Reactive hyperemia: a review of methods, mechanisms, and considerations

AJP Regulatory Integrative and Comparative Physiology, Journal Year: 2020, Volume and Issue: 318(3), P. R605 - R618

Published: Feb. 5, 2020

Reactive hyperemia is a well-established technique for noninvasive assessment of peripheral microvascular function and predictor all-cause cardiovascular morbidity mortality. In its simplest form, reactive represents the magnitude limb reperfusion following brief period ischemia induced by arterial occlusion. Over past two decades, investigators have employed variety methods, including brachial artery velocity Doppler ultrasound, tissue near-infrared spectroscopy, distension venous occlusion plethysmography, tonometry, to measure hyperemia. Regardless used hyperemia, blunted believed reflect impaired function. With advent several technological advancements, together with an increased interest in microcirculation, becoming more common as research tool widely across multiple disciplines. this mind, we sought review various methodologies commonly assess current mechanistic pathways contribute on methodological considerations.

Language: Английский

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Optical imaging and spectroscopy for the study of the human brain: status report

Neurophotonics, Journal Year: 2022, Volume and Issue: 9(S2)

Published: Aug. 30, 2022

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit novel methods to explore brain health function. While first focused on neurophotonic tools mostly applicable animal studies, here, we highlight optical spectroscopy imaging relevant noninvasive human studies. We outline current state-of-the-art technologies software advances, most recent impact these neuroscience clinical applications, identify areas where innovation needed, provide outlook for future directions.

Language: Английский

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Validation of a novel wearable, wireless technology to estimate oxygen levels and lactate threshold power in the exercising muscle

Physiological Reports, Journal Year: 2018, Volume and Issue: 6(7), P. e13664 - e13664

Published: April 1, 2018

There is a growing interest in monitoring muscle oxygen saturation (SmO2), which localized measure of oxidative metabolism and can be acquired continuously noninvasively using near-infrared spectroscopy (NIRS) methods. Most NIRS systems are cumbersome, expensive, fiber coupled devices, with use limited to lab settings. A novel, low cost, wireless, wearable has been developed for athletic training. In this study, we evaluate the advantages limitations new simple continuous-wave (CW) device respect benchtop, frequency-domain (FDNIRS) system. Oxygen hemoglobin/myoglobin concentration exercising muscles 17 individuals were measured simultaneously two systems, while subjects performed an incremental test on stationary cycle ergometer. addition, blood lactate was at end each increment analyzer. During exercise, correlation coefficients SmO2 concentrations between over 0.70. We also found both insensitive presence thin layers varying absorption, mimicking different skin colors. Neither system able predict athletes’ threshold power accurately by simply thresholds. Instead, proprietary software within half one cycling test. These results indicate novel may provide physiological indicator athlete's exertion.

Language: Английский

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Highly parallel, interferometric diffusing wave spectroscopy for monitoring cerebral blood flow dynamics

Optica, Journal Year: 2018, Volume and Issue: 5(5), P. 518 - 518

Published: April 26, 2018

Light-scattering methods are widely used in soft matter physics and biomedical optics to probe dynamics turbid media, such as diffusion colloids or blood flow biological tissue.These typically rely on fluctuations of coherent light intensity, therefore cannot accommodate more than a few modes per detector.This limitation has hindered efforts measure deep tissue with high speed, since weak diffuse fluxes, together low singlemode fiber throughput, result photon count rates.To solve this, we introduce multimode (MMF) interferometry the field optics.In doing so, transform standard complementary metal-oxide-semiconductor (CMOS) camera into sensitive detector array for fluxes that tissue.Specifically, build novel CMOS-based, interferometric diffusing wave spectroscopy (iDWS) system show it can ∼20 speckles simultaneously near shot noise limit, acting essentially independent photon-counting channels.We develop matrix formalism, based MMF mode solutions geometry, predict both coherence speckle number iDWS.After validation liquid phantoms, demonstrate iDWS pulsatile measurements at 2.5 cm source-detector separation adult human brain vivo.By achieving highly parallel CMOS camera, this work promises enhance performance reduce cost optical instruments.

Language: Английский

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Direct assessment of extracerebral signal contamination on optical measurements of cerebral blood flow, oxygenation, and metabolism

Neurophotonics, Journal Year: 2020, Volume and Issue: 7(04)

Published: Oct. 7, 2020

Significance: Near-infrared spectroscopy (NIRS) combined with diffuse correlation (DCS) provides a noninvasive approach for monitoring cerebral blood flow (CBF), oxygenation, and oxygen metabolism. However, these methods are vulnerable to signal contamination from the scalp. Our work evaluated of reducing impact this using time-resolved (TR) NIRS multidistance (MD) DCS. Aim: The magnitude scalp was by measuring flow, metabolic responses global hemodynamic challenge. Contamination assessed collecting data without impeding flow. Approach: Experiments involved healthy participants. A pneumatic tourniquet used cause ischemia, as confirmed contrast-enhanced NIRS, computerized gas system generate hypercapnic Results: Comparing acquired demonstrated that TR-NIRS technique could reduce contributions in signals up 4 times (rSD = 3 cm) 6 cm). Similarly, brain be separated analyzing MD DCS multilayer model. Using techniques, there no change metabolism during hypercapnia, expected, despite large increases CBF oxygenation. Conclusion: NIRS/DCS can accurately monitor appropriate enhancement depth sensitivity, highlighting potential techniques neuromonitoring.

Language: Английский

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A Newcomer's Guide to Functional Near Infrared Spectroscopy Experiments

IEEE Reviews in Biomedical Engineering, Journal Year: 2019, Volume and Issue: 13, P. 292 - 308

Published: Oct. 17, 2019

This review presents a practical primer for functional near-infrared spectroscopy (fNIRS) with respect to technology, experimentation, and analysis software. Its purpose is jump-start interested practitioners considering utilizing non-invasive, versatile, nevertheless challenging window into the brain using optical methods. We briefly recapitulate relevant anatomical foundations give short historical overview. describe competing types of illumination (trans-illumination, reflectance, differential reflectance) data collection methods (continuous wave, time domain frequency domain). Basic components (light sources, detection, recording components) fNIRS systems are presented. Advantages limitations techniques offered, followed by list very recommendations its use. A variety experimental clinical studies sampled, shedding light on many brain-related ailments. Finally, we discuss number freely available presentation packages suited analysis. In conclusion, recommend due ever-growing body applications, state-of-the-art neuroimaging technique manageable hardware requirements. It can be safely concluded that adds new arrow quiver neuro-medical examinations both great versatility limited costs.

Language: Английский

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Effects of food supplementation on cognitive function, cerebral blood flow, and nutritional status in young children at risk of undernutrition: randomized controlled trial

BMJ, Journal Year: 2020, Volume and Issue: unknown, P. m2397 - m2397

Published: July 22, 2020

Abstract Objective To assess the effects of food supplementation on improving working memory and additional measures including cerebral blood flow in children at risk undernutrition. Design Randomized controlled trial. Setting 10 villages Guinea-Bissau. Participants 1059 aged 15 months to 7 years; younger than 4 were primary population. Interventions Supervised isocaloric servings (≈1300 kJ, five mornings each week, 23 weeks) a new supplement (NEWSUP, high plant polyphenols omega 3 fatty acids, within wide variety fortification micronutrients, protein content), or fortified blended (FBF) used nutrition programs, control meal (traditional rice breakfast). Main outcome measurements The was memory, core executive function predicting long term academic achievement. Additional outcomes hemoglobin concentration, growth, body composition, index (CBF i ). In addition an intention-to-treat analysis, predefined per protocol analysis conducted who consumed least 75% (820/925, 89%). assessed by multivariable Poisson model; other linear mixed models. Results Among 4, randomization NEWSUP increased compared with (rate ratio 1.20, 95% confidence interval 1.02 1.41, P=0.03), larger effect population (1.25, 1.06 1.47, P=0.009). also concentration among anemia (adjusted mean difference 0.65 g/dL, 0.23 1.07, P=0.003) meal, decreased mass z score gain (−0.23, −0.43 −0.02, lean tissue accretion (2.98 cm 2 , 0.04 5.92, P=0.046) less fat (−5.82 −11.28 −0.36, P=0.04) FBF. Additionally, CBF FBF both age groups combined (1.14 mm /s×10 −8 0.10 2.23, P=0.04 for comparisons). older, had no significant anemia, but (4.31 0.34 8.28, P=0.03). Conclusions Childhood undernutrition is associated impairment cognition. Contrary current understanding, supplementary feeding weeks could improve function, brain health, nutritional status vulnerable young living low income countries. Further research needed optimize prescriptions regenerative improvements cognitive test effectiveness groups. Trial registration ClinicalTrials.gov NCT03017209 .

Language: Английский

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Review of recent advances in frequency-domain near-infrared spectroscopy technologies [Invited]

Biomedical Optics Express, Journal Year: 2023, Volume and Issue: 14(7), P. 3234 - 3234

Published: June 1, 2023

Over the past several decades, near-infrared spectroscopy (NIRS) has become a popular research and clinical tool for non-invasively measuring oxygenation of biological tissues, with particular emphasis on applications to human brain. In most cases, NIRS studies are performed using continuous-wave (CW-NIRS), which can only provide information relative changes in chromophore concentrations, such as oxygenated deoxygenated hemoglobin, well estimates tissue oxygen saturation. Another type known frequency-domain (FD-NIRS) significant advantages: it directly measure optical pathlength thus quantify scattering absorption coefficients sampled tissues direct measurements absolute concentrations. This review describes current status FD-NIRS technologies, their performance, advantages, limitations compared other methods. Significant landmarks technological progress include development both benchtop portable/wearable sensitive front-end photonic components, high-frequency phase measurements. Clinical technologies discussed context needed areas improvement. The concludes by providing roadmap toward next generation fully wearable, low-cost systems.

Language: Английский

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Effects of exercise training on calf muscle oxygen extraction and blood flow in patients with peripheral artery disease

Journal of Applied Physiology, Journal Year: 2017, Volume and Issue: 123(6), P. 1599 - 1609

Published: Oct. 5, 2017

We employed near-infrared optical techniques, diffuse correlation spectroscopy (DCS), and frequency-domain (FD-NIRS) to test the hypothesis that supervised exercise training increases skeletal muscle microvascular blood flow oxygen extraction in patients with peripheral artery disease (PAD) who experience claudication. PAD ( n = 64) were randomly assigned control groups. Patients group received 3 mo of training. Calf optically monitored before, during, after performance a graded treadmill protocol at baseline both Additionally, measurements ankle-brachial index (ABI) peak walking time (PWT) maximal claudication made during each patient visit. Supervised was found increase calf levels by 29% (13%, 50%) 8% (1%, 12%), respectively [ P < 0.001; median (25th percentile, 75th percentile)]. These improvements across population significantly higher than corresponding changes 0.004). Exercise also increased PWT 49% (18%, 101%) 0.01). However, within statistical error, ABI, resting extraction, recovery half-time for hemoglobin\myoglobin desaturation following cessation not altered The concurrent monitoring hybrid DCS/FD-NIRS instrument revealed enhanced oxidative metabolism physical activity from training, which could be an underlying mechanism observed improvement PWT. NEW & NOTEWORTHY report on noninvasive dynamics before/during/after tracked effects 3-mo improved ability activity.

Language: Английский

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Noninvasive continuous optical monitoring of absolute cerebral blood flow in critically ill adults

Neurophotonics, Journal Year: 2018, Volume and Issue: 5(04), P. 1 - 1

Published: Nov. 23, 2018

We investigate a scheme for noninvasive continuous monitoring of absolute cerebral blood flow (CBF) in adult human patients based on combination time-resolved dynamic contrast-enhanced near-infrared spectroscopy (DCE-NIRS) and diffuse correlation (DCS) with semi-infinite head model photon propogation. Continuous CBF is obtained via calibration the DCS index (BFI) by intermittent intravenous injections optical contrast agent indocyanine green. A coefficient (γ) thus determined, permitting conversion BFI to units at all other times. study acute brain injury (N = 7) carried out ascertain stability γ. The patient-averaged across multiple days was good agreement between two coefficients measured different times during single found. 1.24 × 109 ( mL / 100 g min ) cm2 s applied previously from similar brain-injured patients; this case, underestimated compared XeCT, an effect we show primarily due use homogeneous models head.

Language: Английский

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