Application of Crisp and Fuzzy Clustering Algorithms for Identification of Hidden Patterns from Plethysmographic Observations on the Radial Pulse Sunil Karamchandani, S.N.Merchant Indian Institute of Technology Bombay, Mumbai, India, 400076 sunilk,merchant@ee.iitb.ac.in U.B.Desai Indian Institute of Technology Hyderabad, India 502205 ubdesai@iith.ac.in G.D.Jindal Bhabha Atomic Research Centre Mumbai, India, 400085 gd.jindal@gmail.com Abstract— Radial Pulse forms the most basic and essential physical sign in clinical medicine. The paper proposes the application of crisp and fuzzy clustering algorithms under su- pervised and unsupervised learning scenarios for identifying non-trivial regularities and relationships of the radial pulse patterns obtained by using the Impedance Plethysmographic technique. The objective of our paper is to unearth the hidden patterns to capture the physiological variabilities from the arterial pulse for clinical analysis, thus providing a very useful tool for disease characterization. A variety of fuzzy algorithms including Gustafson-Kessel (GK) and Gath-Geva (GG)have been intensively tested over a diverse group of subjects and over 4855 data sets. Exhaustive testing over the data set show that about 80 % of the patterns are successfully classified thus providing promising results. A Rank Index of 0.7739 is obtained under supervised learning, which provides an excellent conformity of our process with the results of plethysmographic experts. A correlation of the patterns with the diseases of heart, liver and lungs is judiciously performed. Index Terms: Peripheral Pulse Analyzer - Impedance Plethys- mography - fuzzy clustering. I. I NTRODUCTION The pulse of the radial artery is an important diagnostic tool for all physicians. The radial artery is not only easily accessible but is in direct continuation of the heart and close to it. Examination of the pulse throws light on the gravity of illness and gives a guide line for prognosis. The pulse provides evidence of great value both to the state of the central circulatory system and the general pathophysiological conditions of the subject. Fluctuation in physiological con- ditions are reflected as a change in the morphology of the arterial pulse. The pulse identifies the presence and location of disorders in a patient’s body unlike ECG which mainly reflects the electrical activity of the heart, and thus it contains much more useful information than ECG [1]. In traditional Indian medicine the clinician palpates the area above the radial artery at the wrist location of the patient and monitors the rhythm, pulse pressure, pulse propagation and the elasticity of pulse for arriving at the diagnosis in the patient [2]. The diagnosis requires a long period of study and practice by the physician, without the benefit of any recording aids. To extract information from the radial pulse we use the principle of Impedance Plethysmography (IP), a convenient, inexpensive, painless and non invasive technique. IP provides an indirect assessment of blood volume changes in any part of the body segment as a function of time [3]. Since blood is a good conductor of electricity, the amount of blood in a given body segment is reflected inversely as in the electrical impedance of the body segment. The pulsatile blood volume changes in the body segment caused by systemic blood circulation, therefore causes proportional change in the electrical impedance [4]. Using the technique of IP, we record the impedance changes in the radial artery as a measure of the blood flow. After peak detection, pulse waveforms, each consisting of sixty four sample points, are recorded, with twenty sample points prior to the peak and forty four thereafter. Over four thousand such data sets are collected with the help of more than three hundred subjects. We apply clustering algorithms to identify the groups of related data that can further be explored. II. DATA ACQUISITION Pulse signals from the radial artery are measured using the Peripheral Pulse analyzer developed at Bhabha Atomic Research Centre (B.A.R.C), Mumbai, India. The radial artery begins about 1 cm below the bend of the elbow and passes along the radial side of the forearm to the wrist, where its pul- sation can be readily felt. With the subject in supine position, carrier electrodes are applied around the upper arm and the palm while sensing electrodes are applied on the distal segment around the wrist. Peripheral Pulse analyzer uses the principle of IP wherein a sinusoidal current of constant amplitude (2 mA) is allowed to flow across the wrist of the subject using band electrodes. The amplitude of the signal thus obtained is directly proportional to the electrical impedance of the body segment. The waveforms obtained are sampled at 100 Hz as a time series data. The data is recorded in normal and diseased subjects at the Biomedical Division, Modular Labs, B.A.R.C. for about four minutes on LabWindows platform. The subjects are in the range of about 18 to 60 years. Approximately 240 such samples are obtained from a single subject. The observed impedance signal is shown in figure 1. III. PROPOSED CLUSTERING ALGORITHMS We propose to unearth suitable techniques for clustering of plethysmographic data. We assume two scenarios viz when 32nd Annual International Conference of the IEEE EMBS Buenos Aires, Argentina, August 31 - September 4, 2010 978-1-4244-4124-2/10/$25.00 ©2010 IEEE 3978