Magnetic sensor for non-invasive detection of blood pulse and estimation of arterial compliance
01 Nov 2010-pp 170-175
TL;DR: In this paper, the authors presented their experience with the use of a giant magnetic resistance (GMR) based sensor for non-invasive detection of a bio-rhythm.
Abstract: The modulated magnetic signature based method has been recently suggested for non-invasive detection of blood pulse Here we present our experience with the use of a Giant Magnetic Resistance (GMR) based sensor for non-invasive detection of a bio-rhythm The influence of the biasing magnetic field on the amplitude and shape of the detected signal is presented Guidelines for the design of a bio-medical transducer using the principle are also provided The detected biorhythm is compared to other bio signals such as the blood flow velocity and arterial distension to gain insight into the physiological significance of the detected signal The analysis shows that the magnetic sensor provides a signal that is strongly correlated to the blood volume in the neighbourhood of the sensor Finally, the possibility of using the GMR based sensor for estimation of arterial compliance is investigated Simultaneous measurements performed at two different sites on the body show that this sensor can be used to measure arterial pulse wave velocity which is a clinically accepted measure of global arterial stiffness
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TL;DR: This work addresses the development of smart garments for lower limb motion detection, like a textile kneepad and anklet in which soft sensors and readout electronics are embedded for retrieving movement of the specific joint.
Abstract: Revealing human movement requires lightweight, flexible systems capable of detecting mechanical parameters (like strain and pressure) while being worn comfortably by the user, and not interfering with his/her activity. In this work we address such multifaceted challenge with the development of smart garments for lower limb motion detection, like a textile kneepad and anklet in which soft sensors and readout electronics are embedded for retrieving movement of the specific joint. Stretchable capacitive sensors with a three-electrode configuration are built combining conductive textiles and elastomeric layers, and distributed around knee and ankle. Results show an excellent behavior in the ~30% strain range, hence the correlation between sensors’ responses and the optically tracked Euler angles is allowed for basic lower limb movements. Bending during knee flexion/extension is detected, and it is discriminated from any external contact by implementing in real time a low computational algorithm. The smart anklet is designed to address joint motion detection in and off the sagittal plane. Ankle dorsi/plantar flexion, adduction/abduction, and rotation are retrieved. Both knee and ankle smart garments show a high accuracy in movement detection, with a RMSE less than 4° in the worst case.
71 citations
TL;DR: The design and experimental validation of an arterial compliance probe with dual magnetic plethysmograph (MPG) transducers for local pulse wave velocity (PWV) measurement was presented and was capable of detecting high-fidelity blood pulse waveforms.
Abstract: Objective: We present the design and experimental validation of an arterial compliance probe with dual magnetic plethysmograph (MPG) transducers for local pulse wave velocity (PWV) measurement. The MPG transducers (positioned at 23 mm distance apart) utilizes Hall-effect sensors and permanent magnets for arterial blood pulse detection. Methods: The MPG probe was initially validated on an arterial flow phantom using a reference method. Further, 20 normotensive subjects (14 males, age = 24 ± 3.5 years) were studied under two different physical conditions: 1) Physically relaxed condition, 2) Postexercise condition. Local PWV was measured from the left carotid artery using the MPG probe. Brachial blood pressure (BP) was measured to investigate the correlation of BP with local PWV. Results: The proposed MPG arterial compliance probe was capable of detecting high-fidelity blood pulse waveforms. Reliable local pulse transit time estimates were assessed by the developed measurement system. Beat-by-beat local PWV was measured from multiple subjects under different physical conditions. A profound increment was observed in the carotid local PWV for all subjects after exercise (average increment = 0.42 ± 0.22 m/s). Local PWV values and brachial BP parameters were significantly correlated ( r ≥ 0.72), except for pulse pressure ( r = 0.42). Conclusion: MPG arterial compliance probe for local PWV measurement was validated. Carotid local PWV measurement, its variations due to physical exercise and correlation with BP levels were examined during the in vivo study. Significance: A novel dual MPG probe for local PWV measurement and potential use in cuffless BP measurement.
51 citations
TL;DR: A novel blood-flow volume sensor is presented for assessing quality of arteriovenous fistula in hemodialysis patients via noninvasive reflectance-type photoplethysmography (PPG) with high correlation, with the root-mean-squared errors successfully controlled under 289 ml/min.
Abstract: A novel blood-flow volume (BFV) sensor is presented for assessing quality of arteriovenous fistula in hemodialysis patients via noninvasive reflectance-type photoplethysmography (PPG). BFV is nowadays in clinic practices evaluated using an ultrasound Doppler monitor, which is expensive, bulky, and can only be operated by well-trained medical personnels. This study is devoted to develop a low-cost, small-sized, portable, and easy-to-use PPG sensor that is capable of continuous measurement of BFV. New designs of front-end analog circuits, signal processing, and an intelligent neural network calibration method are employed to finally achieve high correlation ( R 2 = 0.7176), as opposed to the ultrasound Doppler monitor, with the root-mean-squared errors successfully controlled under 289 ml/min.
28 citations
Cites background from "Magnetic sensor for non-invasive de..."
...[16], Phua and Lissorgues [17], Ogle [18], and Joseph and Jayashankar [19] proposed the theoretical basis and feasibility test of measuring BFV using magnetic sensors...
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...[15] Joseph and Jayashankar [19] Nishihara et al....
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...[19] J. Joseph and V. Jayashankar, “Magnetic sensor for non-invasive detection of blood pulse and estimation of arterial compliance,” in Proc....
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...Kanai et al. [16], Phua and Lissorgues [17], Ogle [18], and Joseph and Jayashankar [19] proposed the theoretical basis and feasibility test of measuring BFV using magnetic sensors by sensing the changes in magnetic field....
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TL;DR: This review is focused on heart rate measurement methods located on forearm and more specifically on the wrist, and the superposition of motion artefacts over the signal of interest is one of the largest drawbacks for these methods, when used out of laboratory conditions.
Abstract: When evaluating general health condition on a patient, heart rate is an essential indicator as it is directly representative of the cardiac system state. Continuous measurement methods of heart rate are required for ambulatory monitoring involved in preliminary diagnostic indicators of cardiac diseases or stroke. The growing number of recent developments in wearable devices is reflective of the increasing demand in wrist-worn activity trackers for fitness and health applications. Indeed, the wrist represents a convenient location in terms of form factor and acceptability for patients. While most commercially-available devices are based on optical methods for heart rate measurement, others methods were also developed, based on various physiological phenomena. This review is focused on heart rate measurement methods located on forearm and more specifically on the wrist. For each method, the physiological mechanism involved is described, and the associated transducers for bio-signal acquisition as well as practical developments and prototypes are presented. Methods are discussed on their advantages, limitations and their suitability for an ambulatory use. More specifically, the superposition of motion artefacts over the signal of interest is one of the largest drawbacks for these methods, when used out of laboratory conditions. As such, artefact reduction techniques proposed in the literature are also presented and discussed.
21 citations
Cites background from "Magnetic sensor for non-invasive de..."
...Most MMSB devices developed for heart rate measurement from wrist uses single giant magnetoresistance as transducer [58, 66, 67, 68]....
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TL;DR: In this paper, the authors investigated the mechanism of MMSB and found that both blood pulse flowing through the applied magnetic field and the displacement of the GMR sensor caused by blood pulse contribute to the disturbance of magnetic field detected by GMR sensors.
10 citations
Cites background from "Magnetic sensor for non-invasive de..."
...Recently, the MMSB combined with electrocardiographic (ECG) was proposed to continuously measure the blood pressure [1,4,10,12]....
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References
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TL;DR: PWV could help identify normotensive individuals who should be targeted for the implementation of interventions aimed at preventing or delaying the progression of subclinical arterial stiffening and the onset of hypertension.
439 citations
"Magnetic sensor for non-invasive de..." refers background in this paper
...The arterial pulse wave velocity is a clinically accepted measure of global arterial stiffness [5]....
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TL;DR: Reanalysis of waveforms recorded from the Complior system using the foot-to-foot method produced similar values of PWV to those obtained with the SphygmoCor, confirming that the difference between these systems was attributable to the timing algorithm rather than other aspects of signal acquisition.
Abstract: Carotid-femoral pulse wave velocity (PWV), a measure of arterial stiffness, is determined from the time taken for the arterial pulse to propagate from the carotid to the femoral artery. Propagation time is measured variously from the foot of the waveform or point of maximum upslope. We investigated whether these methods give comparable values of PWV at rest, during -adrenergic stimulation, and pacing-induced tachycardia. In subjects at rest (n43), values obtained using the foot-to-foot method (SphygmoCor system) were 1.70.75 m/s (meanSD) greater than those obtained using the maximum slope (Complior system) at a mean value of 12 m/s. Isoprotenerol (0.5 to 1.5 g/min; n10), and pacing (in subjects with permanent pacemakers; n11) increased heart rate but had differential effects on systolic blood pressure and pulse pressure. The increase in heart rate produced by isoprotenerol (183 bpm) and pacing (40 bpm) was associated with an increase in PWV measured using both systems (increases of 0.70.2 m/s and 0.90.2 m/s for SphygmoCor and Complior, respectively, during isoprotenerol and increases of 2.10.5 m/s and 1.10.2 m/s for SphygmoCor and Complior, respectively, during pacing, each P0.001). Reanalysis of waveforms recorded from the Complior system using the foot-to-foot method produced similar values of PWV to those obtained with the SphygmoCor, confirming that the difference between these systems was attributable to the timing algorithm rather than other aspects of signal acquisition. Carotid-femoral PWV is critically dependent on the method used to determine propagation time, but this does not account for variation of PWV with heart rate. (Hypertension. 2005;45:222-226.)
281 citations
"Magnetic sensor for non-invasive de..." refers methods in this paper
...The pulse transit time, which is the time taken by the blood pulse to travel from the carotid to the radial artery measurement site, can be evaluated by estimating the delay between the two waveforms using any of the standard algorithms [7]....
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TL;DR: It is concluded that the instrumentation enables PWV to be measured with high accuracy and precision in real time, if the pressure signals are of high fidelity and the relative amplification of the signals is carefully balanced.
Abstract: Instrumentation for the real-time clinical measurement of pulse wave velocity (PWV) from intra-arterial pressure waveforms is presented. The time delay between pressure waveforms (obtained from two intra-arterial catheter-mounted transducers 5 cm apart) is calculated by a transputer using multiple comparisons between discrete sections of the waveforms. The method is validated by analysis of digital and analogue signals with known time delays and is used to measure changes in PWV in the right common iliac artery (RCIA) during infusions of acetylcholine (2·4, 24 and 240 μg ml−1) in six healthy subjects. The system measures the delay between digitally shifted triangular waveforms and pressure waveforms to a precision of about 50 μs, and it is superior to measurements performed by hand using a high-performance digital storage oscilloscope. When used to measure the effects of acetylcholine on the RCIA, dose-dependent reductions in PWV are recorded (−8·5%, −11·6%, −14·5%). It is concluded that the instrumentation enables PWV to be measured with high accuracy and precision in real time, if the pressure signals are of high fidelity and the relative amplification of the signals is carefully balanced.
24 citations
"Magnetic sensor for non-invasive de..." refers methods in this paper
...Simultaneous measurement of the blood flow pulse at two different sites along the same arterial tree can be utilized to measure the arterial pulse wave velocity [6]....
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05 May 2009
TL;DR: A PC based system for non-invasive, in-vivo measurement of carotid artery compliance is proposed here and the accuracy and resolution has been found to meet the requirements of the application.
Abstract: A PC based system for non-invasive, in-vivo measurement of carotid artery compliance is proposed here. The equipment is a low cost and reliable alternative to the expensive B-mode scanner for vessel wall tracking and stiffness measurement of the artery. The system gives an accurate recording of the distensibility waveform of the carotid artery that could then be used to estimate the various measures of arterial compliance. The system is tested with phantom models of the carotid artery and the accuracy and resolution has been found to meet the requirements of the application. Results obtained from human trials have also been presented to illustrate the capability of the instrument to accurately measure carotid artery compliance.
15 citations
"Magnetic sensor for non-invasive de..." refers methods in this paper
...The distension of the carotid artery was measured using a dedicated system for arterial compliance evaluation [4]....
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01 Jan 2009
TL;DR: The heart rate obtained from the proposed system when measured through non-conductive opaque fabric, is found to be highly correlated to commercially available cardiac monitoring system such as ECG and pulseoximetry.
Abstract: Blood pulse is an important human physiological signal commonly used for the understanding of the individual physical health. Current methods of non-invasive blood pulse sensing require direct contact or access to the human skin. As such, the performances of these devices tend to vary with time and are subjective to human body fluids (e.g. blood, perspiration and skin-oil) and environmental contaminants (e.g. mud, water, etc). This paper proposes a novel method of non-invasive acquisition of blood pulse using the disturbance created by blood flowing through a localized magnetic field. The proposed system employs a magnetic sensor and a small permanent magnet placed on the artery (major blood vessel) of the limbs. The magnetic field generated by the permanent magnet acts both as the biasing field for the sensor and also the uniform magnetic flux for blood disturbance. As such, the system is able to operate at room temperature, reliable for continuous long term acquisition, compact (small size) and convenient for daily usage. The heart rate obtained from the proposed system when measured through non-conductive opaque fabric, is found to be highly correlated to commercially available cardiac monitoring system such as ECG and pulseoximetry.
14 citations
"Magnetic sensor for non-invasive de..." refers background or methods in this paper
...As blood flows below the sensor in a pulsating fashion, it alters the magnetic field intensity near the sensor [1]....
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...While maximizing the peak to peak output may be used as an initial criterion for positioning the magnet in relation to the sensor [1], the above observations indicate that the shape of the detected output signal may be altered by the relative geometry of the artery, magnet and the sensor....
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...It has also been previously reported that the amplitude of the sensor output is maximum only at a particular distance between the sensor and the bias magnet [1]....
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...proposed as a novel technique for non-invasively detecting the blood pulse [1][2]....
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