USB Based Data USB Based Data Acquisition System for Acquisition System for Heart Rate Variability Heart Rate Variability through ECG & PPG through ECG & PPG

SignalsSignalsVibhuti Bagga1, Tanvi Kalra2, Abhinav 3, Sneh Anand 3

 1- Faculty of Sciences, Jamia Hamdard, New Delhi2- Department of Biomedical Engineering, Rayat & Bahra Institute of Engineering & Bio-Technology, Punjab3- Centre for Biomedical Engineering, IIT DELHI

What is HRV?•Refers to the variation in beat-to-beat pacing intervals of heart rate

• It is a measure of heart's ability to respond to normal regulatory impulses that affect its rhythm

• HRV analysis is an important parameter for assessment of the cardiovascular autonomic nervous system

• Bears clinical relevance for both diagnostic & prognostic purposes as they are directly influenced by the sympathetic and parasympathetic systems

Electrocardiograph

Refers to the electrical activity of the heart represented as a vector between two point charges

It measures the rate and regularity of heart beats

PHOTOPLETHYSMOGRAPHY

Optical measurement technique used to detect blood volume changes in the microvascular bed of the tissues during cardiac cycle PPG signal contains components that are synchronous with respiratory and cardiac rhythms It can be used as a replacement of ECG for HRV analysis in healthy subjects. It is also a measure of vessel stiffness.

Systolic peak Dicrotic notch

Reflective Type - PPG

the yellow region shows the path of the photons (emitted by the source) which reach the detector after scattering and absorption into the various layers of the skin

HRV analysis can be done using ECG and PPG

Pulse Transit Time

The time taken for pulse wave to travel from the left ventricle to the peripheral site

Noninvasive measure of arterial compliance

The PTT can be computed from the ECG and PPG waveforms as the time delay in between R wave peak of ECG and upstroke of corresponding PPG pulse .

Can be used for continuous monitoring of vascular reactivity

PTT varies in pace with respiration & so can be used for respiration monitoring

Features include:

USB based ; no external power supply needed

Simultaneous plot of both ECG & PPG

Small size, compact ; portable

Signal processing at the press of a button.*

* Under process…

Functional Block Diagram

ECG Measurement Module

This three leads ECG system includes:

The PPG system includes:

Acquisition Module

Acquisition Module

Graphical User InterfaceA visual basic, windows based application.

Reads data from the USB port in bulk and displays it on the monitor.Features include :

Two selectable channels No of samples :10-500 Selectable time base: 10 us – 1000 ms Data can be stored as a text file and processed as desired. Signal plotted can be smoothened, averaged and inverted

Discussion

The acquisition system & the GUI successfully acquire and plot the noise free ECG signal.

Further improvisations in the plotting software include

User selectable acquisition duration Continuous and dynamic plotting Integration of the various data

processing features for HRV analysis

Selvaraj, N., Jaryal, A. K., Santhosh, J., Deepak, K. K. and Anand, S.

(2009)'Influence of respiratory rate on the variability of blood volume pulse characteristics',Journal of Medical Engineering & Technology

Allen, J., 2007, Photoplethysmography and its application in clinical physiological measurement. Physiological Measurement, 28, R1–R39.

Foo, J.Y.A. and Lim, C.S., 2006, Pulse transit time as an indirect marker for variations in cardiovascular related reactivity. Technology and Health Care, 14, 97–108.

Johansson, A., Ahlstrom, C., Lanne, T. and Ask, P., 2006, Pulse wave transit time for monitoring respiration rate. Medical & Biological Engineering & Computing, 44, 471–478.

Selvaraj, N., Jaryal, A., Santhosh, J., Deepak, K.K. and Anand, S., 2008, Assessment of heart rate variability derived from finger-tip photoplethsmography as compared to electrocardiography. Journal of Medical Engineering & Technology.

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