Desarrollo de un modelo por inteligencia artificial con hemodinamia no invasiva para predecir preeclampsia en embarazos de alto riesgo / Artificial Intelligence Modeling with Non-Invasive Hemodynamics to Predict Preeclampsia in High-Risk Pregnancy

RESUMEN Introducción: la preeclampsia (PE) es la principal causa de morbimortalidad materno-fetal en nuestro país. Alteraciones hemodinámicas precoces durante el embarazo podrían predecir la evolución a PE. El machine learning (ML) permite el hallazgo de patrones ocultos que podrían detectar precozmente el desarrollo de PE. Objetivos: desarrollar un árbol de clasificación con variables de hemodinamia no invasiva para predecir precozmente desarrollo de PE. Material y métodos: estudio observacional prospectivo con embarazadas de alto riesgo (n=1155) derivadas del servicio de Obstetricia desde enero 2016 a octubre 2022 para el muestreo de entrenamiento por ML con árbol de clasificación j48. Se seleccionaron 112 embarazadas entre semanas 10 a 16, sin tratamiento farmacológico y que completaron el seguimiento con el término de su embarazo con evento final combinado (PE): preeclampsia, eclampsia y síndrome HELLP. Se evaluaron simultáneamente con cardiografía de impedancia y velocidad de onda del pulso y con monitoreo ambulatorio de presión arterial de 24 hs (MAPA). Resultados: presentaron PE 17 pacientes (15,18%). Se generó un árbol de clasificación predictivo con las siguientes variables: índice de complacencia arterial (ICA), índice cardíaco (IC), índice de trabajo sistólico (ITS), cociente de tiempos eyectivos (CTE), índice de Heather (IH). Se clasificaron correctamente el 93,75%; coeficiente Kappa 0,70, valor predictivo positivo (VPP) 0,94 y negativo (VPN) 0,35. Precisión 0,94, área bajo la curva ROC 0,93. Conclusión: las variables ICA, IC, ITS, CTE e IH predijeron en nuestra muestra el desarrollo de PE con excelente discriminación y precisión, de forma precoz, no invasiva, segura y con bajo costo.

ABSTRACT Background: Preeclampsia (PE) is the main cause of maternal-fetal morbidity and mortality in our country. Early hemodynamic changes during pregnancy could predict progression to PE. Machine learning (ML) enables the discovery of hidden patterns that could early detect PE development. Objectives: The aim of this study was to build a classification tree with non-invasive hemodynamic variables for the early prediction of PE occurrence. Results: Seventeen patients (15.18%) presented PE. A predictive classification tree was generated with arterial compliance index (ACI), cardiac index (CI), cardiac work index (CWI), ejective time ratio (ETR), and Heather index (HI). A total of 93.75% patients were correctly classified (Kappa 0.70, positive predictive value 0.94 and negative predictive value 0.35; accuracy 0.94, and area under the ROC curve 0.93). Conclusion: ACI, CI, CWI, ETR and HI variables predicted the early development of PE in our sample with excellent discrimination and accuracy, non-invasively, safely and at low cost.

Avaliação Cardiodinâmica Não Invasiva por Cardiografia de Impedância durante o Teste de Caminhada de Seis Minutos em Pacientes com Insuficiência Cardíaca / Non-Invasive Assessment of Cardiodynamics by Impedance Cardiography during the Six-Minute Walk Test in Patients with Heart Failure

Resumo Fundamento O Teste de Caminhada de seis Minutos (TC6M) é comumente usado para avaliar pacientes com insuficiência cardíaca. No entanto, vários fatores clínicos podem influenciar a distância percorrida pelos pacientes no teste. A cardiografia de impedância (CI) na avaliação morfológica é uma ferramenta útil para avaliar a hemodinâmica cardíaca de maneira não invasiva. Objetivo Este estudo teve como objetivo comparar as respostas de aceleração e desaceleração do Débito Cardíaco (DC), da Frequência Cardíaca (FC), e do Volume Sistólico (VS) ao TC6M de indivíduos com insuficiência cardíaca e fração de ejeção reduzida (ICFEr) com as de controles sadios. Métodos Este é um estudo transversal observacional. O DC, a FC, o VS e o Índice Cardíaco (IC) foram avaliados antes, durante e após o TC6M por CI. O nível de significância adotado na análise estatística foi 5%. Resultados Foram incluídos 27 participantes (13 com ICFEr e 14 controles sadios). A aceleração do DC e da FC foi significativamente diferente entre os grupos (p<0,01 e p=0,039, respectivamente). Encontramos diferenças significativas no VS, no DC e no IC entre os grupos (p<0,01). A regressão linear mostrou uma contribuição deficiente do VS à mudança no DC no grupo com ICFEr (22,9% versus 57,4%). Conclusão O principal resultado deste estudo foi o fato de que indivíduos com ICFEr apresentaram valores mais baixos de aceleração do DC e da FC durante o teste de exercício submáximo em comparação a controles sadios. Isso pode indicar um desequilíbrio na resposta autonômica ao exercício nessa condição.

Abstract Background The six-minute walk test (6MWT) is commonly used to evaluate heart failure (HF) patients. However, several clinical factors can influence the distance walked in the test. Signal-morphology impedance cardiography (SM-ICG) is a useful tool to noninvasively assess hemodynamics. Objective This study aimed to compare cardiac output (CO), heart rate (HR), and stroke volume (SV) acceleration and deceleration responses to 6MWT in individuals with HF and reduced ejection fraction (HFrEF) and healthy controls. Methods This is a cross-sectional observational study. CO, HR, SV and cardiac index (CI) were evaluated before, during, and after the 6MWT assessed by SM-ICG. The level of significance adopted in the statistical analysis was 5%. Results Twenty-seven participants were included (13 HFrEF and 14 healthy controls). CO and HR acceleration significantly differed between groups (p<0.01; p=0.039, respectively). We found significant differences in SV, CO and CI between groups (p<0.01). Linear regression showed an impaired SV contribution to CO change in HFrEF group (22.9% versus 57.4%). Conclusion The main finding of the study was that individuals with HFrEF showed lower CO and HR acceleration values during the submaximal exercise test compared to healthy controls. This may indicate an imbalance in the autonomic response to exercise in this condition.

Comparative Study of Cardiac Output Measurement by Regional Impedance Cardiography and Thermodilution Method in Patients Undergoing off Pump Coronary Artery Bypass Graft Surgery

Background:An ideal CO monitor should be noninvasive, cost effective, reproducible, reliable during various physiological states. Limited literature is available regarding the noninvasive CO monitoring in open chest surgeries. Aim: The aim of this study was to compare the CO measurement by Regional Impedance Cardiography (RIC) and Thermodilution (TD) method in patients undergoing off pump coronary artery bypass graft surgery (OPCAB). Settings and Design: We conducted a prospective observational comparative study of CO measurement by the noninvasive RIC method using the NICaSHemodynamicNavigator systemand the gold standardTDmethod using pulmonary artery catheterin patients undergoingOPCAB.Atotal of 150 data pair from the two CO monitoring techniques were taken from 15 patients between 40-70 years at various predefined time intervals of the surgery. Patients and Methods: We have tried to find out the accuracy, precision and cost effectiveness of the newer RIC technique. Mean CO, bias and precision were compared for each pair i.e.TD-CO and RIC-CO as recommended by Bland and Altman.The Sensitivity and specificity of cutoff value to predict change in TD-CO was used to create a Receiver operating characteristic or ROC curve. Results: Mean TD-CO values were around 4.52 ± 1.09 L/min, while mean RIC- CO values were around 4.77± 1.84 L/min. The difference in CO change was found to be statistically not significant (p value 0.667). The bias was small (-0.25). The Bland Altman plot revealed a mean difference of -0.25 litres.The RIC method had a sensitivity of 55.56 % and specificity of 33.33 % in predicting 15% change in CO of TD method and the total diagnostic accuracy was 46.67%. Conclusion: A fair correlation was found between the two techniques. The RIC method may be considered as a promising noninvasive, potentially low cost alternative to the TD technique of hemodynamic measurement.

Correlation between Three Methods of Blood Pressure Measurement (Impedance Cardiography, Sphygmomanometry, and Invasive Methods)

Aims and Objectives: The aims of the study were to find out the correlation between three methods of blood pressure (BP) measurement with impedance cardiography (ICG) device, conventional non-invasive sphygmomanometer, and cath lab-based invasive arterial pressure (AP) study. Patients Materials and Methods: Patients who had definite indications for coronary angiography (CAG) or coronary intervention due to cardiac reasons were selected for the measurement of BP by three methods, namely, by transducer-based invasive central aortic pressure study, by ICG, and by conventional sphygmomanometry. One hundred patients of acute myocardial infarction having chest pain, ST elevation in two or more contiguous leads of electrocardiogram (ECG), biomarker positivity, and echocardiographic evidence of regional wall motion abnormality were selected. Transfemoral or radial access of the ascending aorta allowed the measurement of central aortic pressure during invasive procedure. CAG was done in the cath lab having “Siemens™ Axiom Artis Zee (floor)” equipment. The subjects who were unwilling to participate, who were moribund, critically ill subjects, and patients with concomitant heart failure, arrhythmia, and valvular lesions were excluded from the study. GE™ Vivid 7 Dimension machine was used for ECG-gated echo-Doppler studies. ICG-derived BP values (systolic BP [SBP], diastolic BP [DBP], mean AP [MAP], and pulse pressure) were recorded for comparison with similar pressure data obtained from two other methods. Results and Analysis: Analysis of results show a comparison of data on SBP, DBP, and MAP measured by three methods by sphygmomanometry, invasive, and ICG methods. The analysis also shows the values of correlation coefficients – all of which are significantly positive correlations. ICG has been found to have positive correlation with both sphygmomanometric and invasive methods of BP measurement. It also shows a graphical presentation of the correlation between SBP, DBP, and MAP measured by three methods by sphygmomanometry, invasive, and ICG methods. Conclusion: There is a significant correlation between three methods of BP measurement with ICG device, conventional noninvasive sphygmomanometer-based method, and cath lab-based invasive AP study

Correlation between Coronary Angiography and Impedance Cardiography

Aims and Objectives: The aims of the study were to find out the correlation between coronary angiographic findings and hemodynamic parameters derived from impedance cardiography (ICG) and echo-Doppler study. Patients, Materials and Methods: A total of 200 patients of acute myocardial infarction having chest pain, ST elevation in two or more contiguous leads of electrocardiogram (ECG), biomarker positivity, echocardiographic evidence of regional wall motion abnormality (RWMA), and coronary angiographic evidence of coronary lesions were recruited. Subjects unwilling to participate, moribund, critically ill subjects, and patients with concomitant heart failure, arrhythmia, and valvular lesions were excluded from the study. GE™ Vivid 7 Dimension machine was used for ECG-gated echo-Doppler studies. The left ventricular ejection fraction (LVEF), stroke volume (SV), RWMA, diastolic function, etc., were observed. ICG measured LVEDV, LVESV, LVEF, and other parameters particularly amplitudes of the different waves. Coronary angiography (CAG) was done in the Cath Lab having “Siemens™ Axiom Artis Zee (floor)” equipment. Results and Analysis: Results-analysis revealed there is negative correlation (Pearson’s correlation coefficient, r = −0.8) between augmentation pressure and coronary angiographic stenosis percentage and P value is also significant (P = 0.034). Pulse pressure (PP) also is positively correlated (r = −0.78) with coronary angiographic stenosis percentage and P value is also significant (P = 0.027). There is a negative correlation (r = −0.259) between augmentation index (AIx) and coronary angiographic lesions and that is statistically significant (P = 0.03). Conclusion: There is a positive correlation between ICG -derived hemodynamic parameters and the percentage stenosis of coronary arteries. Rise of augmentation pressure and PP in the ICG waveform is associated with coronary artery disease severity. AIx is negatively correlated with severity of coronary arterial stenosis

Accuracy and Efficacy of Impedance Cardiography as a Non-Invasive Cardiac Function Monitor

PURPOSE: The most common method of monitoring cardiac output (CO) is thermodilution using pulmonary artery catheter (PAC), but this method is associated with complications. Impedance cardiography (ICG) is a non-invasive CO monitoring technique. This study compared the accuracy and efficacy of ICG as a non-invasive cardiac function monitoring technique to those of thermodilution and arterial pressure contour. MATERIALS AND METHODS: Sixteen patients undergoing liver transplantation were included. Cardiac index (CI) was measured by thermodilution using PAC, arterial waveform analysis, and ICG simultaneously in each patient. Statistical analysis was performed using intraclass correlation coefficient (ICC) and Bland-Altman analysis to assess the degree of agreement. RESULTS: The difference by thermodilution and ICG was 1.13 L/min/m², and the limits of agreement were −0.93 and 3.20 L/min/m². The difference by thermodilution and arterial pressure contour was 0.62 L/min/m², and the limits of agreement were −1.43 and 2.67 L/min/m². The difference by arterial pressure contour and ICG was 0.50 L/min/m², and the limits of agreement were −1.32 and 2.32 L/min/m². All three percentage errors exceeded the 30% limit of acceptance. Substantial agreement was observed between CI of thermodilution with PAC and ICG at preanhepatic and anhepatic phases, as well as between CI of thermodilution and arterial waveform analysis at preanhepatic phase. Others showed moderate agreement. CONCLUSION: Although neither method was clinically equivalent to thermodilution, ICG showed more substantial correlation with thermodilution method than with arterial waveform analysis. As a non-invasive cardiac function monitor, ICG would likely require further studies in other settings.

Evaluation of volume overload in critical patients by monitoring change of cardiac output under bed head raising combined with passive leg raising / 中华危重病急救医学

Objective To investigate whether the change of cardiac output (CO) with bed head raising (BHR) combined with passive leg raising (PLR) can be used to assess volume overload in critical patients.Methods A prospective observational diagnostic trial was designed. The patients who underwent fluid resuscitation 6 hours or more, and admitted to intensive care unit (ICU) of Meizhou People's Hospital in Guangdong Province from January to December in 2016 were enrolled. Volume overload were identified with the criteria including the increasing of pulmonary rales, the higher levels of N-terminal brain natriuretic peptide (NT-proBNP) and new pulmonary exudates in chest radiograph. CO and heart rate (HR) were monitored with impedance cardiography at supine position and BHR by 30°(BHR30), 60° (BHR60), and PLR in all patients. The changes of CO (?CO30,?CO60,?COPLR) and HR (?HR30,?HR60,?HRPLR) were calculated at different positions. The receiver operating characteristic curve (ROC) was used to evaluate the predictive values of?CO30,?CO60 and combination of?CO60 and?COPLR on volume overload.Results A total of 62 patients were enrolled in this study, with 44 males and 18 females, age of (58.9±15.9) years, a body mass index of (22.7±2.4) kg/m2, and an acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) score of 18.7±4.4. The CO of 32 patients with volume overload was significantly increased at BHR30 or BHR60 compared with supine position [?CO30 was (14.5±11.5)%,?CO60 was (26.9±17.5)%, bothP 0.05). There was no consistent change of CO at BHR30 or BHR60 compared with supine position in 30 patients without volume overload,?CO30 was (-3.4±9.1)% (P 0.05), while CO was significantly increased after PLR,?COPLR was (12.4±11.3)% (P < 0.01). There was no significant change of HR after BHR and PLR in patients with volume overload and non volume overload. ROC curve showed that when the cut-off value of ΔCO30≥3.3%, the area under ROC curve (AUC) was 0.903±0.039, the sensitivity was 90.6%, the specificity was 80.0%, and the accuracy was 85.5% for predicting volume overload; when the cut-off value of ΔCO60≥5.6%, the AUC was 0.911±0.036, the sensitivity was 96.9%, the specificity was 73.3%, and the accuracy was 85.5% for predicting volume overload. If volume overload was assessed by the increase of ΔCO60 combining with the decrease of ΔCOPLR, the AUC was 0.928±0.034, the optimal cut-off value for the new combined predictive indicator in predicting volume overload was -0.008, and the sensitivity, specificity, accuracy was 96.9%, 83.3%, 90.3%, respectively, and its evaluation effect is better than the use of ΔCO30 or ΔCO60 alone.Conclusion The change of CO with BHR combined with PLR can be used to accurately evaluate volume overload in patient with critically illness.

Adaptation of heart to training A comparative study using echocardiography & impedance cardiography in male & female athletes.

Background & objectives: Intensive regular physical exercise training is associated with a physiological changes in left ventricular (LV) morphology and functions. This cardiac remodeling observed in the athletes is associated with the specific haemodynamic requirements of the exercise undertaken. The main objective of this study is to evaluate the effect of endurance training on cardiac morphology, systolic and diastolic LV functions and haemodynamic parameters both in male and female athletes. Methods: Seventy nine healthy athletes (age 20.0 ± 2.6 yr; 49% male) and 82 healthy sedentary adolescent (age 20.8 ± 2.2 yr, 49% male) volunteered to participate in this study. All subjects underwent transthoracic echocardiography and impedance cardiography. Results: Both female and male athletes had greater LV end-diastolic cavity sizes, LV mass and stroke volume (SV) values when compared with controls. Also, in male athletes, LV mass index was higher than in female athletes. While male athletes had lower resting heart rate compared to female athletes, they had higher mean arterial blood pressure. In male athletes, basal septal and mid septal strain values were higher compared to controls. There were no significant differences in strain and peak systolic strain rate values between female athletes and controls. In male athletes, there was a weak positive correlation between SV and LV mass, basal lateral and septal strain values. In female athletes, only a weak positive correlation was found between SV and basal septal strain values. Interpretation & conclusions: Endurance-trained male and female athletes had higher LV mass, LV cavity dimensions and SV compared to sedentary controls. Although there was no difference in diastolic cardiac functions between athletes and controls, local enhanced systolic function was found with increase of SV. Both morphologic and haemodynamic differences were more evident in male athletes.

The Changes of Noninvasive Hemodynamic Parameters after Device-Guided Slow Breathing Exercise in Hypertensive Patients

BACKGROUND: The device-guided breathing (DGB) exercise is a non-pharmacological treatment of high blood pressure (BP). Changes in hemodynamic variables after DGB remain to be defined. This study evaluated the hemodynamic effects of DGB in hypertensive patients. METHODS: Fifty-nine hypertensive individuals (male, 56%; age, 44 +/- 10 years) with systolic BP (SBP) in the range of 140 to169 mm Hg and diastolic BP (DBP) < 105 mm Hg were divided into two group: control group (n = 17) vs. DGB group (n = 42) who slowed respiratory rate by using 15 minutes daily DBG (RESPeRATE) over 8 weeks. Heart rate, BP and hemodynamic parameters including cardiac index (CI), thoracic fluid content (TFC), systemic vascular resistance index (SVRI) and total arterial compliance index (TACI) were measured using the ICG Monitor (CardioDynamics) at baseline and study end. RESULTS: Baseline characteristics were not different between the two groups. Office BP (SBP/DBP) was reduced from baseline to end value by 13.2 +/- 11.1/6.9 +/- 7.5 mm Hg in DGB group and 2.2 +/- 6.9/0.5 +/- 6.6 mm Hg in control group (p = 0.001, p = 0.004, respectively). Heart rate, CI, stroke index, and TFC were not changed in both groups. However, the SVRI was lower and the TACI was higher in DGB group than control group (SVRI: 2,728 +/- 599 vs. 3,141 +/- 714 dyne sec m2/cm5, p = 0.002; TACI: 0.845 +/- 0.194 vs. 0.761 +/- 0.184 mm Hg/mL/m2, p = 0.041). CONCLUSIONS: Daily device-guided breathing exercise for 8 weeks lowers the BP mediated by reducing the systemic vascular resistance and increasing the total arterial compliance without changes in heart rate and CI.

Evaluación hemodinámica no invasiva con cardiografía de impedancia: aplicaciones en falla cardíaca y en hipertensión arterial / Non-invasive hemodynamic evaluation with impedance cardiography: applications in heart failure and hypertension

La cardiografía de impendancia (CGI) representa un método no invasivo para la evaluación del estado hemodinámico latido a latido. Aunque se introdujo por primera vez hace más de 40 años, la CGI ha mostrado un resurgimiento en la última década, a partir de una serie de estudios clínicos que han demostrado su precisión en la estimación del volumen latido, tanto contra el "gold-standard" invasivo (termodilución), como contra los métodos de referencia no invasivos (ecocardiografía). Diversos estudios demuestran la utilidad de esta técnica en el manejo del paciente con falla cardíaca y en el enfoque diagnóstico y terapéutico de la hipertensión arterial, por lo cual constituyen actualmente dos de las aplicaciones clínicas más importantes de la CGI. En falla cardiaca, los cambios en el volumen de líquido del tórax y del gasto cardíaco evaluados por CGI, han demostrado ser predictores de descompensación aguda, incluso semanas antes del inicio de la sintomatología respiratoria; además, permiten identificar el origen cardiogénico o respiratorio de la disnea cuando el examen físico y los demás paraclínicos no son concluyentes. En los pacientes con hipertensión arterial no controlada o resistente, la CGI permite realizar una mejor caracterización del fenotipo hipertensivo y elegir la estrategia farmacológica más específica para intervenir la alteración hemodinámica predominante (resistencia vascular vs. gasto cardiaco elevado). En este artículo se realiza una revisión de los principios biofísicos de la CGI y su utilidad en la evaluación no invasiva del estado hemodinámico, así como una evaluación crítica de la literatura que da soporte a su aplicación clínica en el tratamiento de la falla cardíaca y la hipertensión arterial.

Impedance cardiography (ICG) represents a non-invasive method for hemodynamic assessment in a beat-to-beat basis. Since its introduction more than forty years ago, a renewed interest in the use of this technique during the last decade has been noticed, mainly as a result of a series of clinical studies showing its precision in the estimation of stroke volume either against invasive gold standard (i.e. thermodilution) or against non-invasive reference methods (i.e. echocardiography). On the other hand, ICG has demonstrated to be useful for the management of heart failure patients and for the diagnostic and therapeutic approach to hypertension, which currently constitute two of the major applications of ICG. In heart failure patients, changes in thoracic fluid content and cardiac output tracked by ICG have shown to be predictors of acute decompensation even weeks before respiratory symptoms appear; also allowing identification of a cardiac vs. respiratory origin of dyspnea when physical examination and laboratory tests are not conclusive. In the particular case of patients with uncontrolled or severe hypertension, ICG makes possible a better characterization of hypertensive phenotype leading to a more specific choice of pharmacological agents to treat the primary hemodynamic alteration (i.e elevated peripheral resistance vs. elevated cardiac output). The present review, provides a review of the biophysical principles of ICG and its precision in measuring stroke volume and present a critical assessment of the literature supporting its clinical application in the management of heart failure and arterial hypertension.

Noninvasive Cardiac Output Measurement in Shock Patients

PURPOSE: Invasive determination of cardiac output (CO) is possible via a pulmonary artery catheter but catheter implantation has risks. Clinicians can assess CO safely using a non-invasive cardiac output device such as a commercially available doppler system (ultrasonic cardiac output monitor, USCOM, USCOM Ltd, Australia) or using impedance cardiography (ICG). The purpose of this study was to investigate the consistency of hemodynamic measurements between ICG and USCOM in shock patients. METHODS: From June 2007 to October 2007, we prospectively evaluated 21 patients with shock, who visited our emergency center. We measured CO and systemic vascular resistance (SVR) using ICG and USCOM on arrival, and at 30, 60, 90, and 120 minutes. RESULTS: The mean difference in CO between ICG and USCOM was 1.08+/-2.13 L/min. The percent limits of agreement (LOA) were -60.0 to 84.7% between ICG and USCOM. The correlation coefficient for CO between ICG and USCOM was 0.76 (p<0.01). CO values measured by ICG and USCOM were 4.3+/-1.7 vs 5.9+/-3.9 initially, 4.8+/-2.2 vs 6.0+/-3.9 at 30 min, 4.3+/-1.6 vs 5.1+/-2.9 at 60 min, 4.2+/-1.6 vs 4.9+/-2.7 at 90 min, and 4.1+/-1.6 vs 5.0+/-2.9 at 120 min, respectively. Statistical significance was observed within each modalities (p=0.03) but we did not find statistical significances between the two modalities. SVR (dynes*sec/cm5) values were measured by ICG and USCOM on arrival, and at 30, 60, 90, and 120 minutes. No statistical significance was seen within and between study groups. CONCLUSION: ICG and USCOM do not show clinically acceptable agreement.

A comparison of hemodynamics in elderly patients that were administered thiopental sodium or propofol to induce general anesthesia / 대한마취과학회지

BACKGROUND: Thiopental sodium and propofol are commonly used to induce anesthesia. This study was conducted to compare the hemodynamic effects of propofol and thiopental sodium during the induction of general anesthesia in elderly patients. METHODS: Forty patients undergoing general anesthesia were randomly divided into two groups. In group T, thiopental sodium was used to induce anesthesia, whereas propofol was used in group P. Hemodynamic changes in the mean blood pressure, heart rate, cardiac index (as determined using a NICCOMO monitor) and bispectral index (BIS) during induction were then compared between the two groups. In addition, the dosage of induction agent, time required until loss of response to verbal order (LOV) and eyelid reflex were compared between groups. RESULTS: The mean blood pressure was significantly lower in group P than in group T during the 1-5 min following LOV and during the 2, 3 min following intubation (P < 0.05). However, the heart rate did not differ significantly between the two groups. The cardiac index also did not differ significantly between groups, except during the first 3 min following LOV. Finally, the BIS value were significantly lower than the baseline values in both groups during induction. CONCLUSIONS: In elderly patients, the heart rate, cardiac index and BIS value did not differ significantly between the two groups. But the mean blood pressure was significantly lower in propofol than in thiopental sodium.

Measurement of Hemodynamic Variables using Impedance Cardiography on Remifentanil-Propofol Infusion during Anesthetic Induction / 대한마취과학회지

BACKGROUND: Remifentanil-propofol combination is used to minimize the cardiovascular responses during anesthetic induction; however, it may generate side effects such as hypotension or bradycardia. The authors investigated the changes of stroke volume and cardiac output using impedance cardiography (ICG) when hypotension or bradycardia is generated during propofol-remifentanil anesthetic induction. METHODS: Ninety ASA physical status class I patients who were scheduled to undergo elective ambulatory surgery were randomly assigned to one of three groups (n = 30 each). Normal saline (Group S), remifentanil 0.25microgram/kg/min (Group R0.25), or remifentanil 0.5microgram/kg/min (Group R0.5) was infused intravenously. Propofol was slowly administered two minutes after the administration of remifentanil or normal saline. Heart rate, mean arterial pressure, cardiac output and stroke volume were measured at preinduction (baseline), preintubation and postintubation. RESULTS: Mean arterial pressure in Group R0.5 at preintubation decreased compared to that of the baseline, however, the stroke volume index was sustained. The stroke volume index at postintubation decreased proportionally as heart rate increased in heart rate in all groups, and then cardiac index was preserved. CONCLUSIONS: Hypotension was generated during induction of anesthesia when remifentanil 0.5microgram/kg/min and propofol 1.0 mg/kg were used, however, the stroke volume index was sustained.

A Comparison of Bioimpedance and Echocardiography in Measuring Cardiac Output in Healthy Male Volunteers

PURPOSE: To manage a critically ill patient effectively, an emergency physician must make an accurate assessment of the patient's hemodynamic status. Although the hemodynamic status can be accurately measured through the use of a pulmonary artery catheter, this device has significant limitations in the emergency department. Instead, the most commonly used method of measuring cardiac output (CO) in the emergency department is transthoracic echocardiography (TTE). However, TTE has been reported to underestimate the CO. Impedance cardiography (ICG) is an established and accurate technique for noninvasive determination of hemodynamic parameters. Thus, this study aimed to assess the agreement between CO measurements made by using TTE and ICG. METHODS: In 20 healthy volunteers, the hemodynamic parameters (stroke volume and CO) obtained by TTE were compared with the parameters derived from simultaneous measurements by ICG. RESULTS: The mean stroke volumes and COs were 63.9+/-11.6 ml and 4.1+/-0.7 L/min, respectively, by TTE, and 77.2+/-10.2 ml and 5.0+/-0.6 L/min by ICG. The correlation coefficients for stroke volume and CO between TTE and ICG were 0.77 and 0.64. The mean difference in stroke volume between TTE and ICG was -13.3+/-6.4 ml (-19.5+/-10.5 %), and the mean difference in CO was -0.88+/-0.48 L/min (-20.1+/-11.6 %). CONCLUSION: In healthy volunteers, the comparison between TTE and ICG showed a good correlation for stroke volume and CO. However, the mean differences in stroke volume and CO between TTE and ICG were -19.5+/-10.5 % and -20.1+/-11.6 %, respectively.

Comparison of Impedance Cardiography with Thermodilution of Hemodynamic Parameters in Critically Ill Patients / 대한구급학회지

BACKGROUND: To evaluate the feasibility of noninvasive hemodynamic monitoring (impedance cardiography, ICG) in critically ill patients, we compared this technique with simultaneous invasive monitoring with a pulmonary artery thermodilution catheter. METHODS: A prospective observational study was done comparing invasive monitoring and noninvasive monitoring in 12 critically ill patients. The cardiac output (CO), the stroke volume (SV) and the systemic vascular resistance (SVR) measured by using a standard thermodilution pulmonary artery catheter technique were compared with the corresponding measurements simultaneously using an ICG. RESULTS: The value of CO, SV and SVR measured by ICG were closely correlated to those by the thermodilution methods [r: 0.659 (p<0.01), 0.536 (p<0.01), 0.738 (p<0.01)]. CONCLUSIONS: ICG can provide hemodynamic information previously available only by invasive monitoring with a thermodilution catheter.

Clinical Significance of B-type Natriuretic Peptide Levels and Impedance Cardiography in Maintenance Hemodialysis Patients / 대한신장학회잡지

BACKGROUND: The risk for cardiovascular morbidity and mortality is higher in hemodialysis (HD) patients than in general population. Early diagnosis, treatment and prevention of cardiovascular disease (CVD) are the best way to reduce the most important cause of death. However, cardiac geometric and/or functional alterations including left ventricular hypertrophy, atherosclerosis and/or systolic and diastolic dysfunction are not easily known to nephrologist in the sense that diagnostic procedure is limited because cardiac angiography and echocardiography are frequently needed. METHODS: To evaluate the cardiac alteration by non-invasive tools, we measured pre- and post-HD B-type natriuretic peptide levels and performed impedance cardiography (ICG) in 40 HD patients and 10 healthy adults as control. RESULTS: Pre- and post-HD BNP level, cardiac index (CI), cardiac output (CO), stroke volume (SV), systemic vascular resistance index (SVRI), systemic vascular resistance (SVR), acceleration index (ACI), velocity index (VI) and thoracic fluid content (TFC) in patients were significantly higher than those in normal control group (p<0.05). Pre-HD BNP level, stroke index (SI), SV and TFC were significantly different after HD (p<0.05). There were significant differences in pre-HD BNP level, SI, SV and VI between diabetes and non-diabetes groups (p<0.05). Pre-HD BNP level correlated significantly with post- HD BNP level, systolic blood pressure, diastolic blood pressure, CO, SVRI, SVR and TFC (p<0.05). In multiple linear regression analysis, SVR and TFC were positively associated with pre-HD BNP level (R2=0.289). The area under the ROC curve for cardiac alterations was 0.749 for pre-HD BNP level. A cut-point of 560 pg/mL for pre-HD BNP level was 80% sensitive and 72% specific in determining cardiac alterations. CONCLUSION: Even though cardiac alterations of patients were heterogeneous in our study, plasma BNP level and some parameters (SVR, TFC) of ICG seem to be available to nephrologist for detecting and monitoring cardiac conditions in HD patients.

Comparison of Cardiac Output Measured by Impedance Cardiography and Thermodilution in Open Heart Surgery / 대한마취과학회지

BACKGROUND: Impedance Cardiography is a noninvasive and simple method of cardiac output determination. The purpose of this study was to compare an impedance device with the thermodilution method during the intraoperative period in patients undergoing open heart surgery. METHODS: The study was undertaken in 12 patients undergoing elective open heart surgery without a shunt. When abnormal impedance signals were obtained, the patients were not included in the analysis. Stroke volume was calculated according to the formula of Bernstein. Cardiac output was measured simultaneously by the impedance cardiograph and thermodilution method. We obtained 41-paired measurements during the surgical procedure. The method described by Bland and Altman and linear regression analysis were used for comparison. RESULTS: The correlation coefficient between the two methods was r = 0.36 (P<0.05). Bias and precision analysis between the two techniques showed a mean difference between techniques of 0.80 L/min and a SD of the differences of 1.71 L/min (95% level of agreement 4.21 L/min to -2.62 L/min). Trending analysis showed the impedance cardiogram to inaccurately track the direction of thermodilution CO changes and to underestimate their magnitude (r = 0.57, intercept -3.29, slope 1.27). CONCLUSIONS: This study reveals clinically significant errors in impedance CO measurements. These inaccuracies may be related to the intraoperative environment and abnormal cardiovascular function. Further investigation of such techniques to improve the performance of the impedance cardiogram in the intraoperative setting is warranted.

The Cardiac Output and the Cardiac Muscle Contractility During Postural Gradient Changes by Tilt Table in Man

The purpose of this study is to investigate changes of the cardiac output and the cardiac muscle contractility during postural gradient changes in man. Subjects consisted of 15 healthy males that they were aged 23-24 years. The Cardiac output and the contractility were calculated using the impedance cardiogram that were recorded by new apparatus developed in Yonsei Medical Center. The impedance cardiogram was recorded in different 7 gradients which were 0degrees, +/-2degrees, +/- 45degrees and +/-90degrees according to the head position, but it was continuously recorded at each gradient. The each postural gradient was changed after supine resting, 15-20 min, and continued in 5 min. Results of this study were following, 1. The cardiac output was decreased at head up posture (+2degrees, +45degrees and +90degrees) because of decreasing stroke volume. But the cardiac output was increased at head down posture (-2degrees, -45degrees and -90degrees) by increasing stroke volume. 2. The cardiac output was significantly changed at +/-45degrees and +/-90degrees after immediately gradient changes, but it was no significant difference at 0 and +/-2degrees postures from that of supine resting state. 3. At +/-45degrees and +/-90degrees, the cardiac muscle contractility was increased, and in head up posture, amounts of change were more larger than in head down posture.

Hemodynamic Changes during Heas-Down and Up Tilt after Ethanol Ingestion

BACKGROUND: The acute effect, of ethanol (EOH) include lowered blood pressure through peripheral vasodilation and decreased circulating blood volume. This study was aimed at examing the effects of EOH on the hemodynamic response to up and down head tilts. METHODS: Ten 21 to 23 year old male adults served as subjects. Each subject participated in both control and EOH experiments. In the EOH experiment, 3 mls of 25% EOH per liter of total body water was administered orally, 35 min were allowed for the blood EOH level to reach maximum before the tilt protocol was initiated. The tilt protocol consisted of 5 stages, each stage was 3-min in duration : supine (0 degrees)-head down tilt (HDT, 15 degrees)-supine (0 degrees)-head up tilt (HUT, 25 degrees)-supine (0 degrees). Hemodynamic parameters were measured with an impedance cardiograph (NCCOM3-R7, BoMed) with two electrodes placed around the neck and two around the thorax. Blood pressure (BP) was measured with an automatic sphygmomanometer (DATEX). Data was collected during every second half-minute throughout the duration of the protocol. RESULTS: In the control, HDT produced an increase in the end-diastolic index (EDI), the stroke index (SI), the cardiac index (CI), and the peak flow index (PFI) ; there were no significant changes in heart rate (HR), the systemic vascular resistance index (SVRI), and BP. In contrast, HUT resulted in a decrease in EDI, SI, EF, CI, and PFI and an increase in HR, SVRI, and BP ; the latter changes sugges a sympathetic overactivation. In the EOH experiment, the basal EDI, SI, and systolic BP were lower and HR was higher than in control. HDT and HUT caused similar changes as in control experiments. CONCLUSIONS: There results indicate that EOH cause volume depletion to result in reduced central blood volume and compensatory tachycardia. These EOH-induced changes were not altered by 15 degreeshead-down and 25 degreeshead-up tilts.

Changes of cardiac output during treadmill exercise by impedance cardiography

Nine athletes and ten nonathletes were selected randomly to study the changes of cardiac function during exercise by impedance cardiography. The speed of the treadmill was maintained at 3.4 mph, and its grade was increased by 1% (Balke protocol). The exercise was continued until the target heart rate (THR), 85% of maximum oxygen uptake (VO2max). The measured parameters for pre- and post-exercise were stroke volume (SV), heart rate (HR), and cardiac output (CO). Average stroke volume of athletes at pre-exercise, 71.1 ml, was higher than that of nonathletes, 64.6 ml, and stroke volume of the former at post-exercise, 97.0 ml, was also higher than that of the latter, 85.2 ml. Therefore, despite the lower heart rate, cardiac outputs of athletes at pre- and post-exercise, 4.98 and 16.3 L/min, were higher than those of nonathletes, 4.87 and 14.2 L/min. For the second phase of the study, cardiac outputs of three subjects were measured during the continuous treadmill exercise with newly developed electrodes and shoes for minimizing motion artifact. Though there were several studies measuring cardiac output during continuous bicycle exercise, this is thought to be the first study in the world measuring cardiac output during continuous treadmill exercise without aid of ensemble averaging.