Electrocardiographic Electrodes Research Articles

Conformable, Thin, and Dry Electrode for Electrocardiography Using Composite of Silver Nanowires and Polyvinyl Butyral

Development of a thin and dry electrode for electrocardiography (ECG) is essential in order to prevent skin irritation, allergic reactions from electrolytic gel, and motion artifacts caused by relative motion between the electrodes and the skin. In this study, we have developed a composite electrode made from Ag nanowires (AgNWs) and polyvinyl butyral (PVB), prepared by inverted layer processing (ILP). The initial composite electrodes were mechanically stable, flexible, and transparent; however, most of the NWs were located beneath the surface of the PVB such that few conductive pathways were exposed and available to contact the skin. In order to resolve this issue, prior to transferring the AgNWs from the temporary glass substrate to the PVB, we irradiated the NWs with intensive pulsed light. This irradiation induced plasmonic heating of the AgNWs, which caused the NWs to sink towards the glass and form a dense layer on the temporary substrate. Subsequent ILP resulted in the fabrication of an AgNWs/PVB composite electrode that demonstrated significant surface coverage of conductive pathways available for stable electrical contact with skin. The resultant composite electrode is an improved ECG electrode that exhibits fewer motion artifacts compared to conventional Ag/AgCl-based wet electrodes since it is both dry and conformable.

The method of stabilization and reduction of noise in the measurement signal through the “dry” electrodes for electrocardiography

The last 10 years have been actively developed for “dry” electrodes. Such electrodes should simplify the use of portable medicine. But scientists around the world are faced with difficulties in development. The article presents arguments about how to improve existing sensors.

Electrode Equivalence for Use in Bioimpedance Spectroscopy Assessment of Lymphedema.

Bioimpedance spectroscopy (BIS) is commonly used in the assessment and monitoring of lymphedema. This study investigated electrodes as a source of variability that could impact the accuracy of BIS in the clinic and determined if Ag/AgCl electrocardiograph (ECG) electrodes could be used as an alternative to instrument-specific electrodes. Two types of Ag/AgCl electrodes were studied: instrument-specific bioimpedance electrodes (bioimpedance) and single tab ECG electrodes (cardiac). Six areas of investigation were addressed: intrinsic electrode resistance; electrode age; drive electrode position; electrode width/surface area; concordance between cardiac and bioimpedance electrodes; and mixing electrode types and batches. Participants included women (n = 26) and men (n = 8), both with (n = 4) and without lymphedema (n = 30). Resistance (R0) of the limbs was measured and used to calculate interlimb BIS ratios. Intrinsic electrode resistance varied between batches (p ≤ 0.001), with cardiac electrodes recording higher resistance. Electrode age had no impact on limb resistance (p = 0.85). Drive electrode position biased limb resistance (0.1%-2.3%) and electrode size/surface area had a small (≤1%), but significant effect on limb resistance (p ≤ 0.001). However, calculation of interlimb BIS ratios negated the impact of these as well as any effect of mixing electrode batches and types (p = 0.15-0.96). Electrode type had no impact on arm and leg resistance, or interlimb BIS ratios (p = 0.173-0.289). Calculation of interlimb BIS ratios improves accuracy of clinical BIS. Ag/AgCl cardiac electrodes can be used as an alternative to device-specific electrodes to measure limb resistance.

Trends in Subcutaneous Cardiac Monitoring Technology.

Ambulatory cardiac monitoring is a rapidly expanding field and one that is likely to progress beyond electrocardiographic (ECG) and blood pressure recordings. To date, the primary cardiac monitoring focus has been ambulatory ECG (AECG) monitoring. In this setting, AECG monitoring has become a diagnostic tool used daily by physicians of many specialties. In this regard, both wearable and subcutaneous ECG monitoring technologies are now widely available, with the appropriate choice for a given patient being best determined by the frequency with which the patient’s symptom recurrences are expected. In other words, the less frequent the symptomatic events, then the longer the monitoring duration requirement should be. However, multiple factors other than the technology used impact success. For example, wearable AECG systems are only capable of monitoring patients for a period of a few days to several weeks due to limited battery longevity, patient intolerance to cutaneous ECG electrodes, the cumbersome nature of the device, or a combination of these factors. Current-generation insertable cardiac monitors (ICMs), on the other hand, offer three years of monitoring and infrequent skin irritation. Additionally, automatic remote download, a valuable feature in many cases, is only offered by certain wearable technologies, but is an option in all currently available ICMs. This report focuses on the current status of subcutaneous ICMs and their indications and limitations. The goal is to highlight the variety of utility of current ICM technologies and to provide insight into potential future subcutaneous ICM applications.

Design and Characterization of Screen-Printed Textile Electrodes for ECG Monitoring

This study was conducted to develop a screen-printed approach for the fabrication of textile electrodes and analyze their characteristic features for use as electrocardiography (ECG) signal sensors. The electrodes were obtained by printing poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) organic bio-compatible polymer-based ink on a finished fabric using a polyester mesh with 43 lines/cm. The physical–chemical properties of the polymer solution were varied to obtain a simple and reproducible fabrication process and a good electrode performance simultaneously. The electrode properties were first assessed by a benchtop measurement instrument and then on human subjects. Several tests under different conditions, for instance, by adding liquid and solid electrolytes, revealed that the electrodes possess the majority of characteristics required by the ANSI/AAMI EC12:2000 standard for gelled ECG electrodes. Furthermore, the benchtop measurements demonstrated that these electrodes preserve their electrical properties and functionality even after several washing cycles (performed under mild conditions), while they suffered physical stretching. While using some electrolytes, the skin contact impedance and the features extracted from the physiological signals were found to be highly similar to those obtained with disposable gelled Ag/AgCl electrodes ( $\rho >0.99$ ). Through the proposed fabrication process, it is possible to change the electrical properties of a specific region of a finished fabric or a garment with an excellent geometrical resolution. This opportunity, along with the obtained results in terms of the electrical characteristics as ECG electrodes, indicates that the proposed approach could possibly be adopted in the future for the development of smart garments that could comfortably detect ECG signals.

Alternative electrocardiography electrode placement

Alternative electrocardiography electrode placement

Fundamental study on strength evaluation of textile electrode for electrocardiography

Fundamental study on strength evaluation of textile electrode for electrocardiography

Simultaneously Capturing Electrocardiography and Impedance Plethysmogram Signals From Human Feet by Capacitive Coupled Electrode System

A microprocessor measurement system is developed for simultaneously capturing electrocardiography (ECG) and impedance plethysmogram (IPG) signals. All the measurement electrodes are coupled with human skin in a non-contact capacitive way. A capacitive coupled pickup circuit is used for obtaining the original ECG and IPG signals. Three differences of electrode configurations are experimentally tested for picking up the ECG signals, i.e., from the plantar area of the feet, from the instep area of the feet, and from a single hand and a single foot. Two different configurations (i.e., two-electrode IPG and four-electrode IPG) are tested to get IPG signals. A singular spectrum analysis (SSA)-based algorithm is embedded in a microprocessor system for signal processing. It is found that the original signals, especially the IPG signals, are quite noisy and can only be used after SSA processing. When both the ECG and IPG signals are measured simultaneously, the ECG signal will be severely ruined by the interference from the excitation current signal of IPG measurement. Relatively satisfied signals can only be simultaneously obtained when one ECG electrode is placed in a hand. The time difference between the ECG R-peak and IPG C-peak (the peak point in IPG) is experimentally tested for its potential application in blood pressure measurement.

Torso geometry reconstruction and body surface electrode localization using three-dimensional photography

We conducted a prospective clinical study (n=14; 29% female) to assess the accuracy of a three-dimensional (3D) photography-based method of torso geometry reconstruction and body surface electrodes localization. The position of 74 body surface electrocardiographic (ECG) electrodes (diameter 5mm) was defined by two methods: 3D photography, and CT (marker diameter 2mm) or MRI (marker size 10×20mm) imaging. Bland-Altman analysis showed good agreement in X (bias −2.5 [95% limits of agreement (LoA) −19.5 to 14.3] mm), Y (bias -0.1 [95% LoA −14.1 to 13.9] mm), and Z coordinates (bias −0.8 [95% LoA −15.6 to 14.2] mm), as defined by the CT/MRI imaging, and 3D photography. The average Hausdorff distance between the two torso geometry reconstructions was 11.17±3.05mm. Thus, accurate torso geometry reconstruction using 3D photography is feasible. Body surface ECG electrodes coordinates as defined by the CT/MRI imaging, and 3D photography, are in good agreement.

Novel Noninvasive Method of Cerebrovascular Blood Volume Assessment Using Brain Bioimpedance.

Cerebrovascular autoregulation (CAR) is the ability of vessels to modulate their tone in response to changes in pressure. As an auto-protective mechanism, CAR is critical in preventing secondary brain injury post-trauma. Monitoring of changes in cerebral blood volume might be valuable in evaluating CAR and response to various therapies. In this study, we utilized an ocular-brain bioimpedance interface to assess real time changes in cerebral blood volume in response to a number of physiological challenges. We hypothesize that changes in brain bioimpedance (dz) would track changes in cerebral blood volume. Anesthetized animals were instrumented for monitoring of intracranial pressure (ICP), mean arterial blood pressure, cerebral perfusion pressure (CPP) and cerebral blood flow (CBF). Bioimpedance was monitored continuously through electrocardiographic electrodes placed over the eyelids. Interventions such as hyperventilation, vasopressor administration, creation of an epidural hematoma, and systemic hemorrhage were used to manipulate levels of ICP, CPP, and CBF. The dz correlated with changes in ICP, CPP, and CBF (r = -0.72 to -0.88, p < 0.0001). The receiver operating characteristic for dz at different thresholds of CPP and CBF showed high impedance performance with area under the curve between 0.80-1.00 (p < 0.003) and sensitivity and specificity varying between 83%-100% and 70%-100%, respectively. Our preliminary tests show that brain bioimpedance as measured through the ocular-brain interface tracks changes in CPP and CBF with high precision and may prove to be valuable in the future in assessing changes in cerebral blood volume and CAR.

Born not breathing: A randomised trial comparing two self-inflating bag-masks during newborn resuscitation in Tanzania

AimsEffective ventilation is crucial to save non-breathing newborns. We compared standard equipment for newborn resuscitation to a new Upright bag, in an area with high neonatal mortality. MethodsNewborns requiring resuscitation at Haydom Lutheran Hospital, Tanzania, were ventilated with 230ml standard or 320ml Upright bag-mask by weekly non-blinded block randomisation. A Laerdal Newborn Resuscitation Monitor collected ventilation data through a flow sensor between mask and bag and heart rate with electrocardiography electrodes. Primary outcome was expiratory tidal volume per birth weight. ResultsOf 6110 babies born, 136 randomised to standard bag-mask and 192 to Upright, both groups had similar birth weight, gestational age, Apgar scores, gender, and mode of delivery. Compared to standard bag-mask, Upright gave higher median expiratory tidal volume (8.6ml/kg (IQR: 3.5–13.8) vs. 10.0ml/kg (IQR: 4.3–16.8) difference ratio 1.29, 95%CI 1.05, 1.58, p=0.014)), increased mean airway and peak inspiratory pressures, and higher early expired CO2 (median at 20s 4.2% vs. 3.2%, p=0.0099). Clinical outcome 30min post-delivery was normal in 44% with standard versus 57% with Upright (p=0.016), but similar at 24h. Conclusion and relevanceUpright provided higher expired tidal volume, MAP, PIP and early ECO2 than the standard bag. Clinical outcome differed at 30min, but not at 24h. Larger volume of Upright than standard bag can be an important factor. The results are relevant for low- and high-income settings as ventilatory and heart rate parameters during resuscitation of newborns are rarely reported. Trial registered at www.ClinicalTrials.gov, NCT01869582.

Five Day Attachment ECG Electrodes for Longitudinal Bio-Sensing Using Conformal Tattoo Substrates

State-of-the-art ECG (electrocardiography) uses wet Silver/Silver-Chloride (Ag/AgCl) electrodes, where a conductive gel is used to provide a resistive, low impedance, connection to the skin. These electrodes are very easy to apply, but have a significant number of limitations for personalized and preventative healthcare. In particular, that the gel dries out giving a limited connection time. This paper presents ECG electrodes manufactured using the inkjet printing of Silver nanoparticles onto a conformal tattoo substrate. The substrate maintains a high quality connection to the body for many days at a time allowing ECG monitoring over periods not previously possible without electrode re-attachment. The design and manufacture of the conformal electrodes is presented, together with detailed characterization of the electrode performance in terms of the signal to noise ratio and baseline wander. The signal to noise ratio is shown to still be over 30 dB five days after the initial electrode attachment.

A Wearable Hydration Sensor with Conformal Nanowire Electrodes.

A wearable skin hydration sensor in the form of a capacitor is demonstrated based on skin impedance measurement. The capacitor consists of two interdigitated or parallel electrodes that are made of silver nanowires (AgNWs) in a polydimethylsiloxane (PDMS) matrix. The flexible and stretchable nature of the AgNW/PDMS electrode allows conformal contact to the skin. The hydration sensor is insensitive to the external humidity change and is calibrated against a commercial skin hydration system on an artificial skin over a wide hydration range. The hydration sensor is packaged into a flexible wristband, together with a network analyzer chip, a button cell battery, and an ultralow power microprocessor with Bluetooth. In addition, a chest patch consisting of a strain sensor, three electrocardiography electrodes, and a skin hydration sensor is developed for multimodal sensing. The wearable wristband and chest patch may be used for low-cost, wireless, and continuous monitoring of skin hydration and other health parameters.

Flexible Graphene Electrodes for Prolonged Dynamic ECG Monitoring.

This paper describes the development of a graphene-based dry flexible electrocardiography (ECG) electrode and a portable wireless ECG measurement system. First, graphene films on polyethylene terephthalate (PET) substrates and graphene paper were used to construct the ECG electrode. Then, a graphene textile was synthesized for the fabrication of a wearable ECG monitoring system. The structure and the electrical properties of the graphene electrodes were evaluated using Raman spectroscopy, scanning electron microscopy (SEM), and alternating current impedance spectroscopy. ECG signals were then collected from healthy subjects using the developed graphene electrode and portable measurement system. The results show that the graphene electrode was able to acquire the typical characteristics and features of human ECG signals with a high signal-to-noise (SNR) ratio in different states of motion. A week-long continuous wearability test showed no degradation in the ECG signal quality over time. The graphene-based flexible electrode demonstrates comfortability, good biocompatibility, and high electrophysiological detection sensitivity. The graphene electrode also combines the potential for use in long-term wearable dynamic cardiac activity monitoring systems with convenience and comfort for use in home health care of elderly and high-risk adults.

Flexible Hybrid Electronics: Direct Interfacing of Soft and Hard Electronics for Wearable Health Monitoring

The interfacing of soft and hard electronics is a key challenge for flexible hybrid electronics. Currently, a multisubstrate approach is employed, where soft and hard devices are fabricated or assembled on separate substrates, and bonded or interfaced using connectors; this hinders the flexibility of the device and is prone to interconnect issues. Here, a single substrate interfacing approach is reported, where soft devices, i.e., sensors, are directly printed on Kapton polyimide substrates that are widely used for fabricating flexible printed circuit boards (FPCBs). Utilizing a process flow compatible with the FPCB assembly process, a wearable sensor patch is fabricated composed of inkjet‐printed gold electrocardiography (ECG) electrodes and a stencil‐printed nickel oxide thermistor. The ECG electrodes provide 1 mVp–p ECG signal at 4.7 cm electrode spacing and the thermistor is highly sensitive at normal body temperatures, and demonstrates temperature coefficient, α ≈ –5.84% K–1 and material constant, β ≈ 4330 K. This sensor platform can be extended to a more sophisticated multisensor platform where sensors fabricated using solution processable functional inks can be interfaced to hard electronics for health and performance monitoring, as well as internet of things applications.

Factors Influencing Diaphragmatic Compound Motor Action Potentials During Cryoballoon Ablation for Atrial Fibrillation.

The diaphragmatic compound motor action potentials (CMAPs) have been used to predict and prevent phrenic nerve injury (PNI) during cryoballoon ablation of right pulmonary veins. We sought to assess factors that influence the amplitude of the surface CMAP recordings. We analyzed CMAPs from consecutive patients undergoing cryoballoon ablation for paroxysmal atrial fibrillation. CMAP recordings were obtained using electrocardiography electrodes positioned in the "modified lead I" method while stimulating the right PN, until loss of capture (ascertained by palpation and fluoroscopy of the right hemi-diaphragm). A total of 55 patients (age 63 ± 11 years; 60% men; body mass index [BMI] 31 ± 6) had adequate CMAP recordings and were included for evaluation of CMAP signals. CMAPs demonstrated 2 distinct components, an early higher amplitude signal (pacing artifact) and a later lower amplitude signal (true diaphragmatic CMAP). There was no significant change in the true CMAP recording amplitude with decrease in stimulus strength (P = 0.1). There was no impact of BMI on CMAP amplitude (P = 0.93). There was a significant phasic respiratory variation in CMAP amplitude with a mean decrease in CMAP amplitude of 10.8% (range: 8-12%) with inspiration lasting an average of 2 beats (P < 0.001). A decrease in CMAP amplitude of >30% was noted in 6 cases (11%) and termination of cryoablation prevented PNI. Diaphragmatic CMAP amplitude is not affected by stimulus strength or BMI. There is a significant respirophasic decrease in CMAP signal amplitude with inspiration. It is important to be aware of this variation to avoid premature termination of cryoablation.

Influence of electrode positioning on accuracy and reproducibility of electrical velocimetry cardiac output measurements

Electrical velocimetry (EV) is one of the most recent adaptions of impedance cardiography. Previous studies yielded diverging results identifying several factors negatively influencing accuracy. Although electrode arrangement is suspected to be an influencing factor for impedance cardiography in general, no data for EV is available. We aimed to prospectively assess the influence of electrode position on the accuracy and reproducibility of cardiac output (CO) measurements obtained by EV.Two pairs of standard electrocardiographic electrodes were placed at predefined positions of the thorax in 81 patients. The inter-electrode gap was varied between either 5 or 15 cm by caudal movement of the lowest electrode. Measurements were averaged over 20 s and performed twice at each electrode position. Reference values were determined using cardiac magnetic resonance imaging (CMR).Mean bias was 1.2 ± 1.6 l min−1 (percentage error 22 ± 28%) between COCMR and COEV at the 5 cm gap significantly improving to 0.5 ± 1.6 l min−1 (8 ± 28%) when increasing the gap (p < 0.0001). The mean difference between repeated measurements was 0.0 ± 0.3 l min−1 for the 5 cm and 0.1 ± 0.3 l min−1 for the 15 cm gap, respectively (p = 0.3).The accuracy of EV can be significantly improved when increasing the lower inter-electrode gap still exceeding the Critchley and Critchley recommendations. Therefore, absolute values should not be used interchangeably in clinical routine. As the reproducibility was not negatively affected, serial hemodynamic measurements can be reliably acquired in stable patients when the electrode position remains unchanged.

ECG by mobile technologies

Mobile electrocardiographs consist of three components: a mobile device (e.g. a smartphone), an electrocardiographic device or accessory, and a mobile application. Mobile platforms are small computers with sufficient computational power, good quality display, suitable data storage, and several possibilities of data transmission. Electrocardiographic electrodes and sensors for mobile use utilize unconventional materials, e.g. rubber, e-textile, and inkjet-printed nanoparticle electrodes. Mobile devices can be handheld, worn as vests or T-shirts, or attached to patient's skin as biopatches. Mobile electrocardiographic devices and accessories may additionally record other signals including respiratory rate, activity level, and geolocation. Large-scale clinical studies that utilize electrocardiography are easier to conduct using mobile technologies and the collected data are suitable for “big data” processing. This is expected to reveal phenomena so far inaccessible by standard electrocardiographic techniques.

FINGER TOUCH BASED ECG MONITORING

Since few years, study discloses that the evaluation of Electrocardiography (ECG) signals offers important advantage for biometric field. Many heart attacks can be judged and prevented by ECG waveform analysis. In health care centers, there is increase in the number of biomedical equipment used at hospital and home, but those lack in ability to provide handheld ECG monitor. In this paper, finger based ECG monitor system has been adopted. Instead of six electrodes, only two electrodes attached to fingers can give useful ECG waveform.ECG waveform can be displayed on thin film transistor i.e. TFT and personal computer i.e. PC. Advanced RISC machine, Instrumentation amplifier, ECG electrode and ECG signal conditioning, thin film transistor (TFT),ARDUINO board are included in hardware design. ARM ADC programming, TFT and ARDUINO programming and MATLAB programming for PC interfacing have been implemented in software design. Patient can touch the electrodes through fingers and his/her ECG will be displayed on TFT .Same ECG signal can be transferred to PC via USB cable. Investigational outcomes revealed that such a handheld ECG machine is appropriate in results, easy to use, and light weight.

Design, fabrication and skin-electrode contact analysis of polymer microneedle-based ECG electrodes

Microneedle-based ‘dry’ electrodes have immense potential for use in diagnostic procedures such as electrocardiography (ECG) analysis, as they eliminate several of the drawbacks associated with the conventional ‘wet’ electrodes currently used for physiological signal recording. To be commercially successful in such a competitive market, it is essential that dry electrodes are manufacturable in high volumes and at low cost. In addition, the topographical nature of these emerging devices means that electrode performance is likely to be highly dependent on the quality of the skin-electrode contact.This paper presents a low-cost, wafer-level micromoulding technology for the fabrication of polymeric ECG electrodes that use microneedle structures to make a direct electrical contact to the body. The double-sided moulding process can be used to eliminate post-process via creation and wafer dicing steps. In addition, measurement techniques have been developed to characterize the skin-electrode contact force. We perform the first analysis of signal-to-noise ratio dependency on contact force, and show that although microneedle-based electrodes can outperform conventional gel electrodes, the quality of ECG recordings is significantly dependent on temporal and mechanical aspects of the skin-electrode interface.