Electrical Impedance Plethysmography Based Device for Aortic Pulse Monitoring Sudipta Ghosh 1 , Satyajit Giri 2 , R.S. Kruthika 3 , Gunit Singh Chabhra 4 M. Mahadevappa 1 , Jayanta Mukhopadhyay 5 1 School of Medical Science & Technology, Indian Institute of Technology(IIT), Kharagpur, India 2 School of Electronics Engineering, Vellore Institute of Technology (VIT), Vellore, India 3 Department of Electronics & Communication Engineering, P.E.S College of Engineering, Mandya, India 4 Department of Electronics & Communication Engineering , Maulana Azad National Institute of Technology, Bhopal, India 5 Department of Computer Science & Engineering, Indian Institute of Technology(IIT), Kharagpur, India sudipta.kanti@gmail.com, mmaha2@smst.iitkgp.ernet.in Abstract—In this paper, we have proposed a novel design for recording aortic pulse wave using electrical impedance technique. Unlike conventional ECG, photo-plethysmography, and pulse oximetry measurements, the proposed design provides a portable, cost effective and instantaneous representation of aortic pulse wave recording. The proposed circuit design has been validated by bench testing it, using a lab standard skin model. The results obtained can be further used for determining various vital health care parameters like arterial stiffness, pulse wave velocity, etc. Keywords—Impedance, Plethysmography, Arterial Stiffness, Aortic pulse waveform, Excitation I. INTRODUCTION Increasing occurrence of cardiovascular-related diseases throughout the world as well the fragility of the cardiovascular system in intensive care patients calls attention to the need for accurate methods of assessing system health. Hemodynamic monitoring which encompasses the study of development and propagation of flow and pressure pulses, including but not limited to: systemic, pulmonary arterial and venous pressures and cardiac output, have traditionally been utilized by the clinicians. However, hemodynamic monitoring methods are mostly invasive in nature. Consequently, they require on-site expert supervision, are costly and suffer the risks of surgical complications [1]. An alternative non-invasive method, impedance cardiography (IC) was first proposed by Kubicek et al. (1966) in the thoracic region. An alternating current flows through the body fluid which has very low electrical resistance when applied to human body. When the electric potential is applied to the human body, the tissue exhibits electrical property called the Bio-Impedance. Compared to bone, fat or air, current flows easily through those parts of the body which are composed mostly of water (blood, urine and muscle). The electric current flows easily through water with ions which human body is composed of. The amount of opposition the body tissue exhibits to the small amount of current applied(less than 10mA) is measured by the BIA (Bio Impedance Analysis) [2]. When electric current is applied, it flows at different rates depending mainly on the fat composition at various parts of the body which is the principle of Bio Impedance analysis. Impedance is mainly the drop across the two electrodes placed on the body surface when a small constant current with a fixed frequency is applied across the electrodes. Compared to few of the other methods of body composition analysis, BIA is chosen because it is portable, easy to use and low cost. The voltage measurement is made between the two electrodes which are quite away from the region where current is applied. Early detection and prevention of any imbalance in the body composition is important and BIA helps in the early detection. Thus to maintain proper functioning of the body, for healthy ageing and for reduced risk of illness BIA measurement is an appropriate solution.. II. IMPEDANCE PLETHYSMOGRAPHY In Impedance Cardiography (IC), an alternating current is injected into the body, where it flows mostly through the conductive body fluid (rather than the more resistive bone, fat or air). Alternating current was chosen over direct current to avoid charge accumulation around electrodes which would continuously contribute to the impedance and could pose health risks to the user. The injected current generates an electric potential across the observed region which is directly proportional to the impedance across the sensing electrodes. Therefore, as blood content, rate of blood flow, etc. changes in observed body regions the impedance characteristics also commensurately change [3]. We track these changes in the amount of opposition the body tissue exhibits to the small amount of current applied (less than 10mA and 100 kHz) through Impedance Plethysmography and Cardiography. Impedance analysis helps in the early detection and prevention of any imbalance in the body composition. It is also a useful Proceedings of 2016 International Conference on Systems in Medicine and Biology 4-7 January 2016, IIT Kharagpur 978-1-4673-7666-2/16/$31.00 ©2016 IEEE 124