Nadi Yantra: A Robust System Design to Capture the Signals from the Radial Artery for Non-Invasive Diagnosis

Radial artery is one of the most significant arteries for non-invasive diagnosis for ages. Ayurvedic and other alternative medical practitioners throughout the world have been diagnosing diseases and the organ at distress by feeling the palpations at three close yet precise positions of the radial artery. This paper presents a robust system Nadi Yantra 1 that monitors pressure variations from the points of interest for pulse diagnosis, thereby eliminating subjective errors and overcomes the limitation of mastering the art of pulse diagnosis with experience. This system comprises of three identical piezo based sensors, amplifier and filter circuit, a mechanical set-up and a data acquisition system (BioPac-150trade) which captures the signal from those three precise positions of the radial artery thereby giving an objective approach to the science of pulse diagnosis. Morphology of the waveforms obtained from our system concurs with standard physiological arterial signals. Our technique reveals subtle variations in real time that holds promise in quantitative assessment of pulse. Advances over the earlier systems are that Nadi Yantra allows recording for hours by an automated external pressure on the three positions thereby completely removing the potential for errors incurred when a person does the job of applying pressure. The locking mechanism significantly resists the motion artifacts as well. Repeatability, reproducibility and stability of the system has been verified. Signal processing techniques were applied to obtain morphological features such as amplitude, power spectral density, bandpower and spectral centroid to reflect variations in signals from the three channels. Data acquired from the system at three points gives unique information and can be used for disease diagnosis.