CLIAMS:We claim
1. A method of measuring arterial compliance of a subject using a single sensor comprising the steps of:
recording radial arterial pulse pressure waveform using said sensor;
assessing arterial diametric variations and beat-to-beat pressure variations from said radial arterial pulse pressure waveform; and
computing ratio between said arterial diametric variations and said beat-to-beat pressure variations to measure said arterial compliance.
2. The method of claim 1, wherein said sensor is Fiber Bragg Grating sensor.
3. The method of claim 1, wherein said radial arterial pulse pressure waveform is recorded during sphygmomanometer examination.
4. The method of claim 1, wherein said radial arterial pulse pressure waveform is recorded by placing said sensor at radial artery to pick arterial perturbations during sphygmomanometer examination.
5. The method of claim 4, wherein said sphygmomanometer examination comprises the steps of:
occluding brachial artery above systolic blood pressure of said subject; and releasing pressure beyond diastolic blood pressure of said subject while said sensor records said arterial perturbations.
6. The method of claim 1, wherein said arterial diametric variation is assessed based on change in mean diametric strain between systolic blood pressure and diastolic blood pressure.
7. The method of claim 6, wherein said mean diametric strain is computed based on mean of dip and raise in said radial arterial pulse pressure waveform.
8. The method of claim 1, wherein said pressure variation is assessed based on change in pulsating pressure strain between systolic blood pressure and diastolic blood pressure.
9. The method of claim 8, wherein said pulsating pressure strain is computed based on difference between curve movement in said radial arterial pulse pressure waveform.
10. A method of assessing Augmentation Index of a subject using a Fiber Bragg Grating sensor comprising the steps of:
recording a plurality of consecutive pulse waveforms of said subject using said sensor;
reading sensor response corresponding to one or a combination of systolic pressure and late systolic pressure based on said plurality of consecutive pulse waveforms; and
computing said Augmentation Index of said subject based on a ratio of late systolic pressure and systolic pressure.
11. The method of claim 10, wherein said method further comprises the step of calculating average pulse from said plurality of recorded consecutive pulse waveforms, and computing said sensor response based on said average pulse.
12. An apparatus for measuring arterial compliance comprising:
a Fiber Bragg Grating (FBG) Sensor mounted on a diaphragm;
a strap operatively coupled to said Fiber Bragg Grating Sensor and provided with a means to fix on wrist of a subject;
a FBG interrogator connected to said FBG sensor through an optical fiber and capable of recording perturbations sensed by said FBG sensor; and
an inflatable cuff with a means to fix on said subject, wherein said FBG interrogator records radial arterial pulse pressure waveform by means of said FBG sensor and uses said radial arterial pulse pressure waveform to asses arterial diametric variations and beat-to-beat pressure variations from said radial arterial pulse pressure waveform to compute ratio between said arterial diametric variations and said beat-to-beat pressure variations and measure said arterial compliance.
13. The apparatus of claim 12, wherein said diaphragm is flexible.
14. The apparatus of claim 12, wherein said diaphragm is stretched and fixed on a frame, and wherein said strap is coupled to said frame.
15. The apparatus of claim 12, wherein said inflatable cuff is a Riva- Rocci cuff.
,TagSPECI:FIELD OF THE INVENTION
The present invention comprises an improvement in, or a modification of the invention claimed in the specification of the earlier patent applied for under the application number 4989/CHE/2012. The earlier invention relates to a novel apparatus using Fiber Bragg Grating (FBG) sensor to record arterial pulse waveform in a non-invasive manner and using it for measurement of blood pressure. The present invention, in continuation with the earlier invention, relates to a novel method of using an improved apparatus for conducting further cardiovascular diagnostic tests and measuring arterial compliance using a Fiber Bragg Grating Pulse Recorder (FBGPR).
The disclosure pertains to the field of medical diagnostics, and more specifically pertains to in-vivo, non-invasive measurement of Arterial Compliance and Augmentation Index (AI), which are vital diagnostic tools for assessing cardiovascular condition of a person.

BACKGROUND OF THE INVENTION
The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Changing lifestyles associated with industrialization and development of societies are resulting with changes in dietary habits causing increased incidences of cardiovascular diseases. According to WHO report, infectious diseases which were the major cause of deaths earlier have been overtaken by cardiovascular diseases as the leading cause now. Also elimination of infectious diseases and availability of better health care leading to increased life expectancy has resulted in aging societies. Larger number of higher age group people has also compounded the situation needing better medical facilities for diagnosis of cardiovascular diseases.
The causes of cardiovascular disease are diverse but atherosclerosis and/or hypertension are the most common. Additionally, with aging come a number of physiological and morphological changes that alter cardiovascular function and lead to subsequently increased risk of cardiovascular disease, even in healthy asymptomatic individuals
Although cardiovascular disease usually affects older adults, antecedents of cardiovascular disease, notably atherosclerosis, begin in early life. Atherosclerosis is a specific form of arteriosclerosis in which an arterial wall thickens and looses its elasticity, as a result of accumulation of calcium and fatty materials such as cholesterol and triglyceride. Therefore, loss of arterial elasticity is a predictor of cardiovascular diseases.
Arterial Compliance is an index and measure of the elasticity of the given vessel. Classic definition of arterial compliance is the change in arterial diameter due to a unit change in arterial blood pressure. Compliance varies depending on age and pathological conditions. Reduced compliance in arteries is regarded as a major risk factor for the development of systolic hypertension. Furthermore, as vessels stiffen, physical forces that oppose aortic valve opening increase and can contribute to ventricular hypertrophy, aortic root dilation, valvular dysfunction and heart failure. Therefore, arterial compliance plays a significant part in modern cardiovascular diagnosis and has established capability to forecast cardiovascular diseases.
Arterial compliance can be measured by several techniques, many of them being invasive. Non-invasive evaluation of arterial compliance falls into three broad groups:
Methods based on measurement of pulse transit time with devices such as Complior system, Sphygmocor system etc.
Methods based on analysis of arterial pressure pulse carried out by Subclavian pulse tracing Doppler–echocardiography, Wrist automatic tonometer etc.
Methods based on direct stiffness calculation using measurements of diameter by Wall Track System, Transesophageal echocardiography etc.
As it is apparent from the definition of arterial compliance, two parameters namely, change in pressure and change in arterial diameter are required to assess arterial compliance. Conventional methods, therefore, need at least two sensors to record these two parameters. Another index commonly used to quantify arterial elasticity or stiffness and a good predictor of future cardiovascular events is Peripheral Augmentation Index (AIx). AIx is a measure of ventricular vascular coupling related to arterial stiffness and wave reflections and is traditionally quantified from arterial pressure waveforms. A part of the arterial pressure wave travelling distally away from the heart towards the extremities is reflected back from peripheral impedance points. For a healthy individual, the arrival of the reflected wave to the aorta is at diastole. With increase in age and in presence of cardiovascular conditions of the subject, arterial compliancy decreases, making the arteries stiffer, which results in the reduction of the transit time between the incident and reflected pressure wave. Consequently, the reflected wave arrives at the aorta during systole of the same cardiac cycle, augmenting the central blood pressures. This augmentation of central pressure can be quantified by AIx, defined as the difference between pressure at the point of late systolic augmentation and diastolic pressure expressed as a percentage of pulse pressure. AIx is associated with cardiovascular risks, ventricular hypertrophy, aortic root dilation and valvular dysfunction. AIx is increased by cardiovascular risk factors such as age, smoking and hypertension and is found to be an independent marker of coronary artery diseases.
There is therefore a need in the art to provide apparatus and methods for measuring arterial compliance and other allied indices, such as peripheral augmentation index, by means of a single sensor, which accurately and reliably measures such attributes/parameters.
All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION
An object of the present disclosure is to resolve problems and disadvantages of conventional technologies as described above.
Another object of the present disclosure is to provide a method and equipment for capturing pulse pressure wave form using a sensor that is compact, immune to electromagnetic interference, has high sensitivity, low noise and is immune to light source.
It is an object of the present disclosure to provide a method and equipment for assessing arterial compliance using only one sensor.
It is an object of the present disclosure to provide a safe and reliable method and equipment for assessing radial arterial compliance.
It is another object of the present disclosure to provide a economical method and equipment for assessing arterial compliance and augmentation index.
It is another object of the present disclosure to provide diagnostic tools that may be widely available for screening of general public for early detection of cardio vascular incidences.

SUMMARY OF THE INVENTION
The present disclosure in continuation of earlier invention discloses an improved apparatus and method for assessing arterial compliance including, but not limited to, radial arterial compliance and peripheral arterial compliance. The proposed method uses a Fiber Bragg Grating Pulse Device (also interchangeably referred to as Fiber Bragg Grating Pulse Recorder (FBGPR) hereinafter) for recording radial arterial pulse pressure waveform (RAPPW) under, say a sphygmomanometer examination. The present disclosure also relates to assessment of arterial distention from captured waveform, which is one of the essential requirements for assessing arterial compliance.
In one aspect, the present disclosure discloses a method of capturing data regarding arterial diametric variations and beat-to-beat pressure variations from arterial pulse pressure waveform recorded during sphygmomanometer examination using FBGPR, and using the captured arterial diametric and pressure variations for assessment of arterial compliance. In another aspect, the present disclosure also discloses a method of computation of peripheral augmentation index based on the RAPPW that is recorded by FBGPR, wherein the peripheral augmentation index indicates a measure of arterial stiffness and in turn assists in computation of peripheral arterial compliance.
In another aspect of the present disclosure, estimation of arterial compliance can be based on analysis of arterial pulse pressure wave. In each cardiac cycle, the heart generates a pressure wave, which propagates through an arterial tree, wherein, along its path, the pressure wave interacts with arterial walls and causes arterial distention movement. In yet another aspect, the present disclosure relates to estimation of arterial compliance based on straight-arm artery model, wherein, when, proximally, brachial artery in the arm is occluded and gradually released using a sphygmomanometric cuff (also known as Riva-Rocci cuff and used interchangeably hereinafter), distally, corresponding change in characteristics of Radial Arterial Pressure Pulse waveform (RAPPW) is noted.
Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects and advantages of the invention will become better understood when the description is read with reference to the accompanying drawings, wherein:
Figure 1(a) illustrates schematic arrangement of FBG pulse recorder in accordance with an embodiment of the present invention.
Figure 1(b) is a photograph of FBG pulse recorder with its accessories in accordance with an embodiment of the present invention.
Figure2 illustrates exemplary RAPPW recorded using FBG pulse recorder for plurality of subjects in accordance with an embodiment of the present invention.
Figure 3(a) illustrates an exemplary FBG pulse recorder response during sphygmomanometer examination of a subject in accordance with an embodiment of the present invention.
Figure 3(b) illustrates an exemplary enlarged view of FBG pulse recorder response of figure 3(a) in accordance with an embodiment of the present invention.
Figure 4(a) illustrates another exemplary FBG pulse recorder response during sphygmomanometer examination of second subject in accordance with an embodiment of the present invention.
Figure 4(b) illustrates another exemplary enlarged view of FBG pulse recorder response of figure 4(a)in accordance with an embodiment of the present invention.
Figure 5 illustrates CDU examination for arterial diameter measurementin accordance with an embodiment of the present invention.
Figure 6 illustrates output of CDU in respect of arterial diameters for first subject in accordance with an embodiment of the present invention.
Figure 7 illustrates output of CDU in respect of arterial diameters for second subject in accordance with an embodiment of the present invention.
Figure8illustrates an exemplary pulse pressure wave detailing various features in accordance with an embodiment of the present invention.
Figure 9 illustrates exemplary RAPPWs of plurality of subjects recorded using FBG pulse recorder in accordance with an embodiment of the present invention.
Figure 10 illustrates averaged RAPPWs of Figure 9in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
According to one embodiment, the present disclosure relates to use of one Fiber Bragg Grating (FBG) sensors, which have advantages such as insensitivity to electromagnetic interference, low fatigue and ultra-fast response, making the proposed FBGPR an effective means for capturing and recording the pulse pressure waveform. FBG is a periodic modulation of refractive index of a core of a single-mode photosensitive optical fiber, along its axis. In implementation, when a broadband light is launched into an FBG, a single wavelength that satisfies the Bragg condition can be reflected back while the rest of the spectrum is transmitted. This reflected Bragg wavelength (?_B) of the FBG can be given by ?_B=2n_eff ?
Here, ? is periodicity of grating and n_effis effective refractive index of fiber core. In the present disclosure, any external perturbation such as strain, temperature, etc. at the grating site of the FBG sensor, can alter periodicity of grating, and in turn change the reflected Bragg wavelength. By interrogating shift in Bragg wavelength, parametric external perturbation can be quantified. For example, strain effect on an FBG sensor can be expressed as,
????_B=?_B [1-?n_eff?^2/2 [P_12-?(P_11-P_12 ) ] ]E
,where, P11 and P12 are components of strain-optic sensor, ? is the Poisson’s ratio and e is the axial strain change. The temperature effect on the FBG sensor can be neglected as the sensor made of FBG can be to be used in controlled environment, also duration of use being small.
Figures 1(a) and 1(b) are an exemplary embodiments of a FBGPR (1) having a FBG sensor and accessories for use as a pulse recorder. As shown, FBGPR (1) includes a Fibre Bragg Grating sensor (2) having a defined gauge length of around 3mm (any other length is also possible and within the scope of the instant disclosure) and can be fabricated in a photo-sensitive germania doped silica fiber, using, for instance, a phase mask grating inscription method. It is to be appreciated that any other method or fabrication technique can be incorporated for use and configuration of the FBG sensor (2). According to one embodiment, strain sensitivity of such a FBG sensor is approximately 1.20 pm/µe.
According to one embodiment, FBG sensor (2) can be placed longitudinally at the centre of and bonded to outer surface of a diaphragm (3), such as silicone diaphragm (3), of suitable size, for example15mm x 15mm x 0.4 mm and made of, for instance, flexible and stretchable material such as but not limited, to silicon rubber. In another embodiment, diaphragm (3), duly stretched, can be adhered onto two free ends of a frame (4), made of light but rigid material such as, but not limited to, plastic, formed in the general shape of, but not limited to, a broad C of equal or unequal proportions with suitable dimensions such as 10mm x 15mm x 10mm.Any other structure for holding the diaphragm (3) can also be incorporated and is within the scope of the present invention.
According to one embodiment, attached to frame (4) is a strap (5) of suitable size so as to facilitate its wrapping around wrist of a person whose arterial compliance is to be assessed. Strap (5) has means attached to it, such as, but not limited to, Velcro strips to facilitate fixing of embodiment at a subjects’ wrist firmly. FBG sensor (2) is in the core of an optical fibre (6), distal end of which is connected to FBG interrogator (7).
According to one embodiment, FBGPR (1) can be placed on wrist of a subject so that FBG sensor (2) is placed on the subject’s skin portion above the Radial Artery (8), so that perturbations caused by pulse pressure variations are picked up by the FBG sensor (2).It may be appreciated that above exemplary embodiment may be modified to meet the requirement of recording pulse pressure wave of other peripheral arteries at other suitable locations.
According to one embodiment, silicone diaphragm facade of FBGPR(1) can be placed on flexor aspect of wrist of the subject, corresponding to the site of maximal impulse of radial arterial pressure pulse. FBGPR(1) can be fixed on the wrist using a Velcro strap 5, which also exerts minimal inward pressure on the silicone diaphragm (3), providing better contact with radial artery. Pulsatile blood flow in the radial artery exerts pressure on the silicone diaphragm (3), creating strain variations on it which is sensed by the FBG sensor (2) to provide fundamental quantitative information of RAPPW as shown in Fig. 2, comprising beat-to-beat pulse pressure and arterial diametrical variations of the subject, also interchangeably referred to as user or individual or patient in the instant disclosure.
According to one embodiment, FBG interrogator (7) can, based on Radial Arterial Pressure Pulse waveform (RAPPW) generated by FBG sensor (2), observe arterial diametrical change and change in pulse pressure in order to accordingly compute radial arterial compliance for a patient/user. RAPPW can also be evaluated to compute peripheral augmentation index, which is a measure of radial arterial stiffness, derived based on augmented systolic pressure in percentage of pulse pressure, which can be realized from recorded RAPPW by the FBGPR (1). Such computation of peripheral augmentation index, which is indicative of peripheral arterial compliance, and computation of radial arterial compliance can, as a result, making proposed FBGPR(1) an effective means for evaluation of arterial compliance.
Figure 2 illustrates exemplary beat to beat pulse pressure waves 200 captured by FBG interrogator (7) on a plurality of subjects using FBG pulse recorder (1).
Figure 3(a) illustrates an exemplary recording of pulse pressure wave captured by FBGPR (1) through the process of occlusion of brachial artery above systolic blood pressure by means of sphygmomanometer cuff to resist the blood flow to distal arteries and, thereafter, gradually releasing cuff pressure till normal pulse wave is regained (referred to as sphygmomanometer examination).Phase1(9) depicts FBG response to normal pulsations prior to the inflation of the cuff. Riva-Rocci cuff is then inflated gradually to a little over SBP of the subject, which causes occlusion of brachial artery, resulting in resistance to blood flow to radial artery that further results in the diametrical collapse of the artery to a certain degree. This is represented by drop in envelope of strain response of FBGPR. This is identified as phase 2 (10) when the radial artery is at its least diametrical dimension. As the pressure in the cuff is released and upon reaching the SBP of the subject, first pulse is recorded in FBGPR response. Systole point(11)(also referred to as S point)in the Figure 3(a) corresponds to this situation. On further deflating the cuff, blood flow in radial artery increases, causing increase in its diameter owing to increase in pressure pulsations in accordance with which, envelop of FBGPR (1) response also increases, which is denoted as phase 3(12). At DBP, turbulent blood is replaced by streamline flow attributed by the maximal arterial distension, is depicted by maximum strain value attained in FBGPR response. Diastole point (13)(also referred to as D point) corresponds to this position. Subsequently as the cuff is deflated below DBP to complete removal of pressure in cuff, radial arterial diameter returns to its original state, observed as decrease in envelope of strain response from FBGPR. Phase 4 (14) corresponds to this position.
Figure 3(b) is an enlarged view 350 of above explained FBGPR response containing portion from S point to D point. The figure defines two terms namely “mean diametrical strain variation” and “pulsating pressure strain” (can also be understood as peak-to-valley strain), which are to be used in succeeding paragraphs for assessing arterial compliance. 15 and 16 are mean diametrical strains at S point(11) & D point(12) respectively, similarly 17 & 18 are pulsating pressure strains at S point & D point and both are self-evident from the figure of pulse waveform.
In an embodiment, a novel methodology to capture relevant data for calculating the arterial compliance is outlined. The methodology is based on finding, during experimentation, the movement of Arterial Pulse Wave is in step with arterial diametrical variations. These findings have been validated by experimentation involving parallel assessment of diametrical measurements using conventional method. Colour Doppler Ultrasound (CDU) was used for measuring arterial diameter as illustrated in Figure 5.
In an implementation, parallel assessment of arterial compliance using FBGPR and CDU in conjunction with sphygmomanometer equipment for blood pressure was carried out on two subjects, and results are illustrated herein. Obtained results are illustrated in two parts; former being the assessment of arterial diametric variation and latter being the computation of arterial compliance.

Assessment of arterial diametric variation
Subject 1: A male subject (aged 23 years) underwent the above mentioned experimental procedure. The arterial pulse wave recordings as illustrated in Fig 3(a) and radial arterial diametrical measurements from CDU as shown in Fig 6. Table 1 depicts data recorded from wave recordings and CDU simultaneously during different phases and at two points namely S point and D point during sphygmomanometer examination. The blood pressure of the subject measured by the conventional method is found to be 121mm Hg at SBP and 80 mm Hg at DBP.
Table 1
Category Description Mean Pulsatile Strain by FBGPR
(µ?) Radial Arterial Diameter by CDU
(cm) CDU
Figure
Phase 1
Pre-test Baseline Normal Pulsations before the inflating the cuff 26.12 0.225 6(a)
Phase 2
SBP The Riva-Rocci cuff is then inflated gradually to a little over the SBP of the subject, which caused occlusion of the brachial artery, in turn collapsing the radial artery. This is represented by the drop in the envelope of strain response of FBGPR. At the SBP, the radial artery is at its least diametrical dimension, denoted by the first pulse recorded in the FBGPR response -142.61 0.192 6(b)
Phase 3
DBP By further deflating the cuff, blood flow in the radial artery is resumed causing increase in its diameter owing to increase in the pressure pulsations. At DBP, turbulent blood flow resumes streamline flow, where maximal arterial distension is observed, depicted by the maximum strain value attained in the FBGPR response 94.46 0.238 6(c)
Phase 4
Post-test Baseline Deflating the cuff below DBP to complete removal of the pressure in the cuff, resulted in the radial arterial diameter returning to its original state, observed as the decrease in the envelope of the strain response from FBGPR 18 0.225 6(d)
Movement in envelope of RAPPW obtained by FBGPR is found to be in step with arterial diametrical variation obtained from CDU during the sphygmomanometric test procedure. The dip and raise in mean pulsatile strain recorded by FBGPR is 168.7µ? and 237.07µ? respectively as observed in Fig 3(a). Similarly, dip and raise in arterial diameter obtained from CDU is 0.013cm and 0.019cm respectively as observed in Fig 6. The dip to raise ratio obtained from FBGPR is 0.711, while that obtained from CDU is 0.714, which are in good agreement, thereby proving that relative arterial diametrical variation can be obtained from RAPPW recorded using FBGPR.
Subject 2: On similar lines, a female subject (24yrs) underwent arterial pulse wave recording under sphygmomanometer test procedure along with CDU measurements for arterial diameters. The arterial pulse recordings from FBG recorder are shown in Fig 4(a) and the radial arterial diametrical measurements from CDU are shown in Fig 7. Readings from FBGPR and CDU are shown in the Table 2 below. Blood pressure of subject measured by the conventional method is found to be 110mm Hg at SBP and 91 mm Hg at DBP

Table 2

Category Mean Pulsatile Strain by FBGPR
(µ?) Radial Arterial Diameter by CDU
(cm) CDU
Figure
Phase 1
Pre-test Baseline 0 0.126 7(a)
Phase 2
SBP -77.04 0.113 7(b)
Phase 3
DBP 36.16 0.132 7(c)
Phase 4
Post-test Baseline 6 0.126 7(d)

From Table 2, dip to raise ratio obtained from FBGPR (113.2/77.04) is 0.680 and from CDU (0.013/0.019) is 0.684, proving the relative arterial diametrical variation from FBGPR is in accordance with the CDU arterial measurement.

Assessment of Arterial compliance:
Based on above results the arterial compliance from pulse wave form is computed by the ratio of change in mean diametrical strain and change in pulsating pressure strain acquired from the recorded pulse wave between systole point and diastole point. Similarly arterial compliance from CDU is calculated by the ratio of the change in the measured arterial diameter to change in the intra-arterial blood pressure which is controlled by the cuff pressure. For subject 1, from Fig 3(b), at systole point, the mean diametrical strain and the pulsating pressure strain recorded are(-)142.61 µ? and 12.92 µ? respectively; simultaneously the arterial diameter recorded by CDU from Fig 6 is 0.192cm at a cuff pressure of 121 mm Hg. At Diastole Point, the mean diametrical strain and the pulsating pressure strain are 94.46 µ? and 108.85 µ? respectively; simultaneously the arterial diameter recorded by CDU is 0.238cm at a cuff pressure of 80 mm Hg. Change in FBGPR diametric response of 237.07 µ? to the change in pulsating pressure of 95.93 µ? resulted in arterial compliance of 2.4712. Simultaneously, a 0.046cm change in the arterial diameter from CDU is observed for change in intra-arterial blood pressure of 41 mm Hg from sphygmomanometer, resulting in arterial compliance of 1.121. The scaling factor for arterial compliance obtained from FBGPR to CDU is found to be 2.204.
Similarly for subject 2, from Figure 4(b) at Systole point, the mean diametrical strain and the pulsating pressure strain are (-)77.04 µ? and 3.02 µ? respectively; simultaneously the arterial diameter recorded by CDU is 0.113cm at a cuff pressure of 110 mm Hg. At diastole point, the mean diametrical strain and the pulsating pressure strain are 36.16 µ? and 53.92 µ? respectively; simultaneously the arterial diameter recorded by CDU is 0.132cm at a cuff pressure of 91 mm Hg. Therefore, arterial compliance values for subject 2 obtained from FBGPR and CDU are 2.223 and 1 respectively, providing a scaling factor for arterial compliance obtained from FBGPR recording to CDU to be 2.223.
Scaling factor obtained from the two subjects (2.204 and 2.223) are in good agreement and hence a normalized scaling factor of 2.21 is realized. Further the arterial compliance obtained from CDU of Subject 1 is 12% higher than subject 2. The arterial compliance obtained from recorded wave form of Subject 1 is 11% higher than subject 2. These results prove that the proposed novel methodology of FBGPR can be used to acquire arterial diametrical variation and arterial compliance in a single sphygmomanometer test procedure.
From the above it is established that a reliable assessment of arterial compliance may be obtained by using following empirical formula:
arterial compliance ( in cm/mmHg)=(change in mean diametric strain)/(change in pulsating pressure strain)÷scaling factor

wherein change in mean diametric strain being difference between mean diametric strain at diastole point& systole point, and change in pulsating pressure strain being difference between pulsating pressure strains at corresponding points of the pulse pressure waveform. Scaling factor, on the other hand, is an empirical constant which has been experimentally established to be 2.21.
In an embodiment of application, FBG interrogator may be equipped with requisite means and user interface to capture relevant data from the waveform on the display screen and provide the calculated arterial compliance values as output.
In another aspect, present disclosure also discloses a method of assessing Augmentation Index from the pulse pressure waveform recorded using FBGPR. Figure 8 illustrates a typical single arterial pulse waveform (19). Peak of the pulse wave is represented by systolic BP (20) of the subject. Lowest point on the wave is represented by Diastolic BP (21) of the subject. In between these two points are two auxiliary peaks representing Late Systolic Pressure (22) and Dicrotic Wave(23).Dicrotic notch (24) falls in between the two. Late Systolic Peak can be of interest as it represents pulse wave reflected from distal ends of artery. Early arrival of this reflected wave causes extra load on heart. As reflected wave is super imposed on main wave, its early arrival leads to higher Late Systolic Peak (22) in absolute terms. Augmentation Index is a measure of this phenomenon.
Figure 9 illustrates pulse waves 600 recorded on a plurality of subjects. Each subject has a unique identification arterial pulse pressure curve and wave pattern. With different pulse rates of each subject, number of cycles recorded in unit time varies accordingly. Ten consecutive pulses of each subject are selected and an average pulse calculated from these. Figure 10 illustrates averaged pulse wave 700 of these subjects. Readings of FBG response at Systolic point (20), Diastole Point(21) and Late Systolic point(22) are taken from these to calculate Augmentation Index which is the ratio of the difference between reflected systole pressure and diastole pressure to the difference between systole pressure and diastole pressure. By this method, the AIx computed for Subject I, II, III, IV and V from figure 7 are 0.775±0.024, 0.8025±0.019, 0.6172±0.029, 0.7884±0.023 and 0.7916±0.018 respectively.

ADVANTAGES OF THE INVENTION
The present disclosure uses only one sensor to compute arterial compliance, making the equipment more reliable.
The present disclosure uses FBG sensor, which are free from electromagnetic interferences and therefore gives more reliable results.
The present disclosure uses FBG sensor, which has low fatigue and ultra-fast response, making the arterial compliance assessment more convenient and making the equipment longer lasting.
The present disclosure enables arterial compliance and augmentation index to be assessed without having to workout absolute values of pressures and diameters.