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Journal of Applied Physiology... Sep 2022Pulse transit time (PTT) is the time it takes for pressure waves to propagate through the arterial system. Arterial stiffness assessed via PTT has been extensively...
Pulse transit time (PTT) is the time it takes for pressure waves to propagate through the arterial system. Arterial stiffness assessed via PTT has been extensively examined in the conduit arteries; however, limited information is available about PTT to the skeletal muscle microcirculation. Therefore, the purpose of this study was to assess PTT to the skeletal muscle microcirculation (PTTm) with near-infrared spectroscopy (NIRS) and to determine whether PTTm provides unique information about vascular function that PTT assessed in the conduit arteries (PTTc) cannot provide. This pilot study was conducted with 10 (male = 5; female = 5) individuals of similar age (21.5 ± 1.2 yr). The feasibility of using the intersecting tangents method to derive PTTm with NIRS was assessed during reactive hyperemia with the cross-correlation of PTTm produced by the intersecting tangents method and a different algorithm that used signal spectral properties. To determine whether PTTm was distinct from PTTc, the cross-correlation of PTTm and PTTc during reactive hyperemia was assessed. Cross-correlation indicated agreement between PTTm derived from both algorithms ( = 0.77, < 0.01) and a lack of agreement between PTTm and PTTc during reactive hyperemia ( = 0.07, < 0.01). Therefore, we conclude that it is feasible to assess PTTm using NIRS, and PTTm provides unique information about vascular function, including skeletal muscle microvascular elasticity, which cannot be achieved with traditional PTTc. PTTm with NIRS may provide a comprehensive and noninvasive assessment of vascular function and health. Pulse transit time to the skeletal muscle microcirculation can be assessed using near-infrared spectroscopy and the intersecting tangents method. Pulse transit analysis to the microcirculation provides a comprehensive assessment of the vascular response to postocclusive reactive hyperemia that pulse transit analysis in the conduit arteries cannot provide. Pulse transit time to the skeletal muscle microcirculation using near-infrared spectroscopy provides unique information about microvascular elasticity in the skeletal muscle. These findings indicate that the combination of near-infrared spectroscopy and pulse transit analysis may be a useful method for assessing the skeletal muscle microcirculation.
Topics: Female; Humans; Hyperemia; Male; Microcirculation; Muscle, Skeletal; Pilot Projects; Pulse Wave Analysis; Spectroscopy, Near-Infrared
PubMed: 35834626
DOI: 10.1152/japplphysiol.00173.2022 -
Frontiers in Immunology 2021In the immunology of sepsis microcirculatory and mitochondrial dysfunction in the gastrointestinal system are important contributors to mortality. Hydrogen sulfide (HS)...
INTRODUCTION
In the immunology of sepsis microcirculatory and mitochondrial dysfunction in the gastrointestinal system are important contributors to mortality. Hydrogen sulfide (HS) optimizes gastrointestinal oxygen supply and mitochondrial respiration predominantly K(ATP)-channels. Therefore, we tested the hypothesis that sodium thiosulfate (STS), an inducer of endogenous HS, improves intestinal and hepatic microcirculation and mitochondrial function K(ATP)-channels in sepsis.
METHODS
In 40 male Wistar rats colon ascendens stent peritonitis (CASP) surgery was performed to establish sepsis. Animals were randomized into 4 groups (1: STS 1 g • kg i.p., 2: glibenclamide (GL) 5 mg • kg i.p., 3: STS + GL, 4: vehicle (VE) i.p.). Treatment was given directly after CASP-surgery and 24 hours later. Microcirculatory oxygenation (µHBO) and flow (µflow) of the colon and the liver were continuously recorded over 90 min using tissue reflectance spectrophotometry. Mitochondrial oxygen consumption in tissue homogenates was determined with respirometry. Statistic: two-way ANOVA + Dunnett´s and Tukey post - hoc test (microcirculation) and Kruskal-Wallis test + Dunn's multiple comparison test (mitochondria). p < 0.05 was considered significant.
RESULTS
STS increased µHbO (colon: 90 min: + 10.4 ± 18.3%; liver: 90 min: + 5.8 ± 9.1%; p < 0.05 vs. baseline). Furthermore, STS ameliorated µflow (colon: 60 min: + 51.9 ± 71.1 aU; liver: 90 min: + 22.5 ± 20.0 aU; p < 0.05 vs. baseline). In both organs, µHbO and µflow were significantly higher after STS compared to VE. The combination of STS and GL increased colonic µHbO and µflow (µHbO 90 min: + 8.7 ± 11.5%; µflow: 90 min: + 41.8 ± 63.3 aU; p < 0.05 vs. baseline), with significantly higher values compared to VE. Liver µHbO and µflow did not change after STS and GL. GL alone did not change colonic or hepatic µHbO or µflow. Mitochondrial oxygen consumption and macrohemodynamic remained unaltered.
CONCLUSION
The beneficial effect of STS on intestinal and hepatic microcirculatory oxygenation in sepsis seems to be mediated by an increased microcirculatory perfusion and not by mitochondrial respiratory or macrohemodynamic changes. Furthermore, the effect of STS on hepatic but not on intestinal microcirculation seems to be K(ATP)-channel-dependent.
Topics: Animals; Antioxidants; Colon; Disease Models, Animal; Liver; Male; Microcirculation; Mitochondria; Rats; Rats, Wistar; Sepsis; Thiosulfates
PubMed: 34163476
DOI: 10.3389/fimmu.2021.671935 -
JACC. Cardiovascular Interventions Apr 2018
Topics: Angiography; Coronary Stenosis; Fractional Flow Reserve, Myocardial; Humans; Microcirculation
PubMed: 29673506
DOI: 10.1016/j.jcin.2018.03.003 -
American Journal of Physiology.... Mar 2020Reactive hyperemia is a well-established technique for noninvasive assessment of peripheral microvascular function and a predictor of all-cause and cardiovascular... (Review)
Review
Reactive hyperemia is a well-established technique for noninvasive assessment of peripheral microvascular function and a predictor of all-cause and cardiovascular morbidity and mortality. In its simplest form, reactive hyperemia represents the magnitude of limb reperfusion following a brief period of ischemia induced by arterial occlusion. Over the past two decades, investigators have employed a variety of methods, including brachial artery velocity by Doppler ultrasound, tissue reperfusion by near-infrared spectroscopy, limb distension by venous occlusion plethysmography, and peripheral artery tonometry, to measure reactive hyperemia. Regardless of the technique used to measure reactive hyperemia, blunted reactive hyperemia is believed to reflect impaired microvascular function. With the advent of several technological advancements, together with an increased interest in the microcirculation, reactive hyperemia is becoming more common as a research tool and is widely used across multiple disciplines. With this in mind, we sought to review the various methodologies commonly used to assess reactive hyperemia and current mechanistic pathways believed to contribute to reactive hyperemia and reflect on several methodological considerations.
Topics: Blood Flow Velocity; Brachial Artery; Humans; Hyperemia; Ischemia; Microcirculation; Vasodilation
PubMed: 32022580
DOI: 10.1152/ajpregu.00339.2019 -
Journal of Thrombosis and Haemostasis :... Sep 2023Microvascular dysfunction is a growing determinant of sex differences in coronary heart disease (CHD). Dysregulation of the coagulation system is involved in CHD...
BACKGROUND
Microvascular dysfunction is a growing determinant of sex differences in coronary heart disease (CHD). Dysregulation of the coagulation system is involved in CHD pathogenesis and can be induced by endothelial glycocalyx (EG) perturbation. However, little is known about the link between EG function and coagulation parameters in population-based studies on sex specificity.
OBJECTIVES
We sought to examine the sex differences in the relationship between EG function and coagulation parameters in a middle-aged Dutch population.
METHODS
Using baseline measurements of 771 participants from the Netherlands Epidemiology of Obesity study (age, 56 years [IQR, 51-61 years]; 53% women; body mass index, 27.9 kg/m [IQR, 25.1-30.9 kg/m]), associations between glycocalyx-related perfused boundary region (PBR) derived using sidestream dark-field imaging and coagulation parameters (factor [F]VIII/IX/XI; thrombin generation parameters; and fibrinogen) were investigated using linear regression analyses, adjusting for possible confounders (including C-reactive protein, leptin, and glycoprotein acetyls), followed by sex-stratified analyses.
RESULTS
There was a sex difference in the associations between PBR and coagulation parameters. Particularly in women, 1-SD PBR (both total and feed vessel, indicating poorer glycocalyx status) was associated with higher FIX activity ([1.8%; 95% CI, 0.3%-3.3%] and [2.0%; 95% CI, 0.5%-3.4%], respectively) and plasma fibrinogen levels ([5.1 mg/dL; 95% CI, 0.4-9.9 mg/dL] and [5.8 mg/dL; 95% CI, 1.1-10.6 mg/dL], respectively). Furthermore, 1-SD PBR was associated with higher FVIII activity (3.5%; 95% CI, 0.4%-6.5%) and plasma fibrinogen levels (5.3 mg/dL; 95% CI, 0.6-10.0 mg/dL).
CONCLUSION
We revealed a sex-specific association between microcirculatory health and procoagulant status, which suggests that microvascular health be considered during early development of CHD in women.
Topics: Middle Aged; Humans; Male; Female; Netherlands; Microcirculation; Obesity; Blood Coagulation; Fibrinogen; Coronary Disease
PubMed: 37301258
DOI: 10.1016/j.jtha.2023.06.001 -
Critical Care (London, England) Oct 2016Oxygen delivery to cells is the basic prerequisite of life. Within the human body, an ingenious oxygen delivery system, comprising steps of convection and diffusion from... (Review)
Review
Oxygen delivery to cells is the basic prerequisite of life. Within the human body, an ingenious oxygen delivery system, comprising steps of convection and diffusion from the upper airways via the lungs and the cardiovascular system to the microvascular area, bridges the gap between oxygen in the outside airspace and the interstitial space around the cells. However, the complexity of this evolutionary development makes us prone to pathophysiological problems. While those problems related to respiration and macrohemodynamics have already been successfully addressed by modern medicine, the pathophysiology of the microcirculation is still often a closed book in daily practice. Nevertheless, here as well, profound physiological understanding is the only key to rational therapeutic decisions. The prime guarantor of tissue oxygenation is tissue blood flow. Therefore, on the premise of intact macrohemodynamics, the microcirculation has three major responsibilities: 1) providing access for oxygenated blood to the tissues and appropriate return of volume; 2) maintaining global tissue flood flow, even in the face of changes in central blood pressure; and 3) linking local blood flow to local metabolic needs. It is an intriguing concept of nature to do this mainly by local regulatory mechanisms, impacting primarily on flow resistance, be this via endothelial or direct smooth muscle actions. The final goal of microvascular blood flow per unit of time is to ensure the needed exchange of substances between tissue and blood compartments. The two principle means of accomplishing this are diffusion and filtration. While simple diffusion is the quantitatively most important form of capillary exchange activity for the respiratory gases, water flux across the blood-brain barrier is facilitated via preformed specialized channels, the aquaporines. Beyond that, the vascular barrier is practically nowhere completely tight for water, with paracellular filtration giving rise to generally low but permanent fluid flux outwards into the interstitial space at the microvascular high pressure segment. At the more leaky venular aspect, both filtration and diffusion allow for bidirectional passage of water, nutrients, and waste products. We are just beginning to appreciate that a major factor for maintaining tissue fluid homeostasis appears to be the integrity of the endothelial glycocalyx.
Topics: Animals; Blood Flow Velocity; Blood Volume; Blood-Brain Barrier; Glycocalyx; Hemodynamics; Humans; Microcirculation; Oxygen Consumption
PubMed: 27765054
DOI: 10.1186/s13054-016-1485-0 -
Microcirculation (New York, N.Y. : 1994) Oct 2022Monitoring microcirculation and visualizing microvasculature are critical for providing diagnosis to medical professionals and guiding clinical interventions. Ultrasound...
OBJECTIVE
Monitoring microcirculation and visualizing microvasculature are critical for providing diagnosis to medical professionals and guiding clinical interventions. Ultrasound provides a medium for monitoring and visualization; however, there are challenges due to the complex microscale geometry of the vasculature and difficulties associated with quantifying perfusion. Here, we studied established and state-of-the-art ultrasonic modalities (using six probes) to compare their detection of slow flow in small microvasculature.
METHODS
Five ultrasonic modalities were studied: grayscale, color Doppler, power Doppler, superb microvascular imaging (SMI), and microflow imaging (MFI), using six linear probes across two ultrasound scanners. Image readability was blindly scored by radiologists and quantified for evaluation. Vasculature visualization was investigated both in vitro (resolution and flow characterization) and in vivo (fingertip microvasculature detection).
RESULTS
Superb Microvascular Imaging (SMI) and Micro Flow Imaging (MFI) modalities provided superior images when compared with conventional ultrasound imaging modalities both in vitro and in vivo. The choice of probe played a significant difference in detectability. The slowest flow detected (in the lab) was 0.1885 ml/s and small microvasculature of the fingertip were visualized.
CONCLUSIONS
Our data demonstrated that SMI and MFI used with vascular probes operating at higher frequencies provided resolutions acceptable for microvasculature visualization, paving the path for future development of ultrasound devices for microcirculation monitoring.
Topics: Microcirculation; Ultrasonography; Microvessels; Ultrasonography, Doppler
PubMed: 35611457
DOI: 10.1111/micc.12770 -
GeroScience Dec 2019Aging of the microcirculatory network plays a central role in the pathogenesis of a wide range of age-related diseases, from heart failure to Alzheimer's disease. In the... (Review)
Review
Aging of the microcirculatory network plays a central role in the pathogenesis of a wide range of age-related diseases, from heart failure to Alzheimer's disease. In the eye, changes in the choroid and choroidal microcirculation (choriocapillaris) also occur with age, and these changes can play a critical role in the pathogenesis of age-related macular degeneration (AMD). In order to develop novel treatments for amelioration of choriocapillaris aging and prevention of AMD, it is essential to understand the cellular and functional changes that occur in the choroid and choriocapillaris during aging. In this review, recent advances in in vivo analysis of choroidal structure and function in AMD patients and patients at risk for AMD are discussed. The pathophysiological roles of fundamental cellular and molecular mechanisms of aging including oxidative stress, mitochondrial dysfunction, and impaired resistance to molecular stressors in the choriocapillaris are also considered in terms of their contribution to the pathogenesis of AMD. The pathogenic roles of cardiovascular risk factors that exacerbate microvascular aging processes, such as smoking, hypertension, and obesity as they relate to AMD and choroid and choriocapillaris changes in patients with these cardiovascular risk factors, are also discussed. Finally, future directions and opportunities to develop novel interventions to prevent/delay AMD by targeting fundamental cellular and molecular aging processes are presented.
Topics: Aging; Choroid; Disease Progression; Humans; Microcirculation; Regional Blood Flow; Retinal Vessels; Wet Macular Degeneration
PubMed: 31797238
DOI: 10.1007/s11357-019-00138-3 -
Neurourology and Urodynamics Jan 2020Oxygen plays a crucial role in wound healing after prolapse surgery. Trauma to the vaginal vasculature might limit the delivery of oxygen to the surgical wound, which...
AIMS
Oxygen plays a crucial role in wound healing after prolapse surgery. Trauma to the vaginal vasculature might limit the delivery of oxygen to the surgical wound, which may negatively affect wound healing and regeneration of connective tissue. This possibly increases the future risk of recurrence. We aimed to determine the effects of vaginal prolapse surgery on the microcirculation of the vaginal wall.
METHODS
We evaluated the vaginal microcirculation in healthy participants without known vascular disease undergoing anterior and/or posterior colporrhaphy. We used incident dark-field imaging for in vivo assessment before and after (1 day, 2 weeks, and 6 weeks) surgery. We studied perfusion (microvascular flow index [MFI]), angioarchitecture (morphology/layout of microvessels) and capillary density.
RESULTS
Ten women were included. Interindividual differences were observed 1 day postoperatively with regard to perfusion and angioarchitecture. Microvascular flow at the surgical site was absent or significantly reduced in some participants, whereas normal microvascular flow was observed in others (MFI range 0-3). Perfusion and angioarchitecture had been restored in all participants after 6 weeks (MFI range 2-3), regardless of the extent of vascular trauma 1 day postoperatively.
CONCLUSIONS
The difference in the extent of vascular trauma between women undergoing seemingly identical surgical procedures suggests that some individuals are more susceptible to vascular trauma than others. Delivery of oxygen to the wound and subsequent wound healing may be compromised in these cases, which could be related to the development of anatomical recurrence. Future studies should investigate whether there is a relationship between the vaginal microvasculature and the recurrence of prolapse.
Topics: Aged; Female; Gynecologic Surgical Procedures; Humans; Microcirculation; Microvessels; Middle Aged; Pelvic Organ Prolapse; Recurrence; Surgical Mesh; Vagina
PubMed: 31691336
DOI: 10.1002/nau.24203 -
Arteriosclerosis, Thrombosis, and... Jul 2019Objectives- Coronary endothelial dysfunction is a precursor of atherosclerosis and adverse outcomes. Whether endothelial dysfunction is a localized or generalized...
Objectives- Coronary endothelial dysfunction is a precursor of atherosclerosis and adverse outcomes. Whether endothelial dysfunction is a localized or generalized phenomenon in humans remains uncertain. We simultaneously measured femoral and coronary vascular function with the hypothesis that peripheral vascular endothelial function will be reflective of coronary endothelial function. Approach and Results- Eighty-five subjects underwent coronary angiography for evaluation of chest pain or abnormal stress tests. Endothelium-dependent and -independent vascular function were measured using intracoronary and intrafemoral infusions of acetylcholine and sodium nitroprusside, respectively. Coronary flow reserve was assessed using intracoronary adenosine infusion. Flow velocity was measured in each circulation using a Doppler wire (FloWire, EndoSonics). Coronary vascular resistance and femoral vascular resistance were calculated as mean arterial pressure (mm Hg)/coronary blood flow (mL/min) and mean arterial pressure (mm Hg)/femoral average peak velocity (cm/s), respectively. Mean age was 53±11 years, 37% were female, 44% had hypertension, 12% had diabetes mellitus, and 38% had obstructive coronary artery disease. There was a correlation between the change in femoral vascular resistance with acetylcholine and acetylcholine-mediated changes in both the coronary vascular resistance ( r=0.27; P=0.014) and in the epicardial coronary artery diameter ( r=-0.25; P=0.021), indicating that subjects with normal endothelial function in the femoral circulation had normal endothelial function in the coronary epicardial and microcirculation and vice versa. The coronary vasodilator response to adenosine also correlated with the femoral vasodilatation with acetylcholine ( r=0.4; P=0.0002). There was no correlation between the coronary and femoral responses to sodium nitroprusside. Conclusions- Endothelial functional changes in the peripheral and coronary circulations were modestly correlated. Thus, peripheral microvascular endothelial function reflects endothelium-dependent coronary epicardial and microvascular function and the coronary flow reserve. Visual Overview- An online visual overview is available for this article.
Topics: Adult; Aged; Coronary Circulation; Coronary Vessels; Endothelium, Vascular; Female; Femoral Artery; Humans; Male; Microcirculation; Middle Aged; Vascular Resistance
PubMed: 31018659
DOI: 10.1161/ATVBAHA.119.312378