Computer Evaluation of Exercise Based on Blood Volume Pulse (BVP) Waveform Changes ARMANDO BARRETO 1,2 , CHAO LI 1 and JING ZHAI 1 1 Electrical & Computer Engineering Department 2 Biomedical Engineering Department Florida International University Miami, Florida, 33174 USA Abstract: - It is well established that the benefits obtained from exercising are enhanced if a sufficiently strong cardiovascular response is achieved as result of the exercise sessions. Frequently, the achievement of that critical exercise level is gauged by estimation of the subjects heart rate and comparison to an appropriate target rate. This paper explores the use of computerized algorithms to assess the changes in the Blood Volume Pulse (BVP) waveform recorded using an infrared finger photoplethysmograph (PPG) at different points in an exercise session, as an alternative (and more comprehensive) evaluation of the cardiovascular response due to physical exercise. The paper focuses on the quantification of a feature of the BVP waveform called the Dicrotic Notch, which has been observed to reduce its depth as exercise progresses. This paper reports on the comparison of three computerized approaches designed to reflect the BVP waveform changes through a single parameter, which could be obtained automatically from the digitized BVP signal. Key-Words: - Exercise Evaluation, Photoplethysmograph, PPG, Blood Volume Pulse, BVP, Dicrotic Notch, Non-invasive monitoring 1 Introduction Most individuals who exercise are faced with the need to gauge the intensity of their exercise sessions, and adjust this intensity to obtain a maximum of benefits, with a minimum risk of negative consequences. This must be an individualized process, since the appropriate level of effort that should be involved in an exercise session must be appropriate to the age and fitness level of the subject [3]. A practical method to quantify the intensity of exercise is by monitoring of the subjects heart rate (HR) during the session. [1][4]. The measured heart rate, compared to the estimated maximum heart rate for the individual, is often used to label the intensity of the exercise session as moderate (60% - 70%), through high (85%) [7]. Heart rate, however, reveals only a facet of the complex cardiovascular changes that take place during exercise. In addition to the changes in heart rate and stroke volume, exercise brings about specific changes in the peripheral resistance of the cardiovascular system [8]. In contrast with the measurement of heart rate, dynamic measurements of perfusion in the periphery of the cardiovascular system will not only reflect changes in the rhythm of the cardiac cycle, but, they will also reveal peripheral changes. Specifically, finger photoplethysmography (PPG) is a non- invasive technique for the monitoring of peripheral perfusion, which does not require costly equipment or specialized personnel. The Blood Volume Pulse (BVP) signal obtained with a PPG transducer has been used in the past to determine the heart rate [6]. However, a more detailed analysis of photoplethysmographic BVP variations may indicate peripheral circulatory changes that take place in an individual due to exercise. Further research has shown that the changes in the single BVP signal through an exercise session (before exercise, immediately after exercise, and after a recovery period) can be measured, characterized, and quantified through signal processing methods that can be implanted in a personal computer [5]. In this paper we present and analyze three such methods, as applied to data collected in a controlled exercise session. 2 Data Gathering Protocol The recording procedure used consisted of three measurements: A, B and C, through a total time of about 18 minutes. Ten healthy volunteers with ages between 22 and 40 participated in the recordings.