Variations In Blood Flow Research Articles

Skin blood flow and temperature oscillations during cold pressor test.

We study the relationship between the blood flow and skin temperature variations under a cold pressor test (CPT). The simultaneous laser Doppler flowmetry (LDF) and skin temperature (ST) measurements were carried out for 8 healthy subjects on the skin surface of the distal phalanx of the second (LDF) and third (ST) fingers. The skin blood perfusion decreases stepwise about twice during contralateral CPT for all 8 subjects. The temperature of the finger pad decays monotonically during the test and dropped about 1°C in mean. The power spectral densities of LDF flow and ST variations are also affected by the CPT, but subjects under study demonstrate two different types of reaction. LDF pulsations at the frequency about 0.1 Hz, which corresponds to the myogenic mechanism of vascular tone regulation, decreases in 5 subjects and increases in other 3 subjects. However in all subjects the ST pulsations behave contradictory, namely, the changes in amplitude of blood perfusion and ST pulsations due to cold pressor test are strongly anticorrelated. We discuss possible mechanisms of vascular reaction that can cause the behavior observed.

Algorithms for the inference of causality in dynamic processes: Application to cardiovascular and cerebrovascular variability.

This study faces the problem of causal inference in multivariate dynamic processes, with specific regard to the detection of instantaneous and time-lagged directed interactions. We point out the limitations of the traditional Granger causality analysis, showing that it leads to false detection of causality when instantaneous and time-lagged effects coexist in the process structure. Then, we propose an improved algorithm for causal inference that combines the Granger framework with the approach proposed by Pearl for the study of causality among multiple random variables. This new approach is compared with the traditional one in theoretical and simulated examples of interacting processes, showing its ability to retrieve the correct structure of instantaneous and time-lagged interactions. These approaches for causal inference are then tested on the physiological variability series of heart period, arterial pressure and cerebral blood flow variability obtained in subjects with postural-related syncope during a tilt-test protocol.

The disturbances of cerebral microcirculation in severe head injury

The aim of the literature review was to present modern views on the possible mechanisms of the disturbances of capillary blood flow in severe brain injury (TBI). The critical analysis of the concept of secondary brain damage and possible mechanisms of the disturbances of cerebral microcirculation in TBI are presented. We also discuss modern methodologies for assessing capillary blood flow in patients with brain damage. The attention is focused on the causes of the disturbances of cerebral microcirculation in TBI, as well as in various forms of fat embolism in severe combined TBI. Possibilities of prevention and early correction of damaged capillary blood flow in brain injury, as well as the supposed reasons for the failure of some clinical trials, including the widely known CRASH, are analyzed. It is noted that an integrative approach to the assessment of cerebral microcirculation in conjunction with brain metabolism reflects not just the variability of cerebral blood flow and functional disorders of perfusion and metabolism coupling in traumatic brain injury. It is emphasized that ischemia is not the only cause of post-traumatic disorders of pial circulation. We highlight directions for future research of posttraumatic disturbances of cerebral microcirculation as a leading factor of secondary brain insults. The possibility of pharmacological and non-pharmacological correction of microcirculatory disorders in TBI is outlined.

Skin temperature variations as a tracer of microvessel tone

Abstract The problem of frequency-by-frequency cross-correlation detection is studied using two characteristics of blood microcirculation: blood flow and skin temperature. Skin blood flow variations are measured by Laser Doppler Flowmetry (LDF) and Skin Temperature (ST) – by a high-resolution (0.001 K) temperature recorder. The wavelet cross-correlation (WCC) is compared with Fourier coherence and demonstrates certain advantages for the frequency-by-frequency analysis of biomedical nonstationary signals. The WCC analysis of the LDF and ST signals performed for 17 healthy subjects reveales a high correlation in the low-frequency range 0.01 ν

Contribution Of The Skeletal Muscle Pump To Blood Flow At The Onset Of Contractions

There is a substantial reserve for increased skeletal muscle blood flow in response to exercise; however, the interaction of neural regulation, vasoactive metabolites, and mechanical characteristics are incompletely understood. The potential contribution of skeletal muscle contraction, the muscle pump (MP), to exercise hyperemia remains in question. PURPOSE: To determine MP contribution to muscle blood flow during transitions from rest to various metabolic rates. METHODS: Canine gastrocnemius muscle (n=7) was isolated and stimulated to produce rhythmic isometric tetanic contractions. The total blood flow (Qwc) kinetics were fitted by a mono-exponential function (tau), and the blood flow response to contraction with the mechanical contribution of MP removed (Qnc) was calculated. The Qnc calculation estimated blood flow in each contraction cycle as a linear variation of blood flow from a point immediately prior to, until the end of each contraction. The following transitions were investigated with spontaneous blood flow response intact: rest to tetanic contractions of 1/3 s; rest to 2/3 s; rest to 1/1 s; and during the transition from 1/3 s to 2/3s. RESULTS: During 1/3 s stimulation, Qnc exceeded Qwc by the second contraction, indicating a negative contribution of MP to total flow from that point on. During 2/3 s stimulation, Qwc exceeded Qnc for at least six contractions but declined rapidly to a negative contribution beyond 20 s. During 1/1 s stimulation, MP contribution declined from onset but Qwc remained greater than Qnc throughout indicating a positive contribution to total flow. In all transitions tau was not different (p=ns) between Qwc and Qnc: 1/3 s stimulation rate, tau = 12.8 ± 5.5 s vs 11.8 ± 3.2 s, respectively; rest to 2/3 s, tau = 25.6 ± 12.0 s vs 22.1 ± 1.3 s; rest to 1/1 s, tau = 16.7 ± 3.0 s vs 22.1 ± 1.3 s; transition from 1/3 s to 2/3s, tau = 21.2 ± 3.4 s vs 21.7 ± 4.8 s. CONCLUSION: MP likely contributes to local perfusion at exercise onset with diminishing returns as rhythmic contractions continue. The benefit to total skeletal muscle blood flow contributed by MP is dependent on contraction frequency. Supported by BBSRC UK, BB/F019521/1.

A human-phantom coupling experiment and a dispersive simulation model for investigating the variation of dielectric properties of biological tissues

Variation of the dielectric properties of tissues could happen due to aging, moisture of the skin, muscle denervation, and variation of blood flow by temperature. Several studies used burst-modulated alternating stimulation to improve activation and comfort by reducing tissue impedance as a possible mechanism to generate muscle activation with less energy. The study of the effect of dielectric properties of biological tissues in nerve activation presents a fundamental problem, which is the difficulty of systematically changing the morphological factors and dielectric properties of the subjects under study. We tackle this problem by using a simulation and an experimental study. The experimental study is a novel method that combines a fat tissue-equivalent phantom, with known and adjustable dielectric properties, with the human thigh. In this way, the dispersion of the tissue under study could be modified to observe its effects systematically in muscle activation. We observed that, to generate a given amount of muscle or nerve activation under conditions of decreased impedance, the magnitude of the current needs to be increased while the magnitude of the voltage needs to be decreased.

Trial‐to‐Trial and Day‐to‐Day Variability in Forearm Blood Flow During Reactive Hyperemia

Reactive hyperemia (RH) following the release of a brief limb occlusion is commonly used to assess resistance vessel function. The purpose of this study was to examine the impact of repeated trials on the within subject day‐to‐day variability of forearm blood flow during RH. Ten young, healthy, non‐smoking subjects (6 female, 4 male) were examined in the fasted state. Brachial artery diameter and blood velocity were assessed with Echo and Doppler ultrasound, respectively. Subjects visited the lab twice and performed four RH trials each visit. The RH protocol was performed on the left arm and included 5 minutes of forearm cuff occlusion at a pressure of 250 mmHg, followed by release. Within subjects trial‐to‐trial and day‐to‐day variability was assessed by the coefficient of variation (CV = (Standard Deviation/Mean) x 100). The Day‐to‐day CV was calculated using 1) Trial 1 from each day and 2) a 4‐Trial average. Peak forearm blood flow did not differ significantly between trials or days (p > 0.05). Within subject trial‐to‐trial variability was consistent between visits (CV, 9.39 ± 7.78% and 10.1 ± 3.19%; p = 0.737). The within subject day‐to‐day CV determined from the first trial on each day was not significantly different from the CV determined from the four trial average (CV, 14.9± 15.1% and 12.0± 9.62%; p = 0.240). In conclusion, averaging over repeated trials on each visit did not significantly reduce the day‐to‐day variability in peak reactive hyperemia blood flow.

0329 : Role of the estrogen receptor alpha (ERalpha) in the vascular response to shear stress in mice

Small resistance arteries regulate peripheral tissue perfusion following variations in arterial pressure and blood flow. An alteration of the acute flowmediated dilation (FMD) in response to an elevation in intra-arterial shear stress is the hallmark of early vascular dysfunction and ageing. We recently showed that flow-dependent arterial remodeling, an adaptive phenomenon lost with age, was controlled by the endothelial estrogen receptor alpha (ERα). Our goal was thus to evaluate the role of ERαin endothelial mechano-sensitive mechanisms related to the acute response to flow, by using multiple models of ERαdeficiency in male mice, avoiding the hormonal influence of estrogens encountered in females. The evaluation of the FMD was performed on pressurized mesenteric resistance arteries mounted on an arteriograph following step increase in intraluminal flow (6-100 μl/min). Arteries were isolated from wild-type (WT) and ERαgenetically modified male mice deficient in (i) total ERα(ERαKO), (ii) the ligand-dependent transactivation function AF2 (AF2°) or (iii) the plasmic membrane-located ERαfollowing a point mutation of the palmitoylation site of the receptor (C451A). We first observed a selective alteration of FMD, without any major modification in response to vasodilator agonists (acetylcholine), in male mice deficient in total ERα. Interestingly, while the activation of the AF2 function involved in the nuclear action of ERαseemed only partially involved (% dilation 50μl/min: AF2: 49,5+/-11,8 vs. WT: 68,0+/-7,9 p=ns.), a default in receptor membrane addressing in C451A male mice markedly altered FMD (% dilation 50μl/min: C451A:29,4+/-5,1 vs. WT:59,3+/-10,6 ; p<0,05). We thus show, for the first time, that membrane ERαcontributes to arterial shear-sensing and could be pointed out as a new therapeutical target in peripheral vascular diseases, overcoming the known pro-cancerous action of nuclear ERαstimulation.

Reduced Common Carotid Artery Blood Flow in Spontaneously Hypertensive Rats is Unaffected by Aging and/or Chronic In Vivo Resveratrol Treatment

This study examined common carotid artery (CCA) blood flow (using a perivascular flowprobe) and pressure (using a catheter‐tip transducer) in anesthetized Adult (20‐24 wk old) and Aging (60‐70 wk old) Wistar Kyoto rats (WKY) and Spontaneously Hypertensive rats (SHR) following 28‐days of in vivo treatment (in drinking water, ab libitum) with either no trans resveratrol (RSV; No‐RSV), a moderate RSV dose (Mod‐RSV; ~0.075 mg/kg/day; to mimic daily red wine consumption), or a high RSV dose (High‐RSV; ~7.5 mg/kg/day). CCA mean, maximal systolic, minimum diastolic, and pulse pressure, and heart rate, were all significantly elevated in SHR vs. WKY (p&lt;0.01). Aging was associated with a significant increase in pulse pressure in WKY (p&lt;0.01). CCA mean, maximal systolic, and minimum diastolic blood flow, and vascular conductance, were all significantly reduced in SHR vs. WKY (p&lt;0.05). Aging did not have a significant effect on the flow parameters in either SHR or WKY. Neither Mod‐RSV nor High‐RSV treatment had a significant effect on the CCA blood pressure and blood flow variables measured. These data demonstrate that the reduction in CCA blood flow found in SHR is unaffected by aging or chronic in vivo RSV treatment. Further investigation into what can account for and alter the reduced CCA blood flow found in SHR is warranted.Funded by NSERC.

Coupling between arterial pressure, cerebral blood velocity, and cerebral tissue oxygenation with spontaneous and forced oscillations

We tested the hypothesis that transmission of arterial pressure to brain tissue oxygenation is low under conditions of arterial pressure instability. Two experimental models of hemodynamic instability were used in healthy human volunteers; (1) oscillatory lower body negative pressure (OLBNP) (N = 8; 5 male, 3 female), and; (2) maximal LBNP to presyncope (N = 21; 13 male, 8 female). Mean arterial pressure (MAP), middle cerebral artery velocity (MCAv), and cerebral tissue oxygen saturation (ScO2) were measured non-invasively. For the OLBNP protocol, between 0 and −60 mmHg negative pressure was applied for 20 cycles at 0.05 Hz, then 20 cycles at 0.1 Hz. For the maximal LBNP protocol, progressive 5 min stages of chamber decompression were applied until the onset of presyncope. Spectral power of MAP, mean MCAv, and ScO2 were calculated within the VLF (0.04–0.07 Hz), and LF (0.07–0.2 Hz) ranges, and cross-spectral coherence was calculated for MAP-mean MCAv, MAP-ScO2, and mean MCAv-ScO2 at baseline, during each OLBNP protocol, and at the level prior to pre-syncope during maximal LBNP (sub-max). The key findings are (1) both 0.1 Hz OLBNP and sub-max LBNP elicited increases in LF power for MAP, mean MCAv, and ScO2 (p ≤ 0.08); (2) 0.05 Hz OLBNP increased VLF power in MAP and ScO2 only (p ≤ 0.06); (3) coherence between MAP-mean MCAv was consistently higher (≥0.71) compared with MAP-ScO2, and mean MCAv-ScO2 (≤0.43) during both OLBNP protocols, and sub-max LBNP (p ≤ 0.04). These data indicate high linearity between pressure and cerebral blood flow variations, but reduced linearity between cerebral tissue oxygenation and both arterial pressure and cerebral blood flow. Measuring arterial pressure variability may not always provide adequate information about the downstream effects on cerebral tissue oxygenation, the key end-point of interest for neuronal viability.

Hemispheric asymmetry in cerebrovascular reactivity of the human primary motor cortex: an in vivo study at 7 T.

Current functional MRI (fMRI) approaches assess underlying neuronal activity through monitoring the related local variations in cerebral blood oxygenation, blood volume and blood flow. This vascular response is likely to vary across brain regions and across individuals, depending on the composition of the local vascular bed and on the vascular capacity to dilate. The most widely used technique uses the blood oxygen level dependent (BOLD) fMRI signal, which arises from a complex combination of all of these factors. The model of handedness provides a case where one brain region (dominant motor cortex) is known to have a stronger BOLD response over another (non-dominant motor cortex) during hand motor task performance. We predict that this is accompanied by a higher vascular reactivity in the dominant motor cortex, when compared with the non-dominant motor cortex. Precise measurement of end-tidal CO2 and a novel sinusoidal CO2 respiratory challenge were combined with the high sensitivity and finer spatial resolution available for fMRI at 7 T to measure BOLD cerebrovascular reactivity (CVR) in eight healthy male participants. BOLD CVR was compared between the left (dominant) and right (non-dominant) primary motor cortices of right-handed adults. Hemispheric asymmetry in vascular reactivity was predicted and observed in the primary motor cortex (left CVR = 0.60 ± 0.15%/mm Hg; right CVR = 0.47 ± 0.08%/mm Hg; left CVR > right CVR, P = 0.04), the first reported evidence of such a vascular difference. These findings demonstrate a cerebral vascular asymmetry between the left and right primary motor cortex. The origin of this asymmetry largely arises from the contribution of large draining veins. This work has implications for future motor laterality studies that use BOLD, and it is also suggestive of a vascular plasticity in the human primary motor cortex.

Development of a handheld blood flow measurement system using laser speckle flowgraphy

A new handheld blood flow measurement system using laser speckle flowgraphy was developed for easy measurement of blood flow. The developed system features a small display unit that allows measurement results to be viewed without a PC. The system is miniaturized, integrated with a microcontroller, a line sensor, and a laser unit. Our experiment was carried out to confirm the usefulness of the developed system to measure the blood flow variation.

A control systems approach to quantify wall shear stress normalization by flow-mediated dilation in the brachial artery.

Flow-mediated dilation is aimed at normalization of local wall shear stress under varying blood flow conditions. Blood flow velocity and vessel diameter are continuous and opposing influences that modulate wall shear stress. We derived an index FMDv to quantify wall shear stress normalization performance by flow-mediated dilation in the brachial artery. In 22 fasting presumed healthy men, we first assessed intra- and inter-session reproducibilities of two indices pFMDv and mFMDv, which consider the relative peak and relative mean hyperemic change in flow velocity, respectively. Second, utilizing oral glucose loading, we evaluated the tracking performance of both FMDv indices, in comparison with existing indices [i.e., the relative peak diameter increase (%FMD), the peak to baseline diameter ratio (Dpeak/Dbase), and the relative peak diameter increase normalized to the full area under the curve of blood flow velocity with hyperemia (FMD/shearAUC) or with area integrated to peak hyperemia (FMD/shearAUC_peak)]. Inter-session and intra-session reproducibilities for pFMDv, mFMDv and %FMD were comparable (intra-class correlation coefficients within 0.521–0.677 range). Both pFMDv and mFMDv showed more clearly a reduction after glucose loading (reduction of ~45%, p≤0.001) than the other indices (% given are relative reductions): %FMD (~11%, p≥0.074); Dpeak/Dbase (~11%, p≥0.074); FMD/shearAUC_peak (~20%, p≥0.016) and FMD/shearAUC (~38%, p≤0.038). Further analysis indicated that wall shear stress normalization under normal (fasting) conditions is already far from ideal (FMDv << 1), which (therefore) does not materially change with glucose loading. Our approach might be useful in intervention studies to detect intrinsic changes in shear stress normalization performance in conduit arteries.

Diurnal Variations in Blood Flow at Optic Nerve Head and Choroid in Healthy Eyes

To investigate the diurnal variations of the ocular blood flow in healthy eyes using laser speckle flowgraphy (LSFG), and to determine the relationship of the diurnal variations between the ocular blood flow and other ocular parameters.This prospective cross-sectional study was conducted at Nagoya University Hospital. We studied 13 healthy volunteers whose mean age was 33.5 ± 7.6 years. The mean blur rate (MBR), expressing the relative blood flow, on the optic nerve head (ONH) and choroidal blood flow was determined by LSFG (LSFG-NAVI) every 3 hours from 6:00 to 24:00 hours. The intraocular pressure (IOP), choroidal thickness measured by enhanced depth imaging optical coherence tomography, systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) in the brachial artery were also recorded. We evaluated the diurnal variations of the parameters and compared the MBR to the other parameters using a linear mixed model.The diurnal variations of the MBR on the ONH varied significantly with a trough at 9:00 hours and a peak at 24:00 hours (P < 0.001, linear mixed model). The MBR of choroid also had significant diurnal variations with a trough at 15:00 hours and a peak at 18:00 hours (P = 0.001). The IOP (P < 0.001), choroidal thickness (P < 0.001), SBP (P = 0.005), DBP (P = 0.001), and HR (P < 0.001) also had significant diurnal variations. Although the diurnal variation of the MBR on the ONH was different from the other parameters, that on the choroid was significantly and positively correlated with the DBP (P = 0.002), mean arterial pressure (P = 0.023), and mean ocular perfusion pressure (P = 0.047).We found significant diurnal variations in the ONH and choroidal blood flow. Although the ONH blood flow had its own diurnal variation because of strong autoregulation, the choroidal blood flow was more likely affected by systemic circulatory factors because of poor autoregulation.

In-office bleaching effects on the pulp flow and tooth sensitivity - case series.

Laser Doppler flowmetry (LDF) is a noninvasive method capable of evaluating variations in pulp blood flow (PBF) and pulp vitality. This method has thus far not been used to assess changes in blood flow after in-office bleaching. The aim of this case series report was to measure changes in PBF by LDF in the upper central incisor of three patients submitted to in-office bleaching. The buccal surfaces of the upper arch were bleached with a single session of 35% hydrogen peroxide gel with three 15-min applications. The color was recorded using a value-oriented Vita shade guide before in-office bleaching and one week after the procedure. The tooth sensitivity (TS) in a verbal scale was reported, and PBF was assessed by LDF before, immediately, and one week after the bleaching session. The lower arch was submitted to dental bleaching but not used for data assessment. A whitening degree of 3 to 4 shade guide units was detected. All participants experienced moderate to considerable TS after the procedure. The PBF readings reduced 20% to 40% immediately after bleaching. One week post-bleaching, TS and PBF were shown to be equal to baseline values. A reversible decrease of PBF was detected immediately after bleaching, which recovered to the baseline values or showed a slight increase sooner than one week post-bleaching. The LDF method allows detection of pulp blood changes in teeth submitted to in-office bleaching, but further studies are still required.

Abstract B05: Harnessing heterogeneity to design better combination therapies

Abstract Background: Significant cellular, molecular, and tissue heterogeneity is widely observed between and within tumors and the potential clinical significance of these variations is increasingly recognized. The intricate dialogue between the tumor cells and their environment selects for tumor phenotypes that are best adapted to survive. However, this environment is temporally and spatially heterogeneous largely due to variations in blood flow which results in local fluctuations of nutrients, growth factors and other cellular populations. This variability can lead to a heterogeneous response of the tumor to a given therapy. Interactions that occur within the cancer ecosystem do so in a dynamic spatio-temporal manner that is almost impossible to dissect via experimentation alone, so we propose a theoretical framework to generate combination therapies that are sensitive to initial tumor heterogeneity. Methods: Using a hybrid multi-scale mathematical model of tumor growth in vascularized tissue, we investigate the selection pressures exerted by spatial and temporal variations in tumor microenvironment and the resulting phenotypic adaptations. A key component of this model is normal and tumor metabolism and its interaction with microenvironmental factors. The metabolic phenotype of tumor cells is plastic, and microenvironmental selection leads to increased tumor glycolysis and decreased pH. Once this phenotype emerges, the tumor dramatically changes its behavior due to acid-mediated invasion, an effect that depends on the heterogeneity of the tumor cell phenotypes and their spatial distribution within the tumor. The tumors grown within this in silico model display much phenotypic variation, and this heterogeneity depends on the conditions of the microenvironment and the plasticity of the tumor cells. Results: Using the model, we generate sets of tumors with different biological parameters, classify them according to their spatial and temporal heterogeneity, and then administer several therapies, including chemotherapy, vascular therapy, pH buffer therapy, and hypoxia-activated drugs. The model predicts that pH buffer therapy will only have a tumor-preventative effect if administered before the tumor acquires the heterogeneous state that leads to acid-mediated invasion. This is in agreement with experimental results from a spontaneous prostate tumor mouse model (TRAMP mouse). In general, the model predicts that the outcomes of each therapy are highly dependent on the initial tumor heterogeneity at the time of commencing treatment. We categorize the ‘signatures’ of each therapy outcome as a function of the heterogeneity class of the initial tumor. By understanding the signature of each drug in isolation, we implement drug combinations in a sequence that promotes synergistic response for a given class of tumor heterogeneity. The signature of the first drug in the sequence is used to pick the following complementary drug. This produces a more intelligent treatment regimen that can be designed to harness tumor heterogeneity and modulate its impact on treatment outcomes. Citation Format: Mark Robertson-Tessi, Robert J. Gillies, Robert A. Gatenby, Alexander RA Anderson. Harnessing heterogeneity to design better combination therapies. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B05. doi:10.1158/1538-7445.CHTME14-B05

Epidural anesthesia improves pancreatic perfusion and decreases the severity of acute pancreatitis.

To study the safety of epidural anesthesia (EA), its effect on pancreatic perfusion and the outcome of patients with acute pancreatitis (AP). From 2005 to August 2010, patients with predicted severe AP [Ranson score ≥ 2, C-reactive protein > 100 or necrosis on computed tomography (CT)] were prospectively randomized to either a group receiving EA or a control group treated by patient controlled intravenous analgesia. Pain management was evaluated in the two groups every eight hours using the visual analog pain scale (VAS). Parameters for clinical severity such as length of hospital stay, use of antibiotics, admission to the intensive care unit, radiological/clinical complications and the need for surgical necrosectomy including biochemical data were recorded. A CT scan using a perfusion protocol was performed on admission and at 72 h to evaluate pancreatic blood flow. A significant variation in blood flow was defined as a 20% difference in pancreatic perfusion between admission and 72 h and was measured in the head, body and tail of the pancreas. We enrolled 35 patients. Thirteen were randomized to the EA group and 22 to the control group. There were no differences in demographic characteristics between the two groups. The Balthazar radiological severity score on admission was higher in the EA group than in the control group (mean score 4.15 ± 2.54 vs 3.38 ± 1.75, respectively, P = 0.347) and the median Ranson scores were 3.4 and 2.7 respectively (P = NS). The median duration of EA was 5.7 d, and no complications of the epidural procedure were reported. An improvement in perfusion of the pancreas was observed in 13/30 (43%) of measurements in the EA group vs 2/27 (7%) in the control group (P = 0.0025). Necrosectomy was performed in 1/13 patients in the EA group vs 4/22 patients in the control group (P = 0.63). The VAS improved during the first ten days in the EA group compared to the control group (0.2 vs 2.33, P = 0.034 at 10 d). Length of stay and mortality were not statistically different between the 2 groups (26 d vs 30 d, P = 0.65, and 0% for both respectively). Our study demonstrates that EA increases arterial perfusion of the pancreas and improves the clinical outcome of patients with AP.

Prediction of fluid responsiveness in mechanically ventilated children using dynamic and static parameters by esophageal Doppler in a pediatric ICU

Prediction of fluid responsiveness is defined by an increase in stroke volume (SV) of at least 10% after volume expansion. Dynamic [1] and static [2] esophageal Doppler (OD) parameters have been proposed in mechanically ventilated children to guide fluid therapy. This study aimed to compare dynamic parameters using the respiratory variation in aortic blood flow with static parameters using Doppler corrected flow times (FTc) obtained by OD.

Feasibility and operator variability of myocardial blood flow and reserve measurements with 99mTc-sestamibi quantitative dynamic SPECT/CT imaging

PurposeMyocardial blood flow (MBF) quantification with dynamic SPECT could lead to widespread utilization of MBF imaging in clinical practice with little cost increase over current standard SPECT myocardial perfusion imaging. This work evaluates the feasibility and operator-dependent variability of MBF and flow reserve measurements with 99mTc-sestamibi (MIBI) dynamic SPECT imaging using a standard dual-head SPECT camera. MethodsTwenty-eight patients underwent dipyridamole-stress and rest imaging with dynamic SPECT/CT acquisition. Quantitative images were iteratively reconstructed with all physical corrections and then myocardial and arterial blood regions of interest (ROI) were defined semi-automatically. A compartmental model was fitted to these ROI-sampled time-activity-curves, and flow-dependent MIBI extraction correction was applied to derive regional MBF values. Myocardial flow reserve (MFR) was estimated as stress/rest MBF ratio. MBF and MFR in low and high risk populations were evaluated for ability to detect disease. Images were each processed twice (≥7 days apart) by one expert and one novice operator to evaluate intra- and inter-operator variability of MBF and MFR measurement in the three coronary artery vascular territories. ResultsMean rest flow, stress flow, and MFR values were 0.83, 1.82 mL·minute−1·g−1, and 2.45, respectively. For stress/rest MFR, the inter-operator reproducibility was r2 = 0.86 with RPC = 1.1. Stress MBF and MFR were significantly reduced (P < .05) in high risk (n = 9) vs low risk populations (n = 19), indicating ability to detect disease. For expert and novice operators very good intra-operator correlations of r2 = 0.98 and 0.95 (n = 168, P < .001) were observed for combined rest and stress regional flow values. Bland-Altman reproducibility coefficients (RPC) were 0.25 and 0.47 mL·minute−1·g−1 for the expert and novice operators, respectively (P < .001). Inter-operator correlation was r2 = 0.91 and Bland-Altman RPC = 0.58 mL·minute−1·g−1 (n = 336). ConclusionsMBF and reserve measurements using 99mTc-sestamibi on a traditional, two-headed camera with fast rotation and with quantitative dynamic SPECT appears to be feasible, warranting further investigation.

Inhaled nitric oxide alters the distribution of blood flow in the healthy human lung, suggesting active hypoxic pulmonary vasoconstriction in normoxia.

Hypoxic pulmonary vasoconstriction (HPV) is thought to actively regulate ventilation-perfusion (V̇a/Q̇) matching, reducing perfusion in regions of alveolar hypoxia. We assessed the extent of HPV in the healthy human lung using inhaled nitric oxide (iNO) under inspired oxygen fractions (FiO2 ) of 0.125, 0.21, and 0.30 (a hyperoxic stimulus designed to abolish HPV without the development of atelectasis). Dynamic measures of blood flow were made in a single sagittal slice of the right lung of five healthy male subjects using an arterial spin labeling (ASL) MRI sequence, following a block stimulus pattern (3 × 60 breaths) with 40 ppm iNO administered in the central block. The overall spatial heterogeneity, spatiotemporal variability, and regional pattern of pulmonary blood flow was quantified as a function of condition (FiO2 × iNO state). While spatial heterogeneity did not change significantly with iNO administration or FiO2 , there were statistically significant increases in Global Fluctuation Dispersion, (a marker of spatiotemporal flow variability) when iNO was administered during hypoxia (5.4 percentage point increase, P = 0.003). iNO had an effect on regional blood flow that was FiO2 dependent (P = 0.02), with regional changes in the pattern of blood flow occurring in hypoxia (P = 0.007) and normoxia (P = 0.008) tending to increase flow to dependent lung at the expense of nondependent lung. These findings indicate that inhaled nitric oxide significantly alters the distribution of blood flow in both hypoxic and normoxic healthy subjects, and suggests that some baseline HPV may indeed be present in the normoxic lung.