Red Blood Cell Speed Research Articles

Quantitative study of spatial and temporal variation in retinal capillary network perfusion in rat eye by in vivo confocal imaging

Microvascular dysfunction is the underlying pathological process in many systemic diseases. However, investigation into its pathogenesis is impeded by the accessibility and complexity of the microvasculature within different organs, particularly for the central nervous system. The retina as an extension of the cerebrum provides a glimpse into the brain through which the microvasculature can be observed. Two major questions remain unanswered: How do the microvessels regulate spatial and temporal delivery to satisfy the varying cellular demands, and how can we quantify blood perfusion in the 3D capillary network? Here, quantitative measurements of red blood cell (RBC) speed in each vessel in the field were made in the in vivo rat retinal capillary network using an ultrafast confocal technique with fluorescently labelled RBCs. Retinal RBC speed and number were found to vary remarkably between microvessels ranging from 215 to 6641 microns per second with significant variations spatially and temporally. Overall, the RBC speed was significantly faster in the microvessels in the superficial retina than in the deep retina (estimated marginal means of 2405 ± 238.2 µm/s, 1641 ± 173.0 µm/s respectively). These observations point to a highly dynamic nature of microvasculature that is specific to its immediate cellular environment and is constantly changing.

In Vivo and In Situ Approach to Study Islet Microcirculation: A Mini-Review.

The pancreas is regarded as consisting of two separate organ systems, the endocrine and exocrine pancreas. While treatment of a disease with either an endocrine or exocrine pathogenesis may affect the function of the entire pancreas, the pancreatic diseases have been treated by clinicians in different medical disciplines, including endocrinologists and gastroenterologists. Islet microcirculation has long been considered to be regulated independently from that of the exocrine pancreas. A new model proposes that pancreatic islet blood flow is integrated with the surrounding exocrine capillary network. This recent model may provide revived or contrasting hypotheses to test, since the pancreatic microcirculation has critical implications for the regulation of islet hormones as well as acinar pancreas functions. In this mini-review, practical applications of in vivo and in situ studies of islet microcirculation are described with a specific emphasis on large-scale data analysis to ensure sufficient sample size accounting for known islet heterogeneity. For in vivo small animal studies, intravital microscopy based on two-photon excitation microscopes is a powerful tool that enables capturing the flow direction and speed of individual fluorescent-labeled red blood cells. Complementarily, for structural analysis of blood vessels, the recent technical advancements of confocal microscopy and tissue clearing have enabled us to image the three-dimensional network structure in thick tissue slices.

Single laser trapping for optical folding and rotation of red blood cells in sickle cell disease in response to hydroxyurea treatment

Optical folding and rotation behavior of red blood cells (RBCs) in polarized laser tweezers are considerably important for understanding the biophysical and biomechanical properties using the fast probing method. Here, a dual-mode polarized single-laser tweezers technique with distinct principal axes exhibiting different polarization states is presented and designed to investigate the deformation, optical folding, and rotation of single living cells with one measurement. RBC optical folding and rotation speed are measured in patients with sickle cell disease (SCD), including follow up of patients after hydroxyurea (HU) treatment for at least three months. Folding angle and rotation speed are significantly lower in patients with SCD and do not significantly differ in patients treated by HU compared with the healthy control group. The RBC folding angle and rotation speed in patients treated with HU drug increase linearly at lower laser powers and rapidly at higher powers, and increase much slowly in patients not treated with HU. The difference in the folding angle and rotation speed of RBCs could be useful for drug response in SCD or predicting pain crisis in SCD.

Validation of red blood cell flux and velocity estimations based on optical coherence tomography intensity fluctuations

We present a validation of red blood cell flux and speed measurements based on the passage of erythrocytes through the OCT’s focal volume. We compare the performance of the so-called RBC-passage OCT technique to co-localized and simultaneously acquired two-photon excitation fluorescence microscopy (TPEF) measurements. Using concurrent multi-modal imaging, we show that fluctuations in the OCT signal display highly similar features to TPEF time traces. Furthermore, we demonstrate an overall difference in RBC flux and speed of 2.5 ± 3.27 RBC/s and 0.12 ± 0.67 mm/s (mean ± S.D.), compared to TPEF. The analysis also revealed that the OCT RBC flux estimation is most accurate between 20 RBC/s to 60 RBC/s, and is severely underestimated at fluxes beyond 80 RBC/s. Lastly, our analysis shows that the RBC speed estimations increase in accuracy as the speed decreases, reaching a difference of 0.16 ± 0.25 mm/s within the 0–0.5 mm/s speed range.

Atherosclerosis is associated with a decrease in cerebral microvascular blood flow and tissue oxygenation.

Chronic atherosclerosis may cause cerebral hypoperfusion and inadequate brain oxygenation, contributing to the progression of cognitive decline. In this study, we exploited two-photon phosphorescence lifetime microscopy to measure the absolute partial pressure of oxygen (PO2) in cortical tissue in both young and old LDLR-/-, hApoB100+/+ mice, spontaneously developing atherosclerosis with age. Capillary red-blood-cell (RBC) speed, flux, hematocrit and capillary diameter were also measured by two-photon imaging of FITC-labelled blood plasma. Our results show positive correlations between RBC speed, flux, diameter and capillary-adjacent tissue PO2. When compared to the young mice, we observed lower tissue PO2, lower RBC speed and flux, and smaller capillary diameter in the old atherosclerotic mice. The old mice also exhibited a higher spatial heterogeneity of tissue PO2, and RBC speed and flux, suggesting a less efficient oxygen extraction.

Mathematical modeling of the magnetic field of red blood cells in narrow capillaries

The red blood cell (RBC) moves in a narrow capillary and asymmetric of its shape lead to tank-treading motion of the membrane. Electric charges on the RBC membrane generate a magnetic field in the surrounding space. A mathematical model imitating the motion of RBC through capillaries with a diameter less than 8 μm is developed in order to estimate the distribution of plasma pressure, plasma velocity and magnetic field strength in the vicinity of RBC. It is assumed that plasma flow between erythrocytes in the capillary satisfies the Poiseuille law, and in the gap between the capillary wall and the RBC membrane satisfies the Reynolds system of equations for the lubricating layer. Calculations made on a computer allow us to estimate the shape of the RBC, the speed of rotation of the RBC membrane, the plasma pressure, the plasma velocity and the magnetic field strength in the vicinity of the RBC. It is shown that the distribution of the magnetic field strength in the vicinity of the erythrocyte is non-uniform and depends on the capillary diameter, RBC speed, RBC charge, volume and surface area of RBC.

Insulin‐induced hypoglycemia directly affects the cerebral microvasculature in vivo

ObjectiveInsulin therapy for patients with diabetes mellitus (DM) carries the risk for acute hypoglycemia (HG). Evidence from human and animal studies has suggested a role for HG in the exacerbation of cardiovascular dysfunction accompanying DM. Specifically, animal studies have shown that recurrent HG promotes increased ischemic brain injury. Furthermore, HG has been shown to affect mitochondrial function in cultured endothelial cells. Therefore, we hypothesized that acute insulin‐induced HG directly affects the cerebral microvascular function in vivo.MethodsWild type C57Bl/6 mice were prepared for long term two‐photon microscopy by removing a 4mm diameter section of bone over the somatosensory cortex which was then sealed with a glass coverslip held in place with cyanoacrylate and dental acrylic. A custom titanium bar was added to the preparation for head fixation during imaging. During imaging sessions, the cerebral vasculature was visualized using FITC‐dextran 40kDa. Mice were imaged under hypoglycemia (63.2 +/− 8.2 mg/dL by imaging start) using 1–2 U/kg of Humulin‐R. Microvessels approximately 3–5μm in diameter were measured for diameter changes using ImageJ. Blood flow through cerebral microvessels was assayed using line scans over the vasculature to determine red blood cell (RBC) traffic and speed. Fluorescence intensity was also measured in ImageJ to determine any changes in BBB permeability.ResultsAcute hypoglycemia induces a vasodilatory effect in cerebral microvasculature (diameter increased by 10.0 +/− 1.7 %, N=7 mice, n=89 microvessels, vs. 1.751 +/− 1.0 % N=6 mice, n=134 microvessels, in saline controls, p = .0007). However, blood flow was not changed between groups (149.0 +/− 7.4 vs. 167.6 +/− 11.3 RBC/sec and 0.979 +/− 0.060 vs. 1.052 +/− 0.068 μm/ms). Additionally, acute hypoglycemia caused no noticeable changes in the permeability of the BBB indicated by the extravasation of FITC‐dextran.ConclusionsOur data show that acute HG causes noticeable changes in the in vivo cerebral microvasculature, however, we did not note any changes in blood flow, potentially due to cerebral auto regulation. We therefore conclude that insulin‐induced HG causes noticeable direct effects on the cerebral vasculature that may play a role in cerebro vascular impairments in DM.Support or Funding InformationNational Institute of Health: National Institute of General Medical Sciences, National Institute of Aging, and National Institute of Neurological Disorders and Stroke (Mostany: R01AG049821; Katakam: R01NS094834).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract 101: ApoE4 Disrupts Cerebrovascular Microcirculation and Undermines White Matter Integrity and Cognitive Function

Background: Small vessel disease leading to subcortical white matter lesions (WML) is the major cause of vascular cognitive impairment. The apolipoprotein E4 (ApoE4) allele, a well-known risk factor for Alzheimer’s disease, is also a risk factor for WML, but the mechanisms of the effect remain unclear. We set out to determine whether the ApoE4 genotype disrupts the cerebral microcirculation and promotes WML and cognitive impairment. Methods: We studied male ApoE4 targeted replacement mice (ApoE4-TR; age 3-4 months). ApoE3 (ApoE3-TR) were used as controls. Cerebral blood flow (CBF) was assessed by ASL-MRI; the CBF increase induced by whisker stimulation (WS) or the endothelium-dependent agent acetylcholine (ACh) was assessed in cranial window preparations by laser-Doppler flowmetry. The corpus callosum (CC) microcirculation was examined by three-photon microscopy (3PM). Bilateral carotid artery stenosis (BCAS) was induced with 0.18 mm microcoils. WML and cognition were tested 4 weeks after BCAS. Results: In ApoE4-TR mice resting cortical CBF was attenuated compared to ApoE3-TR (-13%), as well the increase in CBF produced by WS (-47±3%) or ACh (-38±3%; p<0.05; n=5/group). In the CC, red blood cell (RBC) speed was slower in ApoE4-TR (1.6±0.1) than in ApoE3 mice (1.9±0.1 mm/s; p<0.05; n=5/group). Following 4 weeks of BCAS, cortical CBF was reduced more in ApoE4-TR (-35±4%) than in ApoE3-TR mice (-23±2%; p<0.05; n=8/group). Similarly, in the CC RBC speed was reduced more in ApoE4-TR (-33±3%) than in ApoE3-TR mice (-23±3%; p<0.05; n=5/group). In ApoE4-TR mice BCAS resulted in more marked CC WML (SMI312/MBP ratio, 48%) and cognitive dysfunction (novel object recognition: 18%; Y-maze arm alternation: 14%) than in ApoE3-TR mice (p<0.05; n=8/group). Conclusions: The findings unveil a previously unrecognized ApoE4-dependent failure of critical neurovascular regulatory mechanisms, sufficient to promote white matter damage in the setting of cerebral hypoperfusion. Such alterations may be responsible for the increased susceptibility to hypoxic-ischemic lesions in the subcortical white matter of individuals carrying the ApoE4 allele.

In vivo neurovascular response to focused photoactivation of Channelrhodopsin-2

The rapid growth in the use of optogenetics for neuroscience applications is largely driven by two important advantages: highly specific cellular targeting through genetic manipulations; and precise temporal control of neuronal activation via temporal modulation of the optical stimulation. The difference between the most commonly used stimulation modalities, namely diffused (i.e. synchronous) and focused (i.e. asynchronous) stimulation has not been described. Furthermore, full realization of optogenetics’ potential is hindered by our incomplete understanding of the cellular and network level response to photoactivation. Here we address these gaps by examining the neuronal and cerebrovascular responses to focused and diffuse photostimulation of channelrhodopsin in the Thy1-ChR2 mouse. We presented the responses of photoactivation via 470-nm fiber optic illumination (diffuse) alongside 458-nm raster-scan (focused) stimulation of the barrel field. Local field potentials (LFP) assessment of intracerebral electrophysiology and two-photon fluorescence microscopy measurements of red blood cell (RBC) speed (vRBC) in cortical penetrating vessels revealed ∼40% larger LFP responses (p = 0.05) and twice as large cerebrovascular responses (p = 0.002) under focused vs. diffuse photostimulation (focused: 1.64 ± 0.84 mV LFP amplitude and 75 ± 48% increase in vRBC; diffuse: 1.14 ± 0.75 mV LFP amplitude and 35 ± 23% increase in vRBC). Compared to diffuse photostimulation, focused photostimulation resulted in a ∼65% increase in the yield of cerebrovascular responses (73 ± 10% for focused and 42 ± 29% for diffuse photostimulation) and a doubling of the signal-to-noise ratio of the cerebrovascular response (20.9 ± 14.7 for focused and 10.4 ± 1.4 for diffuse photostimulation). These data reveal important advantages of focused optogenetic photoactivation, which can be easily integrated into single- or two-photon fluorescence microscopy platforms, as a means of assessing neuronal excitability and cerebrovascular reactivity, thus paving the way for broader application of optogenetics in preclinical models of CNS diseases.

The effect of hyperglycemia on neurovascular coupling and cerebrovascular patterning in zebrafish

Neurovascular coupling (through which local cerebral blood flow changes in response to neural activation are mediated) is impaired in many diseases including diabetes. Current preclinical rodent models of neurovascular coupling rely on invasive surgery and instrumentation, but transgenic zebrafish coupled with advances in imaging techniques allow non-invasive quantification of cerebrovascular anatomy, neural activation, and cerebral vessel haemodynamics. We therefore established a novel non-invasive, non-anaesthetised zebrafish larval model of neurovascular coupling, in which visual stimulus evokes neuronal activation in the optic tectum that is associated with a specific increase in red blood cell speed in tectal blood vessels. We applied this model to the examination of the effect of glucose exposure on cerebrovascular patterning and neurovascular coupling. We found that chronic exposure of zebrafish to glucose impaired tectal blood vessel patterning and neurovascular coupling. The nitric oxide donor sodium nitroprusside rescued all these adverse effects of glucose exposure on cerebrovascular patterning and function. Our results establish the first non-mammalian model of neurovascular coupling, offering the potential to perform more rapid genetic modifications and high-throughput screening than is currently possible using rodents. Furthermore, using this zebrafish model, we reveal a potential strategy to ameliorate the effects of hyperglycemia on cerebrovascular function.

Evaluation of a pointwise microcirculation assessment method using liquid and multilayered tissue simulating phantoms.

.A fiber-optic probe-based instrument, designed for assessment of parameters related to microcirculation, red blood cell tissue fraction (), oxygen saturation (), and speed resolved perfusion, has been evaluated using state-of-the-art tissue phantoms. The probe integrates diffuse reflectance spectroscopy (DRS) at two source–detector separations and laser Doppler flowmetry, using an inverse Monte Carlo method for identifying the parameters of a multilayered tissue model. Here, we characterize the accuracy of the DRS aspect of the instrument using (1) liquid blood phantoms containing yeast and (2) epidermis-dermis mimicking solid-layered phantoms fabricated from polydimethylsiloxane, titanium oxide, hemoglobin, and coffee. The root-mean-square (RMS) deviations for for the two liquid phantoms were 11% and 5.3%, respectively, and 11% for the solid phantoms with highest hemoglobin signatures. The RMS deviation for was 5.2% and 2.9%, respectively, for the liquid phantoms, and 2.9% for the solid phantoms. RMS deviation for the reduced scattering coefficient (), for the solid phantoms was 15% (475 to 850 nm). For the liquid phantoms, the RMS deviation in average vessel diameter () was . In conclusion, the skin microcirculation parameters and , as well as, and are estimated with reasonable accuracy.

Effects of voluntary exercise on structure and function of cortical microvasculature

Aerobic activity has been shown highly beneficial to brain health, yet much uncertainty still surrounds the effects of exercise on the functioning of cerebral microvasculature. This study used two-photon fluorescence microscopy to examine cerebral hemodynamic alterations as well as accompanying geometric changes in the cortical microvascular network following five weeks of voluntary exercise in transgenic mice endogenously expressing tdTomato in vascular endothelial cells to allow visualization of microvessels irrespective of their perfusion levels. We found a diminished microvascular response to a hypercapnic challenge (10% FiCO2) in running mice when compared to that in nonrunning controls despite commensurate increases in transcutaneous CO2 tension. The flow increase to hypercapnia in runners was 70% lower than that in nonrunners (p = 0.0070) and the runners’ arteriolar red blood cell speed changed by only half the amount seen in nonrunners (p = 0.0085). No changes were seen in resting hemodynamics or in the systemic physiological parameters measured. Although a few unperfused new vessels were observed on visual inspection, running did not produce significant morphological differences in the microvascular morphometric parameters, quantified following semiautomated tracking of the microvascular networks. We propose that voluntary running led to increased cortical microvascular efficiency and desensitization to CO2 elevation.

Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment

We have developed a new fiber-optic system that combines diffuse reflectance spectroscopy (DRS) and laser Doppler Flowmetry (LDF) for a multi-modal assessment of the microcirculation. Quantitative data is achieved with an inverse Monte Carlo algorithm based on an individually adaptive skin model. The output parameters are calculated from the model and given in absolute units: hemoglobin oxygen saturation (%), red blood cell (RBC) tissue fraction (%), and the speed resolved RBC perfusion separated into three speed regions; 0–1mm/s, 1–10mm/s and above 10mm/s (% mm/s). The aim was to explore microcirculatory parameters using the new optical method, integrating DRS and LDF in a joint skin model, during local heating of the dorsal foot and venous and arterial occlusion of the forearm in 23 healthy subjects (age 20–28years). There were differences in the three speed regions in regard to blood flow changes due to local heating, where perfusion for high speeds increased the most. There was also a high correlation between changes in oxygenation and changes in perfusion for higher speeds. Oxygen saturation at baseline was 44% on foot, increasing to 83% at plateau after heating. The larger increase in perfusion for higher speeds than for lower speeds together with the oxygenation increase during thermal provocation, shows a local thermoregulatory blood flow in presumably arteriolar dermal vessels. In conclusion, there are improved possibilities to assess microcirculation using integrated DRS and LDF in a joint skin model by enabling both oxygenation and speed resolved blood flow assessment simultaneously and in the same skin site. Output parameters in absolute units may also yield new insights about the microcirculatory system.

Assessing the reliability of diffuse correlation spectroscopy models on noise-free analytical Monte Carlo data.

It is shown that an analytical noise-free implementation of Monte Carlo simulations [Appl. Opt.54, 2400 (2015).10.1364/AO.54.002400APOPAI1559-128X] for diffuse correlation spectroscopy (DCS) may be successfully used to check the ability of a given DCS model to generate a reliable estimator of tissue blood flow. As an example, four different DCS models often found in the scientific literature are tested on a simulated tissue (semi-infinite geometry) with a Maxwell-Boltzmann probability distribution function for red blood cell speed. It is shown that the random model is the best model for the chosen speed distribution but that (1) some inaccuracies in the DCS model in taking into account red blood cell concentration and (2) some inaccuracies, probably due to a low-order approximation of the DCS model, are still observed. The method can be easily generalized for other speed/flow probability distribution functions of the red blood cells.

Quantifying morphological heterogeneity: a study of more than 1 000 000 individual stored red blood cells.

The morphology of red blood cells (RBCs) deteriorates progressively during hypothermic storage. The degree of deterioration varies between individual cells, resulting in a highly heterogeneous population of cells contained within each RBC unit. Current techniques capable of categorizing the morphology of individual stored RBCs are manual, laborious and error-prone procedures that limit the number of cells that can be studied. Our objective was to create a simple, automated system for high-throughput RBC morphology classification. A simple microfluidic device, designed to enable rapid, consistent acquisition of images of optimally oriented RBCs, was fabricated using soft lithography. A custom image analysis algorithm was developed to categorize the morphology of each individual RBC in the acquired images. The system was used to determine morphology of individual RBCs in several RBC units stored hypothermically for 6-8 weeks. The system was used to automatically determine the distribution of cell diameter within each morphological class for >1 000 000 individual stored RBCs (speed: >10 000 cells/h; accuracy: 91·9% low resolution, 75·3% high resolution). Diameter mean and standard deviation by morphology class were as follows: discocyte 7·80 ± 0·49 μm, echinocyte 1 7·61 ± 0·63 μm, echinocyte 2 7·02 ± 0·61 μm, echinocyte 3 6·47 ± 0·42 μm, sphero-echinocyte 6·01 ± 0·26 μm, spherocyte 6·02 ± 0·27 μm, stomatocyte 1 6·95 ± 0·61 μm and stomatocyte 2 7·32 ± 0·47 μm. The automated morphology classification procedure described in this study is significantly simpler, faster and less subjective than conventional manual procedures. The ability to evaluate the morphology of individual RBCs automatically, rapidly and in statistically significant numbers enabled us to perform the most extensive study of stored RBC morphology to date.

Optical Coherence Tomography angiography reveals laminar microvascular hemodynamics in the rat somatosensory cortex during activation

The BOLD (blood-oxygen-level dependent) fMRI (functional Magnetic Resonance Imaging) signal is shaped, in part, by changes in red blood cell (RBC) content and flow across vascular compartments over time. These complex dynamics have been challenging to characterize directly due to a lack of appropriate imaging modalities. In this study, making use of infrared light scattering from RBCs, depth-resolved Optical Coherence Tomography (OCT) angiography was applied to image laminar functional hyperemia in the rat somatosensory cortex. After defining and validating depth-specific metrics for changes in RBC content and speed, laminar hemodynamic responses in microvasculature up to cortical depths of >1mm were measured during a forepaw stimulus. The results provide a comprehensive picture of when and where changes in RBC content and speed occur during and immediately following cortical activation. In summary, the earliest and largest microvascular RBC content changes occurred in the middle cortical layers, while post-stimulus undershoots were most prominent superficially. These laminar variations in positive and negative responses paralleled known distributions of excitatory and inhibitory synapses, suggesting neuronal underpinnings. Additionally, the RBC speed response consistently returned to baseline more promptly than RBC content after the stimulus across cortical layers, supporting a “flow-volume mismatch” of hemodynamic origin.

Aging-related differences in cerebral capillary blood flow in anesthetized rats

Age-related decreases in baseline cerebral blood flow have been measured with various imaging modalities, however, the contribution of capillary flow to this phenomenon remain to elucidate. This study used 2-photon laser scanning fluorescence microscopy to measure capillary diameter, red blood cell speed, and flux in individual capillaries in the sensory-motor cortex of 12 adult (3-month-old) and 12 old (24-month-old) male Long-Evans rats under isoflurane anesthesia. The average (± standard deviation) diameter and speed over 921 capillaries were 6.4 ± 1.4 μm and 1.3 ± 1.1 mm/s, respectively. Red blood cell speed and flux were significantly higher, by 48% and 15%, respectively, in old compared with young animals (p < 5%). The diameter also showed a similar tendency (7% higher, p = 5.7%). Furthermore, capillary hematocrit and density were significantly lower in the older group (p < 5%), by 32% and 20%, respectively.

Assessment of speed distribution of red blood cells in the microvascular network in healthy volunteers and type 1 diabetes using laser Doppler spectra decomposition

We applied a recently reported method of decomposition of laser Doppler power density spectra for in vivo monitoring of speed distributions of red blood cells (RBCs) in the microvascular network. The spectrum decomposition technique allows us to derive the distribution of RBC speed (in absolute units (mm s−1)) versus RBC concentration (in arbitrary units). We carried out postocclusive reactive hyperaemia (PORH) test in 15 healthy volunteers and 21 diabetic patients in which the duration of type 1 diabetes was longer than 10 years. Measurements were carried out simultaneously with the use of a typical laser Doppler commercial instrument and speed resolved laser Doppler instrument utilizing the new technique based on decomposition of the laser Doppler spectra. We show that for the classical laser Doppler instrument, none of the PORH parameters revealed a statistical significance of difference between the groups analyzed. In contrast, the RBC speed distributions obtained from laser Doppler spectra during rest in the control group and type 1 diabetes are statistically significant. This result suggests that speed distribution measurements in the rest state (without any kind of stimulation test) allows for the assessment of microcirculation disorders. Measurements carried out in healthy subjects show that the first moment of speed distributions (mean speed of the distributions) is 2.32 ± 0.54 mm s−1 and 2.57 ± 0.41 mm s−1 for optodes located on the toe and finger of the hand, respectively. Respective values in type 1 diabetes were higher: 3.00 ± 0.36 mm s−1 and 3.10 ± 0.48 mm s−1.

Hyperkalemic cardiac arrest in pediatric patients undergoing massive transfusion: unplanned emergencies

Hyperkalemic cardiac arrest in pediatric patients undergoing massive transfusion: unplanned emergencies

Multiple-Capillary Measurement of RBC Speed, Flux, and Density with Optical Coherence Tomography

As capillaries exhibit heterogeneous and fluctuating dynamics even during baseline, a technique measuring red blood cell (RBC) speed and flux over many capillaries at the same time is needed. Here, we report that optical coherence tomography can capture individual RBC passage simultaneously over many capillaries located at different depths. Further, we demonstrate the ability to quantify RBC speed, flux, and linear density. This technique will provide a means to monitor microvascular flow dynamics over many capillaries at different depths at the same time.