J Hum Hypertens. 2014 Dec;28(12):736-42.

Radial arterial compliance measurement by fiber Bragg grating pulse recorder.

 

U Sharath1, C Shwetha2, K Anand3 and S Asokan1,4

1Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore, India;

2Department of Clinical Neurosciences, National Institute of Mental Health and Neuro Sciences, Bangalore, India

3Department of Radio Diagnosis, M S Ramaiah Medical College, Bangalore, India

4Applied Photonics Initiative and Robert Bosch Center for Cyber Physical Systems, Indian Institute of Science, Bangalore, India.

 

Correspondence: Professor S Asokan, Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India.

E-mail: sundarrajan.asokan@gmail.com or sasokan@iap.iisc.ernet.in

 

Abstract:

In the present work, we report a novel, in vivo, noninvasive technique to determine radial arterial compliance using the radial arterial pressure pulse waveform (RAPPW) acquired by fiber Bragg grating pulse recorder (FBGPR). The radial arterial compliance of the subject can be measured during sphygmomanometric examination by the unique signatures of arterial diametrical variations and the beat-to-beat pulse pressure acquired simultaneously from the RAPPW recorded using FBGPR. This proposed technique has been validated against the radial arterial diametrical measurements obtained from the color Doppler ultrasound. Multiple trials have been carried out in this work and the results from both techniques have been found to be in good agreement with each other.

 

Supplement:

The evaluation of arterial compliance is an important part of cardiovascular diagnosis, in view of its established capability to forecast cardiovascular diseases. The classic definition of arterial compliance is the change in arterial diameter because of a given change in arterial blood pressure. Arterial compliance is an index of the elasticity of the given vessel. The arterial compliance varies with position along a vessel depending on the age and pathological conditions. Reduced compliance in arteries is regarded as a major risk factor for the development of systolic hypertension. Furthermore, as the vessels stiffen, the physical forces that oppose aortic valve opening increase and can contribute to ventricular hypertrophy, aortic root dilation, valvular dysfunction and heart failure. Reduced compliance is prominent in pre-hypertensives, hypertensives, diabetics and smokers, which aggravates atherosclerosis and leads to increased cardiovascular risk.

In the present technique, the radial arterial compliance is evaluated using the radial arterial pressure pulse waveform (RAPPW), which is recorded using the Fiber Bragg Grating Pulse Recorder (FBGPR) developed, by simultaneously observing the arterial diametrical change and the pulse pressure. The FBGPR differs from the other conventional devices used, by its ability to simultaneously record both arterial diametrical variation and beat-to-beat pulse pressure in the RAPPW. The present technique eliminates the use of two sensors, as in the case of conventional methods (volumetric/diametric sensor and pressure sensor). The use of fiber Bragg grating (FBG) sensors brings potential advantages such as insensitivity to electromagnetic interference, low fatigue and ultra-fast response, making the proposed FBGPR an effective means for evaluation of radial arterial compliance.

 

Illustration

Arterial diametrical variation for Subject:

A male subject (aged 23 years) underwent the above mentioned experimental procedure, where the FBGPR as represented in Figure 1 is wound on the wrist of the subject. The beat to beat radial arterial pulse pressure recorded from FBGPR is shown in Figure 2. The CDU probe is positioned adjacent to the FBGPR which records the radial arterial diameter as shown in Figure 3. The RAPPW recordings from FBGPR as shown in Figure 4 and radial arterial diametrical measurements from CDU as shown in Figure 5, are analyzed in the following 4 phases of the procedure. Table 1 depicts the segregation of the phases and the subsequent data recorded from both FBGPR and CDU simultaneously at each phase.

su fig1

Fig 1. Design and pictorial representation of FBGPR

 

su fig2Fig 2. RAPPW recorded from FBGPR

su fig3Fig 3. FBGPR and the electronic stethoscope showing simultaneous data acquisition during sphygmomanometry

su fig4

Fig 4. The FBGPR response during Sphygmomanometric examination.

su fig5Fig 5. (a) The CDU response during various Phases of sphygmomanometric examination.

 

Table 1. Data recorded by FBGPR and CDU during sphygmomanometric examination for subject 1

su tab1

 

 

The movement in the envelope of the RAPPW obtained by the FBGPR is found to be in step with the arterial diametrical variation obtained from the CDU during the sphygmomanometric test procedure.

 

Arterial Compliance for the Subject:

The arterial compliance of the subject is obtained by the ratio of change in the arterial diameter to the change in blood pressure. The segment between phase 2 and phase 3 is considered for the radial arterial compliance computation purpose, in view of the fact that phase 2 and phase 3 are the least and maximum arterial diameters attained by the radial artery, which is also attributed to SBP and DBP of the subject respectively during the sphygmomanometric test.

The arterial compliance from FBGPR is computed by the ratio of change in arterial diameter to change in the beat-to-beat pulse pressure simultaneously acquired from the recorded RAPPW between phase 2 and phase 3. 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. It was observed that the arterial compliance obtained from both the FBGPR and CDU methodologies are in good agreement with each other.

In conclusion, a novel, in-vivo, noninvasive, image-less technique for the measurement of radial arterial compliance using FBGPR is demonstrated in this work. The FBGPR developed has the ability to record the RAPPW, which indicates the arterial diametrical variations and the beat-to-beat pulse pressure simultaneously. The results obtained from FBGPR technique correlates significantly with the arterial compliance estimated with using the CDU.

 

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