Applications of the Transthoracic Impedance Signal during Resuscitation

Defibrillators acquire both the ECG and the transthoracic impedance (TI) signal through defibrillation pads. TI represents the resistance of the thorax to current flow, and is measured by defibrillators to check that defibrillation pads are correctly attached to the chest of the patient. Additionally, some defibrillators use the TI measurement to adjust the energy of the defibrillation pulse. Changes in tissue composition due to redistribution and movement of fluids induce fluctuations in the TI. Blood flow during the cardiac cycle generates small fluctuations synchronized to each heartbeat. Respiration (or assisted ventilation) also causes changes in the TI. Additionally, during cardiopulmonary resuscitation (CPR), chest compressions cause a disturbance in the electrode-skin interface, inducing artifacts in the TI signal. These fluctuations may provide useful information regarding CPR quality, length of pauses in chest compressions (no flow time), presence of circulation, etc. This chapter explores the new applications of the transthoracic impedance signal acquired through defibrillation pads during resuscitative attempts

Monitoring Chest Compression Rate in Automated External Defibrillators Using the Autocorrelation of the Transthoracic Impedance

Aim High-quality chest compressions is challenging for bystanders and first responders to out-of-hospital cardiac arrest (OHCA). Long compression pauses and compression rates higher than recommended are common and detrimental to survival. Our aim was to design a simple and low computational cost algorithm for feedback on compression rate using the transthoracic impedance (TI) acquired by automated external defibrillators (AEDs). Methods ECG and TI signals from AED recordings of 242 OHCA patients treated by basic life support (BLS) ambulances were retrospectively analyzed. Beginning and end of chest compression series and each individual compression were annotated. The algorithm computed a biased estimate of the autocorrelation of the TI signal in consecutive non-overlapping 2-s analysis windows to detect the presence of chest compressions and estimate compression rate. Results A total of 237 episodes were included in the study, with a median (IQR) duration of 10 (6-16) min. The algorithm performed with a global sensitivity in the detection of chest compressions of 98.7%, positive predictive value of 98.7%, specificity of 97.1%, and negative predictive value of 97.1% (validation subset including 207 episodes). The unsigned error in the estimation of compression rate was 1.7 (1.3-2.9) compressions per minute. Conclusion Our algorithm is accurate and robust for real-time guidance on chest compression rate using AEDs. The algorithm is simple and easy to implement with minimal software modifications. Deployment of AEDs with this capability could potentially contribute to enhancing the quality of chest compressions in the first minutes from collapse.The Basque Government provided support in the form of a grant for research groups (IT1087-16) for authors Sofia Ruiz de Gauna, Jesus Maria Ruiz, and Jose Julio Gutierrez. The Spanish Ministry of Economy, Industry and Competitiveness provided support in the form of a grant for research projects (RTI2018-094396-BI00) for authors Sofia Ruiz de Gauna, Jesus Maria Ruiz, and Jose Julio Gutierrez; and in the form of the program Torres Quevedo (PTQ-16-08201) for author Digna Maria Gonzalez-Otero. The University of the Basque Country (UPV/EHU) provided support in the form of a grant for collaboration between research groups and companies (US18/30) for authors Sofia Ruiz de Gauna, Jesus Maria Ruiz, and Jose Julio Gutierrez. Bexen Cardio, a Spanish medical device manufacturer, provided support in the form of a salary for author Digna Mara Gonzalez-Otero. None of the above funding organizations had any additional role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific role of each author is articulated in the Author Contributions section. Authors Daniel Alonso, Carlos Corcuera, and Juan Francisco Urtusagasti received no funding for this work

Audiovisual Feedback Devices for Chest Compression Quality during CPR

During cardiopulmonary resuscitation (CPR), chest compression quality is the key for patient survival. However, several studies have shown that both professionals and laypeople often apply CPR at improper rates and depths. The use of real-time feedback devices increases adherence to CPR quality guidelines. This chapter explores new alternatives to provide feedback on the quality of chest compressions during CPR. First, we describe and evaluate three methods to compute chest compression depth and rate using exclusively the chest acceleration. To evaluate the accuracy of the methods, we used episodes of simulated cardiac arrest acquired in a manikin model. One of the methods, based on the spectral analysis of the acceleration, was particularly accurate in a wide range of conditions. Then, we assessed the feasibility of using the transthoracic impedance (TI) signal acquired through defibrillation pads to provide feedback on chest compression depth and rate. For that purpose, we retrospectively analyzed three databases of out-of-hospital cardiac arrest episodes. When a wide variety of patients and rescuers were included, TI could not be used to reliably estimate the compression depth. However, compression rate could be accurately estimated. Development of simpler methods to provide feedback on CPR quality could contribute to the widespread of these devices

Disponibilidad, accesibilidad a las drogas y su incidencia en el consumo de sustancias

The objective of this research was to analyze the connection between availability/accessibility of illegal drugs with the development of consumption levels among youngsters of 12 to 18 years of age in different communities of the Argentine Republic. Data was collected through interviews and an anonymous survey, voluntary and self- administered in different cities of the country. The result of this survey showed that the increase of consumption of illegal drugs is due to many factors, considering the offer of drugs in our country nowadays and the easy access to them one of the most important of these. Social tolerance and anomie are added, leading many youngsters to start consuming at early ages. Besides, the general objective proposed, to analyze availability/accessibility to illegal drugs, led to the connection with the development of the levels of consumption among the population and the most usual ways to access to such consumptions were identified. Thus it is confirmed that the greater the offer the higher the increase of consumption and social tolerance. Prevalence of the use of different drugs in relation to their accessibility/availability was analyzed and the conclusion was that this is a very important risk factor. The research of this report shows a highly significant fact: that the answers referring to the ease of getting drugs and thus the availability are mostly affirmative. Another aspect to stress –which is a finding for the research team– is the strong correlation existing between those who admit that they consume or have consumed illegal substances and family consumption, and this increases the easy access to them as well as its predictor effect on consumption. The need to develop prevention actions regarding the three dimensions of the phenomenon- offer control, decrease of demand and preventive work within family and social context- is the result of this research.La investigación tuvo como objetivo analizar la relación entre la disponibilidad/accesibilidad de drogas ilegales con el desarrollo de los niveles de consumo en jóvenes de 12 a 18 años, en distintas comunidades de la República Argentina. Se recabaron datos a través de entrevistas y una encuesta anónima, voluntaria y autoadministrada en distintas ciudades del país. Como resultado se constata que el aumento del consumo de drogas ilícitas se debe a múltiples factores, entre los cuales se considera como muy importante la oferta de drogas existente en nuestro país en la actualidad y la facilidad de acceso a ellas. A esto se suma la tolerancia social y la anomia que lleva a muchos jóvenes al consumo en edades tempranas. Asimismo, el objetivo general propuesto, analizar la disponibilidad/accesibilidad a drogas ilegales, fue relacionado con el desarrollo de los niveles de consumo en la población analizada, con lo cual pudieron identificarse los modos más habituales de acceder a esos consumos. Se confirma que, a mayor oferta, hay aumento del consumo y de su tolerancia social. Se analizaron las prevalencias del uso de diferentes drogas en relación a su accesibilidad/disponibilidad, concluyendo que este se constituye en un factor de riesgo muy importante. De la investigación objeto de este informe resulta, como dato altamente significativo, que las respuestas referidas a la facilidad para obtener drogas y la accesibilidad a ellas son mayoritariamente afirmativas. Otro aspecto a destacar, que constituye un hallazgo para el equipo investigador, es la fuerte correlación que existe entre los que dicen que consumen o han consumido sustancias ilegales y el consumo familiar, lo cual aumenta la facilidad del acceso y su efecto predictivo del consumo. Como resultado de la investigación se concluye debe sostenerse el desarrollo de acciones de prevención en las tres dimensiones del fenómeno: control de la oferta, disminución de la demanda y trabajo preventivo en el contexto familiar y social

Waveform Capnography for Monitoring Ventilation during Cardiopulmonary Resuscitation: The Problem of Chest Compression Artifact

Sudden cardiac arrest (SCA) is the sudden cessation of the heart’s effective pumping function, confirmed by the absence of pulse and breathing. Without appropriate treatment, it leads to sudden cardiac death, considered responsible for half of the global cardiac disease deaths. Cardiopulmonary resuscitation (CPR) is a key intervention during SCA. Current resuscitation guidelines emphasize the use of waveform capnography during CPR in order to enhance CPR quality and improve patient outcomes. Capnography represents the concentration of the partial pressure of carbon dioxide (CO2) in respiratory gases and reflects ventilation and perfusion of the patient. Waveform capnography should be used for confirming the correct placement of the tracheal tube and monitoring ventilation. Other potential uses of capnography in resuscitation involve monitoring CPR quality, early identification of restoration of spontaneous circulation (ROSC), and determination of patient prognosis. An important role of waveform capnography is ventilation rate monitoring to prevent overventilation. However, some studies have reported the appearance of high-frequency oscillations synchronized with chest compressions superimposed on the capnogram. This chapter explores the incidence of chest compression artifact in out-of-hospital capnograms, assesses its negative influence in the automated detection of ventilations, and proposes several methods to enhance ventilation detection and capnography waveform

Limitations in the use of the IEC standard method for detection and analysis of rapid voltage changes in power system networks

IEC 61000-4-30 has recently defined a method for detection and analysis of rapid voltage changes in power system networks. This paper presents some of the results obtained in the application of the IEC standard method in different low-voltage and medium-voltage power system networks with different load types and some of the limitations found in the standard method for the correct detection and characterization of these voltage events

Modeling the impact of ventilations on the capnogram in out-of-hospital cardiac arrest

Aim Current resuscitation guidelines recommend waveform capnography as an indirect indicator of perfusion during cardiopulmonary resuscitation (CPR). Chest compressions (CCs) and ventilations during CPR have opposing effects on the exhaled carbon dioxide (CO2) concentration, which need to be better characterized. The purpose of this study was to model the impact of ventilations in the exhaled CO2 measured from capnograms collected during out-of-hospital cardiac arrest (OHCA) resuscitation. Methods We retrospectively analyzed OHCA monitor-defibrillator files with concurrent capnogram, compression depth, transthoracic impedance and ECG signals. Segments with CC pauses, two or more ventilations, and with no pulse-generating rhythm were selected. Thus, only ventilations should have caused the decrease in CO2 concentration. The variation in the exhaled CO2 concentration with each ventilation was modeled with an exponential decay function using non-linear-least-squares curve fitting. Results Out of the original 1002 OHCA dataset (one per patient), 377 episodes had the required signals, and 196 segments from 96 patients met the inclusion criteria. Airway type was endotracheal tube in 64.8% of the segments, supraglottic King LT-D (TM) in 30.1%, and unknown in 5.1%. Median (IQR) decay factor of the exhaled CO2 concentration was 10.0% (7.8 - 12.9) with R-2 = 0.98(0.95 - 0.99). Differences in decay factor with airway type were not statistically significant (p = 0.17). From these results, we propose a model for estimating the contribution of CCs to the end-tidal CO2 level between consecutive ventilations and for estimating the end-tidal CO2 variation as a function of ventilation rate. Conclusion We have modeled the decrease in exhaled CO2 concentration with ventilations during chest compression pauses in CPR. This finding allowed us to hypothesize a mathematical model for explaining the effect of chest compressions on ETCO2 compensating for the influence of ventilation rate during CPR. However, further work is required to confirm the validity of this model during ongoing chest compressions.The Basque Government provided support in the form of a grant for research groups (IT1087-16) for authors Jose Julio Gutierrez, Jesus Maria Ruiz, Sofia Ruiz de Gauna, and Mikel Leturiondo; and in the form of a predoctoral grant (PRE-2017-2-0201) for author Mikel Leturiondo (https://www.euskadi.eus).The Spanish Ministry of Economy, Industry and Competitiveness provided support in the form of a grant for research projects (RTI2018-094396-B-I00) for authors Jose Julio Gutierrez, Jesus Maria Ruiz, Sofia Ruiz de Gauna, and Mikel Leturiondo; and in the form of the program Torres Quevedo (PTQ-16-08201) for author Digna Maria Gonzalez-Otero (http://www.ciencia.gob.es/).Bexen Cardio, a Spanish medical device manufacturer, provided support in the form of a salary for author Digna Mari ' a Gonza ' lez-Otero. None of the above funders had any additional role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific role of each author is articulated in the "author contributions" section. Authors James Knox Russell, Carlos Corcuera, Juan Francisco Urtusagasti, and Mohamud Ramzan Daya received no funding for this work

Flicker Characteristics of Efficient Lighting Assessed by the IEC Flickermeter

We present an experimental study of the behavior of modern lighting technologies under supply voltage fluctuations. Some studies have reported that flicker severity measurements could exceed the compatibility levels without leading to flicker complaints when modern lighting is in use. Such conclusions have resulted in two main proposals regarding the assessment of flicker: to relax the flicker compatibility indexes and to adapt standardized procedures to assess flicker based on a new reference lamp instead of the current reference, the incandescent lamp. Our work presents alternative tools for analyzing the effect of efficient lighting on the assessment of flicker. Our main findings challenge the assumption that efficient modern lighting is not sensitive to voltage fluctuations, at least over a considerable frequency range. Furthermore, the results oppose the use of the standardized functional model of the incandescent lamp for assessing the flicker severity produced by modern lamps.This work received financial support from the Government of Basque Country through the PhD studentship BFI-2012-315 and from the University of the Basque Country UPV/EHU through the project UFI11/16 and the PhD studentship PIF2011/169

Experimental Study of the Response of Efficient Lighting Technologies to Complex Voltage Fluctuations

The replacement of incandescent lamps with more energy-efficient lighting technologies has a direct influence on the way flicker is measured. The International Electrotechnical Commission (IEC) established in the 61000-4-15 standard the functional specifications of a flickermeter, taking a standard incandescent lamp’s response to voltage fluctuations as the reference. During the past ten years, different works have studied the sensitivity of modern lamps to analytical voltage fluctuations of low complexity. From these studies, the most widespread conclusion is that modern lamps are less sensitive to flicker than are incandescent lamps. Based on these results, international standardization organizations are currently studying two different possibilities for updating the flicker assessment procedure: adjusting the IEC flickermeter according to a new less sensitive reference lamp, or increasing the established compatibility levels for voltage fluctuations. This work presents for the first time a sensitivity analysis of a set of modern lamps subjected to real voltage signals that are more complex than analytical voltage fluctuations. The obtained results lead to the following conclusions: not all efficient lamps have a lower sensitivity to fluctuations than do incandescent lamps; the response of some lamps depends on the complexity of the input voltage fluctuation; and the response of some lamps in real scenarios, i.e., more complex voltage fluctuations, does not correlate with their response to simple voltage fluctuations

An Alternative Strategy to Improve the Flicker Severity Measurement

The IEC 61000-4-15 standard defines a flickermeter that is universally accepted as the meter used for the objective measurement of a disturbing light flicker. The accurate results provided by the IEC flickermeter under uniform fluctuations stand in contrast with its unpredictable behavior under real conditions when voltage fluctuations are not uniform over time. Under nonuniform fluctuations, the IEC flickermeter can indicate wrong values, and this could explain the absence of users’ complaints at sites where high flicker levels were measured. This work presents a new strategy for flicker measurement that overcomes the deficiencies presented in the IEC flickermeter, properly relating flicker severity values and temporal evolution of the fluctuation. The manuscript describes in detail the functional and design specifications of the new strategy, as well as the results obtained during the validation process in which the IEC flickermeter and the new strategy were subjected to input signals with different temporal fluctuation patterns. The manuscript also presents a comparison between the response of the two strategies to real voltage signals, which are complex and nonuniform in nature. The results confirm the differences between both strategies, despite both meet the same requirements established by the standard.This work received financial support from the Government of the Basque Country through the PhD studentship BFI-2012-315 and from the University of the Basque Country UPV/EHU through the project UFI11/16 and the PhD studentship PIF 2011/169