Nadi Yantra: a robust system design to capture the signals from the radial artery for assessment of the autonomic nervous system non-invasively

Abstract

Ayurvedic and other alternative medical practitioners throughout the world have been using pulse diagnosis to detect disease and the organ at distress by feeling the palpations at three close yet precise positions of the radial artery. This paper presents a robust electro-mechanical system, 'Nadi Yantra' which uses piezoelectric based pressure sensors to capture the signals from the radial artery. Morphology of the waveforms obtained from our system concurs with standard physiological arterial signals. Reproducibility and stability of the system has been verified. Signal processing techniques were applied to obtain features such as amplitude, power spectral density, bandpower and spectral centroid to reflect variations in signals from the three channels. Further, wavelet based techniques were used to process the pressure signals and percussion peaks were identified. The interval between the percussion peaks was used to calculate Heart Rate Varibility (HRV), a useful tool for assessing the status of the autonomic nervous system of the human body noninvasively. Time domain indices were calculated from direct measurement of peak-peak (PP) intervals and from differences between the PP intervals. Frequency domain indices such as very low frequency (VLF) power, low frequency (LF) power, high frequency (HF) power, LF/HF ratio were also calculated. Thereafter, nonlinear Poincare analysis was carried out. A map of consecutive PP intervals was fitted to an ellipse using least squares method. Results from 7 datasets are depicted in this paper. A novel pressure pulse recording instrument is developed for the objective assessment of the ancient science of pulse diagnosis. The features calculated using multi resolution wavelet analysis show potential in the evaluation of the autonomic nervous system of the human body.

Automated Pulse-Based Diagnosis: Role of TIM Diagnostic Features

“…Renewed interest in the non-invasive, holistic diagnostic approach of pulse-examination followed in the traditional Chinese and Indian medicine has gained momentum with advanced instrumentation and digital recording (e.g. [12]- [14]). For pulse-based diagnosis/prognosis in Ayurveda-Traditional Indian medicine (TIM), patterns of pulse-velocity and pulse-movement are of crucial importance together with the pathological indicators in terms of doshas and several other features of pulse-sensation.…”

Nonlinear Processing of Wrist Pulse Signals to Distinguish Diabetic and Non-Diabetic Subjects

“…The pressure applied on the wirst is varied to obtain the maximal pulse and also the different phases of the pulse. [1]. Just like most of the other physiological signals, wrist pulse also contained some singularities which vary rapidly for a very small change in time [2].…”

Traditional East Asian Medical Pulse Diagnosis: A Preliminary Physiologic Investigation

“…[1][2][3][4][5] While a widely used method in TEAM, pulse diagnosis has over time been described and used in many different ways. 6 A number of studies have examined the reliability of pulse diagnosis, [7][8][9][10][11][12][13] and some methods of instrumentation have been developed, [14][15][16] leading in some cases to clinical applications (for example, the ZM-IIIC TCM Pulse Pattern Diagnostic System). 17 Despite several theoretical models, 18 there has been little study of the potential underlying physiologic changes associated with variations in pulse qualities.…”