Evaluation of cardiac output using non-uniform hybrid electrical impedance model based on forward lumped parameter and both-hands impedance measurement system

Abstract

In this dissertation, cardiac output using non-uniform hybrid electrical impedance model, which is based on the forward lumped parameter and the both-hands impedance measurement system,is proposed. This noninvasive method for cardiac output monitoring has been clinically accepted as areplacement for thermo dilution, the gold standard in cardiac output measurement.Alternatively, measurement using impedance cardiogram, which has several distinctadvantages, has been identified as a promising method for cardiac output measurements. Thethoracic impedance cardiogram (ICG) has been proposed as a noninvasive, continuous,operator-independent, and cost-effective method for cardiac output monitoring. However, thismethod is generally regarded to be restrictive because measurements are performed using aband or spot-type electrode adhered to the body. Traditionally, lead has been used for suchmeasurements, thus rendering the entire system highly inconvenient because the assistance of a specialist is required. Further, the development and attachment of the lead electrode, used with the traditional system, is both expensive and complicated. In this dissertation, we evaluate the effectiveness of the proposed non-uniform hybrid model, which is based on the forward lumped parameter. This system seeks to combine the existing lumped parameter method and the non-uniform hybrid model to create a coherent system capable of leveraging the advantages of both approaches. For developing an effectiveness rating for cardiac output measurements using both hands, the presented model was mathematically interpreted and the relevant results were compared and analyzed against the stroke volume and the cardiac output of the thoracic impedance measurements (Physio FlowⓇ-PF104D, Manatec Biomedical, France). To develop the non-uniform hybrid electrical impedance model, based on the forward lumped parameter and the both-hands impedance measurement system, 80 subjects (58 male, 22 female) from Yonsei University and the surrounding areas, aged 18–74 years, participated in this study. All participating subjects completed stroke volume and cardiac output tests through PhysioFlow and the developed system. In the developed system, electrodes are used to gripping on both-hands instead of attaching to the chest. Similar to previously adopted noninvasive cardiac output tests, the developed system measures stroke volume through impedance changes over each cardiac cycle. Additionally, this study compares cardiac output measurements in the thorax and in both hands. These measurements and comparisons were verified using the presented non-uniform hybrid model.To verify the proposed approach, statistical methods such as correlation analyses, pairedT-test, and the Bland-Altman plot were used. For verification of the non-uniform hybridelectrical impedance model, the presented value of r, scatter plot, and the Bland-Altman plotof measured and estimated SV and CO were used. The results were as follows: 1) The SV/CO obtained from the PhysioFlow and the proposed approach (developed system) showed significant correlation in both male and female SV (r = 0.715, P < 0.001; r = 0.704, P < 0.001, respectively) and CO (r = 0.826, P < 0.001; r =0.804, P < 0.001, respectively). 2) The SV/CO obtained from the PhysioFlow and the proposed approach (non-uniform hybrid electrical impedance model based on the forward lumped parameter) demonstrated significant correlation in both male and female SV (r = 0.735,P < 0.001; r = 0.827, P < 0.001, respectively) and CO (r = 0.767, P < 0.001; r = 0.853, P <0.001, respectively). 3) The SV/CO obtained from the non-uniform hybrid electrical impedance model and the development system showed significant correlation in both male and female SV (r = 0.788,

P < 0.001; r = 0.812, P < 0.001, respectively) and CO (r = 0.802, P < 0.001; r = 0.823, P < 0.001, respectively). From these results, it can be concluded that SV and CO can be measured using the bothhands cardiac output measurement method at low cost and convenient without the help of a specialist. Furthermore, this system was verified by using the developed model as a substitute for the existing method.This noninvasive method for cardiac output monitoring has been clinically accepted as a replacement for thermo dilution, the gold standard in cardiac output measurement. Alternatively, measurement using impedance cardiogram, which has several distinct advantages, has been identified as a promising method for cardiac output measurements. The thoracic impedance cardiogram (ICG) has been proposed as a noninvasive, continuous, operator-independent, and cost-effective method for cardiac output monitoring. However, this method is generally regarded to be restrictive because measurements are performed using a band or spot-type electrode adhered to the body. Traditionally, lead has been used for such measurements, thus rendering the entire system highly inconvenient because the assistance of a specialist is required. Further, the development and attachment of the lead electrode, used with the traditional system, is both expensive and complicated.In this dissertation, we evaluate the effectiveness of the proposed non-uniform hybrid model, which is based on the forward lumped parameter. This system seeks to combine the existing lumped parameter method and the non-uniform hybrid model to create a coherent system capable of leveraging the advantages of both approaches. For developing an effectiveness rating for cardiac output measurements using both hands, the presented model was mathematically interpreted and the relevant results were compared and analyzed against the stroke volume and the cardiac output of the thoracic impedance measurements (Physio Flowⓡ-PF104D, Manatec Biomedical, France).To develop the non-uniform hybrid electrical impedance model, based on the forward lumped parameter and the both-hands impedance measurement system, 80 subjects (58 male, 22 female) from Yonsei University and the surrounding areas, aged 18?74 years, participated in this study. All participating subjects completed stroke volume and cardiac output tests through PhysioFlow and the developed system. In the developed system, electrodes are used to gripping on both-hands instead of attaching to the chest. Similar to previously adopted noninvasive cardiac output tests, the developed system measures stroke volume through impedance changes over each cardiac cycle. Additionally, this study compares cardiac output measurements in the thorax and in both hands. These measurements and comparisons were verified using the presented non-uniform hybrid model. To verify the proposed approach, statistical methods such as correlation analyses, paired T-test, and the Bland-Altman plot were used. For verification of the non-uniform hybrid electrical impedance model, the presented value of r, scatter plot, and the Bland-Altman plot of measured and estimated SV and CO were used.The results were as follows: 1) The SV/CO obtained from the PhysioFlow and the proposed approach (developed system) showed significant correlation in both male and female SV (r = 0.715, P < 0.001; r = 0.704, P < 0.001, respectively) and CO (r = 0.826, P < 0.001; r = 0.804, P < 0.001, respectively). 2) The SV/CO obtained from the PhysioFlow and the proposed approach (non-uniform hybrid electrical impedance model based on the forward lumped parameter) demonstrated significant correlation in both male and female SV (r = 0.735, P < 0.001; r = 0.827, P < 0.001, respectively) and CO (r = 0.767, P < 0.001; r = 0.853, P < 0.001, respectively). 3) The SV/CO obtained from the non-uniform hybrid electrical impedance model and the development system showed significant correlation in both male and female SV (r = 0.788, P < 0.001; r = 0.812, P < 0.001, respectively) and CO (r = 0.802, P < 0.001; r = 0.823, P < 0.001, respectively).From these results, it can be concluded that SV and CO can be measured using the both-hands cardiac output measurement method at low cost and convenient without the help of a specialist. Furthermore, this system was verified by using the developed model as a substitute for the existing method.