A Review on Ayurvedic Approach in Sphygmology: Characteristics, Traditional Parameters and Existing Sensors in Sphygmology

INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

A Review On Ayurvedic Approach In Sphygmology: Characteristics, Traditional Parameters And Existing Sensors In Sphygmology

Ammu Anna Mathew, Dr. S. Vivekanandan

Abstract : Ayurveda is a word derived from the Sanskrit language with meaning Ayur as life and Veda as knowledge or science, hence Ayurveda is known as Knowledge of Life. Sphygmology is the science of pulse diagnosis which deals with the principles and practices in Nadi Pariksha. According to Ayurveda, Nadi Pariksha is an extensive method used to find the root cause of illness in a human being. This method forewarns about possible health risks. This paper surveys on the characteristics of pulses, traditional parameters and sensors used in this field for disease identification using pulse diagnosis. The character of the pulse in good health and the changes which will occur in illness are of great attention in determining the cause of diseases. Nadi Pariksha helps in identifying more than 80 varieties of diseases from the three pulses on the radial artery thereby analyzing the diseases at its initial stage in a non-invasive way and curing them at an early stage.

Index Terms: Darshana, Kapha, Nadi Pariksha, Pitta, Prakruti, Prashna, Sparshana, Sphygmology, Tridosha, Vata, Vikruti ——————————  ——————————

1 INTRODUCTION Ayurveda is the art of everyday living in synchronization with the commandments of nature. Ayurveda is the oldest healing science which is believed to have a history of more than 5000 years in India and was conveyed to us through sutras or small phrases. Ayurveda is an applied, clinical, medical discipline. The maintenance of perfect wellbeing of a healthy person through avoidance is the main aim and objective of Ayurveda. It also aims to cure the disease progression in an unhealthy person through proper diet, way of life, purification therapy and transformation [1]. According to Ayurvedic tradition, the entire physical world is described in terms of five elements: space or ether, air, fire, water, and earth [2]. These five elements are not treated as some purely physical substances but are considered as energetic patterns with each having a particular feature.

• Earth is considered to have features like cold, heavy, Fig. 1 Tridosha solid, stable and dry. This element is denoted by dirt. • Water is considered to have qualities like cold, mobile, These five elements exist in all things at all times; including heavy, soft and liquid such as Ocean. in the body and each has its own precise role to play [2]. As • Hot, subtle, mobile, dry and sharp are the qualities of shown in figure 1, the three primary principles known as Fire. Sun is its purest manifestation in nature, which tridosha is the manifestation of the five basic elements in provides warmness to the earth and sky. the human body. The bodily air principle called vata is the • Space / Ether, like that of the sky, is vast, cold, light combination of Ether and Air. The fire principle called pitta is and clear. The form and existence of all other things the combination of Fire and Water elements. The Earth and are aided by this element. Water elements exhibit as the water principle known as • Dryness, cold, rough and full of motion is the features Kapha. In normal conditions, the individual constitution is of air. The characteristic of this quality is whipping by determined by these three doshas and it governs the an aggressive wind. functions of the body. The imbalance between these three doshas will lead to the disease process. The general characteristics of the doshic pulse are compared with the ______movements of different animals, called gati. The mobility of • Ammu Anna Mathew, Research Scholar, School of Electrical Engineering, the vata pulse is called sarpa gati or cobra pulse Vellore Institute of Technology, Vellore, India, PH-9496324828. E-mail: (curvilinear motion), that of pitta is called manduka gati or [email protected] frog pulse (jumping nature), while the motion of kapha pulse • Dr. S. Vivekanandan, Associate Professor, School of Electrical Engineering, is called hamsa gati or swan pulse (mandagati) as shown in Vellore Institute of Technology, Vellore, India PH-8124274447. E-mail: [email protected] Corresponding author mail ID: fig. 2. [email protected]

Fig. 2 Pulse Movement [1]

Nadi Pariksha is a primitive Ayurvedic practice of identification through the pulse. Both physical and mental illnesses and imbalances can be accurately diagnosed using this technique. This indicative tool forewarns us of possible health risks. It is consigned that the knowledge of pulse science was coined a few years back in various medical treatments of the world, like in Greek medicine,

Chinese medicine, Turkish, Arab remedies, Homeopathy, Fig. 3 Nadi Pariksha [3] Allopathic etc. and it expanded as a necessary tool for an accurate diagnosis. From the past eras, Nadi has been acknowledged as the essential signal of one's life, and the 2 CHARACTERISTICS OF PULSE AND pathology as well as the physiology of the body is being PULSE FORMATION recognized by the Vaidya through proper Nadi Pariksha. Even in today‘s chaotic routine, under emergency clinical 2.1 Characteristics of Pulse situations, modern physicians seek help by the Pariksha of The characteristic of Nadi of a healthy person mainly Nadi, as it is believed to show the present working efficacy means identification of the normal features of the pulse of of heart, and the rate of pulse, its rhythm, volume of flow that person. These variations can be identified only by and character of the pulse which indicates clearly the experience on a large number of possibly healthy persons, condition of the patient in various aspects. These pulses thereby appreciating the path precise variations in the can be analyzed through Nadi Pariksha. It is done by pulse. The face of a healthy person looks cheerful, and the placing the index, middle, and ring fingers at the wrist of the pulse movement is similar to the movement of a swan or an subjects over the radial artery as shown in fig. 3. It elephant [5]. Table 1 below gives a summary of the three discloses the characteristics of doshic imbalance, the basic and vital pulses: Vata, Pitta and Kapha, which can be nature of diseases and expected prognosis. The vibratory used to analyze a variety of diseases and its symptoms in a frequency of human pulse at different pressure levels at the human being. radial artery is identified using Nadi Pariksha. Parameters to be considered while taking pulses are the frequency, 2.1.1 Vata amplitude and quality of the pulse. Usually for the female The characteristics of vata pulse are Fast, Irregular, Narrow, left-hand pulse and for the male right-hand pulse is Feeble, Cool. The pulse rate will be in the range of 80-100 considered for accurate results [1-3]. Some restrictions and beats per minute. The Vata pulse is obtained by the proper conditions are followed while examining the pulse reading. placement of the index finger. When the vata pulse The pulse waves of people who had just bath, just taken predominates, there will be a strong throb feeling under the food, who are having thirst and hunger, just undergone oil index finger and the pulse movement will be felt like that of massage or fat intake (snehana), and who is asleep cannot a snake, quick and slippery [5]. be recognized by specialists properly. While analyzing the pulse reading, some additional physical conditions along 2.1.2 Pitta with general conditions are noted. The response of the The characteristics of pitta pulse include jumping, warm, patient hunger, behaviors of the patient facial expression, charged, prominent, moderate and standard. Rate of the the response toward the climatic situations, strength, nature pulse is 70-80 beats per minute. The pulse of Pitta is of sleep, breathing pattern history of diseases is also obtained by placing the middle finger. When the pitta pulse needed to be confirmed. The experts can come to the predominates, a stronger feel is obtained under the middle conclusion of the diseases based on these factors [4]. finger whose movement is active and jumpy similar to that of a frog [5].

at the radial artery using three fingers: index finger, middle 2.1.3 Kapha finger and ring finger, corresponding to vata, pitta and A slow, strong, stable, soft, wide, regular and hot pulse kapha respectively (Nadi Pariksha). Due to the anatomical character is obtained in kapha pulse. The rate of pulse is 60 variation in these positions on the wrist at the radial artery, -70 beats per minute. The pulse of Kapha is acquired under the pulse obtained will show three different characteristics, the ring finger. When the kapha pulse is predominating, a especially in terms of movement, frequency, rate and stronger effect is felt under the ring finger. This pulse rhythm. Hence, from a person one can analyze three movement is slow and reminds us of the floating of a swan different pulses leading to a personalized and individual [5]. prediction which is detailed and accurate. The root cause of a disease can be detected using this Ayurvedic method. 2.1.4 Sannipata Pulse This proposed Ayurvedic pulse diagnosis method can be A very fast pulse rate is felt below all the three fingers when correlated with Allopathic approach. In the Allopathic all the three Doshas are dominant for a person. The three approach, these three signals from the wrist at the radial pulses seem to have a movement like that of quail (Lava) artery are analyzed and averaged as a single pulse signal for vata, Francolin partridge (Titara) for pitta and Batera for as the allopathic treatment is kapha pulse [5].

2.1.5 Dual Dosha Pulse When the pulses of two Doshas are combined, it contains the characteristics of both the Doshas involved. For instance, we can feel the pulse of Vata Pitta below both the index and middle fingers which may be of full volume, but its other characteristics like rate, rhythm, and volume may vary in a short span of time that too may be within quarters of minutes. Similarly, when both Pitta and Kapha pulses are dominant, below both the middle finger and ring finger can get a feel of the same and so on [5].

2.2 Pulse Formation The mechanism of pulse formation can be related to a tube concentrated on the symptoms of the disease and not on attached with the piston and tied into an artery. As the blood the root cause of the disease. All the parameters mentioned is incompressible when the piston is pushed forward below for pulse diagnosis are taken care in allopathic towards the right into the tube, the vessel distends locally. approach but in terms of modern parameter. These There is a local increase of pressure due to the immediate parameters are averaged and interpreted as a single signal incompressible column of blood produced. This has little giving more preference to its rate and rhythm rather than effect on the advancing piston which is a mass of focusing on movement of the pulse. In Ayurvedic approach, incompressible blood. The wave of pressure travels along movement of the pulse is given more importance compared the vessel wall due to the stretching of next artery section to all other parameters mentioned below. and does not involve actual blood transmission. This distension wave is transmitted along the arteries and is felt pulse. In short, pulse is actually a wave formed in the 3 TRADITIONAL PARAMETERS OF PULSE vessel walls by the systole of the ventricle. The pulse does From ancient days, Nadi Pariksha is considered as an not depend on the passage of blood along the arteries. The Ayurvedic tool of diagnosis. Nadi Pariksha is the science of elasticity property of arterial walls helps in the generation life which observes the pulse from a perception of diagnosis and transmission of pressure wave of the pulse. The of the human body, sub-conscious and the mind [6]. pressure wave travels in meters per second, to be more Usually, Nadi Pariksha is done by identifying the pulse at precise 7 meters per second the movement of the red blood three positions over the radial artery and estimating doshas cells or plasma is much slower at 10 to 20 centimeter per by feeling the pulse. The nature or properties of the Nadi second. The factors that affect the speed of the blood are important in evaluating doshas. Most of the standard include blood pressure gradient, viscosity and area of cross textbooks have highlighted the unique quality of the pulse, section of the blood vessel. The rate of flow of blood is the importance of gati, which plays a main part in disease inversely proportional to the total cross section of the analysis [7]. The determinate qualities of Nadi which is vascular bed. The factors that affect the pulse pressure are strictly related with the pulse movement parameters of stroke volume and compliance. When the stroke volume modern pulses like wave velocity, rate variability of pulse increases, there is an increase in the amount of blood and stiffness of artery are gati (movement), vega (speed), which is to be accommodated in the arterial tree during sthiratva (stability) and kathinya (hardness of the artery) of each heartbeat. This leads to rise in pressure during systole pulse respectively. According to Ashtanga Hridayam, for and pressure fall during diastole. There is a slight decrease disease diagnosis and specifically for considering doshas in the compliance as the arterial pressure rises from low to there are twenty qualities or gunas which plays a vital part. high values. A person with high arterial pressure but normal They are gurubhArika (heavy), manthara (slow), haima stroke volume output has increased pulse pressure. The (cold), medura (unctuous), medura (smooth), ghana (solid), pulse formed due to the above mentioned mechanism is mudula (soft), susthira (stable), atisUkSma (subtle), visada detected at three different and precise positions on the wrist (non-slimy) and their counterparts aguru (light), javana

(quick, fast), upatapta (hot), vasu (dry), durga (roughness) sara (liquid), kaThora (hard), lola (moving), mahan (big), lindu (slimy) [7]. Gati plays an important role in evaluating the predominant dosha and expert traditional ayurvedic doctors do the assessment of gati from Nadi.

3.1 Gati (Movement of Pulse) The word gati means movement. Gati is a very distinctive way of diagnosis in Ayurveda used for assessing the dosha predominance where the pulse movements are compared with the movement of animals, reptiles and birds [7]. The varieties and complexities in three basic pulses in pulse reading can be determined by the variations in these pulses or gatis [1]. In addition to the three basic doshic gatis, there are other pulses which help to identify specific diseases as shown in table 2. Based on the Ayurvedic concept, the movement of vata pulse known as sarpa gati, will be curved like the movement of a snake (sarpa) and leech (jaluka). The significance of vata pulse is curved and zigzag nature of the movement. The pitta pulse movement called manduka gati, is hopping and jumping in nature hence was compared with the frog movement. When the movement is slow named as manda gati (also called as hamsa gati) is the importance of kapha pulse and is compared with the swan movement. The importance of gati of the pulse comes into significance when there is a presence of more than one dosha, for instance the nature of gati will be of sarpa and manduka if both vata and pitta doshas are in magnification, similarly it will be of sarpa and hamsa in nature if there is an aggravation of both vata and kapha doshas and it will be of manduka and hamsa in nature if there is an aggravation of both pitta and kapha doshas [7].

3.2 Vega (Rate) Vega means the rate of the pulse, in other words, the number of beats per minute. Vega can be varied due to Vega depends on the physical, emotional and exercise, anxiety, and excitation or any anatomical, pharmaceutical states of the person, for example, the pulse intellectual and medicinal conditions of the person. The rate rate is high in certain pathological conditions. Tall people of the pulse is widely used in medical practice which gives a have slower heart rates and shorter people have faster primary assessment about the condition of the health. It heart rates [1-7]. The rate is inversely proportional to height. also warns about the need for further examinations for Table 3 shows the predominant pulse based on different disease diagnosis [1-7]. To get an accurate reading certain age categories. When the pulse rate is slow, metabolism precautions are taken. Usually, the pulse reading is noted in will be slow and for faster pulse rate, the metabolism will be early morning in restful condition. Vega is normally high in fast. Agni governs metabolism. The quality of Agni can be vata in the range of 80 to 95 beats per minute, moderate in determined from the general examination of pulse that is pitta in the range of 70 to 80 beats per minute and low in when agni is strong, there will be fast, light and hot pulse kapha, in the range 50 to 60 beats per minute. This law is but when agni is slow, the pulse will be slow, heavy and applicable when dosha is governing vega. The rate of the cool. pulse is measured by feeling the pulse for one minute and counting the number of pulsations.

3.3 Tala (Rhythm) diastolic pressure [1-7]. It is not mandatory to depress the Tala also known as rhythm is defined as the time interval radial artery but one can experience the uplift while placing between two consecutive or successive uplifts [1-7]. For the finger lightly on the artery. The volume of the pulse balance, healthy and normal tala, the time interval is corresponds to the systolic blood pressure. The systolic regular, uninterrupted and rhythmic. When there is an out of blood pressure becomes higher when volume is high and balance in vata it will create irregularity in pulse. Vata and vice versa. Table 6 below shows the relationship between pitta can be blocked by Kapha and vata can be blocked by dosha and volume of pulse. pitta but only vata can push pitta and kapha. Pitta blocking Vata leads to an irregularly irregular tala, a crazy pulse that involves both vata and pitta as both are mobile. Also the pulse becomes fast, feeble and irregular when Vata is blocking Vata. Table 4 shows the comparison of different dosha with tala.

By pressing the ring finger to stop the pulsation of the radial

artery, tension can be felt and also the tension can be felt 3.4 Bala (Force) under the middle and index fingers as the blood behaves Bala is the force or pressure of the pulse which can be like a rubber tube full of water. experienced when three fingers are pressed against the 3.6 Tapamana (Temperature) and Kathinya artery. As per Newton‘s third law of motion, every action has an equal and opposite reaction; therefore the amount of (Consistency of the vessel walls) force pressing on the blood vessel will be exerted back onto Tapamana means Temperature. The is a relationship the fingers. The force is the difference between the systolic between gati of the pulse, the wave of the pulse, the and diastolic pressure, which produces a ratio called pulse temperature of the pulse, agni and metabolic fire of the pressure (PP). When there is a high pulse pressure, the individual as shown in table 7. The consistency of the heart will be working under great stress. In short, bala vessel wall, analyzed by rolling the artery between the corresponds to the pulse pressure. Table 5 shows the palpating finger and the radial bone, is called kathinya. relation between dosha and bala.

From individual to individual, the amount of pressure varies depending on the prakruti and volume of blood in the radial But before this analysis, the radial artery should be emptied artery. When deeper pressure is used to stop the artery the by pressure on the brachial artery in the bicipital groove force will be higher. against the humerus. This way of palpation helps to find whether the vessel is thick or thin, elastic or plastic, rigid, 3.5 Akruti (Volume and Tension) hard or rough [1-7]. Table 8 shows the relation between Akruti indicates volume and tension. Volume is experienced dosha and Kathinya. as the uplift to the palpating finger and an estimate of left ventricular output per beat (stroke volume) is given by the duration. Tension is the pressure between two uplifts, 7192 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

4 COMPARISON OF TRADITIONAL As per the studies, in modern medicine pulse wave velocity has significant results and the role of wave velocity of the PARAMETERS WITH MODERN PARAMETERS pulse in Tridosha analysis in the context of Ayurveda has to Based on Ayurvedic conventional texts, pulse qualities or be explored. Based on traditional texts, there is no direct properties such as Gati (pulse movement), Vega (Rate or relationship between the pulse wave velocity and vega but speed of the pulse), Tala (rhythm or stability of the pulse), can be closely associated to it. By the pulse wave velocity Bala (force), Akruti (Volume and Tension), Tapamana measurement, the variations in doshas can be considered. (Temperature) and Kathinya (Consistency of the vessel Table 9 gives the summary about PWV based on Tridosha. walls) plays an important part in Nadi Pariksha and these properties were investigated above in this review. Among 4.3 Pulse Rate Variability these properties mainly Gati, Vega, Tala and Kathinya of The palpation of pulse gives the pulse rhythm which is by pulse can be matched with the parameters of the modern nature more qualitative. The time pulse series enables the pulse specifically pulse movement, wave velocity of pulse, pulse rhythm which is to be analyzed quantitatively by variation of pulse rate and stiffness of artery. acquiring through instruments. The study on pulse rate variability (PRV), which is considered as a surrogate pointer 4.1 Pulse Movement of heart rate variability (HRV) is of great interest in the For thousands of years, the traditional practice followed by recent past [11-13]. PRV cannot be compared with any Ayurveda in the assessment of gati of the pulse is very equivalent terms in traditional texts but there is a close subjective in manner. In the view of research based on association between intermittent Nadi and PRV. This is evidence, the scientific way of assessing the gati nature is because intermittent Nadi and its nature can be clearly of importance with a perfect considerate of its biological explained on the basis of some important parameters such significance. The physiological importance of gati from rate, as analysis of pulse rate variability and its missing peaks, volume and character of the pulse is discussed by beat to beat variation in the interval of pulse etc. Based on Upadhyaya in his medical and investigational studies on the pulse wave obtained from Nadi Tarangini, there are Nadi Pariksha which states that the gati resembles sarpa significant variations based on different age groups and gati whose character is curvilinear when the pulse rate is disorders depending on the beat to beat alterations [14]. fast and small volume, it signifies vata pulse whereas when Significant differences across age and disorders in the the rate is slow and volume is high with jumping character, pulse intervals of artery (API) are obtained in the analysis similar to Chapala gati it resembles pitta pulse. Kapha pulse based on the time domain, frequency domain and nonlinear is obtained when there is slow rate with volume in between measurements [15]. There is a major role in Nadi Pariksha vata and pitta [8]. for the pulse stability or rhythm but detailed description is lacking in the textbooks about its relationship with 4.2 Pulse Wave Velocity Tridoshas. The measurement of the swiftness of the pressure waves that travel along the segments of the artery is called Pulse 4.4 Arterial Stiffness Wave Velocity (PWV). The distance or the traveling time of The arterial stiffness examined from velocity of pulse wave the pulse wave between two assessing positions of the (PWV) is of great importance in the field of research as it is pulse is termed as the PWV [9]. Compared to the peripheral considered as a cardio-vascular events predictor [16]. Due network, blood flows faster in aorta with a speed variation to age and atherosclerosis, the arteries stiffen. In from m/s in aorta to mm/s in peripheral network. Pulse cardiovascular risk assessment, the role of arterial pulse wave velocity (PWV) is the velocity of the pulse wave and it wave analysis is discussed in detail by Alberto et al. [28]. is ranging from 5 to 15 m/s. Cardiovascular risks are The longitudinal study done by Boutouyrie provided the first indicated with the help of the Pulse wave velocity (PWV) in direct evidence on the fact that the aortic stiffness is a self- the recent past [10]. Based on the longitudinal studies, the determining interpreter of primary coronary even in aortic PWV is observed as a perfect interpreter of hypertensive patients [29]. An independent study done by impending cardiovascular events and all-cause mortality. Laurent claims that the stiffness of aorta is believed to be in an independent analyst of all-cause and cardiovascular death in hypertensive patients. The pulse wave velocity is 7193 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 considered as an arterial stiffness surrogate measurement, prevention [32]. The basic material used for fabrication of closely corresponding to the depiction of mrityu nadi. The the graphene-coated fiber is a type of double covered yarn, measurement of stiffness of the aorta is termed as stiffness highly elastic polyurethane (PU) fiber core which is wrapped index (SI). This is measured from the radial artery and is by two helically-wound polyester (PE) fibers. This has closely corresponding to the volume of the pulse measured characteristics like good linearity, sensitivity, stability, using photoplethysmograph (PPG). There is pulse reproducibility together with the fast response and recovery amplification at peripheral artery when the pressure wave is suitable for a smart radial artery pulse sensor. Here the propagating from central to peripheral arteries, due to sensing element is PDCY-RGO as shown in fig. 5 [32]. multiple reflections from various reflection sites and these reflection sites are closer to peripheral arteries while comparing with central arteries. The peripheral arteries do not give precise results in cardiovascular studies due to the above reason so the arterial stiffness measured from peripheral arteries cannot be used as a surrogate for aortic and carotid stiffness [27-29]. As there is a major role for radial artery in Ayurveda, where SI measured from radial artery is reflected as major parameter in Tridosha analysis.

5 SPHYGMOLOGY SENSORS There are varieties of sensors used for pulse diagnosis. Sensors ranging from normal piezoelectric sensor (Lead Zirconate Titanate) to heart beat sensor (SEN-11574) can be used for this purpose. Proper positioning of sensors on the radial artery along with a perfect signal conditioning unit will give three perfect waveforms: Vata, Pitta and Kapha. A variety of systems have been designed for pulse diagnosis in Ayurvedic as well as Allopathic field. This section covers Fig. 4 The IPMC-pulse extraction setup installed on an the existing sensors used for pulse diagnosis. individual [31]

5.1 Soft Wearable Ionic Polymer Sensors 5.3 Compound Pressure Sensor Array Based on sensing applications, a new bio-compatible In disease diagnosis, it is important to collect the pulse flexible structure sensor made of IPMC (Ionic-Polymer- wave from different points on the radial artery under Metal-Composites) is introduced as shown in fig. 4. With a different static pressure. This type of pulse acquisition is not soft-wearable IPMC-sensing unit they were able to explore possible by single type sensor and the feasibility of setting the bio-potential measurement domains thereby recording three sampling points for detecting the variation in radial the natural auscultations in wrist artery. The IPMC strip artery pulse wave is also less. Thus for this purpose a novel used is made of Nafion. A configured digital stethoscope flexible compound pressure sensor array is used. This was used to measure the simultaneous pulse tracks. The combination includes both piezoelectric and piezoresistive natural auscultation due to the pulsating blood flow is sensor for measuring the pulse wave and static pressure recorded with the sensor-strip placed over the wrist artery. individually. The inverted waveform occurrence and signal These will be demonstrated as periodic impacts on the intensity are guaranteed by the bending structure of the polymer strips. The electrical potential produced due to the sensor. The poroelastic materials help in flexible connection trusted mechanical stimuli is accepted through a pulse rate and reduction of interference in sensors as shown in fig. 6 extraction scheme yielding the number of beats produced [33]. The physical characteristics of sensor are important for per minute [31]. A sub-tensioned surface is posed by the collecting valid data from pulse wave and are satisfied by polymer which can be pressed against the posterior aspect the dynamic pressure sensor and static of the wrist. The IPMC output voltage is passed through a signal conditioning and beat detection unit. This experiment suggests a novel material for pulse bit sensing and pulse rate monitoring.

5.2 Stretchable Graphene-Coated Fiber Pulse Sensor The human health status is analyzed by using a newly designed and fabricated facile, scalable and portable radial artery pulse sensor. Here the sensing component is a stretchable graphene-coated fiber which has properties like good linearity and sensitivity towards the tensile strain. Due to the smart structure of sensor it can exactly detect the periodic pulse waves and its changes while doing exercise and disease. These signals are precise and repeatedly available. This single waveform has all the medical analysis characteristics for evaluating the cardiovascular risk factors in patients specifically artery stiffness and disease Fig. 5 PDCY-RGO pulse sensor [32] 7194 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

Fig. 6 Schematic diagram of the compound pressure sensor [33] pressure sensors. The structure includes a bending Fig.7 (a) Three piezoelectric diaphragm sensors (b) A dynamic sensor, PVDF piezoelectric sensor (produces silicon piezoresistive sensor [34] deformation due an external force) and a contactor. The static pressure sensor detects the bending pressure and the pressure reflected at the wrist. An innovative bendable compound pressure array was designed for achieving in- depth information about the radial artery pulse wave under various static pressures. The full attention of all the points on a patient according to TCM theory depends on the arrangement and size of the proposed sensors [33].

5.4 Pressure Sensors: Piezoelectric and Piezoresistive Radial artery pulse signals are pressure signals so pressure sensors are used to convert the mechanical pressure to electrical signal by placing the sensors over the radial artery at the wrist. This helps in digitization of pulse signals for Nadi Pariksha. The pressure sensor for this purpose includes both piezoelectric and piezoresistive. The sensor is the main element of a pulse acquisition system which also includes an analog signal conditioner and digitizer units. Electrical signals from the sensor are passed through Fig. 8 Pulse signal obtained the using piezoelectric and the analog signal conditioning unit followed by amplifier and piezoresistive sensor-based based system [34] filter circuits. Finally the signal is send to the digital circuit for ADC conversion. The signal is stored and further pressure units. In differential mode, the experienced processed in the PC [34]. The piezoelectric effect in pressure is converted to electrical signal which is then measuring the variations in pressure, force or strain, digitized using the 16-bit multifunction data acquisition card acceleration is done using the piezoelectric sensor Murata‘s NI USB-6210 [35]. Nadi is obtained in the form of time 7BB-15-6LO, which produces an electrical signal when a series as shown in fig. 8. The fingertip exerts pressure at dynamic force is applied (active transducer). Piezoelectric the artery which is sensed as nadi pulses. Three pressure sensors are used to measure the pulse signals as they are transducers on the wrist will sense the very minute in dynamic nature as shown in fig. 7 [34]. A pressure is pulsations in pressure units. In differential mode, the formed on the silicon substrate is measured through the experienced pressure is converted to electrical signal which diaphragm using a piezoresistive pressure sensor is then digitized using the 16-bit multifunction data MPX5010G6U. When pressure is applied the sensor bends acquisition card NI USB-6210 [35]. Three Millivolt Output as a result of which deformation occurs in the diaphragm Medium Pressure Sensors (strain gauge transducer) of size crystal lattice. The resistivity of the material changes due to 1cm×1cm having a tiny flexible diaphragm at the center deformation. The piezoelectric sensor is inferior to with 0–4 inch H2O pressure is attached on the wrist to piezoresistive pressure sensor in terms of accuracy, sense three location pulses, namely vata, pitta and kapha positioning MPX5010G6U and sensitivity [34]. Nadi is as shown in fig. 9. The strain is converted to electrical obtained in the form of time series as shown in fig. 8. The signal with the help of a Wheatstone bridge circuit with fingertip exerts pressure at the artery which is sensed as three constant resistors and a variable resistor [35]. As nadi pulses. Three pressure transducers on the wrist will shown in figure 10, piezoresistive MPXM2053D sensor from sense the very minute pulsations in FREESCALE is used to sense the wrist pulse. Signal conditioning unit using instrumentation amplifier is connected to the sensor followed by a real-time monitoring using myRIO DAQ card in LabVIEW myRIO 2014. Frequency domain analysis is done to extract the band energy. The advantage over piezoelectric sensor is that it

7195 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 does not require shielding. This sensor provides both dynamic and static responses. This sensor gives satisfactory results for wrist pulse [36]. Human pulse is detected using a piezoelectric sensor and the signals are processed a using signal processing circuit which includes signal amplifier, filters and noise- reduction circuit. The shape of pulse, rate of repetition and amplitude were found to be different for different doshas [37]. The transducer on operating will reject the static pulse pressure and detect the dynamic pulse pressure at the wrist. Pulse acquisition is done with help of an IC with PIC16F877A chip level programming and MPLAB IDE software. Heart rate is displayed using LCD. Signal processing is done with MATLAB while the SNR signals are exhibited with the mean Fig. 10 Soldered SMD MPXM2053D sensor [36] factor for vata, pitta and kapha. Increment in pulse and the normal pulse for each is detected with the help of mean factor as shown in fig. 11 [37]. Piezoelectric sensor specifically Grove-Piezo vibration sensor shown in fig. 12 is considered due to its specialties such as flexibility, vibration, impact and touch sensitivity, dimension, thickness and so on. The computational models and biostatic approaches help in analysis of waveform. These signals will help in disease analysis. The disease diagnosis is done based on certain specific factors like viscosity of blood, volume of blood etc. This sensor proved itself by giving better results compared to existing ones [38].

5.5 Optical Sensors Very minute details were captured using Optical sensor HOA 709 in its reflective mode and thereby acquiring pulse signals at the pitta point at radial artery. The sensor recorded the data before and after food and also the important changes in signal contour. The pulse contour obtained at wrist using optical sensor is similar to the signal obtained from the radial artery catheter. Figure 13 shows the experiment setup. Feature extraction is done on the information obtained from the pitta location. Several clinical parameters are also taken care with this experiment [39]. Fig. 11 Mean factor of pulse [37]

Fig. 9 Line diagram of pulse diagnosing system Sensor [35] Fig. 12 Nadi Pariksha System with Grove-Piezo vibration sensor [38]

kapha in accordance with PPG signal mean values [40]. The three phases Sparshana, Darshana and Prashna phases are used for Ayurvedic disease diagnosis. Three optical sensors at the three locations on the radial artery are used for implementing the first phase of Sparshana. These sensors are interfaced with the Arduino Uno microcontroller via USB connection which requires a 5V supply for operation. The captured analog output of sensor is converted to digital values using ADC in Arduino. Figure 15 shows the experimental setup [41]. A Velcro strap is used to attach three pulse sensors and also minimizes the external interference. This is wrapped around the wrist of the subject to get the pulse readings. A non- invasive system of Nadi Pariksha is designed to assist the medical practitioners in the diagnosing various ailments. The pulse palpation by three fingers at the wrist helps in finding the affected organ. Timely observation and identification of abnormal situation will help in saving a patient‘s life. The Sparshana phase is included by incorporating optical sensors and then to identify the Prakruti of the patient Fig. 13 Wrist Pulse Signal Acquisition [39] Artificial Neural Network algorithm is applied on the output waveform. Finally a decision tree algorithm is applied that resembles the other two phases Darshana and Prashna [41].

Fig. 14 (a) Sensor arrangements in transmission mode and reflection mode (b) PPG sensor design in transmission and reflection modes [40] Fig. 15 Hardware Setup [41] The blood flow rate is monitored using a photoplethysmographic (PPG) sensor. This sensor is 5.6 Image Sensors placed at identifiable points on radial artery corresponding A CCD based device is used to detect the pulse image for to Vata, Pitta and Kapha respectively and its output is diagnosis according to Traditional Chinese Medicine. Here analyzed with the help of LabVIEW software. This method the three pulses are Cun-Guan-Chi. Synchronous pulse is a non-invasive method for detecting pulse with a light image data of distinctive pulse condition is collected using source and detector. The change in blood volume is MM-3 pulse model. The characteristic pulses comprise of indicated by the PPG signal. These changes are noted the standard pulse, the slippery pulse, the gentle pulse and mainly at the peripheral parts of the body such as fingertips, the spineless pulse. The pulse waves were removed by earlobe etc. The rate of blood flow is identified using the using the area method based on lens imaging principle. The light intensity variation which is passing through the skin or restricting of 3D pulse condition image is done. Important reflected from it [40]. The PPG signal detection has two features were extracted including the modes: transmission mode and reflection mode. The finger is located between LED and photodiode during transmission mode whereas in reflection mode both LED and photodiode are positioned on one side of the fingertip as shown in fig. 14. There is a variation for vata, pitta and 7197 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

5.7 PVDF based Pulse Sensor The three pulses from the radial artery are obtained by designing and analyzing a PVDF material based pulse sensor. The sensitivity of the material is also analyzed. Frequency and amplitude analysis is done to determine the shape of the pulse. The design is shown fig. 17 [43]. The factors that determine the length and breadth of the PVDF required for the sensor are as follows:  The radial artery diameter and its sheath above which varies from 2mm-4mm without sheath and with sheath it varies from 3mm-5mm.  The length of sensor should be more than or twice the diameter with sheath. Therefore the length is (5x2) mm that is 10mm.  The length should not be more than the distance between the two tendons: Abductor pollicis longus and Extensores pollicis longus. This can vary from individual to individual from 10 mm to 20 mm; therefore Fig. 16 The section of three detection probes (1 – the length was restricted to 14mm. The breadth of the Computer, 2 – CCD image sensor, 3 – Translucent glass PVDF depends on the placement of sensor at three lens of sealed chamber,4 – Intake of sealed chamber, 5 – points on the wrist. Light source, 6 – Pressure sealed chamber, 7 – Printed with  The three pulses are obtained at a distance of 7mm black and white checkerboard silicon film, 8 – The skin center to center thus the breadth is restricted to 5mm. surface of Cun-Guan-Chi) [42] Plexiglas is used for making the handle for holding the PVDF material [43] The sensors are placed on the wrist at the locations identified by Siddha experts. The system necessary for getting the radial artery pulses is tested initially with signals from the function generator which resembled in shape with any other pulse system such as PPG. PVDF (polyvinylidene fluoride) is a piezoelectric polymer which is highly non-reactive. It is a pure thermoplastic fluoropolymer. The hidden physiological signals are found by experts using palpation techniques hence pulse reading becomes a haptics technique [44].

5.8 USB-based Doppler ultrasonic blood analyzer The wrist pulse signals are collected by using a USB-based Doppler ultrasonic blood analyzer. The collected signals are transmitted using a USB interface and for further processing and analysis it's stored in PC. The signals are collected in three steps. Initially a rough location is found in the wrist by feeling the pulse fluctuation using three fingertips. As there is only single probe for the Doppler ultrasound device, the pulse fluctuation is detected at one position. Pulse fluctuation at the second position is more compared to others, hence this position is chosen. The Fig. 17 Design of PVDF based Pulse sensor [43, 44] second pulse is Guan according to TCM (Pitta in Ayurveda) as shown in fig. 18. The next step is to obtain the most period, the frequency, the width, and the length as shown significant signal by varying the probe positions, slightly fig. 16 [42]. On a particular pulse diagnosis pressure, the changing the angle of against the skin. Finally, this wrist CCD image sensor with three probes detects the random pulse is recorded and saved as Doppler spectrograms. To multi-point dynamic images on the diagnosis parts. The 3-D reduce the measurement errors, the above steps are pulse illness information can be developed from the repeated several times. dynamic image. Above three vertically placed probes, one CCD image sensor is placed. The dynamic image is acquired whenever there is a pulse beat. The 3D data and all-inclusive pulse state characteristic can be attained. Further analysis is needed to make more pulse information from skin surface on Cun-Guan-Chi to develop the objective pulse diagnoses [42].

This article does not contain any studies with human participants performed by any of the authors.

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