: 0,1031 mV, Ag/AgCl: 0,0316 mV). In addition, it was proven that the final prototype could be used to measure dEMG in healthy adults. The breathing frequency measured by the final prototype was equal to the breathing frequency measured by the Ag/AgCl electrode, whilst showing no significant difference in amplitude of the peaks of the breathing curve (p = 0,0830).
Discussion:
Design improvements could be made by eliminating the 50 Hz peak, decreasing diameter even further, creating a new version where the cable could pivot around the electrode or exploring wireless options.
Conclusion:
In this paper, it has been proven that a textile prototype is well capable of measuring dEMG in humans and offers several improvements over the Ag/AgCl electrode.