Thoracic Impedance Measurements Research Articles

Experimental Investigation of Possibility of Simultaneously Monitoring Lung Perfusion/Cardiomotility and Ventilation via Thoracic Impedance Measurement

Experimental Investigation of Possibility of Simultaneously Monitoring Lung Perfusion/Cardiomotility and Ventilation via Thoracic Impedance Measurement

Study on the Improvement of Electrical Facility System of Automated External Defibrillators by Real-Time Measurement of Thoracic Impedance

Sudden Cardiac Arrest (SCA) is a serious emergency disease that has increased steadily every year. To this end, an Automated External Defibrillator (AED) is placed in a public place so that even non-professional medical personnel can respond to SCA. However, the thoracic impedance of patients changes due to CardioPulmonary Resuscitation (CPR) and artificial respiration during first aid treatment. In addition, changes in chest statues due to gender, age, and accidents cause changes in thoracic impedance in real time. The change in thoracic impedance caused by this has a negative effect on the intended electrical energy of the automatic heart shocker to the emergency patient. To prove this, we divided it into adult and pediatric modes and experimented with the energy error of the AED according to the same impedance change. When the first peak current was up to 56.4 (A) and at least 8.4 (A) in the adult mode, the first peak current was up to 32.2 (A) and at least 4.8 (A), respectively, when the impedance changed, the error of the current figure occurred. In this paper, the inverse relationship between thoracic impedance and electric shock energy according to the state of the cardiac arrest patient is demonstrated through the results of the experiment, and the need for an electric facility system that can revise for changes in thoracic impedance of the cardiac arrest patient by reflecting them on electric shock energy in real time is presented.

The Added Value of In-Hospital Tracking of the Efficacy of Decongestion Therapy and Prognostic Value of a Wearable Thoracic Impedance Sensor in Acutely Decompensated Heart Failure With Volume Overload: Prospective Cohort Study.

BackgroundIncomplete relief of congestion in acute decompensated heart failure (HF) is related to poor outcomes. However, congestion can be difficult to evaluate, stressing the urgent need for new objective approaches. Due to its inverse correlation with tissue hydration, continuous bioimpedance monitoring might be an effective method for serial fluid status assessments.ObjectiveThis study aimed to determine whether in-hospital bioimpedance monitoring can be used to track fluid changes (ie, the efficacy of decongestion therapy) and the relationships between bioimpedance changes and HF hospitalization and all-cause mortality.MethodsA wearable bioimpedance monitoring device was used for thoracic impedance measurements. Thirty-six patients with signs of acute decompensated HF and volume overload were included. Changes in the resistance at 80 kHz (R80kHz) were analyzed, with fluid balance (fluid in/out) used as a reference. Patients were divided into two groups depending on the change in R80kHz during hospitalization: increase in R80kHz or decrease in R80kHz. Clinical outcomes in terms of HF rehospitalization and all-cause mortality were studied at 30 days and 1 year of follow-up.ResultsDuring hospitalization, R80kHz increased for 24 patients, and decreased for 12 patients. For the total study sample, a moderate negative correlation was found between changes in fluid balance (in/out) and relative changes in R80kHz during hospitalization (rs=-0.51, P<.001). Clinical outcomes at both 30 days and 1 year of follow-up were significantly better for patients with an increase in R80kHz. At 1 year of follow-up, 88% (21/24) of patients with an increase in R80kHz were free from all-cause mortality, compared with 50% (6/12) of patients with a decrease in R80kHz (P=.01); 75% (18/24) and 25% (3/12) were free from all-cause mortality and HF hospitalization, respectively (P=.01). A decrease in R80kHz resulted in a significant hazard ratio of 4.96 (95% CI 1.82-14.37, P=.003) on the composite endpoint.ConclusionsThe wearable bioimpedance device was able to track changes in fluid status during hospitalization and is a convenient method to assess the efficacy of decongestion therapy during hospitalization. Patients who do not show an improvement in thoracic impedance tend to have worse clinical outcomes, indicating the potential use of thoracic impedance as a prognostic parameter.

A Wrapper Feature Selection Algorithm: An Emotional Assessment Using Physiological Recordings from Wearable Sensors.

Assessing emotional state is an emerging application field boosting research activities on the topic of analysis of non-invasive biosignals to find effective markers to accurately determine the emotional state in real-time. Nowadays using wearable sensors, electrocardiogram and thoracic impedance measurements can be recorded, facilitating analyzing cardiac and respiratory functions directly and autonomic nervous system function indirectly. Such analysis allows distinguishing between different emotional states: neutral, sadness, and disgust. This work was specifically focused on the proposal of a k-fold approach for selecting features while training the classifier that reduces the loss of generalization. The performance of the proposed algorithm used as the selection criterion was compared to the commonly used standard error function. The proposed k-fold approach outperforms the conventional method with 4% hit success rate improvement, reaching an accuracy near to 78%. Moreover, the proposed selection criterion method allows the classifier to produce the best performance using a lower number of features at lower computational cost. A reduced number of features reduces the risk of overfitting while a lower computational cost contributes to implementing real-time systems using wearable electronics.

Hemodynamic effects of epinephrine in rats: evaluation by impedance cardiography.

This study was aimed to examine how inotropic effects of intravenously injected epinephrine change thoracic impedance measurements and to reveal the possible effects of this change on other hemodynamic parameters by using the technique of impedance cardiography. 10 male Wistar Albino rats were divided into two equal groups: control and epinephrine. 0.2 mg/kg of epinephrine was administered to the rats in the epinephrine group via the tail vein. All hemodynamic parameters obtained by impedance cardiography [the base impedance (Z0), the maximum rate of change in impedance (dZmax/dt), the left ventricular ejection time (LVET), stroke volume (SV), cardiac output (CO), contractility index (IC), thoracic fluid content (TFC), heart rate (HR)] were recorded using the EBI 100C, DA 100 and ECG modules in the BIOPAC MP100 system. CO (p ≤ 0.05), HR (p ≤ 0.001), dZmax/dt (p ≤ 0.05) and IC (p ≤ 0.05) increased statistically significantly in the epinephrine group compared to the control group. However, LVET (p ≤ 0.001) decreased statistically significantly in the epinephrine group compared to the control group. Tachycardia was detected in the epinephrine group. There was an inverse correlation between LVET and dZmax/dt and IC. This is based on the fact that epinephrine increases inotropic effect (Tab. 2, Fig. 4, Ref. 30).

242 - Thoracic Impedance & Pulmonary Artery Pressure Monitoring in Prevention of Heart Failure Hospitalizations

Introduction: According to 2006 estimates, there are over 5.1 million patients with heart failure in the United States, with the incidence expected to increase. Heart failure patients also account for over a million hospitalizations each year with up to a 24% readmission rate. New technologies such as thoracic impedance monitoring and pulmonary artery (PA) pressure monitoring have been developed to detect early heart failure exacerbation and prevent rehospitalizations. It is currently unknown whether one technology is superior to the other in preventing hospitalizations. Objective: Evaluate whether thoracic impedance and PA pressure correlate and predict heart failure hospitalizations. Methods: Patients with a CardioMEMs PA pressure sensor implanted at the time of euvolemia and a concurrent Medtronic Automatic Implantable Cardioverter Defibrillators with thoracic impedance (OptiVol) sensor were recruited from the Northwell Health North Shore University Hospital and Long Island Jewish Medical Center Heart Failure Clinics. Data was abstracted from the patients' devices and charts were reviewed for hospitalizations for heart failure. Analysis was then performed for overall correlation between the two modalities as well as in changes in each modality in the 14 days preceding the patients' hospitalizations for heart failure. Results: 15 patients with an average age of 65.7 years, predominantly men (80%), 67% of whom had ischemic cardiomyopathy and an average ejection fraction of 34% were recruited for the study. Over the average follow up period of 7.5 month, 7 patients had 11 hospitalizations for heart failure. There was only a weak negative correlation of −0.31 between all the available PA diastolic and thoracic impedance measurements. In the two weeks preceding each hospitalization, there was no clear pattern in changes in PA diastolic pressure or thoracic impedance that would allow for prediction of hospitalization. Conclusions: In a small cohort of heart failure patients, no significant changes in either PA diastolic pressures or thoracic impedance measurements preceded heart failure hospitalization events. Furthermore, no correlation between them was observed. This may be confounded by the lack of the variation in PA diastolic pressures during the follow-up period. Larger randomized trials are needed to evaluate which variables can predict heart failure hospitalizations.

Subclinical pulmonary congestion is prevalent in nephrotic syndrome.

In patients with nephrotic syndrome (NS), the lung is considered an organ protected from the risk of edema. However, data on objectively measured lung water in NS patients is lacking. Here we measured lung water by an ultrasound (US) technique as well as by transthoracic impedance in 42 asymptomatic patients with active NS, in 14 stage G5D CKD patients on chronic hemodialysis, and in 21 healthy individuals. In patients with active NS, the median number of US-B lines (a metric of lung water) after 5 min in a supine position was significantly higher (12; interquartile range: 7-25) compared with that in healthy individuals (4; 2-9) but similar to that in hemodialysis patients (23; 10-39). The difference between NS patients and healthy individuals was significantly amplified (16; 10-35 vs. 4; 2-9) after 60 min of supine resting and significantly attenuated after 5 min of standing (10; 7-25 vs. 3; 1-6). Posture-dependent changes in lung water in patients with active NS were significantly accentuated compared with both hemodialysis patients and healthy individuals. After NS remission, the number of US-B lines was significantly reduced to 5 (4-18) at 5 min and to 6 (5-22) at 60 min approaching the normal range. Lung congestion in patients with active NS was confirmed by transthoracic impedance. Thus, asymptomatic pulmonary congestion is pervasive in patients with NS. A clinical trial is needed to assess the utility of lung US for the management of patients with NS.

Internal Thoracic Impedance - A Useful Method for Expedient Detection and Convenient Monitoring of Pleural Effusion

Measurement of internal thoracic impedance (ITI) is sensitive and accurate in detecting acute pulmonary edema even at its preclinical stage. We evaluated the suitability of the highly sensitive and noninvasive RS-207 monitor for detecting pleural effusion and for demonstrating increased ITI during its resolution. This prospective controlled study was performed in a single department of internal medicine of a university-affiliated hospital between 2012-2013. One-hundred patients aged 25–96 years were included, of whom 50 had bilateral or right pleural effusion of any etiology (study group) and 50 had no pleural effusion (controls). ITI, the main component of which is lung impedance, was continuously measured by the RS-207 monitor. The predictive value of ITI monitoring was determined by 8 measurements taken every 8 hours. Pleural effusion was diagnosed according to well-accepted clinical and roentgenological criteria. During treatment, the ITI of the study group increased from 32.9±4.2 ohm to 42.8±3.8 ohm (p<0.0001) compared to non-significant changes in the control group (59.6±6.6 ohm, p = 0.24). Prominent changes were observed in the respiratory rate of the study group: there was a decrease from 31.2±4.0 to 19.5±2.4 ohm (35.2%) compared to no change for the controls, and a mean increase from 83.6±5.3%-92.5±1.6% (13.2%) in O2 saturation compared to 94.2±1.7% for the controls. Determination of ITI for the detection and monitoring of treatment of patients with pleural effusion enables earlier diagnosis and more effective therapy, and can prevent hospitalization and serious complications, such as respiratory distress, and the need for mechanical ventilation.Trial RegistrationThe study is registered at ClinicalTrials.gov NCT01601444

Worsening thoracic impedance as a ventricular tachyarrhythmia risk.

The use of heart failure classification to identify patients with systolic dysfunction who are at risk for ventricular tachyarrhythmias (VAs), sudden cardiac death, and shocks from implantable cardioverter defibrillators (ICDs) is limited by its subjectivity. Measurement of thoracic impedance offers a more objective tool for assessing worsening of heart failure. We sought to look at the correlation between ventricular arrhythmia and heart failure as assessed objectively by thoracic impedance. We reviewed device interrogation data on thoracic impedance from ICD with Medtronic's OptiVol® feature (Medtronic Inc., Minneapolis, MN) at two medical centers. Data from the last two interrogations of the same device separated by at least 2 months were included. An OptiVol fluid index threshold of 60 represented early heart failure prior to appearance of symptoms. VAs included were ventricular fibrillation and/or ventricular tachycardia lasting more than 16 beats. Chi square distribution test was used in statistical data analysis. There were 24 VAs identified among the 322 interrogations reviewed (7.5%). Elevated OptiVol fluid index was seen in 71% (17/24), whereas normal OptiVol index was seen in the remaining 29% (7/24) of these interrogations with VA (P < .05). Our review shows that heart failure patients who have VA are approximately 2.5 times as likely to have worsening thoracic impedance as assessed objectively by the OptiVol fluid index. Careful monitoring of the OptiVol fluid index may identify a population at high risk of VA that merits more intense attention.

A model of end-expiratory lung impedance dependency on total extracellular body water

Electrical impedance tomography (EIT) is an attractive method for clinical monitoring of patients during mechanical ventilation. This study evaluates lung impedance measurements using Dräger PulmoVista 500 EIT system on an animal model. Mechanically ventilated model was created. Vital signs were monitored as well as mechanical ventilation parameters. Extracellular fluid balance and blood volume were handled as follows: 30–40% of total blood volume were removed and returned back, 0.5 to 1 litre of Ringer's solution was injected afterwards. The quantity of injected fluids was recorded for each animal. During this process thoracic electrical impedance measurement was performed. Recorded data from PulmoVista 500 EIT system were analysed using the official Dräger EIT Data Analysis Tool. The dependency of end-expiratory lung impedance on the change of fluid balance was observed. The relation between end-expiratory (minimum impedance value) frames and changes of fluid balance is shown. Preliminary results strongly support the expectation that electrical impedance of thorax can be affected by total extracellular fluid change.

Measurement of Thoracic Impedance and Approximations: A Diagnosis Technique for Clinical Utilisation

The purpose of this paper is to facilitate the readers and the researchers about the implementations and applications of thoracic impedance measurements and approximations for diagnosis of several related diseases. In this study, two entirely non-invasive approaches and simple assumptions are taken into consideration to measure the transthoracic electrical impedance and lung volume. In the first method, the fluid volume is calculated by considering a pre-defined curve and anthropometric dimensions of the human thorax, whereas in the second method, the thorax is considered as a cylinder and the cylindrical mathematical standard formulae are utilised for approximation of the lung volume. The thoracic impedance is measured directly by placing the tetrapolar electrodes on the right side of the human thorax. The right side of the thorax is considered in order to avoid the incorporation of the geometrical aspects and the behaviour of the heart. The anthropometric dimensions are taken for six normal male subjects of sound health. With the help of these parameters, the thoracic fluid volume is predicted using two methods. In the first method, the thoracic volume is predicted by considering the thorax as a cylinder and by using basic relations of the periphery and volume of the cylinder. Human thorax dimensions are approximated as height and breadth of the cylinder and certain approximations have been adopted. The anthropometric dimensions are taken for the chest at normal resting conditions and at breath-hold positions. In both the approaches, the difference between the measured and the predicted impedances and volumes are clearly observable.

Abstract 196: Measurement of Depth, Thrust and Thoracic Impedance During Mechanical Cardiopulmonary Resuscitation: Is Thoracic Impedance a Potential Indicator of Effective External Cardiac Massage in a Porcine Model of Cardiac Arrest?

Purpose of the Study: The 2010 AHA guidelines currently recommend a depth of at least 2 inches (5cm) during external cardiac massage. The purpose of this study was to determine if the use of an alternative measure to depth could assist in quantifying the effectiveness of CPR in an out-of-hospital setting and to determine how achievable depths of at least 2 inches are in experimental models of cardiac arrest. Materials and Methods: A total of 12 porcine models were used each weighing 30.7±4.2kg. Depth (mm), thrust (kg); End-tidal CO 2 , and Cardiac Output (CO) were measured at 2 minute intervals for each model. The Impedance Cardiogram (ICG)/Thoracic Impedance (non-invasive measure of cardiac output) was recorded via 2 standard defibrillation electrodes, as a method of detecting the presence of effective CPR. Ethical approval was granted by the Northern Ireland Home Office. Models were anaesthetised using Isoflurane and connected to a Datex Ohmeda® for anaesthesia monitoring. Depth and rate of CPR were continuously measured using Q-CPR®, Philips. CPR was administered using the HLR-201®, Michigan Instruments. Recordings from each experiment were acquired using the Datex Ohmeda for statistical analysis using Microsoft Access®. Results: During CPR, cardiac output was maintained at an average of 21% of normal CO levels. At thrusts of 60kg and a rate 112±2 compressions per minute, the average depth (using Q-CPR®, Philips) achieved using a stabilised mechanical CPR system was 37.12mm±3 (1.46±0.12inches). Using the HLR-201®, Michigan Instruments the average depth achieved was 50mm (1.97inches). A strong linear correlation was achieved when comparing depth (mm) using Q-CPR® and the thrust (kg) using the HLR-201®, Michigan Instruments; r=0.856. In addition a strong linear correlation was attained when the Impedance cardiogram (ICG) (ohms) was compared with depth (mm) using Q-CPR®, Philips of; r=0.86. Conclusions: A depth of at least 2 inches was almost unattainable in this porcine model, even at thrusts of 60 kg. An algorithm will incorporate the results from this study, providing feedback to the operator on the quality of CPR by measuring the ICG amplitude which has been strongly correlated with standard measures of depth as well as a number of physiological parameters.

ORAL PRESENTATION

ORAL PRESENTATION

Remote monitoring via implanted devices in heart failure: rising star or lame duck?

Remote monitoring via implanted devices in heart failure: rising star or lame duck?

End-tidal CO2 and invasive cardiac output measurements versus thoracic impedance measurements during mechanical CPR as an indicator of effective CPR in a porcine model of cardiac arrest

Purpose of the study: A number of physiological indicators were explored to determine if ICG amplitude could be used as a determinant of effective CPR to guide lay responders in administering optimized cardiac massage thereby improving survival rates from out of hospital cardiac arrest.Materials and methods: A total of seven porcine models around 52.8 ± 9 kg were used. End-tidal CO2 (ETCO2), Cardiac Output (CO), Carotid Flow and the Impedance Cardiogram (non-invasive measure of cardiac output) were utilized as a basis for detecting the presence of effective CPR. Ethical approval was granted by the Northern Ireland Home Office. Models were anaesthetised using Propofol and Isoflurane and connected to a Datex Ohmeda® monitor. Carotid flow and coronary perfusion pressure were measured via the carotid and thermodilution via the jugular. Recordings from each experiment were acquired using HEM® Notocord software for analysis.Results: ETCO2 levels averaged 23.3 mmHg during CPR compared to the models who did not receive CPR producing values close to of 3 ± 1 mmHg. Cardiac Output values of >22% of the normal CO were achieved which, reported as adequate for ROSC. Carotid Flow increased with depth of CPR. ICG amplitude increased with CO as did ETCO2. The results show that the physiological parameters used were good indicators of CPR efficacy.Conclusions: These findings are potentially significant in the field of resuscitation. An algorithm will incorporate the results from this study, providing feedback to the operator on the quality of CPR by measuring the ICG amplitude which can be correlated to the basic physiological parameters recorded during this study. Purpose of the study: A number of physiological indicators were explored to determine if ICG amplitude could be used as a determinant of effective CPR to guide lay responders in administering optimized cardiac massage thereby improving survival rates from out of hospital cardiac arrest. Materials and methods: A total of seven porcine models around 52.8 ± 9 kg were used. End-tidal CO2 (ETCO2), Cardiac Output (CO), Carotid Flow and the Impedance Cardiogram (non-invasive measure of cardiac output) were utilized as a basis for detecting the presence of effective CPR. Ethical approval was granted by the Northern Ireland Home Office. Models were anaesthetised using Propofol and Isoflurane and connected to a Datex Ohmeda® monitor. Carotid flow and coronary perfusion pressure were measured via the carotid and thermodilution via the jugular. Recordings from each experiment were acquired using HEM® Notocord software for analysis. Results: ETCO2 levels averaged 23.3 mmHg during CPR compared to the models who did not receive CPR producing values close to of 3 ± 1 mmHg. Cardiac Output values of >22% of the normal CO were achieved which, reported as adequate for ROSC. Carotid Flow increased with depth of CPR. ICG amplitude increased with CO as did ETCO2. The results show that the physiological parameters used were good indicators of CPR efficacy. Conclusions: These findings are potentially significant in the field of resuscitation. An algorithm will incorporate the results from this study, providing feedback to the operator on the quality of CPR by measuring the ICG amplitude which can be correlated to the basic physiological parameters recorded during this study.

Part 5: Adult Basic Life Support

Part 8 : Advanced life support : 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations

Part 5: Adult basic life support: 2010 International consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations

Part 5: Adult basic life support: 2010 International consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations

A reply to both of the above letters

A reply to both of the above letters

The contribution of the lungs to thoracic impedance measurements: a simulation study based on a high resolution finite difference model

A high resolution electrical finite difference model of the human thorax based on a 43 slice MRI data set along with lead field theory was used to examine the contribution of the lungs to the total impedance for a typical mid-thoracic 2D EIT eight and sixteen electrode configuration. Regional analysis of the thoracic sources of impedance revealed that the maximum contribution of lungs to the total impedance was approximately 22% for the eight electrode array and 25% for the sixteen electrode array. Analysis of impedance distribution of the lungs using a mid-thoracic application showed that the contribution of impedance of each slice followed closely the volume of the lungs in the given slice. This suggests that the mid-thoracic application gives results reflecting the entire lung. The contributions of the lung impedance for the various electrode positions showed that the eight electrode configuration had a more smooth change between adjacent electrodes compared to the 16 electrode arrangement.

Pacemaker Auto‐Interference by Thoracic Impedance Measurement for the Rate Response Function

This report describes two cases of pacemaker auto-interference caused by thoracic impedance measurements for the rate response function of a dual chamber pacemaker. Mechanisms of this phenomenon and reprogramming strategies are discussed.