Impedance Cardiography Method Research Articles

Impact of age and sex on heart rate variability and cardiometabolic function in healthy adults

Heart rate variability (HRV) is a non-invasive measure of cardiac autonomic function. A clearer understanding as to whether resting autonomic function represented by HRV could be associated with changes in peak exercise cardiac function remains unanswered. This study evaluated the effect of age and sex on HRV, cardiometabolic function, and determined the correlation between HRV and cardiac function in healthy individuals. Sixty-eight participants (age range: 19–78 years old, females, n = 28) were recruited. Participants were stratified according to age (younger (<40 years old, n = 43, females, n = 17) and older age groups (>55 years old, n = 25, females, n = 11). Firstly, HRV was measured using non-invasive impedance cardiography method (TaskForce, CNSystems, Graz, Austria) and recorded at rest (supine position) for 30 min. HRV measures included: low frequency (LF) power, high frequency (HF) power (both normalised (nu) and absolute units (ms2)) and LF/HF ratio. Participants then completed a progressive cardiorespiratory exercise test using a semi-recumbent cycle ergometer (Corival, Lode, Groningen, Netherlands) with simultaneous gas exchange measurements (Metalyzer 3B, Cortex, Leipzig, Germany). Cardiac function was represented by peak exercise cardiac power output index (CPO). After controlling for body mass index and physical activity, males had significantly higher mean vales of RR interval than females (males = 1043 ± 165; females = 952 ± 128 ms, p = 0.02). There was no significant main effect of age, sex or their interaction on any of the other HRV measures. In younger and older females, resting RR interval had a significant relationship with peak exercise CPO (young females: r = 0.54, p < 0.05; old females: r = 0.81, p < 0.01). There was also a significant relationship between resting HF power and peak exercise CPO in younger females (r = 0.70, p < 0.01). HRV was not influenced by age but RR interval was associated with peak exercise CPO in females regardless of age, whilst HF power was significantly associated with CPO in younger females only.

Determination using impedance cardiograph of the chronic effects of different doses of radiotherapy on the cardiovascular system of rats

Aim Cardiac damage caused by radiation in the long term varies according to the radiation dose received by the heart. In this study, it was aimed to evaluate the damage caused by different radiation doses in the heart, together with hemodynamic parameters, immunhistochemistry, and histopathological analyzes for long term. Method and materials The animals were divided into four groups: The rats in control group (Group 1) were not irradiated; the rats in group 2 were irradiated with 5 Gy; the rats in group 3 were irradiated with 10 Gy and the rats in group 4 were irradiated with 20 Gy. Hemodynamic parameters and indices were determined from the impedance cardiography (ICG) recording in the whole groups before they were irradiated with RT and 180 days after RT. And then, interleukin-1β, interleukin-10, TNF-α, apopthosis were determined in all groups. In addition, histological changes of heart and aorta were evaluated. Results Histopathologic, cytokine and hemodynamic findings supported that cardiac damage increased with increasing radiation dose. Conclusion it is important in terms of being an alternative and supportive method to other methods to be able to detect heart diseases caused by RT with the ICG method.

Interventional Heartworm Extraction in Two Dogs: The Clinical Application of Impedance Cardiography.

This study aimed to assess the efficacy of using impedance cardiography (ICG) as a non-invasive approach for monitoring CO during interventional HW extraction. Two cases of HW infections were treated via surgical extraction. The CO and mean arterial pressure (MAP) were monitored using the ICG technique during the anesthesia stabilization, extraction process, and post-extraction phases. In Case 1, the CO increased by 115% post-procedure, and in Case 2, the CO increased by 116%. In contrast, the MAP varied between the two cases. The ICG method provided real-time CO data without major disruptions during the extraction surgery. The ICG technique for CO monitoring during interventional HW extractions is effective.

Зміни варіабельності серцевого ритму та периферичної гемодинаміки під час впливу об’ємного пневмопресингу в осіб з різним типом регуляції автономної нервової системи

Intermittent pneumatic compression (IPC) widely used in the therapy of preventing the formation of blood clots, improving the oxygenation of peripheral tissues. IPC is an established method in the therapy of post-operative recovery and in geriatrics and sports medicine. The purpose of our study was to determine functional changes in heart rate variability (HRV) and peripheral hemodynamics during exposure to lowintensity IPC depending on different types of regulation of the autonomic nervous system. We investigated 62 participants in age of 18-22 years. Testing sessions that included pressure of 40 mmHg and 20-minute period of temporary occlusion of the lower extremities was performed by intermittent pneumatic compression with Recovery Pump PRX device (“Mego Aftek AC Ltd”, Israel). During the procedure exposure and recovery period, arterial blood pressure was recorded with Korotkov’s auscultative method by mercury tonometer (“Dr. Frei”A-10, Switzerland). Heart Rate was monitored using a Cardio Trainer Polar H9 (“Polar Electro Oy”, Finland). For monitoring hemodynamic changes, impedance cardiography (ICG) method (“ХАІ-medica”, Kharkiv, Ukraine) was applied by 15 s. Based on the spectrum power values in the range of 0.15–0.4 (HFnorm), 3 groups of volunteers were determined using sigma deviations. Group 1 included 29 volunteers with an advantage of the sympathetic link of regulation of the autonomic nervous system (the background HFnorm was less than 40 nu). Group 2 included 19 persons with a normotonic type of autonomic nervous system regulation (HFnorm from 40 to 60 nu). Group 3 included 14 individuals with predominance of the parasympathetic link of the autonomic nervous system (HFnorm above 60 nu). In conclusion, IPC treatment in groups 1 and 2 inhibited the sympathetic activation, increased the blood flow in the large femoral arteries and tone of small arteries. In group 3, the blood outflow from the lower extremities was predominance, the blood flow volume and speed decreased. Therefore, we conclude effectivity of the low intensity IPC using. Also, HRV and peripheral hemodynamics depend on the types of regulation of the autonomic nervous system.

Ejection Fraction Measurement Based on Impedance Cardiography

Ejection fraction (EF) is an important indicator of cardiac function, especially in clinical conditions. Unlike imaging technology such as echocardiography, impedance cardiography (ICG) is a low-cost, non-invasive and continuous method of monitoring EF. However, the accuracy of the ICG method to evaluate the EF value needs to be further improved. This paper uses a simplified ventricular model to simplify the complex relationship between the EF value and the relevant ICG parameters, and proposes a method for calculating the EF value through these relevant ICG parameters. We tested this method with 52 subjects. Experimental results show that compared with the traditional ICG method, the proposed method has a higher correlation and closer agreement with the EF measurement by echocardiography. The proposed scheme effectively improves the reliability of the measurement of the EF value relying on the ICG signal.

Effect of Carbohydrate-Enriched Drink Compared to Fasting on Hemodynamics in Healthy Volunteers. A Randomized Trial.

Fasting prior to surgery can cause dehydration and alter hemodynamics. This study aimed to determine the impact of a carbohydrate-enriched drink (NutriciaTM Pre-op®) on selected hemodynamical parameters, measured in a non-invasive manner. We enrolled 100 healthy volunteers and measured their weight, height, systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), thoracic fluid content (TFC), thoracic fluid index (TFCI), stroke volume (SV), stroke volume variation (SVV), stroke index (SI), cardiac output (CO), cardiac index (CI), heather index (HI), systolic time ration (STR), systemic time ratio index (STRI), systemic vascular resistance (SVR), and systemic vascular resistance index (SVRI) by a Niccomo™ device, implementing the impedance cardiography (ICG) method. Measurements were performed at the beginning of the study, and after 10 h and 12 h. We randomly allocated participants to the control group and the pre-op group. The pre-op group received 400 mL of Nutricia™ preOp®, as suggested in the ERAS guidelines, within 10 h of the study. Student’s t-test or the Mann–Whitney U test were used to compare the two groups, and p < 0.05 was considered significant. We did not observe any changes in hemodynamical parameters, blood pressure, and heart rate between the groups. We have proven that carbohydrate-enriched drink administration did not have a significant impact on the hemodynamical parameters of healthy volunteers.

Bayesian inference of multi-sensors impedance cardiography for detection of aortic dissection

PurposeThis paper aims to introduce a non-invasive and convenient method to detect a life-threatening disease called aortic dissection. A Bayesian inference based on enhanced multi-sensors impedance cardiography (ICG) method has been applied to classify signals from healthy and sick patients.Design/methodology/approachA 3D numerical model consisting of simplified organ geometries is used to simulate the electrical impedance changes in the ICG-relevant domain of the human torso. The Bayesian probability theory is used for detecting an aortic dissection, which provides information about the probabilities for both cases, a dissected and a healthy aorta. Thus, the reliability and the uncertainty of the disease identification are found by this method and may indicate further diagnostic clarification.FindingsThe Bayesian classification shows that the enhanced multi-sensors ICG is more reliable in detecting aortic dissection than conventional ICG. Bayesian probability theory allows a rigorous quantification of all uncertainties to draw reliable conclusions for the medical treatment of aortic dissection.Originality/valueThis paper presents a non-invasive and reliable method based on a numerical simulation that could be beneficial for the medical management of aortic dissection patients. With this method, clinicians would be able to monitor the patient’s status and make better decisions in the treatment procedure of each patient.

Dual impedance cardiography: An inexpensive and reliable method to assess arterial stiffness.

Pulse wave velocity (PWV) is a common measure of arterial stiffness. Non-invasive methods to measure PWV are widely used in biomedical studies of aging and cardiovascular disease, but they are rarely used in psychophysiology. Barriers to wider use include the prohibitive costs of specialized equipment and need for trained technicians (e.g., ultrasonographers). Here, we describe an impedance cardiography method to measure PWV. By this method, impedance signals are dually collected from the thorax and calf. Combined with ensemble averaging of vascular signals, this dual impedance cardiography (d-ICG) method allows for the measurement of aortic flow onset and the arrival time of peripheral pulse waveforms to compute PWV. In a community sample of adults (aged 19-78years), PWV measured with d-ICG exhibited a strong positive correlation with age. Moreover, age-specific mean PWV values were within the normative reference intervals established by large scale studies using other techniques. PWV derived from d-ICG exhibited high test-retest reliability across several days, as well as excellent inter-rater reliability. Last, PWV exhibited expected associations with known cardiovascular disease risk factors and indicators of autonomic cardiovascular control. d-ICG is an inexpensive and reliable method to assess arterial stiffness.

Automatic diagnosis of valvular heart diseases by impedance cardiography signal processing

Valvular heart diseases (VHDs) are an abnormal activity of the heart caused by a damage of one of the four heart valves. The impedance cardiography (ICG) is a non-invasive method employed to identify and classify the heart abnormalities. Despite its importance, there are not many works in scientific literature that use the ICG method in order to diagnose VHDs. Therefore, this paper deals with the ICG signal processing for the classification of normal (N) and various VHDs classes of heartbeats. In this work, six types of heartbeat classes of VHD are used, namely: aortic insufficiency (AOI), aortic stenosis (AOS), aortic disease (AOD), mitral disease (MD), mitral-aortic heart disease (MAOHD) and tricuspid insufficiency + mitral disease (TI + MD). The classification of these heartbeat classes is performed using a combination among statistical, morphological and spectral features. For each ICG heartbeat, the statistical features (median, mean, standard deviation, kurtosis, skewness, central moment and Shannon entropy) are computed from the first four intrinsic mode functions (IMFs) calculated using the empirical mode decomposition (EMD) technique. These statistical features are subjected to principal component analysis (PCA) to reduce the dimensionality. Then, the morphological features are extracted by calculating maximums and minimums of the peaks existing in the ICG heartbeat signal and determining the intervals which separate these peaks. Besides, the spectral features are calculated from the first three harmonics of each heartbeat ICG spectrum. From these three types of features, we selected the most significant of them by applying the analysis of variance (ANOVA) test. In order to obtain the best classification performance, three combination of the selected features are investigated and tested using the decision tree (DT), the random forest (RF) and the support vector machine (SVM) classifiers: i) spectral + morphological, ii) statistical + morphological, iii) statistical + morphological + spectral. The achieved results showed that the use of the third combination of features coupled with the RF classifier gave the highest overall accuracy of 96.34 %, average class-accuracy of 98.95 %, average specificity of 99.38 %, average positive predictivity of 96.73 % and average negative predictivity of 99.44 % using 10-fold cross validation. Thus, our developed method seems robust and very efficient for automatic detection of normal and VHDs ICG classes.

Non-invasive assessment of haemodynamic parameters in patients after Fontan procedure.

Single ventricle anomaly is one of the complex congenital heart defects. A dependable non-invasive method of evaluation of Fontan circulation haemodynamics for early diagnosing unstable patients is hardly available in routine clinical practice. The aim of the study is non-invasive evaluation of the haemodynamic parameters in patients after Fontan operation. The study involved 11 participants (age 24.4±4.3 years) with functionally univentricular hearts after Fontan operation. Evaluation of haemodynamic parameters was performed in supine and sitting positions using the impedance cardiography method. In comparative analysis, heart rate (70.1 vs.78.3 1/min; p=0.001), diastolic blood pressure (73.9 vs. 76.7 mm Hg; p=0.026), mean arterial blood pressure (84.5 vs. 88.0 mm Hg; p=0.013), systemic vascular resistance (1284.8 vs. 1334.9 dyn*s*cm-5; p=0.024), systemic vascular resistance index (2178.7 vs. 2272.8 dyn*s*cm-5*m2 ; p=0.018), pre-ejection period (124.2 vs. 136.2 ms; p=0.009), systolic time ratio (0.43 vs. 0.53; p=0.0001), and Zo (26.2 vs. 28.7 Ω; p<0.00001), were significantly higher in the sitting position. Stroke volume (75.4 vs. 68.5 ml; p=0.013), stroke index (42.7 vs. 39.0 ml*m-2; p=0.014), thoracic fluid content (38.5 vs. 35.4 1*kΩ-1; p=<0.00001), thoracic fluid content index (22.8 vs. 21.0 1*kΩ-1*m-2; p=<0.00001), and leftventricular ejection time 291.1 vs. 260.1 ms; p <0.00001, were significantly higher in the supine position. In patients after Fontan procedure, impedance cardiography can be a useful tool the assessment of shortterm haemodynamic changes provoked by postural changes. Its clinical value in patients with congenital heart defects should be further investigated.

Associations of Uncoupling Protein 2 Ala55Val and Uncoupling Protein 3-55C/T Polymorphisms with Heart Rate Variability in Young Oarsmen-a Pilot Study

Background: Human heredity is known to determine about 50% of heart rate variability (HRV) based on a twin study; however, genetic polymorphisms causing increased HRV in athletes are not known. Objectives: This article is aimed at studying the associations of uncoupling protein 2 (UCP2) Ala55Val (rs660339) and UCP3-55C/T (rs1800849) polymorphisms with heart rate variability (HRV) in trained oarsmen. Methods: HRV indices (standard deviations of NN intervals (SDNN), root mean square of successive differences (RMSSD), HF, LF, VLF), stroke index and cardiac index of the young oarsmen (age 17.6 ± 1.6 years old, n = 23) were determined by impedance cardiography method in the supine and standing positions. The maximum oxygen consumption (VO2max) was examined with a rower ergometer by means of a gas analyzer. Polymorphisms of the UCP2 Ala55Val and the UCP3-55T/C were genotyped by polymerase chain reaction (PCR) method and length analysis of restriction products. Results: It was found that both polymorphisms were not associated with VO2max. The UCP2 Val/Val genotype compared to the combined variant (Ala/Ala + Ala/Val) containing the 55 Ala allele, as well as the UCP3 T/T genotype compared to the combined variant (C/T + C/C) containing the -55C allele were associated with low HR and increased HRV: SDNN, RMSSD and HF vagal indices in the supine position. Moreover, the athletes with the UCP3-55T/T genotype had a pronounced increase in heart rate (ANOVA, P < 0.001) and a decrease in stroke index (ANOVA, P = 0.005) in response to active orthostasis compared to C/T and C/C genotypes. Conclusions: The UCP2 Val/Val and the UCP3 T/T genotypes may be genetic markers of increased HRV in the highly trained athletes, suggesting an influence of these UCP2/UCP3 polymorphisms on autonomic cardiovascular regulation.

Effect of individualised physical rehabilitation programmes on the functional state of the cardiovascular system in women with post-mastectomy syndrome

Background/Aims The purpose of this study was to determine the effectiveness of individualised physical rehabilitation programmes aimed at improving cardiovascular function in women with post-mastectomy syndrome. Methods The following methods were applied: theoretical analysis of scientific and methodologic literature data, impedance cardiography, and mathematical statistical methods. A total of 115 women with late symptoms of post-mastectomy syndrome who completed the interventions were included in this study. The participants were randomly enrolled into three groups for the first individualised programme (Group 1, n=45), for the second individualised programme (Group 2, n=40) and for the third individualised programme (Group 3, n=30). The first programme included aqua aerobics (aqua jogging, aqua building, aqua stretching), conditional swimming and recreational aerobics; the second programme included conditional swimming and Pilates exercises; the third programme included yoga-based exercises and stretching. The study was conducted during the ambulatory rehabilitation stage and lasted for 12 months. Results It was found that most of the investigated hemodynamic parameters in all groups steadily improved during the year of rehabilitation. The average values of stroke volume, cardiac output, left ventricular work, left ventricular power after 12 months of rehabilitation were statistically better (P&lt;0.05) in the first main group compared with the second and third main groups. Conclusions Individualised programmes of physical rehabilitation were effective in improvement of cardiovascular function of all studied patients with post-mastectomy syndrome.

Cardiovascular Responses to Selected Cranial Osteopathic Manipulations in Hypertensive Patients

Background and PurposeOsteopathic cranial manipulations (CM) have been used as a part of therapeutic management of hypertensive patients. However, our knowledge about physiological responses to CM in cardiac patients is limited. A quantitative relationship between applied CM and cardiovascular parameters has not been well established. The purpose of this study was to measure changes in heart rate, autonomic input to the heart by using the heart rate variability test, cardiac contractility by using impedance cardiography, and systemic blood pressure in response to selected CM, namely occipital‐atlantal decompression, occipital‐mastoid decompression, and compression of the fourth ventricle.MethodHypertensive 65–75 year old subjects, three men and two women, were involved in this study. Hypertension was controlled by an angiotensin‐converting enzyme inhibitor (3 subjects), calcium channels blocker (1 subject) and beta‐blocker (1 subject). Each subject participated in the experimental (CM) and control (sham) groups. A non‐invasive impedance cardiography method was used to measure changes in cardiac parameters before and after manipulations. Data were recorded and analyzed using BIOPAC Systems, Inc. equipment and software. Blood pressure was measured before and after manipulations by using a sphygmomanometer. All manipulations were performed by the same osteopathic physician.ResultsCranial and sham manipulations resulted in different responses by the subjects. CM produced a decrease in systolic (5%) and mean arterial (6%) pressures, and revealed a trend towards an increase in sympathetic and decrease in parasympathetic cardiac activity based on heart rate variability test. Sham manipulations did not affect blood pressure and were associated with a trend towards a decrease in sympathetic and increase in parasympathetic cardiac activity. No changes in cardiac contractility were recorded for CM and sham manipulations.Discussion and conclusionIt appears that cranial manipulations may enhance the antihypertensive effect of medication through the effect on autonomic nervous system. The physiological effect of CM on autonomic control of systemic hemodynamics needs further investigation.Support or Funding InformationThis project was funded by the TUN Research Grant AwardThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Perkütan Mitral Balon Valvuloplastinin Etkinliğini Değerlendirmede Empedans Kardiyografinin Kullanımı

Objective: Impedance Cardiography (ICG) method, facilitates measuring hemodynamic parameters indirectly by recording thoracic impedance variations induced by cyclic changes in blood flow. The aim of this study is to evaluate alterations in hemodynamic parameters obtained by impedance cardiography (ICG) in addition to conventional echocardiographic and catheterization data after percutaneous mitral balloon valvuloplasty (PMBV). Material and Methods: 18 patients with severe rheumatic mitral stenosis to whom PMBV had been performed were included in this study. Impedance cardiographic measurements were performed in addition to routine echocardiographic examination and invasive left atrial and pulmonary arterial pressure recordings before and after the procedure. Cardiac output was calculated with direct Fick method before PMBV. Average values of several measurements were used to obtain the most accurate results for atrial fibrillation patients in the study group. Results: Following successful PMBV, in impedance cardiographic evaluation an increase in cardiac output (4.69±1.46 and 5.68±1.3 l/min, before and after PMBV, respectively, p<0.001) and cardiac index (2.72±0.81 and 3.29±0.73 l/min/m2, before and after PMBV, respectively, p<0.001) an evident prolongation in ejection period (246.8±40.3 and 275.2±32.1 msec, before and after PMBV, respectively, p<0.001); and a statistically significant reduction in pre-ejection period (103.7±41.8 and 82.7±16.8 msec, before and after PMBV, respectively, p=0.033), and thoracic fluid content (34.3±11.2 and 27.7±5.31/kΩ, before and after PMBV, respectively, p=0.037) was observed. There was a strong correlation between preprocedural cardiac output calculations of ICG and direct Fick method (r:0.89, p<0.001). Conclusion: In addition to the conventional methods, serial recordings of impedance cardiographic outputs may yield beneficial information for the assessment of PMBV efficacy. As a non-invasive and easily applicable method, it might be utilized during in-hospital follow-up.

Cardiac responses to selected cranial osteopathic manipulations in healthy young men (LB656)

Background and Purpose: Cranial manipulations (CM) as a part of osteopathic manipulative treatment have been used to treat patients. However, physiological responses to CM are not well defined in literature. The purpose of this study was to measure changes in heart rate (HR), heart rate variability (HRV), stroke volume index (SI), and cardiac index (CI) in response to selected CM and sham manipulation.Method: Healthy 25‐35 year old men participated in this study. Non‐invasive impedance cardiography method was used to measure changes in cardiac parameters before and after manipulations. Data were recorded and analyzed using BIOPAC Systems, Inc. equipment and software. All manipulations were performed by the same osteopathic physician.Results: CM increased parasympathetic input (70%) to the heart resulting in decreased HR (5%) and CI (7%) without significant effect on SI. These changes were not seen in sham manipulation.Conclusion: Selected CM decreased CI by decreasing HR without significant effect on cardiac contractility in healthy young men. Future studies will compare gender and age differences in response to osteopathic techniques.Grant Funding Source: This project was funded by the TUN Research Grant Award

COMPARISON OF NON-INVASIVE CARDIAC OUTPUT MEASUREMENT USING INDIGENOUS IMPEDANCE CARDIOGRAPHY (ICG) WITH INVASIVE FICK METHOD

Introduction: Cardiac output (CO) is a functional tool to evaluate the cardiovascular performance. To estimate CO, several invasive methods like the Fick method and thermodilution method are available which require catheterization of the patient. Impedance cardiography (ICG) is well-established noninvasive technique for measurement of cardiac output. The cardiac output monitor based on ICG has been indigenously designed and developed by Bhabha Atomic Research Center, Mumbai. For validatation of this indigenous equipment, we compared measurement of cardiac output using ICG with conventional Fick method. Materials and methods : We simultaneously measured cardiac output in 10 patients (mean age 40 years, range 21-54 years, 6 males and 4 females) using impedance cardiography versus that derived after utilization of Ficks principle in cardiac catheterization laboratory patients undergoing cardiac catheterization. We compared the cardiac indices obtained by two methods. Results: There is a very good correlation (r=0.9, for n=10) between the cardiac index obtained by impedance cardiography and that derived invasively after cardiac catheterization using the Fick method. The mean values of cardiac indices by ICG method and the Fick method were 3.80.6 l/min/m 2 and 2.90.5 l/min/m 2 respectively. The average bias from the ICG to Fick is 0.8 l/min/m 2 whereas individual variability is 0.3 l/min/m 2 . Conclusion: These results support use of this indigenous ICG equipment in patient care for monitoring cardiac output measurement with the further validation.

Clinical evaluation of a new tracheal impedance cardiography method

Non-invasive cardiac output measurement by means of impedance cardiography has been evaluated before, and agreement with other methods has been variable. We decided to study a newly developed tracheal impedance device, that is claimed to be more accurate and reliable. This incorporates new software and mathematical formulae, that are designed to reduce signal noise from diathermy, leading to improved accuracy. In 25 cardiothoracic surgery patients, simultaneous measurements were performed using both pulmonary artery thermodilution and the tracheal impedance device, at five peri-operative time points: before skin incision; after weaning from cardiopulmonary bypass; after sternal closure; and 30 min and 2 h after arrival in the intensive care unit. Mean cardiac output, bias and 95% limits of agreement were 5.3, 0.03 and -2.8 to 2.8 l.min(-1) , respectively. Tracheal impedance showed good correlation with measurement trends using thermodilution in 88% of measurements, with a mean (95% limit of agreement) angular bias of -9.0° (-83.3 to 65.3°). However, the wide limits of agreement and high percentage error of 53% that were apparent in this study mean that, in its present guise, tracheal impedance is not an acceptable alternative to thermodilution in cardiac surgical patients.

P-51 Clinical evaluation of a new endotracheal impedance cardiography method

P-51 Clinical evaluation of a new endotracheal impedance cardiography method

The Effect of Trendelenburg Position, Lactated Ringer’s Solution and 6% Hydroxyethyl Starch Solution on Cardiac Output After Spinal Anesthesia

The aim of our study was to evaluate the effects of Trendelenburg position, infusion of 6% hydroxyetyl starch solution or lactated Ringer's solution on changes in cardiac output (CO) after spinal anesthesia in patients older than 50 yr. Seventy patients scheduled for lower extremity orthopedic surgery under spinal anesthesia were allocated randomly to one of the three treatment groups. In the Trendelenburg group, the patients were placed in the Trendelenburg position immediately after the spinal block for 10 min. In the hydroxyethyl starch group and the lactated Ringer's group, the patients received an infusion of 500 mL of 6% hydroxyethyl starch solution or 1000 mL of lactated Ringer's solution over 20 min after the spinal block. CO was measured continuously from 15 min before until 30 min after spinal anesthesia using the impedance cardiography method and arterial blood pressure with an automated device. P < 0.05 was considered statistically significant. The differences among treatment groups in CO were not statistically significant. Differences in the CO changes from baseline over time were significant. In the Trendelenburg group, CO did not change while the patient was in the Trendelenburg position. In the hydroxyethyl starch group, CO increased significantly after the block and remained significantly increased until the end of measurements. In the lactated Ringer's group, CO increased significantly 10 and 20 min after the block but, after stopping the infusion, CO started to decrease. Our study demonstrated that a decrease in CO after spinal anesthesia is prevented by placing the patient in the Trendelenburg position, or infusion of either lactated Ringer's solution or 6% hydroxyetyl starch solution. Although the effects of the infusion of the lactated Ringer's solution are transient, the effects of the infusion of 6% hydroxyethyl starch solution are extended beyond the time the infusion.

Therapeutic Optimization of Atrioventricular Delay in Cardiosurgical ICU Patients by Noninvasive Cardiac Output Measurements versus Pulse Contour Analysis

Optimizing atrioventricular (AV) delay improves cardiac output and postoperative outcome. Impedance cardiography (ICG) is a non-invasive method for CO measurement. This study evaluates the ability of two ICG methods to determine the optimal AV delay (OAVD) and to compare ICG with invasive PICCO measurements. In 14 cardiosurgical ICU patients (age 70.4 +/- 12.0 yrs) with temporary pacing wires, OAVD was determined by pulse contour analysis (PICCO) and ICG (conventional ICG [CI] and electrical velocimetry [EV] ICG monitors). Cardiac output (CO) and stroke volume (SV) were measured during DDD pacing with AVD varying from 70 to 270 ms in 20-ms increments. Measured OAV showed a linear correlation between PICCO and ICG: CI (r = 0.82, P < 0.0002) and EV (r = 0.84, P < 0.0002). The mean OAVD deviation between PICCO and ICG was 15.7 +/- 21.0 ms (CI) and 17.1 +/- 20.5 ms (EV). Hemodynamic parameters (SV increase OAVD against worst case) improved significantly (+ 11.7 +/- 7.2 %, P < 0.0001). Inappropriate selection of AVD can compromise the hemodynamic situation of cardiosurgical patients. As it is totally noninvasive, ICG is a reliable and effective tool for tailoring AVD. Both systems (CI and EV) offer valid OAV determination.