Pulse Reflection Research Articles

Inter-arm differences in regional arterial stiffness and geometry lead to inter-arm systolic blood pressure differences: A modelling study

An inter-arm systolic blood pressure difference (ISBPD), if substantial in magnitude (typically defined as ≥10 mmHg), is a potential cardiovascular risk factor in adults, due to its association with cardiovascular events/mortality. A substantial ISBPD occurs in approximately 10% of the adult population, and, although associations with vascular disease and elevated stiffness have been reported, the mechanisms underlying ISBPD remain unknown. The aim of this study was to investigate whether inter-arm differences in segmental pulse wave velocity, cross-sectional area, or vascular bed compliance/resistance could give rise to substantial differences in brachial pressures between arms; for example, due to differences in pulse wave transmission and reflection. Using an established one-dimensional model of the major systemic arteries, pulse wave velocity (PWV) was uniformly increased or decreased in arteries of 1) the supra-aortic region leading up to the arm, 2) the brachial region, 3) the forearm, and 4) all of these (entire arm pathway); for the left arm, right arm, and both arms. Cross-sectional area and vascular bed compliance and resistance of the arms were similarly varied. Inter-arm differences in segmental PWV and cross-sectional area (but not bilateral changes) led to associated substantial inter-arm SBP differences, which were observed with changes to brachial, forearm and/or entire arm pathways and were related to altered transmission of forward waves and amplitude/timing of reflected waves. Vascular bed compliance and resistance had minimal influence. We conclude that inter-arm differences in arterial stiffness and geometry may contribute to inter-arm systolic blood pressure differences, warranting further investigation.

Reflection and Transmission of Pressure Pulses Through a Gas Hydrate-Saturated Layer in a Porous Medium

Reflection and Transmission of Pressure Pulses Through a Gas Hydrate-Saturated Layer in a Porous Medium

Novel Pressure Wave Separation Analysis for Cardiovascular Function Assessment Highlights Major Role of Aortic Root.

ObjectiveA novel method was presented to separate the central blood pressure wave (CBPW) into five components with different biophysical and temporal origins. It includes a time-varying emission coefficient (γ) that quantifies pulse wave generation and reflection at the aortic root.MethodsThe method was applied to normotensive subjects with modulated physiology by inotropic/vasoactive drugs (n = 13), hypertensive subjects (n = 158), and virtual subjects (n = 4,374).Resultsγ is directly proportional to aortic flow throughout the cardiac cycle. Mean peak γ increased with increasing pulse pressure (from <30 to >70 mmHg) in the hypertensive (from 1.6 to 2.5, P < 0.001) and in silico (from 1.4 to 2.8, P < 0.001) groups, dobutamine dose (from baseline to 7.5 μg/kg/min) in the normotensive group (from 2.1 to 2.7, P < 0.05), and remained unchanged when peripheral wave reflections were suppressed in silico. This was accompanied by an increase in the percentage contribution of the cardiac-aortic-coupling component of CBPW in systole: from 11% to 23% (P < 0.001) in the hypertensive group, 9% to 21% (P < 0.001) in the in silico group, and 17% to 23% (P < 0.01) in the normotensive group.ConclusionThese results suggest that the aortic root is a major reflection site in the systemic arterial network and ventricular-aortic coupling is the main determinant in the elevation of pulsatile pulse pressure.SignificanceVentricular-aortic coupling is a prime therapeutic target for preventing/treating systolic hypertension.

Recognition of 3D objects in a monostatic laser location system via intelligent analysis of pulsed reflectance profiles

Subject of study. A physics-based expert model of initial features for the recognition of anthropogenic 3D objects in a monostatic laser location system is proposed. Method. The model is based on an intelligent analysis of data obtained using digital simulation modeling of temporal profiles of pulsed reflectance profiles of the object. Informative features are formed using the method of principal components. Main results. A cluster structure in the space of principal features is demonstrated and investigated. The parameters of several algorithms for the clustering and classification of 3D objects are identified using machine learning methods and their quality is tested in an informative space. Practical significance. The stages of solving the clustering and classification tasks for anthropogenic objects by a monostatic laser location system are described in chronological order.

Second systolic peak in fetal middle cerebral artery Doppler after intrauterine transfusion

ObjectiveTo evaluate functional relationship between fetal circulatory response to intrauterine transfusion (IUT) as a circulatory challenge and appearance of second systolic peak (P2) in middle cerebral artery (MCA) based on hemodynamic principles.MethodsAccording to the concept of pulse wave (PW) propagation and reflection in adults, PWs arrive twice at cerebral circulation, as primary wave caused by left ventricle ejection and secondary after reflection in peripheral arteries. Thus adults show a biphasic contour of systolic blood flow in cerebral arteries. Similar waveforms may appear in fetal MCA-Doppler, as a response to IUT as a circulatory challenge. This is a proof-of-principle study, applying classical hemodynamic principles to fetal circulation. Accordingly, appearance of MCA-P2 may indicate vasoconstriction with increased PW reflection and timing of P2(Δt) should agree with the additional PW travel time down to reflection and return (Tr). To test this agreement, we searched our database for IUTs performed for severe fetal anemia, and compared Δt, obtained by Doppler, with Tr, obtained by hemodynamic calculation using human fetal data. Level of agreement was assessed using Bland–Altman-Plots.ResultsWe identified 21 fetuses with adequate Doppler quality for Δt evaluation. In four cases (19%) MCA-P2 was observed before the intervention, and in 17 interventions (81%) thereafter; a highly significant association between IUT and P2 appearance (p < 0.001). In these 17 interventions good agreement of P2 timing was found between Doppler assessment: Δt = 80 ± 8 ms, and hemodynamic calculation: Tr = 76 ± 4 ms.ConclusionP2 appearance in fetal MCA-Doppler seems to indicate PW reflection due to increased vasoconstriction after IUT. Thus hemodynamic considerations might enable Doppler monitoring of fetal vasoconstriction.

Normalization of photoplethysmography using deep neural networks for individual and group comparison

Photoplethysmography (PPG) is easy to measure and provides important parameters related to heart rate and arrhythmia. However, automated PPG methods have not been developed because of their susceptibility to motion artifacts and differences in waveform characteristics among individuals. With increasing use of telemedicine, there is growing interest in application of deep neural network (DNN) technology for efficient analysis of vast amounts of PPG data. This study is about an algorithm for measuring a patient's PPG and comparing it with their own data stored previously and with the average data of several groups. Six deep neural networks were used to normalize the PPG waveform according to the heart rate by removing uninformative regions from the PPG, distinguishing between heartbeat and reflection pulses, dividing the heartbeat waveform into 10 segments and averaging the values according to each segments. PPG data were measured using telemedicine in both groups. Group 1 consisted of healthy people aged 25 to 35 years, and Group 2 consisted of patients between 60 and 75 years of age taking antihypertensive medications. The proposed algorithm could accurately determine which group the subject belonged with the newly measured PPG data (AUC = 0.998). On the other hand, errors were frequently observed in identification of individuals (AUC = 0.819).

Beaufort Sea observations of 11 to 12.5 kHz surface pulse reflections near 50 degree grazing angle from summer 2016 to summer 2017.

Sea-surface acoustic scattering is investigated using observations from the 2016-2017 Canada Basin Acoustic Propagation Experiment. The motions of the low-frequency acoustic source and/or receiver moorings were measured using long-baseline acoustic navigation systems in which the signals transmitted once per hour by the mooring instruments triggered high-frequency replies from the bottom-mounted transponders. The moorings recorded these replies, giving the direct path and single-bounce surface-reflected arrivals, which have grazing angles near 50°. The reflected signals are used here to quantify the surface scattering statistics in an opportunistic effort to infer the changing ice characteristics as a function of time and space. Five scattering epochs are identified: (1) open water, (2) initial ice formation, (3) ice solidification, (4) ice thickening, and (5) ice melting. Significant changes in the ice scattering observables are seen using the arrival angle, moment of reflected intensity and its probability density function, and pulse time spread. The largest changes took place during the formation, solidification, and melting. The statistical characteristics across the experimental region are similar, suggesting consistent ice properties. To place the results in some physical context, they are interpreted qualitatively using notions of the partial and fully saturated wave fields, a Kirchhoff-like approximation for the rough surface, and a thin elastic layer reflection coefficient model.

Feasibility Study of Wood-Leaf Separation Based on Hyperspectral LiDAR Technology in Indoor Circumstances

Wood–leaf separation aiming at classifying LiDAR points into wood and leaf components is one of the most important genres for improving leaf area index estimation and forestry survey accuracy. The wood return signals could artificially increase the apparent foliage content, which needs to be screened out for deriving vital tree attributes accurately. Previous research works tended to use intensity, waveform, and geometric information extracted from a single wavelength LiDAR for wood–leaf separation. This article employs a revised hyperspectral LiDAR (HSL) to obtain spatial and ultrawide spectral data simultaneously. We also propose a simple three steps method to separate wood and leaf components based on HSL spatial and spectral measurements under the laboratory circumstances. First, the preprocessing is conducted to acquire 3-D spatial information and the multiband laser pulse reflectance for further separation. Second, preliminary separation (band division, key feature parameter calculation, and judgment) is implemented based on reflectance. Third, we employ K-Nearest Neighbor (KNN) method to enhance separation results based on preliminary separation results and spatial features and then update the results by recorrection. Then, 3-D reconstruction is accomplished by fusing wood–leaf separation results. The experimental results demonstrate that the proposed method can separate wood and leaf components with high accuracy and indicate tree attributes straightforwardly.

Applanation Arterial Tonometry Assesment Of Arterial Stiffness

Applanation arterial tonometry is a modern non-invasive method that allows indirect measure-ment of the intraaortic pressure in different phases of the cardiac cycle and the calculation of different arte-rial stiffness indicators using the data of the reflect-ed pulse wave. Systolic, diastolic, and pulse intraaortic pressure (used for optimal control in the treatment of hypertension), augmentation pressure (assessing arte-rial stiffnes), and subendocardial viability (an indica-tor of the blood supply to the heart muscle) can be mea-sured by brachial artery aplanning. Pulse wave veloc-ity is measured by brachial and femoral artery aplan-ning. Because changes in arterial stiffness precede the formation of atherosclerotic plaques, the method is relevant for determining cardiovascular risk and for monitoring patients with hypertension and persons with risk factors for atherosclerosis.

Aortic Root Dimensions and Pulse Wave Velocity in Young Competitive Athletes

The assessment of aortic root dimensions is a cornerstone in cardiac pre-participation screening as dilation can result in severe cardiac events. Moreover, it can be a hint for an underlying connective tissue disease, which needs individualized sports counseling. This study examines the prevalence of aortic root dilatation in a cohort and its relationship to arterial stiffness as an early marker of cardiovascular risk due to vascular aging. From May 2012 to March 2018, we examined 281 young male athletes (14.7 ± 2.1 years) for their aortic root dimension. Moreover, we noninvasively assessed arterial stiffness parameter during pre-participation screening. Mean aortic diameter was 25.9 ± 3.1 mm and 18 of the 281 (6.4%) athletes had aortic root dilation without other clinical evidence of connective tissue disease. After adjusting for BSA, there was no association of aortic root diameter to pulse wave velocity (p = −0.054 r = 0.368) nor to central blood pressure (p = −0.029 r = 0.634). Thus, although a significant proportion of young athletes had aortic root dilatation, which certainly needs regular follow up, no correlation with arterial stiffness was found. It could be suggested that a dilated aortic root in young athletes does not alter pulse waveform and pulse reflection, and thus there is no increased cardiovascular risk in those subjects.

Enabling Continuous Wearable Reflectance Pulse Oximetry at the Sternum.

In light of the recent Coronavirus disease (COVID-19) pandemic, peripheral oxygen saturation (SpO2) has shown to be amongst the vital signs most indicative of deterioration in persons with COVID-19. To allow for the continuous monitoring of SpO2, we attempted to demonstrate accurate SpO2 estimation using our custom chest-based wearable patch biosensor, capable of measuring electrocardiogram (ECG) and photoplethysmogram (PPG) signals with high fidelity. Through a breath-hold protocol, we collected physiological data with a wide dynamic range of SpO2 from 20 subjects. The ratio of ratios (R) used in pulse oximetry to estimate SpO2 was robustly extracted from the red and infrared PPG signals during the breath-hold segments using novel feature extraction and PPGgreen-based outlier rejection algorithms. Through subject independent training, we achieved a low root-mean-square error (RMSE) of 2.64 ± 1.14% and a Pearson correlation coefficient (PCC) of 0.89. With subject-specific calibration, we further reduced the RMSE to 2.27 ± 0.76% and increased the PCC to 0.91. In addition, we showed that calibration is more efficiently accomplished by standardizing and focusing on the duration of breath-hold rather than the resulting range in SpO2. The accurate SpO2 estimation provided by our custom biosensor and the algorithms provide research opportunities for a wide range of disease and wellness monitoring applications.

All-optical pulse-train generation through the temporal analogue of a laser

We propose a novel scheme for the all-optical generation of pulse trains in optical fibers based on the reflection and refraction of pulses at a time boundary, and the temporal analogue of a laser cavity with gain. Furthermore, this scheme is shown to provide an original and simple way to measure distributed fiber parameters. In particular, we put forth an application of the temporal laser to the distributed sensing of the fiber group-velocity dispersion parameter.

Laser requirements for the designof fast laser-driven semiconductor switches for THz and mm-waves.

A reduced parameter model of fast laser-driven semiconductor switches of THz and mm-waves has been developed. The model predicts peak reflectivity and minimum transmissivity of switches, showing good agreement with experimental data, while requiring fewer inputs than published models. This simplification facilitated a systematic survey of laser parameters required for efficient switching. Laser energy density requirements are presented as a function of laser wavelength, laser pulse width, switched frequency, reflection angle, and semiconductor material (silicon or gallium arsenide). Analytical expressions have been derived to explain the dependence of laser requirements on switch parameters and to derive practical minima of required laser energy density. Diffusion is shown to quickly negate the shallow absorption advantage of laser wavelengths shorter than about 500nm in silicon or 800nm in gallium arsenide. Decreasing laser pulse width, to a derived limit, and switching S-polarized THz or mm-wave signals are shown to be means of lowering required laser energy. This is an especially useful result for devices operating at high power levels or THz frequencies, where extended switches are used in quasioptical systems.

Subnanosecond breakdown of air-insulated coaxial line initiated by runaway electrons in the presence of a strong axial magnetic field

Flow of runaway electrons (RAEs) propagating in a radial, air-filled gap of coaxial line (CL) changes the dynamics of breakdown in the field of traveling voltage pulse. However, despite the effect of RAEs, breakdown does not occur if subnanosecond pulse is less in duration and amplitude than some values. In this work, we study the influence of an external axial magnetic field (B z) on the breakdown development. We demonstrate the transformation of the voltage pulse reflection from the ionized (breakdown) zone with changing B z. Due to gyration of fast electrons in an applied magnetic field, the gas region ionized by RAEs does not reach the anode. The ionized bridge between the cathode and anode is gradually replaced by a near-cathode plasma layer representing a discrete, reflecting/absorbing inhomogeneity in the CL.

Influence of Measurement Location on Reflectance Pulse Oximetry in Sleep Apnea Patients: Wrist vs. Upper Arm.

Peripheral oxygen saturation (SpO2) plays a key role in diagnosing sleep apnea. It is mainly measured via transmission pulse oximetry at the fingertip, an approach less suited for long-term monitoring over several nights.In this study we tested a more patient-friendly solution via a reflectance pulse oximetry device. Having previously observed issues with pulse oximetry at the wrist, we investigated in this study the influence of the location of our device (upper arm vs. wrist) to measure SpO2. Accuracy was compared against state-of-the-art fingertip SpO2 measurements during a full overnight polysomnography in nine patients with suspected sleep apnea.The upper arm location clearly showed a lower root mean square error ARMS = 1.8% than the wrist ARMS = 2.5% and a lower rate of automatic data rejection (19% vs 25%). Irrespective of the measurement location the accuracies obtained comply with the ISO standard and the FDA guidance for pulse oximeters. In contrast to the wrist, the upper arm location seemed to be more resilient to deteriorating influences such as venous blood.Reflectance pulse oximetry at the wrist remains challenging but the upper arm could provide remedy for more robust SpO2 estimates to reliably screen for sleep apnea and other diseases.Clinical Relevance- The performance of reflectance pulse oximetry measured at the upper arm during sleep is superior to measurements at the wrist which are perturbed by undesired large fluctuations suspected to be caused by venous blood. If confirmed, this could also apply to the optical measurement of other vital signs such as blood pressure.

Effect of nanostructuring on picosecond acoustics in a Zr film

Using the picosecond ultrasonic technique, we studied the effect of the formation of nanocrystallites on the surface of a metal transducer film. We found that the velocity of sound and the elastic constant are enhanced due to the nanocrystalline structures. The acoustic echo’s shape, resulting from the reflection of the acoustic pulse at the surface, is modified, and an echo with an asymmetric bipolar shape is obtained. The shape of the acoustic echo can be explained, taking into account the formation of nanocrystallites at the film’s surface.

Design of Reflectance Pulse Oximeter and BPM using the Max30100 Sensor in Early Detection of Hypoxemia in Patients with Cardiovascular Disorders

Blood oxygen saturation meter is a tool used to monitor the state of oxygen saturation in the blood and also the patient's heart rate (BPM) and to assist in the physical assessment of the patient without going through blood gas analysis. Oxygen saturation measuring devices usually use the difference in the wavelengths of red and infrared led light that will be captured by the photodiode. The purpose of this research is to make a pulse oximeter equipped with a display of SPO2, BPM values ​​and an additional SP02 signal. The design of this measuring instrument uses the MAX30100 sensor, the minimum system circuit of Arduino ATmega328p and OLED (Organic Light-Emitting Diode). Data from the MAX30100 sensor enters the I2C pin on the minimum Arduino system, then the microcontroller is processed to produce the percentage of SPO2 value, BPM value, and SPO2 signal which is then displayed on the OLED. The test is done by comparing the module with standard measuring instruments which produces the largest % error of 0.81% for Spo2 and 0.87% for BPM. The error presentation is obtained from factor measurements, if there is finger movement it will cause a large error. From the results obtained, the tool is still feasible to use because in the "Guidelines for Testing and Calibrating Medical Devices" Ministry of Health RI 2001, the maximum limit in the pulse oximeter error tolerance is for Spo2 1% and BPM 5%.

Aortic diameter, pulse wave velocity, central aortic pulse pressure, left ventricular parameters, and diastolic dysfunction in patients with aortic aneurysm

Abstract Background The enlargement of aortic aneurysm can alters pulse wave propagation and reflection, which may influence to left ventricular (LV) afterload changes. The relevance of pulse wave velocity (PWV) and central blood pressure depending on the locus of the aneurysm for LV structure and diastolic function (DF) are not clearly unknown. Purpose Assess the relationship between central pulse pressure (CPP), PWV and LV structure and DF in patients with ascending aortic aneurysm (AA) and abdominal aortic aneurysm (AAA). Methods 121 patients (95 male, 63±12 years) with aortic aneurysms and preserved LV systolic function were enrolled before aortic repair. 51 patients (37 male, 54±13 years) had AA and 70 patients (58 male, 69±7 years) had AAA. CPP and PWV were measured using applanation tonometry. A echocardiographic exam was performed with a Vivid 7 GE (USA). LV mass index (LVMI) and relative wall thickness (RWT) were calculated according to standard formulas. LV filling pressure (E/Em) was estimated by Doppler-derived ratio of mitral inflow velocity (E) to septal (Em) by tissue Doppler. Transmitral flow patterns (E/A ratio of E to late (A) ventricular filling velocities) were measured with the pulsed doppler method. Results Concentric LV hypertrophy (LVH) was observed in 51 (42%), eccentric LVH – in 35 (29%) patients. CPP was positively related with LVMI (r=0.362, P=0.001), but PWV was inversely associated with LVMI (r=−0.244, P=0.029). CPP was not associated with RWT (P≥0.5), whereas PWV was positively related (r=0.223, P=0.004). PWV decreased with increasing aortic diameter in AA and AAA (r=−0.360, P=0.029 and r=−0.315, P=0.019, respectively). 12 (23%) patients with AA and 36 (56%) patients with AAA had grade I diastolic dysfunction, 20 (40%) patients with AA and 12 (18%) patients with AAA had grade II diastolic dysfunction (P&amp;lt;0.001). Consequently, the E/A ratio was higher in patients with AA than in patients with AAA (1.21±0.39 vs 0.83±0.33; P=0.007). CPP and PWV was inversely associated with LV DF (E/A: r=−0.352 and −0.238; E/Em: r=−0.292 and −0.279, respectively; both P&amp;lt;0.05). E/A and E/Em increased with the expansion of the maximum aortic diameter at the level of the AA and AAA (E/A: r=0.612 and 0.416; E/Em: r=0.719 and 0.339, respectively; both P&amp;lt;0.005). RWT and LVMI were correlated with the aortic diameter at the level of the AA (r=−0.439, P=0.008 and r=0.286, P=0.05, respectively), but bore no relation with the aortic diameter at the level of the AAA. Conclusions In patients with aortic aneurysm CPP and PWV were conjointly but differently related to LV structure. Eccentric LV hypertrophy was accompanied by a significant decrease of PWV. Reduced PWV and decreased CPP exhibited association with more severe LV diastolic dysfunction, possibly due to the apparent effect of increased aortic aneurysm diameter. LV DF was severely reduced in the patients with AA compared by patients with AAA. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Almazov National Medical Research Centre

Fine detection technology of rock mass structure based on borehole acousto-optic combined measurement

Aiming at the problem of rock mass structure fine detection, a solution idea of synchronous data acquisition based on acoustic scanning technology and borehole panoramic image technology is proposed. Based on the omni-directional acoustic pulse reflection sequence data and panoramic optical borehole image, the problem of difficult calculation of typical borehole structure scale and extended azimuth positioning is solved. A 3D modeling and data visualization optimization scheme of borehole rock mass structure based on full pulse acoustic scanning data and forward-looking borehole optical image is formed. By combining the acoustic scanning characteristics of section and the optical image characteristics of rock wall, the extraction technology of borehole rock mass structural characteristic parameters is formed. The 3D imaging and characteristic parameter extraction technology system of borehole rock mass structure is formed, which is applied to the actual borehole rock mass structure detection. The detection results are consistent with the actual characteristics.

Reflection and transmission of electromagnetic pulses at a planar dielectric interface: Theory and quantum lattice simulations

There is considerable interest in the application of quantum information science to advance computations in plasma physics. A particular point of curiosity is whether it is possible to take advantage of quantum computers to speed up numerical simulations relative to conventional computers. Many of the topics in fusion plasma physics are classical in nature. In order to implement them on quantum computers, it will require couching a classical problem in the language of quantum mechanics. Electromagnetic waves are routinely used in fusion experiments to heat a plasma or to generate currents in the plasma. The propagation of electromagnetic waves is described by Maxwell equations with an appropriate description of the plasma as a dielectric medium. Before advancing to the tensor dielectric of a magnetized plasma, this paper considers electromagnetic wave propagation in a one-dimensional inhomogeneous scalar dielectric. The classic theory of scattering of plane electromagnetic waves at a planar interface, separating two different dielectric media, leads to Fresnel equations for reflection and transmission coefficients. In contrast to plane waves, this paper is on the reflection and transmission of a spatially confined electromagnetic pulse. Following an analytical formulation for the scattering of a Gaussian pulse, it is deduced that the maximum transmission coefficient for a pulse is n2/n1 times that for a plane wave; the incident and transmitted pulses propagate in dielectric media with refractive indices n1 and n2, respectively. The analytical theory is complemented by numerical simulations using a quantum lattice algorithm for Maxwell equations. The algorithm, based on the Riemann–Silberstein–Weber representation of the electromagnetic fields and expressed in terms of qubits, is an interleaved sequence of entangling operators at each lattice site and unitary streaming operators, which transmit information from one site to an adjacent lattice site. Besides substantiating results from the theory for Gaussian pulses, numerical simulations show their validity for non-Gaussian pulses. Apart from their time-asymptotic forms, the simulations display an interplay between the incident, reflected, and transmitted pulses in the vicinity of the transition region between two dielectric media.