Role of machine learning techniques in classification of peripheral pulse morphology

Recording of peripheral pulse serves as a very important and essential non-invasive tool used widely by doctors for the diagnosis of various diseases. The morphology of pulse is seen to vary as a function of time in a given individual and also from individual to individual. There are many variations in morphological patterns of peripheral pulse in different disease conditions, which lead to difficulty in accurate diagnosis. The peripheral pulse waveforms are extracted from radial arteries as time series data using a peripheral pulse analyzer which is designed on the principle of impedance plethysmography. It was first introduced by Nyober in the mid-nineteen hundreds and ameliorated further by Kubicek. It involves the recording of the instantaneous blood volume by the measurement of electrical impedance as a function of time. Therefore, the study of peripheral pulse morphology has gained much attention in the past few years among researchers. Physiological variability is one of the recent investigations added during the last two decades for the objective assessment of autonomic function and the assessment of prognosis in severe sicknesses namely myocardial infarction, diabetic neuropathy, etc. In addition to heart rate variability studied worldwide, few researchers have studied blood pressure variability and peripheral blood flow variability. In this computer era, artificial intelligence and machine learning techniques have become more important day-by- day, and different types of algorithms were used for the identification of hidden patterns from plethysmographic observations on the radial pulse such as support vector machine as well as crisp and fuzzy clustering. Eight patterns were classified with a yield of 80%–90% and helped with the diagnosis of disorders such as myocardial infarction, pulmonary tuberculosis, coronary artery disorders, cirrhosis of the liver, and bronchial asthma. This paper briefly describes the use of machine learning techniques for the classification of peripheral pulse morphologies.

Seventy-five Years of Use of Impedance Plethysmography in Physiological Data Acquisition and Medical Diagnostics.

Impedance plethysmography (IPG) came into existence in 1940 as a result of Jan Nyboer’s pioneering work in the noninvasive assessment of central and peripheral blood flow. The technique got an impetus after introduction first-time derivative of the impedance for accurate determination of stroke volume (SV) and various cardiac intervals. Later, this signal was employed by Parulkar et al for estimation of blood flow index (BFI) and differential pulse arrival time (DPAT) in various segments of the extremity, which were adequate to detect the aortic and peripheral arterial blocks and estimate collateral circulation and distal arterial runoff. The technique was widely used for measurement of respiration and body water. All these applications have resulted into use of bioimpedance for body composition analysis and continuous monitoring of cardiac output as US Food and Drug Adminstration (FDA) approved technologies, which are being used worldwide. Physiological variability has added more value to this technique as single data acquisition gives variability in heart rate and SV (or peripheral blood flow). Morphology index thus derived is very useful in screening patients suspected with coronary artery disease (CAD). All these milestones are briefly described in this paper.

Evaluation of Vascular Response using Impedance Plethysmography in Patients with Spinal Cord Injury

OBJECTIVE: To determine abnormal vascular response to cuff ischemia in patients with spinal cord injury (SCI). METHOD: Ankle blood pressure (ABP) and ankle-brachial index (ABI) in 20 SCI patients (14 men, 6 women, mean age 39.8 years) and control group (14 men, 6 women, mean age 40.2 years) were measured using impedance plethysmography at rest and after distal thigh cuff compression for 5 and 10 minutes. The patients were divided into tetraplegia (10), paraplegia (10), complete injury (8) and incomplete injury (12). RESULTS: There was no significant difference in ABP and ABI at rest and 5 minutes of ischemic compression between the patients and control groups. However, ABP and ABI decreased more at 10 minutes of ischemic compression in SCI compared to control groups (p<0.001). Changes of ABP and ABI between tetraplegia and paraplegia were not different. Complete injury of SCI decreased more than incomplete injury at 10 minutes of ischemia in the APB and ABI (p<0.001). CONCLUSION: Vascular control was significantly impaired in patients with spinal cord injury. Impedance plethysmography can be a useful and objective tool in evaluation of vascular response for the patients with spinal cord injury.