Electrical cardiometry for hemodynamics

Few reports have focused on hemodynamics around delivery in pregnant women because of the difficulty of continuous and noninvasive measurement. Electrical cardiometry allows noninvasive continuous monitoring of hemodynamics and has recently been used in non-pregnant subjects. We compared the use of electrical cardiometry versus transthoracic echocardiography in healthy pregnant women and evaluated hemodynamics immediately after vaginal delivery. In Study 1, electrical cardiometry and transthoracic echocardiography were used to measure cardiac output in 20 pregnant women with threatened premature delivery. A significant correlation was found between the two methods, with electrical cardiometry showing the higher cardiac output. In Study 2, heart rate, stroke volume, and cardiac output were continuously measured in 15 women during vaginal delivery up to 2 h postpartum. Cardiac output increased markedly because of an increased heart rate and stroke volume at the time of newborn delivery. The heart rate then immediately returned to baseline, while cardiac output remained elevated for at least 2 h after delivery because of a sustained high stroke volume. Electrical cardiometry was as readily available as transthoracic echocardiography for evaluating hemodynamics and allowed for continuous measurement during labor. High intrapartum cardiac output was sustained for at least 2 h after vaginal delivery

Analyzing the formation of normal and abnormal O waves in thoracic impedance graph using the impedance change components for aorta, blood vessels in lung and ventricles

Background: Many measurements of thoracic impedance graph show that the small C wave and big O wave appear often for patients with cardiac insufficiency, and the O/C ratio is bigger. And for the normal body, especially a younger one, the bigger O wave may also appear. But since the amplitude of the C wave of a normal body is bigger, the O/C ratio is smaller. The aim of the present paper is to investigate the formation mechanism of the normal and abnormal O waves in thoracic impedance graph. Methods and Results: The thoracic mixed impedance changes are measured with 6 leads consisting of 15 electrodes. The impedance change components for the aorta (AO), blood vessel in left lung (PL), blood vessel in right lung (PR), left ventricle (LV) and right ventricle (RV) are separated from thoracic mixed impedance changes by means of establishing and solving the thoracic impedance equations. The amplitudes of the O and C waves of various impedance change components are measured for 50 normal healthy adults and 34 patients with cardiac insufficiency. The formation mechanism of normal and abnormal O waves in thoracic impedance graph is analyzed using the superposition of the O waves of the above impedance change components. Detection subjects are 50 healthy adults and 34 hospital patients with cardiac insufficiency. (1) Thoracic impedance graph: The O/C ratios of the normal group are significantly smaller than that of the abnormal group, p < 0.001. The O wave of first lead (E1-E1’) is significantly bigger than that of leads 4 and 5 (E4-E4’ and E5-E5’) in the normal group, p < 0.001. (2) The impedance change component: The O waves of the AO, PL, and PR are significantly smaller than that of the LV and RV in the normal group, p < 0.001. The O wave and O/C of the AO, PL and PR of normal group are significantly smaller than that of the abnormal group, p < 0.001. Conclusions: The O wave of the thoracic impedance graph is formed due to the superposition of the O waves of the impedance change components for the aorta, blood vessels in lung and ventricles

Novel characterization method of impedance cardiography signals using time-frequency distributions

The purpose of this document is to describe a methodology to select the most adequate time-frequency distribution (TFD) kernel for the characterization of impedance cardiography signals (ICG). The predominant ICG beat was extracted from a patient and was synthetized using time-frequency variant Fourier approximations. These synthetized signals were used to optimize several TFD kernels according to a performance maximization. The optimized kernels were tested for noise resistance on a clinical database. The resulting optimized TFD kernels are presented with their performance calculated using newly proposed methods. The procedure explained in this work showcases a new method to select an appropriate kernel for ICG signals and compares the performance of different time-frequency kernels found in the literature for the case of ICG signals. We conclude that, for ICG signals, the performance (P) of the spectrogram with either Hanning or Hamming windows (P¿=¿0.780) and the extended modified beta distribution (P¿=¿0.765) provided similar results, higher than the rest of analyzed kernels.Peer ReviewedPostprint (published version

Comparison of Different Methods for Estimating Cardiac Timings: A Comprehensive Multimodal Echocardiography Investigation

Cardiac time intervals are important hemodynamic indices and provide information about left ventricular performance. Phonocardiography (PCG), impedance cardiography (ICG), and recently, seismocardiography (SCG) have been unobtrusive methods of choice for detection of cardiac time intervals and have potentials to be integrated into wearable devices. The main purpose of this study was to investigate the accuracy and precision of beat-to-beat extraction of cardiac timings from the PCG, ICG and SCG recordings in comparison to multimodal echocardiography (Doppler, TDI, and M-mode) as the gold clinical standard. Recordings were obtained from 86 healthy adults and in total 2,120 cardiac cycles were analyzed. For estimation of the pre-ejection period (PEP), 43% of ICG annotations fell in the corresponding echocardiography ranges while this was 86% for SCG. For estimation of the total systolic time (TST), these numbers were 43, 80, and 90% for ICG, PCG, and SCG, respectively. In summary, SCG and PCG signals provided an acceptable accuracy and precision in estimating cardiac timings, as compared to ICG

Evaluation of cardiac output by bioimpedance method with patients with pacemaker

Tato práce se zabývá možností využití bioimpedančního signálu k výpočtu srdečního výdeje. Jsou zde rozebrány zejména Kubíčkova, Šrámkova a Šrámek-Bernsteinova metoda. Tyto metody byly aplikovány na předložený soubor dat, která byla měřena u subjektů s implantovanými kardiostimulátory. Těmto subjektům byla pomocí programování kardiostimulátoru měněna tepová frekvence. Měřená data díky tomu nebyla zatížena artefakty spojenými se změnou tepové frekvence způsobenou zátěží organismu, nebo jinými vlivy. Na základě statistického zpracování předloženého souboru naměřených dat byl studován vliv tepové frekvence na velikost srdečního výdeje.This thesis deals with the possibility of using impedance cardiography for calculating cardiac output. Kubicek’s, Sramek‘s and Sramek-Bernstein‘s methods are discussed here. These methods were applied to a data set, obtained by measuring on subjects with implanted cardiostimulators. The subjects’ heart rate was being changed by the programing of cardiostimulators. Thanks to this procedure the measured data were not affected by artifacts, connected with the heart rate change caused by a body stress, or other influences. An influence of heart rate on a cardiac output value based on the statistical processing of the data set was studied.

The impedance cardiography technique in medical diagnosis

Background: Thoracic Electrical Bioimpedance (TEB) Technology sometimes called the Impedance Cardiography (ICG).  In 1940, the Impedance Cardiography emerged; the studies of this technique are realized to the cardiovascular diseases detection which used hemodynamic parameters measurements based on the skin electrodes contact by injecting a low amplitude alternating signal. The objective of this article is to review the various studies based on this signal type and to present the multiple methods used for the treatment and to have a correct analysis. Methods: This ICG technique consists for applying an electric field longitudinally across a segment of the thorax with amplitude in mean, high frequency and low amplitude current. To analyze the ICG signal, the signal denoising is necessary that’s why a multiple filters are proposed, and the Discrete Wavelet Transform (DWT) denoising is also used. Results: The ICG is considered advantageous compared to other invasive conventional techniques; it gives a good correlation, and solves the Doppler ultrasound and Thermodilution problems. According to the studies, the Daubechies wavelet family (db8) is the best DWT to eliminate the noises. There are several algorithms for the signal characteristic point’s detection. Conclusion: For the purpose of cardiovascular disease diagnosis and monitoring, the non-invasive ICG technique comes to solve the complexity problem for measurement and analyzing heart disease based on the thoracic electrical impedance change assessment that is due to blood velocity and resistivity changes (blood volume changes) in order to estimate several hemodynamic parameters. Keywords: ICG, cardiovascular disease, hemodynamic parameters, diagnosis and monitoring, correct analysis. &nbsp

Vergleich verschiedener Methoden zur Messung des Herzzeitvolumens im Großtiermodell

Das HZV zählt zu den wichtigsten Parametern des erweiterten hämodynamischen Monitorings. Dabei folgt die Messung dieses Parameters dem aktuellen Trend, weniger invasive Verfahren zu verwenden. Dem Kliniker steht dabei eine Vielzahl an unterschiedlichen Messmethoden zur Verfügung, deren Stellenwert im klinischen Alltag, aufgrund von fraglicher Genauigkeit und Präzision, unklar ist. Diese Studie vergleicht daher drei minimal- bzw. non-invasive Messmethoden (PiCCO, ICONTM, ProAQT®) in Bezug auf ihre Genauigkeit, Präzision, Trendfähigkeit sowie Fähigkeit zur Detektion kurzfristiger Volumenänderungen miteinander. Die kontinuierliche HZV-Messung wurde an zehn maschinell beatmeten Schweinen der deutschen Landrasse zu unterschiedlichen Volumenzuständen über je 96 Stunden durchgeführt. Zur Bestimmung der Genauigkeit und Präzision wurde eine Bland-Altman-Analyse durchgeführt und der prozentuale Fehler ermittelt. Dabei wurden sowohl die einzelnen Methoden untereinander, als auch gegen ein zusammengefasstes HZV aus allen verwendeten Methoden (Z-Statistik), verglichen. Um die Trendfähigkeit der Methoden zu untersuchen, wurde ein 4-Quadranten-Plot angefertigt und die Konkordanz berechnet. Des Weiteren wurde der HZV-Verlauf während der Apnoe- und Trendelenburgmanöver untersucht. Die Auswertung ergab ein Bias von 0,399 l/min (ICONTM-PiCCO), 1,02 l/min (ICONTM-ProAQT®) und 0,68 l/min (ProAQT®-PiCCO) mit Limits of agreement von ±0,98 l/min, ±1,17 l/min und ±1,04 l/min. Die zugehörigen prozentualen Fehler lagen bei 39%, 50% und 30,5%. Die Untersuchung der Trendfähigkeit ergab niedrige Konkordanzraten von 61%, 65% und 71%. Im Vergleich zur Z-Statistik konnte für alle Messmethoden eine akzeptable Präzision erzielt werden. Hier ergaben sich ein Bias und Limits of agreement von 0,11 ±0,55 l/min (PiCCO), 0,47 ±0,63 l/min (ICONTM) und -0,58 ±0,66 l/min (ProAQT®). Die prozentualen Fehler lagen bei 23%, 27% und 28%. Bei der Betrachtung der kurzfristigen Volumenerhöhung durch das Trendelenburg- und das Apnoe-Manöver konnte keine der Messmethoden eine kontinuierliche Performance zeigen. Sie sollten je nach durchgeführtem Manöver und Volumenstatus individuell ausgewählt werden. Es konnte gezeigt werden, dass die untersuchten Methoden untereinander nicht austauschbar sind. Für zukünftige Studien sollte eine größere Anzahl an Messmethoden für die Z-Statistik gewählt werden, um das Ergebnis dieser Studie zu bestätigen