Electrocardiographic Activity Research Articles

The effects of C-tactile stimulation on temporal summation of second pain: A study of the central and peripheral neural correlates

Affective touch is mediated by specialized receptors sensitive to gentle and slow touch called C-tactile afferents (CT). The activation of these receptors has shown promise in reducing subjective pain ratings, however, how this type of touch can affect central sensitization processes is poorly studied. This work aimed to investigate if affective touch is able to modulate pain sensitization and its electrophysiological correlates during Temporal Summation of Second Pain (TSSP), a phenomenon characterized by an increase in pain perception due to repeated noxious stimuli.Thirty-seven participants underwent a TSSP protocol involving three conditions: TSSP alone, TSSP during vibrotactile stimulation, and TSSP during CT stimulation (administered with a brush mounted in a robot arm). We measured subjective pain ratings, electroencephalographic (N2-P2 complex) and electrocardiographic activity during these conditions.Participants reported a significantly lower increase of pain during CT stimulation compared to vibrotactile stimulation, but not to TSSP alone. In addition, TSSP was reduced when administered in the ipsilateral arm compared to the other somatosensory stimulation. Subjective reports of attention towards painful stimuli, amplitude of the N2-P2 complex, and heart rate were also reduced during CT stimulation. Conclusion: Our results indicated that the activation of CT receptors may reduce sensitization compared to other types of somatosensory stimulation, which is possibly related to the reduction of the attention devoted to nociceptive stimulation. Our results suggest that activation of CT receptors may alleviate the occurrence of central pain sensitization.

Behavioral and electrophysiological study in Colossoma macropomum treated with different concentrations of Nepeta cataria oil in an immersion bath revealed a therapeutic window for anesthesia.

The purpose of this study was to characterize the activity of essential oils from Nepeta Cataria (EON) at concentrations of 125 L-1, 150 L-1, 175 L-1, and 200 L-1 on the behavior of loss of the posture reflex and recovery of the posture reflex and electrocardiographic activity and recording of the opercular beat of Colossoma macropomum during immersion bathing for a period of 5min, in order to obtain a window for safe use during anesthesia. The fish (23.38 ± 3.5g) were assigned to the following experiments: experiment 1 (latency to loss and recovery of the posture reflex): (a) 125 L-1, (b) 150 L-1, (c) 175 L-1, and (d) 200 L-1 (n = 9) per group. Experiment 2 (electrocardiographic and heartbeat recordings): (a) control group; (b) vehicle control group (2ml of alcohol per liter of water), (c) 125 L-1, (d) 150 L-1, (e) 175 L-1, and (f) 200 L-1 (n = 9), per group. All the concentrations used showed efficacy in inducing loss of the posture reflex and reversibility with recovery of the posture reflex, but the electrocardiographic recordings indicated morphographic changes such as bradycardia during induction and p wave apiculation during recovery at the highest concentrations tested. In this way, we suggest a safe use window for short-term anesthesia with EON in the concentration range of 125 to 150 L-1 for juvenile Colossoma macropomum.

Electrocardiographic activity depends on the relative position between intimate persons

Interpersonal space (IPS) refers to the area surrounding the body in which we engage in social interactions while maintaining our comfort. Numerous previous studies have reported the psychological and physiological changes associated with the proximity of two people engaged in face-to-face interaction. Currently, there is limited knowledge about how the relative position between two socially intimate individuals affects their psychological and physiological states. This research measured the subjective discomfort and electrocardiographic responses of participants when standing static at various relative positions. The highest discomfort, lowest heart rate, and highest heart rate variability (HRV; parasympathetic activity index) were observed when the friend stood in the face-to-face position. Interestingly, heart rate also decreased when the friend stood on the right side, although HRV did not change. We interpreted the results as suggesting that the presence of a familiar person elicits the electrocardiographic responses associated with an increase in parasympathetic activity.

Cryoanesthesia in tambaqui Colossoma macropomum: Behavioral and electrocardiographic responses

Cryoanesthesia is a low-cost procedure that has advantages for use in fish, however, there are only a few studies dealing with the electrophysiological evaluation and its safety-related aspects. The relationship between behavior and electrocardiographic activity allows for the monitoring of functional changes in cardiac activity in fish submitted to low temperatures. This study aimed to describe the behavior and cardiac effects of cryoanesthesia in juvenile tambaqui (Colossoma macropomum) through electrocardiographic assessment. For this purpose, 27 juveniles of tambaqui (28.9 ± 4.2 g) were used and essayed into two experiments. Experiment 1: behavioral evaluation (n = 9) and Experiment 2: electrocardiographic recordings with control group (n = 9), and fish submitted to water at 5 °C in baths followed by subsequent recovery at a temperature of 26 ± 2 °C (n = 9). Each cardiac activity recording lasted 1200 s, after which fish were immediately transferred to a bath in water at 26 ± 2 °C, for 600 s. Heart rate, QRS amplitude, QRS complex duration and RR, PQ and QT intervals were analyzed. The results showed that four tracing patterns emerged which characterized the induction phases of cryoanesthesia throughout exposure to water at 5 °C. In phase 1, there was a decrease in the amplitude of the QRS complex. In phase 2, there was an increase in the amplitude of the QRS complex and maintenance of sinus rhythm. Phase 3 showed a gradual loss of cardiac function with the onset of an atrioventricular blockade. In phase 4, a cardiac arrest occurred, albeit reversible. Heart rate decreased as exposure time was longer at low temperatures. The fish recovered completely from cryoanesthesia after the increase in temperature, showing normal heartbeats, and QRS complex duration, QT, RR, and HR intervals being restored with maintenance of sinus rhythm, indicating recovery of fish hemodynamics. Overall, tambaqui juveniles at 5 °C showed a time-dependent and gradual reduction of motor activity with loss of postural reflex and immobility. Cardiac response was a function of temperature and progressed to a reversible cardiac arrest. During recovery, stages similar to those of induction were observed, but in the opposite direction, until recovery of the postural reflex. Cryoanesthesia can be used as an alternative method for the immobilization of C. macropomum.

Electronic cigarettes exposures modulate Heart Rate and Heart Rate Variability

Background: Despite a lack of empirical data, an unprecedented rise in electronic cigarettes (ECs) has been widely perceived as safe. Multiple studies support a causal link between tobacco cigarette (TC) use and cardiovascular (CV) diseases; however, there is a lack of data with EC use. We have previously shown that chronic and acute EC use decreases heart rate variability (HRV) in humans, likely via increased sympathetic nervous system activation. Objective: We aimed to evaluate HRV effects induced by brief EC exposures utilizing an in-vivo model for freely moving C57BL/6 mice. Methods and Results: Telemetry devices were implanted in the abdomen of six 10-week-old C57BL/6 male mice to monitor electrocardiographic activity continuously. Mice underwent an exposure protocol designed to reflect human vaping topography with two EC exposures, each lasting 15-minutes (4-sec puff/ 26-sec Air) followed by 45-min post-exposure periods. Air (primary control) and PBS (secondary control) were also included, each with their own post-exposure events. During EC exposures, we observed bradycardic effects in heart rate (HR) with the standard deviation of NN intervals (SDNN), root mean square of successive differences (RMSSD), and the proportion of adjacent normalized RR intervals that differed by more than 6 ms (pNN 6 ) significantly (p< 0.05) altered as compared to Air exposures. After EC exposures, SDNN, RMSSD and pNN 6 parameters significantly decreased compared to Air. No significant differences between Air and PBS were observed in these parameters. Frequency domain parameters also indicated significant changes in HRV; the low frequency (LF) and high frequency (HF) bands showed marked increases during and after the EC exposures, while the log (LF/HF) ratio remained relatively unchanged, suggesting a possible coactivation of both parasympathetic and sympathetic branches of the autonomic nervous system. Conclusion: Short-term EC exposures lower heart rate and altered HRV in mice in an acute manner, suggesting that ECs may not be safe as previously assumed. This work was funded by the Tobacco-Related Disease Research Program (TRDRP) which included the High Impact Pilot Research Award [28IP-0036], the Cornelius Hopper Diversity Award Supplement and the Student Research Award Supplement, the UCLA Center for Occupational and Environmental Health (COEH) Student Project Award, and in part by the National Institute of Environmental Health Sciences (NIEHS) via the Student-to-Scientist Bridge program at California State University, Northridge [5R25ES025507]. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of different simulated submarine escape depths by free ascent in animal models.

Objective: If a damaged submarine cannot be rescued in time, it is necessary to carry out a submarine escape by free ascent. Decompression illness is the greatest threat to the safety of submariners. The maximum depth at which a safe escape can be carried out is unknown. This study intends to explore the maximum safe escape depth by observing the effects of simulated submarine escape at different depths on animal models. Methods: We evaluated pulmonary function indexes, blood gas values, blood cell counts, the myocardial enzyme spectrum, coagulation parameters, and proinflammatory cytokine levels in rats, electrocardiographic activity in rabbits after simulated 150-m, 200-m, 220-m, and 250-m submarine escape by free ascent. Results: An escape depth of 150m did not cause significant changes in the indicators. An escape depth of >200m led to pulmonary ventilation and gas diffusion dysfunction, hypoxemia, myocardial ischemia, and activation of the fibrinolytic and inflammatory systems. The magnitudes of the changes in the indicators were proportional to escape depth. Conclusion: An escape depth of 150m in animal models is safe, whereas escape at > 200m can be harmful.

Non-Contact Electrocardiograms Acquisition Method Based on Capacitive Coupling

Electrocardiogram (ECG) monitoring is an essential method for medical diagnosis [1], [2]. With the development of technology, better quality physiological signals can be easily recorded [3]. Long-term monitoring of electrocardiographic activity is helpful to monitor potential cardiac dysfunction. The Ag/Agcl electrode with conductive gel can record ECG signals with good signal quality and has been widely used in hospitals. However, the gel needs to be replaced regularly to achieve good signal quality because the quality of the signal deteriorates due to the gel drying over a long time. In addition, wet electrodes may not be suitable for long-term ECG monitoring because they may cause skin redness, swelling, and discomfort, especially for those patients with allergic reactions. Also, direct contact between electrodes and the human body is not applicable in many cases, such as skin injury patients, infants, etc. The goals of disease monitoring technology based on physiological signals are to reduce the amount invasive of equipment, increase the comfort of patients and improve the quality of life while pursuing high-quality signals.

Tonic pain reduces autonomic responses and EEG functional connectivity elicited by affective stimuli.

Most pain studies have focused on only two aspects of pain: the influence of pain on attentional processing and the modulation of pain perception by affective stimuli. However, the influence of tonic pain on the attentional processing of affective stimuli has not been studied. In this study, we investigated the effects of tonic pain on the attentional processing of affective stimuli, focusing on autonomic responses and their relationship with both EEG power and functional connectivity. Forty participants (20 men and 20 women) received tonically painful and nonpainful thermal stimulation while viewing blocks of pleasant, unpleasant, or neutral images. The galvanic skin conductance response (SCR), electrocardiographic activity, and electroencephalographic (EEG) activity in the delta and theta bands were recorded. Participants rated the unpleasantness of the pain at the end of each block. Typical affective SCR and heart rate (HR) patterns were found in the no‐pain condition, but when the pain was delivered, these patterns disappeared. EEG power and functional connectivity results showed that tonic pain affected the delta band in the central region during pleasant and unpleasant image blocks. Our findings suggest that tonic pain captured attentional focus and reduced the cognitive resources available for processing affective stimuli, altering the emotional experience associated with pain.

Neural Respiratory Drive Estimation in Respiratory sEMG with Cardiac Arrhythmias.

Neural respiratory drive as measured by the electromyography allows the study of the imbalance between the load on respiratory muscles and its capacity. Surface respiratory electromyography (sEMG) is a non-invasive tool used for indirectly assessment of NRD. It also provides a way to evaluate the level and pattern of respiratory muscle activation. The prevalence of electrocardiographic activity (ECG) in respiratory sEMG signals hinders its proper evaluation. Moreover, the occurrence of abnormal heartbeats or cardiac arrhythmias in respiratory sEMG measures can make even more challenging the NRD estimation. Respiratory sEMG can be evaluated using the fixed sample entropy (fSampEn), a technique which is less affected by cardiac artefacts. The aim of this work was to investigate the performance of the fSampEn, the root mean square (RMS) and the average rectified value (ARV) on respiratory sEMG signals with supraventricular arrhythmias (SVA) for NRD estimation. fSampEn, ARV and RMS parameters increased as the inspiratory load increased during the test. fSampEn was less influenced by ECG with SVAs for the NRD estimation showing a greater response to respiratory sEMG, reflected with a higher percentage increase with increasing load (228 % total increase, compared to 142 % and 135 % for ARV and RMS, respectively).

Design and development of a digital stethoscope encapsulation for simultaneous acquisition of phonocardiography and electrocardiography signals: the SmartHeart case study

The stethoscope is a major symbol of modern medicine. It is used for diagnosis of different conditions and enables physicians to listen to internal body sounds. Electrocardiography was only introduced in medicine in the beginning of the twentieth century. Today measuring heart’s electrical activity is also fundamental cardiac diseases diagnosis. Although performed with independent devices, requiring physician and patient presence in the same physical space, in combination they enhance cardiovascular assessment. In this paper, a digital stethoscope encapsulation was designed, adding new functionality to this advanced medical device. Today wired and wireless communications enable different medical devices to share data and information, over long distances. Using low-cost hardware technologies, the encapsulation will add the ability to acquire and transmit via Bluetooth the Electrocardiographic activity, determined in the same cardiac focus and synchronised with the Phonocardiographic sound recordings. Several encapsulation concepts were developed and prototyped using 3D printing. They were easily fitted to the digital stethoscope and tested in a hospital environment for ergonomics, acoustic and electric signals acquisition. The best concept was chosen with the help of a physician’s opinion and the final prototype performance was very satisfactory.

Bradycardia at the onset of pulseless electrical activity arrests in hospitalized patients is associated with improved survival to discharge

BackgroundRecent studies have suggested that the incidence of in-hospital pulseless electrical activity (PEA) arrests is increasing. Bradycardia in patients with in-hospital PEA is common but it is unknown if it is associated with respiratory arrest or patient outcomes. ObjectiveTo determine risk factors and outcomes associated with bradycardic-PEA arrests, and relationship between bradycardia and respiratory arrest. MethodsThis was a retrospective cohort study of all inpatient cardiac arrests at an academic medical center over a four-year period. Patient demographics, comorbidities, vital signs, arrest event data, and outcomes were abstracted from the medical record. PEA arrest was defined as a non-shockable rhythm with loss of pulse requiring cardiopulmonary resuscitation and having organized electrocardiographic activity. Bradycardia was classified as a HR < 60 bpm at the time of pulse loss. The primary outcomes were survival of arrest and survival to hospital discharge. ResultsBetween July 2013 and August 2017, there were 176 in-hospital patients with PEA arrests. While 105 (59.7%) survived the arrest, only 38 (21.6%) survived to discharge. A total of 66 (37.5%) were bradycardic-PEA arrests. Patients with bradycardic PEA arrests were no more likely to have their arrest precipitated by respiratory failure than non-bradycardic PEA patients (36.4% vs 27.3%, P = 0.24), but patients with non-bradycardic PEA arrests were more likely to have a CIED than non-bradycardic PEA patients (14.5% vs 3.0%, P = 0.02). On multivariate analysis, bradycardic PEA was associated with improved survival to hospital discharge (OR = 3.31, 95% CI: 1.41–7.79, p = 0.006), but not survival of arrest (OR 1.45, 95% CI: 0.68–3.09, p = 0.34). Respiratory arrest was an independent predictor of survival of code (OR 2.62, 95% CI: 1.36–5.47, P = 0.01) and to hospital discharge (OR 3.47, 95% CI: 1.35–8.91, P = 0.01). Other predictors of survival to discharge include history of coronary artery disease, and non-use of epinephrine, atropine, and sodium bicarbonate. ConclusionIn a retrospective study of hospitalized patients in the intensive care unit and non-intensive care, bradycardia at the time of PEA cardiac arrest was associated with improved survival to hospital discharge but not survival of arrest. Respiratory arrest was an independent predictor of survival, but there was no association between respiratory arrest and bradycardic PEA arrest.

The falling asleep process in adolescents.

To investigate the pre-sleep psychophysiological state and the arousal deactivation process across the sleep onset (SO) transition in adolescents. Data were collected from a laboratory overnight recording in 102 healthy adolescents (48 girls, 12-20 years old). Measures included pre-sleep self-reported cognitive/somatic arousal, and cortical electroencephalographic (EEG) and electrocardiographic activity across the SO transition. Adolescent girls, compared with boys, reported higher pre-sleep cognitive activation (p = 0.025) and took longer to fall asleep (p < 0.05), as defined with polysomnography. Girls also showed a less smooth progression from wake-to-sleep compared with boys (p = 0.022). In both sexes, heart rate (HR) dropped at a rate of ~0.52 beats per minute in the 5 minutes preceding SO, and continued to drop, at a slower rate, during the 5 minutes following SO (p < 0.05). Older girls had a higher HR overall in the pre-sleep period and across SO, compared to younger girls and boys (p < 0.05). The EEG showed a progressive cortical synchronization, with increases in Delta relative power and reductions in Alpha, Sigma, Beta1, and Beta2 relative powers (p < 0.05) in the approach to sleep, in both sexes. Delta relative power was lower and Theta, Alpha, and Sigma relative powers were higher in older compared to younger adolescents at bedtime and across SO (p < 0.05). Our findings show the dynamics of the cortical-cardiac de-arousing process across the SO transition in a non-clinical sample of healthy adolescents. Findings suggest a female-specific vulnerability to inefficient sleep initiation, which may contribute to their greater risk for developing insomnia.

Heart rate variability reduction is related to a high amount of visceral adiposity in healthy young women.

Several heart rate variability (HRV) studies show abnormalities in autonomic nervous control in obese and overweight subjects. However, some of the results appear to be controversial. Here we investigate the HRV profile in seventy adult normotensive women and its association with general and visceral adiposity. Specifically, we recorded the electrocardiographic (ECG) activity in subjects during a supine resting state for five minutes in a quiet room late in the morning. Total fat mass (TFM) and visceral adipose tissue (VAT) were instead estimated using dual-energy X-ray absorptiometry (DXA). Finally, we used simple a linear regression analysis of frequency and time-domain parameters to study the relationship between HRV and adiposity. Our data showed an overall reduction of the HRV related to an increase of TFM although this regression appeared significant only for high frequencies (HF). When the linear regression was applied between HRV variables and VAT, the slope of the line increases, thus unveiling a statistically significant relation (i.e. the more VAT, the lower HRV). Finally, a control analysis showed that age does not alter the relation between HRV and VAT when used as a confounding factor in multiple regression. To conclude, these findings point to abnormal activity of the autonomic nervous system (ANS) in subjects with an excess of VAT and represent a starting point to determine a non-invasive index of cardiac wellness for clinical and nutritional application.

Electrocardiographic Fragmented Activity (II): A Machine Learning Approach to Detection

Hypertrophic cardiomyopathy, according to its prevalence, is a comparatively common disease related to the risk of suffering sudden cardiac death, heart failure and stroke. This illness is characterized by the excessive deposition of collagen among healthy myocardium cells. This situation, which is medically known as fibrosis, constitutes effective conduction obstacles in the myocardium electrical path, and when severe enough, it can be outlined as additional peaks or notches in the QRS, clinically entitled as fragmentation. Nowadays, the fragmentation detection is performed by visual inspection, but the fragmented QRS can be confused with the noise present in the electrocardiogram (ECG). On the other hand, fibrosis detection is performed by magnetic resonance imaging with late gadolinium enhancement, the main drawback of this technique being its cost in terms of time and money. In this work, we propose two automatic algorithms, one for fragmented QRS detection and another for fibrosis detection. For this purpose, we used four different databases, including the subrogated database described in the companion paper and incorporating three additional ones, one compounded by more accurate subrogated ECG signals and two compounded by real and affected subjects as labeled by expert clinicians. The first real-world database contains QRS fragmented records and the second one contains records with fibrosis and both were recorded in Hospital Clínico Universitario Virgen de la Arrixaca (Spain). To deeply analyze the scope of these datasets, we benchmarked several classifiers such as Neural Networks, Support Vector Machines (SVM), Decision Trees and Gaussian Naïve Bayes (NB). For the fragmentation dataset, the best results were 0.94 sensitivity, 0.88 specificity, 0.89 positive predictive value, 0.93 negative predictive value and 0.91 accuracy when using SVM with Gaussian kernel. For the fibrosis databases, more limited accuracy was reached, with 0.47 sensitivity, 0.91 specificity, 0.82 predictive positive value, 0.66 negative predictive value and 0.70 accuracy when using Gaussian NB. Nevertheless, this is the first time that fibrosis detection is attempted automatically from ECG postprocessing, paving the way towards improved algorithms and methods for it. Therefore, we can conclude that the proposed techniques could offer a valuable tool to clinicians for both fragmentation and fibrosis diagnoses support.

Electromyography-Based Respiratory Onset Detection in COPD Patients on Non-Invasive Mechanical Ventilation.

To optimize long-term nocturnal non-invasive ventilation in patients with chronic obstructive pulmonary disease, surface diaphragm electromyography (EMGdi) might be helpful to detect patient-ventilator asynchrony. However, visual analysis is labor-intensive and EMGdi is heavily corrupted by electrocardiographic (ECG) activity. Therefore, we developed an automatic method to detect inspiratory onset from EMGdi envelope using fixed sample entropy (fSE) and a dynamic threshold based on kernel density estimation (KDE). Moreover, we combined fSE with adaptive filtering techniques to reduce ECG interference and improve onset detection. The performance of EMGdi envelopes extracted by applying fSE and fSE with adaptive filtering was compared to the root mean square (RMS)-based envelope provided by the EMG acquisition device. Automatic onset detection accuracy, using these three envelopes, was evaluated through the root mean square error (RMSE) between the automatic and mean visual onsets (made by two observers). The fSE-based method provided lower RMSE, which was reduced from 298 ms to 264 ms when combined with adaptive filtering, compared to 301 ms provided by the RMS-based method. The RMSE was negatively correlated with the proposed EMGdi quality indices. Following further validation, fSE with KDE, combined with adaptive filtering when dealing with low quality EMGdi, indicates promise for detecting the neural onset of respiratory drive.

The effect of electrical head-to-chest stunning on the EEG in sheep

AbstractHead-to-body stunning is regarded as ‘best practice’ stunning for sheep. The benefits are loss of consciousness followed by cardiac arrest, death, prevention of animal movements post stun/kill and improved meat quality. Commercial equipment places electrodes on the head and back, which is known to cause pelt burning, thus reducing the value of the skins. The aim was to demonstrate that passing current at 1.5 A and 50 Hz from the top of the head to the chest in lambs for 3.1 s would result in epilepsy. Electroencephalographic (EEG) and electrocardiographic (ECG) activity was recorded in sheep using non-invasive electrodes. Measurements in this trial were successfully performed on three lambs (live weight 25 to 39 kg) which were anaesthetised and given neuromuscular blockers to inhibit muscle activity. EEG information showed that the head-to-chest stunning produced an epileptic-like episode, which was followed by an isoelectric output. ECG recordings showed that ventricular fibrillation (VF) was induced and coincided with the epileptic brain activity observed. No animals regained brain activity or sinus heart rhythm after applying the stated stunning conditions. As a conclusion, it is postulated that modified stunning equipment passing an electrical current from the top of the head to the sternum in lambs (1.5 A, 50 Hz; 3.1 s) may induce an epileptic seizure and VF.

Assessment of Respiratory Muscle Activity with Surface Electromyographic Signals Acquired by Concentric Ring Electrodes.

The assessment of respiratory muscle activity by surface electromyography (sEMG) is a promising noninvasive technique for the diagnosis and monitoring of chronic obstructive pulmonary disease. The diaphragm is the most important muscle in breathing, although in forced inspiration other muscles, such as sternocleidomastoid, are activated and contribute to the respiratory process. The measurement of the sEMG in these muscles (sEMGdi and sEMGscm, respectively) by means of two electrodes in conventional bipolar configuration (BEs) is a common practice to evaluate the respiratory muscle activity and allows to indirectly quantify the level of muscular activation. However, the resulting signals are usually contaminated by electrocardiographic (ECG) activity, hindering the assessment of the activity of these muscles. sEMG signals can also be recorded using concentric ring electrodes (CREs). CREs have greater spatial resolution and attenuate distant bioelectrical interferences. In this scenario, the objective of this work has been to evaluate the applicability of CREs for the acquisition of sEMGdi and sEMGscm. For this purpose, both sEMG signals were recorded simultaneously with BEs and CREs in healthy subjects while performing an inspiratory load protocol. To evaluate the effect of the cardiac interference, the ratio between the mean power in inspiratory segments without ECG and the mean power in expiratory segments with ECG (Rcardio) was calculated. Additionally, the ratio between the mean power in inspiratory segments without ECG and the mean power in expiratory segments without ECG (Rinex) was also calculated. The results revealed that the Rcardio and bandwidth is greater in sEMG signals acquired with the CREs, while the Rinex is higher in the signals acquired with BEs. These results suggest that the use of CREs is a recommended alternative for the acquisition of sEMG in muscles with high cardiac interference, such as the diaphragm muscle.

Abstract 221: Bradycardia at the Onset of Pulseless Electrical Activity Arrests in Hospitalized Patients is Associated With Improved Survival to Discharge

Background: Recent studies have suggested that the incidence of in-hospital pulseless electrical activity (PEA) arrests is increasing. Bradycardia in patients with in-hospital PEA is common but it is unknown if it is associated with patient outcomes. Objective: To determine risk factors and outcomes associated with bradycardic-PEA arrests. Methods: This was a retrospective study of all inpatient cardiac arrests at an academic medical center. Patient demographics, comorbidities, vital signs, arrest event data, and outcomes were abstracted from the medical record. PEA arrest was defined as a non-shockable rhythm with loss of pulse requiring cardiopulmonary resuscitation and having organized electrocardiographic activity. Bradycardia was classified as a HR &lt; 60 bpm at the time of pulse loss. Obvious vasovagal events were excluded. The primary outcomes were survival of arrest and survival to hospital discharge. Results: Between July 2013 and August 2017, there were 176 in-hospital PEA arrests. While 105 (59.7%) survived the arrest, only 38 (21.6%) survived to discharge. A total of 65 (36.9%) were bradycardic-PEA arrests. Bradycardia was associated with improved survival to hospital discharge (χ2 8.60, p=0.003), but not survival of arrest (χ2 2.15, p=0.14). Hypoxemia increased (OR 2.72, 95% CI: 1.26-5.87, p=0.01) and a cardiac implanted electronic device decreased (OR 0.17, 95% CI: 0.04-0.78, p = 0.02) the odds of an arrest being preceded by bradycardia. On multivariate analysis, bradycardia remained a predictor of survival to discharge (OR 2.46, 95% CI 1.14-5.32, p=0.02). Other predictors of survival to discharge included hypoxemia (OR 3.38, 95% CI 1.45-7.89, p=0.005) and coronary artery disease (OR 2.29, 95% CI 1.03-5.09, p=0.04). Conclusion: While a significant proportion of hospitalized patients survive a PEA arrest, many fewer survive to discharge. Bradycardia at the time of PEA arrest was associated with improved survival to discharge but not survival of arrest. Bradycardia was associated with hypoxemic arrests, in which rapid airway management should be a priority to improve the chance of successful resuscitation.

Electrocardiographic Analysis of Runners Before, During, And After An Ultramarathon

It is known that ultra-endurance exercise places extraordinary stress on the cardiovascular system. Still, limited data are available examining cardiac physiology throughout an ultramarathon. Additionally, such events have been implicated in augmented ectopic activity and sudden cardiac death. Therefore, detecting arrhythmias during an ultramarathon event would be of interest. PURPOSE: The purpose was to evaluate electrocardiographic activity continuously before, during, and after a mountainous ultramarathon run. METHODS: Twenty-seven runners who registered for either a 44 kilometer (5 men, age 49.2 ± 1.6y ; 4 women, age 43.8 ± 11.9y) or 163 km (14 men, age 40.1 ± 7.8y; 4 women, age 38.8 ± 11y) trail race underwent continuous EKG monitoring 1 day before an ultramarathon run (baseline), during, and a minimum of 24 hours postrace. Electrocardiograms were analyzed for the presence of arrhythmias. Participants completed a survey that included detailed health and running histories. RESULTS: There were no recognizable differences between men and women in HR or rhythms, so sexes were combined for group analyses. Ultramarathon experience ranged from 1 to 36y of racing with most racing 4-6y. No runners reported a history of coronary artery disease, and besides caffeine, no runners reported use of substances that would affect HR or rhythm. Minimum HR the night before the race was 42 ± 6 BPM and ranged from 31-53 BPM. Rare PVCs and/or PACs occurred in 17 of 18 runners, and throughout the observational period, clinically relevant arrhythmias were observed in 5 runners. Generally, occurrences of arrhythmias were no different during or after than before the race. CONCLUSIONS: In a small sample of endurance runners at one ultramarathon run, the prevalence of arrhythmias during and after an ultramarathon race was not different from baseline.

Improvement in Neural Respiratory Drive Estimation From Diaphragm Electromyographic Signals Using Fixed Sample Entropy.

Diaphragm electromyography is a valuable technique for the recording of electrical activity of the diaphragm. The analysis of diaphragm electromyographic (EMGdi) signal amplitude is an alternative approach for the quantification of the neural respiratory drive (NRD). The EMGdi signal is, however, corrupted by electrocardiographic (ECG) activity, and this presence of cardiac activity can make the EMGdi interpretation more difficult. Traditionally, the EMGdi amplitude has been estimated using the average rectified value (ARV) and the root mean square (RMS). In this study, surface EMGdi signals were analyzed using the fixed sample entropy (fSampEn) algorithm, and compared to the traditional ARV and RMS methods. The fSampEn is calculated using a tolerance value fixed and independent of the standard deviation of the analysis window. Thus, this method quantifies the amplitude of the complex components of stochastic signals (such as EMGdi), and being less affected by changes in amplitude due to less complex components (such as ECG). The proposed method was tested in synthetic and recorded EMGdi signals. fSampEn was less sensitive to the effect of cardiac activity on EMGdi signals with different levels of NRD than ARV and RMS amplitude parameters. The mean and standard deviation of the Pearson's correlation values between inspiratory mouth pressure (an indirect measure of the respiratory muscle activity) and fSampEn, ARV, and RMS parameters, estimated in the recorded EMGdi signal at tidal volume (without inspiratory load), were 0.38±0.12, 0.27±0.11 , and 0.11±0.13, respectively. Whereas at 33 cmH2O (maximum inspiratory load) were 0.83±0.02, 0.76±0.07, and 0.61±0.19 , respectively. Our findings suggest that the proposed method may improve the evaluation of NRD.