Waveform Amplitude Research Articles

Association between Postoperative Neck Pain and Intraoperative Transcranial Motor-Evoked Potential Waveforms of the Trapezius Muscles in Patients with Cervical Myelopathy Who Underwent Cervical Laminoplasty.

Retrospective study. Cervical laminoplasty is safe and effective for treating cervical myelopathy but has a higher frequency of postoperative axial pain compared to other methods. Several studies have reported on the causes of postoperative axial pain, but none have fully elucidated them. This study aimed to investigate the association between postoperative neck pain and intraoperative transcranial motor-evoked potential (MEP) waveforms of the trapezius muscles using transcranial MEPs. Few studies have investigated the association between postoperative neck pain and intraoperative transcranial MEP waveforms of the trapezius muscles in patients with cervical laminoplasty. A total of 79 patients with cervical myelopathy who underwent cervical laminoplasty at our facility between June 2010 and March 2013 were included in this study. Intraoperative control and final waveform were evaluated based on the trapezius muscle MEPs by measuring the latency and amplitude. A neck pain group comprised patients with higher neck pain Visual Analog Scale scores from preoperative value to 1 year postoperatively. The cross-sectional areas of the trapezius muscles and the MEP latencies and amplitudes were compared between patients with and without neck pain. The latency and amplitude of the control waveforms were not significantly different between groups. The neck pain group had a significantly shorter final waveform latency (neck pain: 23.6±2.5, no neck pain: 25.8±4.5; p =0.019) and significantly larger amplitude (neck pain: 2,125±1,077, no neck pain: 1,630±966; p =0.041) than the no neck pain group. Postoperative neck pain was associated with the final waveform latency and amplitude of the trapezius muscle MEPs during cervical laminoplasty. Intraoperative electrophysiological trapezius muscle abnormalities could cause postoperative neck pain.

Cooley-Tukey FFT Algorithm based on GDFT for Phasor Estimation by PMU under Power Quality Disturbances

Due to the high penetration of renewable energy sources, such as photovoltaic panels and wind turbines, in addition to the use of different electric power supplies in the power grid, there are major disturbances in the forms of electric waves. These variations and disturbances must be monitored and controlled for the efficient management of transmission and distribution of electrical energy, safety, and electrical protection systems. Nowadays, Phasor Measurement Unit (PMU) technology is an essential tool to develop the supervision, protection, and control of the electrical power grid. PMUs measure the amplitude and angle of current and voltage waveforms on a Coordinated Universal Time (UTC) time scale and speedily measure the fundamental frequencies and their rates of change using fast and accurate estimation algorithms. This paper presents a phasor estimation using a Modified Cooley-Tukey Fast Fourier Transform algorithm based on the Generalized Discrete Fourier Transform (DFT) used in PMUs, using simulations in MATLAB. This algorithm was utilized to accelerate and simplify the computation of DFTs. To validate the performance under waveform disturbances, several tests with different waveforms and disturbances were simulated and interpreted according to the standard and compared with DFT.

Optimization of overshoot in the pulsed radio frequency inductively coupled argon plasma by step waveform modulation

The pulsed inductively coupled plasma (ICP) has considerable potential to satisfy multiple stringent scaling requirements for use in the semiconductor industry. However, overshoot of plasma parameters during the rising period of the pulse affects the stability and uniformity of the plasma and can lead to a breakdown of the wafer and over-sputtering of the film. In this study, a step waveform modulation method is used to reduce the overshoot at the initial stage of the pulse. The behavior of the discharge is monitored by measuring (i) the modulated step waveform signal on the function generator, (ii) the input power (by a time-resolved VI-probe), and (iii) the amplitudes of the coil voltage and current (by voltage and current probes, respectively), as well as (iv) the plasma parameters including the electron density, the effective electron temperature, and the electron energy probability distribution function (by a time-resolved Langmuir probe). It was found that the state of the plasma can be controlled by changing the waveform, such as varying the time of the rising edge, varying the initial amplitude, and varying the duration of the low-high amplitude. The results indicated that the overshoot value of the electron density can be reduced by using a low-high step waveform. When the amplitude of the waveform was 500/550 mV and the duration was 200/300 μs, the overshoot value observed was 1/4 of that of the conventional ICP pulse discharge. In addition, increasing the duty cycle of the pulse could also reduce the overshoot value due to the high electron density that occurs during the afterglow period. Moreover, the plasma can reach a steady state more quickly at high pressure by using a step waveform of high amplitude.

DDPM simulation of the erosion of immersed tubes in a pulsating fluidized bed

In this study, the effects of the type of pulsating inlet waveform, pulsation frequency, and pulsation amplitude on the stability of fluidized beds and the erosion of immersed tubes were investigated by numerical simulation. Compared with rectangular and triangular inlet flows, sinusoidal flow induced the lowest immersed-tube erosion rate and pressure-drop fluctuation in the fluidized bed. Furthermore, under sinusoidal flow with a pulsation frequency of 1 Hz and pulsation amplitude of 0.25um, the immersed-tube erosion rate was lower by 1.8 %, standard deviation of pressure drop by 14.16 %, and energy generated from bubble rupture by 47.83 % than those under uniform flow. A dimensionless parameter χp that can represent immersed-tube erosion during pulsating flow was proposed, which reflects the effect of particle flow characteristics, particle fluidization degree, and pulsation frequency on immersed-tube erosion.

Nonlinear studies of binary black hole mergers in Einstein-scalar-Gauss-Bonnet gravity

We study the nonlinear dynamics of binary black hole systems with scalar charge by numerically evolving the full equations of motion for shift-symmetric Einstein scalar Gauss-Bonnet gravity. We consider quasi-circular binaries with different mass-ratios, varying the Gauss-Bonnet coupling and quantifying its impact on the emitted scalar and gravitational waves. We compare our numerical results to post-Newtonian calculations of the radiation emitted during the inspiral. We demonstrate the accuracy of the leading-order terms in post-Newtonian theory in modeling the amplitude of the scalar waveform, but find that, at least for the last few orbits before merger, the currently available post-Newtonian theory is not sufficient to model the dephasing of the gravitational wave signal in this theory. We further find that there is non-negligible nonlinear enhancement in the scalar field at merger, but that the effect on the peak gravitational wave emission is small.

Computational Fluid Dynamic Simulation of Leakage Acoustic Waves Propagation Model for Gas Pipelines

When leakage occurs for natural gas pipelines, acoustic waves generated at the leakage point will propagate to both ends of the pipe, which will be measured and processed to detect and locate the leakage. When acoustic waves propagate in the gas, the amplitude will attenuate and the waveform will spread, which decides the installation distance of acoustic sensors. Therefore, computational fluid dynamic (CFD) simulation research on the acoustic wave propagation model is accomplished and verified by experiments to provide the foundation for the acoustic leak location method. The propagation model includes two parts: amplitude attenuation model and waveform spreading model. Both can be obtained by the established CFD simulation model. Additionally, the amplitude attenuation model can be verified by the experiments. Then, the simulation method is applied to conclude the propagation model under variable conditions, including different flow directions, Reynolds numbers, and diameters. Finally, the experimental demonstration of the leak location based on the propagation model is given. The results indicate that not only the gas viscosity but also the gas flow can influence the propagation model, and the leak location method based on the propagation model is effective. Conclusions can be drawn that CFD simulation on the propagation model for natural gas pipelines is an efficient way to carry out research and provide the theoretical basis for acoustic leak location method application.

Control of Distributed Generation Using Non-Sinusoidal Pulse Width Modulation

The islanded mode is one of the connection modes of the grid distributed generation resources. In this study, a distributed generation resource is connected to linear and nonlinear loads via a three-phase inverter where a control method needing no current sensors or compensator elements is applied to the distribute generation system in the islanded mode. This control method has two main loops in each phase. The first loop controls the voltage control loops that adjust the three-phase point of common coupling, the amplitude of the non-sinusoidal reference waveform and the near-state pulse width modulation (NSPWM) method. The next loop compensatesthe harmonic compensator loop that calculates the voltage harmonics of the point of common coupling in each phase, and injects them to compensate the non-sinusoidal reference waveforms of each phase. The simulation results in MATLAB/SIMULINK show that this method can generate balanced three-phase sinusoidal voltage with an acceptable total harmonic distortion (THD) at the joint connection point.

Fatigue life prediction of a Durga flyover bridge at vijayawada using wireless sensors

It is essential to inspect and assess any fatigue damage to the components of a structure in order to determine how long it will last. This is necessary for constructions such as concrete bridges, which are subjected to fluctuating loads with high intensity and frequency. This study presents a computer application method for calculating the fatigue life of the Durga flyover (reinforced concrete) bridge. The damage to bridge components can be evaluated based on the dynamics of the interaction between the bridge and vehicles caused by actual traffic. The computer code initially calculates the fluctuation of stresses caused by the passage of various types of vehicles in a given segment of a bridge. The other module has a continuous set of loads to measure the strains and calculate the stress variations across the section components. The rainflow method is used to count stress cycles owing to the fact that the peak intensities of the stress cycles are not steady, and the appropriate S-N curves are utilized to determine the damage caused by each cycle. In this analysis, the stress range amplitude waveform and fatigue toughness characteristics of bridge elements were employed to systematically detect continuous bridge girder fatigue damage. The most severe flexural stresses induced by vehicles were detected, and a stress-range frequency waveform was created while accounting for the total traffic volume. Linear damage accumulation theory was used to calculate the cumulative damage index and bridge fatigue life. The Miner's rule was used to calculate the overall damage caused by the passage of the vehicles. The major factors affecting the fatigue life are the effects of the span, pavement quality, increase in the speed of operation, weight, and suspension characteristics of the bridge.

Deep Learning-Based Channel Modeling for Free Space Optical Communications

Instead of conventional knowledge-driven modeling, this study introduced data-driven channel modeling methods based on deep learning (DL) in a free-space optical (FSO) communication system to achieve low complexity, less modeling difficulty, high fidelity, and differentiability. The FSO channel was modeled via three DL algorithms: generative adversarial network (GAN), bidirectional long short-term memory (BiLSTM), and Bayesian neural network (BNN). Consequently, their performance was comprehensively compared in terms of optical amplitude waveforms, Kullback-Leibler (KL) divergence, 95% confidence interval, data distribution, and fitted probability density functions. The results indicated that the GAN-based channel exhibited optimal performance, implying its suitability for learning the stochastic distribution of the FSO channel. In addition, the performance of GAN-based channels was examined under different conditions: turbulence intensities (weak, moderate, and strong), transmission distances (3, 4, and 5 km), launch powers (0, 10, and 20 dBm), modulation formats (on-off keying, pulse position modulation, and pulse amplitude modulation 4), and the adaptability to channel variation. The test results were satisfactory and confirmed the ability of the GAN to learn the approximate distribution function of the FSO channel. Thus, the primary aim was to prove that for FSO channels with statistical distribution characteristics, a data-driven DL model can not only serve as an effective surrogate model for specific scenarios but also provide a potential tool for future modeling methods.

Nucleation Process of the 2017 Nuugaatsiaq, Greenland Landslide

Seismic precursors prior to the failure of rocks are essential for probing the nucleation process and mitigating hazards. However, such precursory events before large landslides are rarely reported possibly due to the lack of near-source observations. The 2017 Nuugaatsiaq, Greenland landslide that was preceded by an abundance of small earthquakes and captured by a local seismic station is a notable exception and offers us a valuable opportunity to investigate how a large landslide initiated. Prior work suggests that accelerated creeping plays an important role during the landslide nucleation process. However, by analyzing the temporal evolution of the waveform similarities, waveform amplitudes, and inter-event times of the seismic precursors, we find that the Nuugaatsiaq landslide was very likely triggered by a series of accelerated and migratory small earthquakes approaching the nucleation area of the upcoming landslide, thus providing important insights into the failure initiation of massive landslides.

Dermal Sensory Regenerative Peripheral Nerve Interface for Reestablishing Sensory Nerve Feedback in Peripheral Afferents in the Rat.

Without meaningful, intuitive sensory feedback, even the most advanced myoelectric devices require significant cognitive demand to control. The dermal sensory regenerative peripheral nerve interface (DS-RPNI) is a biological interface designed to establish high-fidelity sensory feedback from prosthetic limbs. DS-RPNIs were constructed in rats by securing fascicles of residual sensory peripheral nerves into autologous dermal grafts, with the objectives of confirming regeneration of sensory afferents within DS-RPNIs and establishing the reliability of afferent neural response generation with either mechanical or electrical stimulation. Two months after implantation, DS-RPNIs were healthy and displayed well-vascularized dermis with organized axonal collaterals throughout and no evidence of neuroma. Electrophysiologic signals were recorded proximal from DS-RPNI's sural nerve in response to both mechanical and electrical stimuli and compared with (1) full-thickness skin, (2) deepithelialized skin, and (3) transected sural nerves without DS-RPNI. Mechanical indentation of DS-RPNIs evoked compound sensory nerve action potentials (CSNAPs) that were like those evoked during indentation of full-thickness skin. CSNAP firing rates and waveform amplitudes increased in a graded fashion with increased mechanical indentation. Electrical stimuli delivered to DS-RPNIs reliably elicited CSNAPs at low current thresholds, and CSNAPs gradually increased in amplitude with increasing stimulation current. These findings suggest that afferent nerve fibers successfully reinnervate DS-RPNIs, and that graded stimuli applied to DS-RPNIs produce proximal sensory afferent responses similar to those evoked from normal skin. This confirmation of graded afferent signal transduction through DS-RPNI neural interfaces validate DS-RPNI's potential role of facilitating sensation in human-machine interfacing. The DS-RPNI is a novel biotic-abiotic neural interface that allows for transduction of sensory stimuli into neural signals. It is expected to advance the restoration of natural sensation and development of sensorimotor control in prosthetics.

Visualizing Contralateral Suppression of Hearing Sensitivity via Acoustic and Electric Brainstem Audiometry in Bimodal Cochlear Implant Patients: A Feasibility Study

Introduction: The medial olivocochlear reflex (MOCR) is a part of the binaural processing strategies and influences the efferent auditory pathway in normal-hearing individuals. Patients with asymmetric hearing loss often benefit from a bimodal hearing solution with a cochlear implant (CI) and a hearing aid (HA). However, hearing performances may vary with some surprisingly high- or low-performing CI/HA users. A potential role of the MOCR among these patients warrants further investigation. Otoacustics emissions are an established method to visualize the reflex; however, this technique implies some disadvantages. To visualize the MOCR via auditory brainstem response (ABR) could be a promising alternative. Methods: Twenty-three bimodal CI/HA users were enrolled. Experimental setup was as follows: I. electrical ABR on the CI side was recorded with and without simultaneous contralateral noise signal at the HA side, II. acoustic ABR was recorded on the HA side with and without simultaneous contralateral noise at the CI side. Brainstem thresholds and amplitudes of waveforms I–V with and without contralateral noise were compared. Potential correlations of patient-related factors and hearing performances were analysed. Results: In four individuals, a reduction of brainstem audiometry thresholds could be observed at the acoustic brainstem audiometry. In these cases, results could be reproduced. Summarizing ABR measurements at the HA side of all individuals, no relevant changes of ABR thresholds (dB nHL) or waveform amplitude reductions (nV) could be observed irrespective of the presence or absence of a contralateral suppression signal. Conclusion: Threshold changes of acoustic ABR upon presentation of a contralateral suppression signal could not generally be measured in bimodal CI users. However, in a subgroup, a highly reproducible effect was demonstrated if a contralateral suppression signal was applied. A reactivated rather than rehabilitated MOCR may have accounted for this effect in this subgroup. One could speculate that in these patients, bimodal fitting could be affected by the MOCR efferents.

Fluid Substitution-Based Reservoir Studies and Seismic Response in ‘Vyshion’ Field, Niger Delta

A case study of how fluid substitution affects the seismic waveforms is presented. Direct hydrocarbon prediction on the seismic data is prone to inaccuracy without investigating the impact of fluids on the seismic waveforms since the seismic data is influenced by mineral composition, porosity, salinity, pressure, and other factors in addition to fluid type. The study relies on 3D seismic data and log data gathered from 3 wells. Petrophysical and rock physics models were computed in order to understand the seismic dataset. In the analysis, prolific hydrocarbon intervals were identified. Then, model compressional velocities and densities obtained for various fluid scenarios were generated by using the Gassmann fluid substitution theory. Normalized bulk modulus approach was used to reduce the ambiguities that shales portend on the velocity models. Model synthetics were generated. The synthetic seismograms were compared with the seismic dataset in order to understand how fluid saturation and lithology impacts the seismic data. In the analysis, two major hydrocarbon bearing reservoirs were delineated. Other mapped reservoirs have characteristic indices that make them unsuitable for the fluid modelling. The results show that the model oil velocity model better approximates the field velocity. The density models produced the same kind of results, suggesting that the reservoir fluid is oil. The generated synthetic diagrams show that replacing the in-situ fluid with either gas or oil models has no appreciable impact on the seismic dataset’s amplitude waveform. This is because seismic reflection amplitude only slightly increases each time gas is assumed. By using the seismic data from this field of study, hydrocarbons cannot be directly predicted from amplitude anomalies because the lithology better influences the seismic waveforms than the fluid composition.

Contactless SpO2 with an RGB camera: experimental proof of calibrated SpO2.

Camera-based blood oxygen saturation (SpO2) monitoring allows reliable measurements without touching the skin and is therefore very attractive when there is a risk of cross-infection, in case of fragile skin, and/or to improve the clinical workflow. Despite promising results, productization of the technology is hampered by the unavailability of adequate hardware, especially a camera, which can capture the optimal wavelengths for SpO2 measurements in the red near-infrared region. A regular color (RGB) camera is attractive because of its availability, but also poses several risks and challenges which affect the accuracy of the measurement. To mitigate the most important risks, we propose to add low-cost commercial off-the-shelf (COTS) components to the setup. We executed two studies with this setup: one at a hypoxia lab with SpO2 values in the range 70 - 100% with the purpose to determine the calibration model, and the other study on volunteers to investigate the accuracy for different spot-check scenarios. The proposed processing pipeline includes face tracking and a robust method to estimate the ratio of relative amplitudes of the photoplethysmographic waveforms. Results show that the error is smaller than 4 percent points for realistic screening scenarios where the subject is seated, either with or without head support and/or ambient light.

Laser Generated Broadband Rayleigh Waveform Evolution for Metal Additive Manufacturing Process Monitoring

This work proposes that laser pulses can generate finite amplitude Rayleigh waves for process monitoring during additive manufacturing. The noncontact process monitoring uses a pulsed laser to generate Rayleigh waves, and an adaptive laser interferometer to receive them. Experiments and models in the literature show that finite amplitude waveforms evolve with propagation distance and that shocks can even form in the in-plane particle velocity waveform. The nonlinear waveform evolution is indicative of the material nonlinearity, which is sensitive to the material microstructure, which in turn affects strength and fracture properties. The measurements are made inside a directed energy deposition additive manufacturing chamber on planar Ti-6Al-4V and IN-718 depositions. By detecting the out-of-plane particle displacement waveform, the in-plane displacement and velocity waveforms are also available. The waveform evolution can be characterized (i) for one source amplitude by reception at different points or (ii) by reception at one point by applying different source amplitudes. Sample results are provided for intentionally adjusted key process parameters: laser power, scan speed, and hatch spacing.

Very fast transient overvoltage calculation and evaluation for 500‐kV gas insulated substation power substation with double circuit and long gas insulated substation busbar

The operation of disconnectors in gas insulated substation (GIS) or power plant will produce very fast transient overvoltage (VFTO), which is considered to have serious harm to transformer longitudinal insulation and other high-voltage equipment insulation. VFTO may also lead to secondary circuit failure. In this paper, the holistic modelling of 500 kV GIS step-up substation equipment with a double circuit and long GIS busbar in a coastal power plant is established using Electromagnetic Transient Program (EMTP). The authors calculated the VFTO waveform that may be generated in different operations of the GIS substation. The authors analyze the amplitude and frequency characteristics of the VFTO waveform at lightning arresters and the entrance of transformers and find that the amplitude of VFTO at the entrance of #1 MT is less than its impulse withstand voltage. In some cases, the VFTO waveform at the entrance of #1 MT has high-frequency content with fast attenuation. The VFTO waveform generated when operating the disconnector close to the arrester will cause the arrester to act many times and count frequently in a short time.

A multi-frame space-time coding method for the phase-coded signal in MIMO radars

Code-division multiplexing (CDM) has become the focus of designing orthogonal waveforms of multiple-input multiple-output (MIMO) radars as it occupies fewer resources than time-division multiplexing (TDM) and frequency-division multiplexing (FDM). As one of the standard CDM waveforms, conventional inter-pulse phase-coded waveform possesses non-ideal diversity performance. That is, the orthogonality of the signals will reach the threshold after the codes extend to a certain length. To circumvent the coding restrictions, space-time coding (STC) makes use of spatial resources. This paper proposes a multi-frame STC method to improve the orthogonality among waveforms. Specifically, we first design the orthogonal transmitted signals and corresponding matched filters for MIMO radars. Then the signal expressions and the radar ambiguity function (AF) are deduced to verify the proposed method theoretically. Compared with conventional STC, such a method can save half of the time domain resources and make the most of coding resources. Furthermore, the output signal-to-noise ratio (SNR) is well improved as the proposed method effectively suppresses the cross-correlation energy of the waveform. The proposed multi-frame STC waveform can be easily implemented in practical radar applications because of its constant waveform amplitude. The theoretical analysis and simulation results demonstrate the effectiveness of the method.

Electrochemical enhancement of carbon black-infused poly(lactic acid) filament for additive manufactured electronic applications

Here we present an electrochemical method to enhance the electrical conductivity of commercially available, carbon-black infused polylactic acid (PLA) for use in material extrusion-based additive manufacturing (MEAM). After fabrication, the carbon-black infused PLA structure was processed in aqueous solutions consisting of either hydrochloric acid (HCl), nitric acid (HNO3), or sulfuric acid (H2SO4). This study examines the effects of acid concentration of the three types of acids, input waveform shape applied during the electrochemical process, waveform amplitude, and the frequency of the waveforms on the bonding of the negatively charged ions to the conductive PLA. We found that inputting a DC square pulse in a 7 M H2SO4 solution yielded a 51% reduction in electrical resistance. X-Ray diffraction (XRD) analysis shows that line width does shift to lower 2θ values without affecting the d-spacing and the 2θ peaks decay indicating that the ions introduced through the electrochemical doping process are being diffused into the conductive workpiece. Energy dispersive X-ray spectroscopy (EDS) showed the presence of sulfur ions located throughout the processed carbon-infused PLA, even at the core. Throughout this study, we found that this electrochemical process can create electrically in-active dead zones that occurs from higher current densities. XRD analysis reveals that peaks in these dead zones move to higher 2θ, rather than lower 2θ in the improved areas. This points to a shrinking of the lattice structure and verifies that structural changes are occurring. Electrically improved areas can be utilized in conjunction with electrically in-active dead zones to create conductive areas with insulating zones, mimicking copper traces on a PCB. This electrochemical process provides the opportunity for fused filament fabrication to be used in more electrical applications.

Quantitative Investigation of Acoustic Emission Waveform Parameters from Crack Opening in a Rail Section Using Clustering Algorithms and Advanced Signal Processing.

Acoustic emission (AE) is an emerging technology for real-time non-destructive testing of structures. While research on a simulated AE source in rail and testing on rail material using small beam samples have been conducted, a study is required in lab environment to investigate AE waveform characteristics generated by crack in rail. In this paper, a three-point bending test is conducted on an actual rail section of 1500 mm with transverse damage of 38% head area to simulate AE source due to crack opening in the rail. AE signals are recorded for three different loads. For data analysis, unsupervised machine learning algorithms such as k-means, fuzzy-C mean and gaussian mixture model are used to cluster and filter out usable signals from the whole dataset corrupted by noisy signals from various sources. k-mean with principal component was observed to be best technique based on silhouette score. The frequency and amplitude of waveform have been discussed in relation to load and crack opening displacement. This study establishes a baseline for linking load, crack opening, and AE wave characteristics. This work can ultimately aid in the development of robust denoising, and damage analysis algorithms based on the frequency content and dispersion of the AE waveform.

Contactless skin perfusion monitoring with video cameras: tracking pharmacological vasoconstriction and vasodilation using photoplethysmographic changes

Objectives. Clinical assessment of skin perfusion informs prognosis in critically ill patients. Video camera monitoring could provide an objective, continuous method to monitor skin perfusion. In this prospective, interventional study of healthy volunteers, we tested whether video camera-derived photoplethysmography imaging and colour measurements could detect drug-induced skin perfusion changes. Approach. We monitored the lower limbs of 30 volunteers using video cameras while administering phenylephrine (a vasoconstrictor) and glyceryl trinitrate (a vasodilator). We report relative pixel intensity changes from baseline, as absolute values are sensitive to environmental factors. The primary outcome was the pre- to peak- infusion green channel amplitude change in the pulsatile PPGi waveform component. Secondary outcomes were pre-to-peak changes in the photoplethysmographic imaging waveform baseline, skin colour hue and skin colour saturation. Main results. The 30 participants had a median age of 29 years (IQR 25–34), sixteen (53%) were male. A 34.7% (p = 0.0001) mean decrease in the amplitude of the pulsatile photoplethysmographic imaging waveform occurred following phenylephrine infusion. A 30.7% (p = 0.000004) mean increase occurred following glyceryl trinitrate infusion. The photoplethysmographic imaging baseline decreased with phenylephrine by 2.1% (p = 0.000 02) and increased with glyceryl trinitrate by 0.5% (p = 0.026). Skin colour hue changed in opposite direction with phenylephrine (−0.0013, p = 0.0002) and glyceryl trinitrate (+0.0006, p = 0.019). Skin colour saturation decreased with phenylephrine by 0.0022 (p = 0.0002), with no significant change observed with glyceryl trinitrate (+0.0005, p = 0.21). Significance. Drug-induced vasoconstriction and vasodilation are associated with detectable changes in photoplethysmographic imaging waveform parameters and skin hue. Our findings suggest video cameras have great potential for continuous, contactless skin perfusion monitoring.